modifying heads for proper squish height, squish area / velocity, and dome cc, (& a little porting info)

[KDXGarage]

Have you ridden a 125 in the woods? I have not. I have a 2005 KX125 that I rode on a MX track. My left foot needed to be a professional tap dancer to keep the power delivery optimal. Every missed shift was the gavel of justice being banged for me not riding it with high precision. I can only imagine me riding it in the woods. :-)

[Chuck78]

Have you ridden a 125 in the woods? I have not. I have a 2005 KX125 that I rode on a MX track. My left foot needed to be a professional tap dancer to keep the power delivery optimal. Every missed shift was the gavel of justice being banged for me not riding it with high precision. I can only imagine me riding it in the woods. :-)

I have ridden a 2000 Honda CR125R in the woods, and a 1980's KX125. The early KX water cooled engine was a chore. The CR125 is a top end screamer. Keeping the revs up and gearing the thing down was necessary. It's my brother's bike. It chokes on steep slow hill climbs.
I've been trying to convince him for years to have Eric Gorr do a woods porting job and big bore on that thing to 144cc, but no such luck...
This is why I'm looking to use a 2000 KX125, or perhaps a '99, or '97 ('96-'98?) for already having better low end torque porting than the purple '96 KX125 that'd be my dream ('00 cylinder modified to fit the '96-'98 engines, '00 had the best low/mid torque stock). Then I'd plan to mill the base gasket surface down to achieve altered port timing catered more to low end torque (& subsequently not need to mill the head down much at all to get proper squish, but rather likely need to cut into the squish area both to gain back enough squish band height, but also as I'd need to widen the 125 MX'er squish band to also focus the power more towards the low end/mid range torque. And of course porting improvements and a SmartCarb SC2 36 for additional low rpm throttle response gains.
Gearing it down from stock as well, to give it an enduro first gear ratio with a closer gear spread following.

Have you ever ridden a YZ125X or a European 144cc woods bike? They do soooo much better in the woods than a 125 motocrosser...still requiring more clutch/throttle control than a KDX220 or a 300 though...

The biggest concern for me is the aggressive MX ignition timing advance curve that's going to either require swapping a different ignition box, or else have to settle for taming the violent MX throttle response with an 11oz or so flywheel weight.

[KDXGarage]

I have not ridden either of those. I am glad they came back around, though!

[Chuck78]

If I do this 144cc woods bike build, now I'm thinking I might go with a 2003, same wheelbase as a '94-'02 125 & a KDX200, but slightly lazier steering angle unfortunately, but lowering the front and raising the rear slightly may return that to sharper steering. This bike's redesign for '03-'08 gave it a narrower chassis up front for a much more compact feel, as well as the most advanced of all KX 125 engine designs, which I've heard people say was borrowing a lot from the ultra-successful YZ125 engines

More common used parts as well at present, lots of 03-05/08 parts can be found on eBay for much cheaper than the 94-02 parts I've been browsing! I can always get retro purple '96 style graphics made up for an '00 or '03... Vintage racing though would require '98 & older... '97-'98 (& '99-'00 or '02?) only have 134cc pistons available though... unless Eric Gorr has a big stock of his custom pistons on hand... I would really like to have a good strong low/mid porting job done on one of these, and a 2-ring piston. All of the Wiseco and Wossner 134cc & 144cc pistons are single ring designs, less friction for more power, but far less longevity unfortunately. I don't want to be doing 1 top end per weekend or per month... 32:1 really helps out with that, despite the claims modern oil manufacturers like to boast

[Chuck78]

Revisiting the squish / head profile machining topic again...

In seeking out just the swingarm from the international version '94+ KDX220B aka KDX220SR road legal model via http://auction.yahoo.co.jp as they have a far superior frame-mounted kickstand on a chain roller tab kickstand combo bracket, and no lug welded to the swingarm for the clunky "offroad model kickstand" we got, I also happened upon some KDX220SR cylinder heads which have a much wider squish band than the more mid/high RPM focused 220R, as @kdxdazz had pointed this out as the SR head being much more torque oriented than the 220R head and the high RPM oriented KDX200H head.

Chopperpilot brought up the subject of the Millennium Technologies KDX200 "225" big bore kit. This led me to look at the KDX200 "225" page out of their 4 pages of Kawasaki big bore kits, and realize the "1742" casting # on the cylinder pictured was in fact a real KDX200H "225" kitted cylinder, head, and gasket kit + Wiseco 70.00mm A-size piston (apparently Millennium sells a 70.01mm B-sized Wiseco KDX220 piston as well, although Wiseco lists zero B or C sized pistons on their website, only 66.00mm 200 & +0.50mm, +1.00mm up to 68.00mm, + 69.00mm and 70.00mm KDX220 size.



In looking at the picture of the actual KDX200 "225" kit (223.2cc actual), the head popped out to me immediately as having a noticeably wider squish band than the stock 220R or the marginally wider RB modded 220 heads. This is really what I was after, and I thought perhaps just widening a stock 200 head's total chamber from 69.xx mm to 70.03mm would give me a bit more of what I wanted, to boost the low-midrange power so that the monstrous power surge of the Pro Circuit Platinum 2 pipe's midrange would be less noticeable with more power below that point.
Pictured below:
RB'd 220 69mm head (TIGHT squish height & slightly wider than stock) *vs* KDX220SR stock (VERY TIGHT squish clearance!, extremely wide squish band width) vs stock KDX220R head (very lazy/tall squish height, just a hair less squish width than RB's).



The Millennium 225 kit profile is roughly what I was hoping to create out of one of these two KDX220SR heads, and now while thinking about it, the 220SR head (with building a lathe fixture for '94+ 220A (220R), 220B (220SR) & 200H heads + some lathe work) is really perhaps better for my used somewhat unknown performing CV Tech ported 70.00mm big bore 223cc cylinder (Canadian company, new owners and different name now), as it would take very little in mods after making a fixture for a metal lathe's 4-jaw chuck in order to modify a 69mm 220SR head for my ported 70mm cylinder...

Playing around with a compression ratio calculator and knowing that the stock KDX220 has a low speed compression ratio of 9.4:1 (high speed compression ratio of 7.9:1 stock), I see that the SR head opened up to 70.02mm total diameter with the Cometic .254mm (0.010") thick 70mm head gasket, the 220SR head (*if* same volume as a stock 220R head) after opening up the chamber for the +1.00mm big bore, would bump the stock low speed compression ratio from 9.4:1 up to 9.6:1. Shaving off only 0.70cc worth of head volume to enlarge the dome/chamber and reduce the squish width slightly would then yield stock compression ratio of 9.4:1 again.

At a mere 0.70cc of aluminum removed to dial back the squish band width slightly, & being a rookie at 2-stroke head machining, I see I'll need to make my lathe fixture a 2-piece design with a flat thick plate to clamp in the lathe chuck jaws and get the head centered in and out and radially with, then a smaller diameter plate bolted flat to that first flat plate, with the head mounting fixturing provisions to bolt the coolant flange down to the plate from the back side of the plate, then another pair of standoff blocks bolted to the 2nd plate to clamp the headstay in between to support the head on the opposite side of the coolant flange. This way, I could readily remove the head and majority of the fixture without disturbing it's positioning in the lathe chuck jaws, 2 dowels would be a requirement for this interface between the base plate and the fixturing, as would a very clean surface.

This would facilitate removing the head frequently to check the dome volume in cc's with the head upside down and a plexiglass sheet with 2 small holes in it, 1 tiny hole on the outer area to bleed off trapped air, and a second in the middle to use a graduated 50ml (50cc) oral syringe to fill water into the chamber to measure. This is because if I enlarge the chamber (reducing the squish) too much (adding overall head volume while narrowing the 220SR's massive squish width), I'll then need to turn down or mill down the head gasket surface and then further cut down the squish band deeper into the head to compensate for cutting the inner diameter of the squish band (outer portion of the chamber/dome) which enlarges the head volume.


I should note that the '94+ KDX220SR head has a 5.5mm deeper chamber than the RB head, and has even tighter squish clearance than the RB head. Tighter squish and wider squish width both will work with the porting and the expansion chamber to give more low end torque and better throttle response.

It should also be noted that squish band width is just a part of the equation. The squish band has to be under a certain clearance height in order to be largely effective. Generally speaking, anything over 1.6mm head to piston height at TDC (not factoring in rod stretch at 8000RPM or thermal expansion, just cold static clearance) is not going to yield the type of performance, efficiency, or precise jetting that a tighter squish clearance gives, due to the fact that nearing TDC, the air/fuel mixture around the perimeter of the cylinder (away from the spark plug the furthest) isn't going to be pushed out at as high of velocity towards the spark/flame front. Too tight of a squish clearance, and the air/fuel mixture will be superheated through localized compression, and may detonate on it's own prior to the flame front igniting it, and at great pressures that cause destruction to the aluminum head and piston in micro areas. Higher octane will help fend off a minor amount of this, but higher octane fuel is less desirable for it's lesser throttle response and slower burning, unless trying to squeeze the absolute most compression and performance from an engine, low-mid performance in the case of a 2-stroke.
The angle of the squish band must match the piston's angle precisely, or else open up ever so slightly taller on the side closer to the center of the head/piston, NEVER the reverse of that.
Now that the squish band has been machined down to a highly effective height, the width of the squish band width is a tuning parameter as to how much volume of squished air/fuel mixture is rapidly expelled toward the flame front. Generally, this should be matched to the port timing. This is an area that I have no significant expertise in yet, but Jaguar on here and other forums aka Michael Forrest certainly can educate us a bit on this, and would be able to read everything I've learned and posted here and correct me on quite a few things, I'd imagine! I wish Ron Black were still active on here (user RBD), but he seems fully retired now. If he were within an 8-hour drive of me, I would have already tried to persuade him to let me visit him and pay him good money for a weekend worth of schooling on KDX heads and machining them... If I became competent enough, heck I'd even do up batches of heads for others and send Ron some money order funds or cash as his royalties!

I am noting that it's likely I can't narrow the squish width too much to get closer to the Millennium or RB head widths as then I'd also have to mill down the head and then re-do the squish band surface to reset the squish clearance back to 1.00mm with compressed head gasket thickness figured in,,,
I do like the idea of keeping more metal thickness in the head for better cooling capacity and warpage resistance, so I may also try to find another stock 220 head to give my own version of the RB treatment to, but for a 70.01mm piston/bore size.
The engine I bought from someone on here for $400-ish from Canada had this 70.00mm Wiseco piston and replated 70.00mm bore and fairly substantial transfer port and intake side porting work, oddly had a stock bore 220 cylinder head on it, and I could literally see on the edges of the piston where it had smacked the edge of the gasket surface of the head which was overhanging 0.50mm over into the cylinder all around since it hadn't been done up to match the enlarged bore size... SMH!?!?!?!

[Chuck78]

Here's a cut and paste image comparison, not to exact scale, of the squish band widths of the KDX220SR 69mm head vs Millennium "225" big bore kit head @ 70mm vs a 69mm RB'd head:

KDX200-220-225_head-squishband-comparison.jpg (352.73 KiB) Viewed 9428 times

I'm actually surprised at how wide that Millennium 225 kit's squish band width is.... it's not quite an apples to apples comparison since the bore size was enlarged 1.0mm, but close enough for a rough visual comparison's sake.

Jaguar has a squish velocity width height etc calculator program made in Excel I believe, which I will have to dig deep into or just ask him to do some calculations for me which he volunteered his services for a small fee to anyone viewing his website, in order to get a better grasp on exact squish velocity and volume I'd be ending up with here.

I'm still uncertain what the differences in the 220SR cylinder are, but I'd imagine it most definitely has to have different port timing than the 220R cylinder, although kdxdazz thought that perhaps it might be the same porting configuration and that the differing part numbers only differed in the exhaust attachment type (SR has a bolt-on exhaust flange, 220R has a slip-in fit retained by springs).




Interesting that my friend Sebastien pointed out that the E-Series KDX200 heads have a lot wider squish band than the KDX200H, and perhaps this is a large part of the reason why some people really preferred the 200E power over the 200H power, also paired with more initial ignition advance in the CDI curve on the 200E which will again emphasize more bottom end...


EDIT - adding info gathered from a 2006 thread on here where Ron Black the man himself (RBD username) stated that .040" / 1.00mm is the magic number for squish clearance height. Idaho Charley commented that his KTM's called for .055"-.060" (.060" = 1.5mm), and Ron Black stated that the KTM's run taller squish clearance because they run higher compression, and this is a fairly necessary compromise to avoid detonation or race fuel requirements.
I believe it was IdahoCharley or someone else who said that one KDX had a head with 45% squish area calculated, done by Eric Gorr, and the other had a head done by someone named Clay at a well known performance engine shop at that time, with a 50% squish area, and although the cylinders had different porting (one mildly ported, the other stock?), the engine with the Gorr 45% squish area vs 55% chamber area had better top end and bottom end ("pulled harder right off idle and rev'd higher with EG head") than the 50% squish area / 50% chamber area head. This was on a 200 I believe.

viewtopic.php?p=30852#p30852

It's far more complicated than just a percentage of squish area vs chamber area, height is also figured in, and RB did remind that the 1.00mm squish height is the magic number WHEN paired with the correct squish width.

I'll see how this 220SR head with my mods ends up doing with this ported cylinder, and then I'll try to replicate the squish area percentage of the RB head on a stock head made out to 70mm bore, and then do back to back tests on similar weather conditions days and see how they perform...

[Chuck78]

Here's some good info from the man Ron Black himself, I thought I would cut and paste this from elsewhere on the forum just to have it all in one place that's more current:
viewtopic.php?p=35622&hilit=Head+gasket+thickness#top

A stock 200 head has a head volume of about 19 cc's

A stock 220 head has a head volume of about 24 cc's

A 200 has a 66 mm bore.

A 220 has a 69 mm bore.

As you can see, there is a 3 mm (almost 1/8") difference in bore sizes. You can also see that there is a large difference in head volumes. There is also a difference in port timings between the two.

There is more to a head mod than just bumping up compression. It has more to do with the configuration of the squish area and the combustion chamber volume.

Lets say you could put a 200 head on a 220 without crashing the piston into the head, you would be bumping the static compression over 50 Lbs.

Now did you say race gas and special blends and what are we doing about the detonation features that are now a problem without a proper squish configuration?

YES, I can modify a 200 head to work on the 220, it would be expensive $80.00 to $90.00 to re-cut and re-shape the 200 head and get the head volume right and still run pump gas. Oh and one more thing, a spacer maybe required under the spark plug as the bowl area that needs to be removed to get the proper volume, would have the spark plug threads sticking through into the combustion chamber.

Ron

viewtopic.php?p=50964&hilit=Squish+area#p50964

It is part of the machining process.....

If you look at a KDX 200 head, the entire combustion chamber and squish area are cast into it's shape.

When you look at a KDX 220 head you see that the entire combustion chamber and squish band are machined to it's shape.

If you have not guessed by now the 200 and 220 use the same casting and the only difference is the 200 head is uses the cast combustion chamber. The 220 head is a 200 casting and the combustion chamber is machined larger for the larger displacement of the 220 (the little dimple is part of the machining process).

OK...., now for the hard part for you to understand is, you really can not take a 200 head and machine it to a 200. WHY???? you ask, if the 220 head starts out as a 200...., why not.

The answer is that when the machine the spark plug hole and spot face it for the spark plug depth. the 200 head is machined deeper into the head because the combustion chamber is smaller.

So if you try and cut the 200 head to the 220 specs the spark plug would stick through into the combustion chamber about 3 to 4 mm, not a good idea.

Just a note, I have machined a 200 head here lately for a guy that want to experiment with high elevations 10,000 ~ 12,000 feet. I know this head will not work at sea level but at 2 mile high I think there is a chance. I have not heard anything back yet on how it works out.

Ron

And Jaguar's comments/quick analysis of RB's methods, & an email reply he received from Ron:
viewtopic.php?p=173506&hilit=Squish+area#p173506

Looking at the before and after head pictures at http://www.kdxrider.net/forums/viewtopic.php?t=2444
and from the following email from Ron I'd say the RB head mod shaves off some of the mating surface, lowers the angle of the squish area, and increases the combustion volume to keep the cranking pressure from rising too much. That would serve to increase the squish velocity, something that decreases the time from spark to peak combustion pressure. So without adjusting the timing plate it would be akin to advancing the timing. If you disagree then just reconsider Rons own words on his site: "This mod will increase torque, snap, ride-ability and helps with fuel mileage too! "
Here is Rons response to my email: "Our mods are for premium pump gas and there is only certain things we can do to the 200 heads to help clean up the combustion without pinging and detonation problems for pump gas by squish angle reconfigured and machined combustion chamber. We have no MSV specs for you. We pretty much maintain the stock finished volume with maybe a 2 to 5 pounds increase in static compression"
For anyone that wants to MX a KDX then it's probably best to tell him to keep the same squish angle in order to not increase the velocity much.
If you want to calculate the squish velocity then go to www.torqsoft.net/squish-velocity.html

& a very detailed thread from Jaguar on squish velocity:

viewtopic.php?p=173578&hilit=Squish+area#p173578

[brademan76]

Here's some good info from the man Ron black himself, I thought I would cut and paste this from elsewhere on the forum just to have it all in one place that's more current:
......

So the idea I've had about getting my 200E head milled to eek out any more bottom end power is probably not a good one?

Glad I started reading this thread. While I know more than I did about porting, squish bands/velocity, etc. I still have a lot to learn before I UNDERSTAND any of it. Thanks for putting all this information into one place.

[Chuck78]

From what I understand, the 200E is already set up with a wider squish band than the 200H, and more initial ignition advance in the ignition CDI box then what the H series has, both giving it more torque.
Shaving the head slightly will definitely tighten up the squish band and give you a higher squish velocity which will boost the low end even more, but perhaps will require at least 93 octane or adding VP octane booster if you don't have the head re-chambered.
I would contact Pro Circuit's engine building department, Tom Morgan Racing (Morgan Racing Engines), and Boyko Racing to talk to them about some basic porting cleanup work and squish band modification. Ultimately if you want more torque, in my opinion it is best to send the cylinder out to have the base gasket surface cut down ever so slightly, which will lower all Port timing, then have the ports cleaned up for a very basic mild porting job, and then the head may not even need touched as you will be lowering the head as well as the cylinder so it will tighten up the squish band. This really I feel is the preferred method for all of the 200 water-cooled engines. The 220 has lower port timing to begin with, so it really is the one that is in most need or most practical to do only the head mod to. I've always found the 200 H (as stock) to be lacking in low-mid torque and quite underwhelming UNLESS you ride it like a 125 2-stroke, at which point it's a blast and very fast. If you don't ride it like a 125, it will choke in the steep gnarly technical terrain unless you are slipping your clutch profusely all the time, as it really takes an adjustment to riding style, and rides like a modern 150.
The 200E on the other hand definitely is not a 220 power delivery, but does seem to have more torque. I've only experienced two different 200 E Series bikes owned by friends locally, only one now, whereas most of my KDX friends locally have 200 H or a few 220's.

Ted Boyko has done some incredible work to my buddy's bike out on the other side of the country, and it has even more torque than his modded RMX250 or his stock porting/head KDX200E, & the 200H is still on stock bore at 198cc!
I would be inclined, since you have an E-Series that cannot be bored out to more than one or two millimeter oversized (cannot do 220 sized 69mm/70mm big bores on a 200E cylinder, not enough thickness and powervalve components are in the way), to send Ted Boyko @ Boyko Racing your wonder and had after doing a squish band mock-up measurement using some rosin core solder placed along the wrist pin axis on the left and right of the piston, then reinstalling head and gasket and kicking the engine over gently to smash down the solder to show him the squish band clearance you have, then have him do the same porting & head work that he did for Sebastien Salvant's bike. Then you could even swap to a Lectron Billetron Pro Series carb or perhaps on an E-Series, you could fit a SmartCarb SC2 36. The SmartCarb SC2 36 will not fit on an H series at all due to frame interference with the shock crossmember and head stay mount, but I know there are a few guys that run them on a KDX engine in a KX 125 hybrid and most highly about them.

[Chuck78]

I will emphasize regarding my above comments for the 200 engines, these comments really only apply if you are looking for a big increase in low end and mid-range torque, although the work that Ted Boyko had done boosted power everywhere for Sebastien's bike, top end and bottom end. Some people absolutely love the explosive upper mid-range and top end of a 200, and talk bad about the 220. It's all a matter of what type of terrain they ride to a small degree, how they ride regarding using the clutch and throttle and technical terrain with low ground speed. For a 200 owner who doesn't feel the need for any more low-end torque mostly because they Don't Ride technical terrain, the head mod and supporting cleanup will definitely be awesome for them. But the squish velocity should not be too high though when figuring this, however too wide of a squish band will make the squish effect not very prominent, so there is a fine line of creating more squish velocity and boosting low end torque, versus having two wide of a squish band clearance and not having an effective squish area whatsoever.

[Chuck78]

On a 200, regardless of E-Series or H-series, if you are looking for more low-end torque and wanted a slightly tighter squish clearance, I would look into having Cometic cut you a thinner than stock base gasket, as that will lower the port timing, and although it may seem like a very slight and perhaps insignificant port timing change, it doesn't take much at all.

You can't lower it any lower than what the squish clearance will allow, though. Making changes for squish clearance also does need to keep in mind the condition of the crank and rod bearings. A sloppy bearing will measure a slightly different squish clearance. So you need to check for play in the bearings when determining your squish clearance on the current engine. Then I would measure the base gasket if possible after removed, and then order a thinner version based on that. That might be difficult with old stuck/hardened base gasket removal, but you could also pull the cylinder, install any new gasket, measure the uncompressed thickness, torque everything down and do your squish test with the solder on the left and right sides above the wrist pin axis, then remove and use those measurements to determine how much tighter you can make the squish by reducing the base gasket thickness. You can also measure the compressed thickness after installing, although it will expand slightly even after being clamped down and then removed.

This will both lower the port timing slightly as well as tighten up the squish clearance & velocity to alter the combustion timing.

1.0mm is a good squish band height clearance to shoot for, and I believe Ron Black himself has said this is a good number to go by. 1.1mm works well. 1.6 is where it really starts to lose effectiveness as there isn't enough velocity created nearing top dead center with that large of a gap.
If you do frequent bottom end rebuilds, you might be able to get away with 0.85mm squish clearance, but I wouldn't push it, as that will create a lot more heat around the perimeter of the piston and head from the compression of the mixture alone, and could potentially cause some detonation when the engine is really hot or when running lower octane.
With any tightening up of the squish without re-chambering the head to increase the head volume, or rather put the head volume back to where it was before the squish was tightened up through base gasket or head milling, it would be a good idea to run VP octane booster or at least add some toluene as octane booster into your pre-mix when you're mixing the oil in, making sure to substitute it for a small portion of gasoline astronaut dilute the oil ratio.

[brademan76]

I will emphasize regarding my above comments for the 200 engines, these comments really only apply if you are looking for a big increase in low end and mid-range torque, although the work that Ted Boyko had done boosted power everywhere for Sebastien's bike, top end and bottom end. Some people absolutely love the explosive upper mid-range and top end of a 200, and talk bad about the 220. It's all a matter of what type of terrain they ride to a small degree, how they ride regarding using the clutch and throttle and technical terrain with low ground speed. For a 200 owner who doesn't feel the need for any more low-end torque mostly because they Don't Ride technical terrain, the head mod and supporting cleanup will definitely be awesome for them. But the squish velocity should not be too high though when figuring this, however too wide of a squish band will make the squish effect not very prominent, so there is a fine line of creating more squish velocity and boosting low end torque, versus having two wide of a squish band clearance and not having an effective squish area whatsoever.

Definitely more concerned with maximizing bottom end power/torque, but probably without needing to go beyond 93pump gas. I do have a lectron (not the new billetron).

Thanks for all of you consideration. Time to figure out which direction to go.

[kdxdazz]

I will emphasize regarding my above comments for the 200 engines, these comments really only apply if you are looking for a big increase in low end and mid-range torque, although the work that Ted Boyko had done boosted power everywhere for Sebastien's bike, top end and bottom end. Some people absolutely love the explosive upper mid-range and top end of a 200, and talk bad about the 220. It's all a matter of what type of terrain they ride to a small degree, how they ride regarding using the clutch and throttle and technical terrain with low ground speed. For a 200 owner who doesn't feel the need for any more low-end torque mostly because they Don't Ride technical terrain, the head mod and supporting cleanup will definitely be awesome for them. But the squish velocity should not be too high though when figuring this, however too wide of a squish band will make the squish effect not very prominent, so there is a fine line of creating more squish velocity and boosting low end torque, versus having two wide of a squish band clearance and not having an effective squish area whatsoever.

Definitely more concerned with maximizing bottom end power/torque, but probably without needing to go beyond 93pump gas. I do have a lectron (not the new billetron).

Thanks for all of you consideration. Time to figure out which direction to go.

I don't have any knowledge on the E series but just throwing it out there, most 2 stroke bikes I come across aren't jetted that well in the low end and nothing creates more low down torque than a perfectly jetted bike
Also make sure you are still running the airbox lid and snorkel as that is it's purpose to produce more low end torque, my kdx220sr has the tiniest of snorkels but boy does it have some low to midrange grunt
I know it's off topic from squish band, but I have 3 kdx's and all of them wouldn't pull the skin off a rice pudding because of how badly they were jetted
Another example is when I first bought my kdx220 it had an RB carb, RB modded head, procircuit platinum 2 pipe, boysen reeds and it had less torque and power than my scooter, the owner had no clue and he followed RB jetting recommendation but likewise there was many other issues with it too.
As another side note, I also emailed RB in the early days complaining how bad the bike run and I think this might be one of the reasons he stopped working on second hand carbs, not just my email obviously but I don't think he could produce good results on carbs with even slightly worn emulsion tubes

[brademan76]

Got into the engine on the '93 200E this afternoon. Compression tested at ~135 totally cold, a bit low. Tried the solder to check squish and best I could get was somewhere around 1.40-1.45mm. I changed piston and rings probably 3 years ago, stock piston was in it then.

I suppose I should yank the whole cylinder off and have someone who knows what they're looking at measure the bore size and check wear. I should have the all steel KIPS form BDK in the mail shortly so will be handy to have it out get those in.

20250224_154612.jpg (3.48 MiB) Viewed 8358 times

[Chuck78]

I would see about sending that out to someone with the cylinder for them to do some basic porting cleanup and perhaps turn down the base of the cylinder in a lathe fixture to remove *up to* about 0.30mm or 0.35mm to lower the port timing, particularly the transfer port heights, and reshape the other ports to the builder's preferred more power everywhere / more torque type KDX porting formula... Boyko Racing, Tom Morgan Racing - these guys are the best small time shops, long time veteran 2-stroke builders, Tom worked for Kawasaki as an engineer and race engine builder, Ted Boyko has been in the industry since the beginning of long travel 2-stroke woods bikes as well! They can measure the plating and tell you where you stand with it, and can send it out for you after they do their work...

[brademan76]

Definitely going to get in touch with them about those options, thanks!

[brademan76]

Talked with Ted Boyko this afternoon. He's gonna do as suggested above. So looking forward to see what he does. I'll update and get some before and after pics.

[Chuck78]

AWESOME! My friend Sebastien hangs around Ted's shop and helps out some, and had Ted Boyko do his KDX200H cylinder, with extremely pleasing results... He's also running a Lectron Billetron Pro Series carb, which is the best carb you can get for our bikes, and the carb was almost perfectly dialed as set up by Lectron for this porting job and squish clearance tightening up...
The 200E head itself is a bit better for low-end torque than the 200H head as well, so a 200E could really come close to a 220's torque minus 20cc's worth...

Ted Boyko is really one of the greats, these guys won't be around for much longer before they fade off into retirement and out of our spotlight, so it's important too get this type of knowledge put into your cylinder while it's still available... Luckily Gary Braun at Millennium, the big 2-stroke porting guy there, is younger than me at around 40 I believe, so we'll at least have one top professional with an awesome reputation, I'm sure there's more that will step up but it's not going to be as common as it used to be as time goes on. It really pays to have someone who is really familiar with your particular model as well, or who has buddies who are also old-time veterans that have good porting specs for these bikes. Luckily Millennium being a big company has a lot of this stuff well documented as for what works best with what bikes