head squish

[Kx200x]

I know RB designs no longer sells or mods parts. How is the fredette head mod? Im going to install a ported cylinder on my 99Kx125 e series hybrid. Thinking of sending the head out unless someone has an e series rb head laying around or a carb. I could use a carb boot as I've got a boyeson rad valve but picked up a vforce 3 but didnt come with one. I have a spare cylinder but would need to be sleeved or seriously repaired I could trade. Plus the rest of the engine that came with the cylinder. Idk I thought I'd put it out there

[brademan76]

from what has been discussed here the E series head is already pretty good compared to and H series head, squish band is much wider, produces more low end power, etc. Chuck78 can fill you in with a more long-winded reply.
I sent my E series head and cylinder to Ted Boyko in Southern CA and he removed a little material from cylinder base slightly milled the hea, in addition to some port work. Very noticeable low and mid power improvement.

some previous discussion: viewtopic.php?t=26022&start=20
viewtopic.php?p=230368#p230368

[Kx200x]

Thanks for the reply. Im really looking for more top end power then bottom end. I've got an H series pro circuit platinum pipe and shorty silencer fromm a kx 250 and Jaguars cdi box paired with a 08 crf450r coil. Same spacing as the kdx. Im kinda wanting it to have more top end then bottom end. The cdi box definitely helped. It gave it a noticeable bottom end gain as well as over rev and midrange. It's funny after I installed it I held the kill switch down for the normal amount of time and when I let of instead of the engine shutting down it lit back up. Maybe I'll just leave it be. I've searched ebay for heads that looked like they had work done to them and carbs with divider plates but no avail. Thought I would see if anyone here wanted to part with any.

[Molly's 70]

I had RB do a head mod for me less than a year ago. I'd contact them. I found a clean, stock head on Ebay.

[Kx200x]

I asked him recently he said no. I just put my top end together. Bought an IMD piston. Cast piston. I have a sleeve and went with .25mm over. Just buttoning up the engine today. I doubt I'll find an Rb head. Maybe ill send one to Fredette. Check out the IMD piston. Cast. Made in Japan. Slightly higher dome then the wiseco and has 4 holes drilled on the exhaust side to help cooling. Hopefully this new cylinder and piston give me the power I was looking for

[brademan76]

interesting on the imd piston. thanks for sharing!

[Chuck78]

I asked him recently he said no. I just put my top end together. Bought an IMD piston. Cast piston. I have a sleeve and went with .25mm over. Just buttoning up the engine today. I doubt I'll find an Rb head. Maybe ill send one to Fredette. Check out the IMD piston. Cast. Made in Japan. Slightly higher dome then the wiseco and has 4 holes drilled on the exhaust side to help cooling. Hopefully this new cylinder and piston give me the power I was looking for

If you're looking for more top end, and if that IMD piston has more dome volume than stock, you aren't going to simply just want the head milled (which I believe is all that Fredette is set up to do on KDX heads, no reshaping etc). You'll need to measure the cc of the piston dome (or inquire with the manufacturer as to the dome volume technical specs), & get with a Kawasaki 2-stroke expert engine builder (& former Kawasaki race team engine builder) like Tom Morgan of Tom Morgan Racing Engines, & have the head squish band width narrowed down slightly. You'll also likely need to provide him with an as-installed squish band height clearance spec along the wrist pin axis at the left and right edges of the piston (assemble top end with a piece of soft solder folded up at the edges of the cylit, torque the head and cylinder down, then crank the engine over to compress the solder to give a true as-installed distance measurement reference at the edges of the cylinder.

After the squish height is set by milling, the squish band width can be altered by removing material from the edges of the cylinder head's dome, cc volume checked, & head chamber dome volume adjusted to bet the compression ratio to where you'd want it based on your fuel preference.

Generally a squish band clearance of 1.0mm-1.2mm is excellent, and the trapped squish volume is tuned by the width of the squish band profile width in the head. Wider = more low end and mid range, narrower squish width profile = more top end power.

Higher compression really only boosts low end and hurts high RPM rev out.

Call Tom Morgan up, he has some well proven porting and head setups that he does to our KDX engines. Ask him about your E-Series head work and what he'd recommend for optimizing it and getting more top end power out of the bike. Let us know what he says.

https://morganracingengines.com/


Looking at a 200E vs 200H head, the 200E has a wider squish band profile for more torque, the 200H is clearly more of a high RPM head profile.

[Kx200x]

Thanks for the tom Morgan racing info. Honestly Im strapped for cash right now. Im probably not going to get that technical i to it. Ive alreadt spent a heap of money on a 350 xcf only to prefer a 99 kx125/200 hybrid track or trails. I was under the impression that rb could get the squish spot on fairly easily. I ended up doing a port job on the cylinder and opening the exit of the exhaust port up to the size of the inner diameter of the procircuit pipe. Then I opened the rest and blended in the corners of the boost ports. I polished the kips valves with 1500 grit sandpaper and the entire exhaust port nice and shiny. I slightly raised and widened the exhaust port and matched the center powervalve so everything was flush and raised it slightly. I left the intake rough and the 3 ports under the reed cage I opened. Who ever installed the liner did a porting job of their own with the intake ports abs transfer ports. As far as the head I sanded down the corner of the dome slightly and sanded off the sharp edges around the outside of the combustion chamber and resurfaced it on emery cloth on glass. Theb I polished the dome in the head with 1500 grit and rubbing compound but left the squish area a rough texture. I added a spacer on the left kips valve, I have a 36.5mm pwk #6 slide cek needle. Jaguars cdi box paired with a 08 crf450r coil and accell high performance coil wire. Pro Circuit h series platinum pipe and 99-02 kx250 pro circuit shorty. I have to play with jetting and Jaguars cdi box for optimal timing a little. More but I spent the day finishing the engine build and rode it. Seems to run great dont think I need much more.

[Chuck78]

Can you go into more detail with what you said about adding a spacer to the left KIPS valve?
Are you talking about making a spacer for the KIPS subport resonator chamber on the left hand side of the engine?

I've got a pretty heavily ported cylinder although the timing was not altered drastically, intake side was opened up quite a bit although the transfer ports have knife edges on the wrong side of them, that was the old school way to do it, the way that the mixture flows should hit a rounded edge and not a knife edge, same way air flow goes over an airplane wing. The knife edge should be at the air-exiting side & not the air-entering side.
Since that cylinder was bored out to 70.00mm for a Wiseco oversized 223cc piston, & I don't have a head to match it, I'm going to attempt to taking a KDX220SR head with its low end and mid-range torque profile completely different from the 220r head, and open it up 1.0mm by taking 0.50mm off of the gasket surface edge of the squish area to match, and then I will work with that head and maybe do a couple different reshaping operations and test runs. I'm going to send out my other cylinders for more professional cording of known porting and engine building gurus versus this current one that came from Canada (shop formerly called CV Tech did the work and it has low hours since then from previous owner).
I'll have to compare the port timing but I don't think it's drastically altered, and this is going to be my experiment to build a tractor engine... Although how much the ports are opened up might not work well with the low RPM focused head profile. The 220SR has something like a 13.5mm wide squish band platform vs the RB head being closer to stock at maybe 9.5mm wide squish band with 1.0mm total squish clearance as installed with head gasket included.

After I finish rehabbing my old house and sell it I'll have some money to play with and will be sending some cylinders out this winter to Tom Morgan Racing Engines (cylinder and head) and to Ted Boyko @ Boyko Racing (cylinder-only, to work with an RB'd 220 head).

[Chuck78]

Thanks for the Tom Morgan Racing info.

I'm probably not going to get that technical into it.

I've alreadt spent a heap of money on a 350 XC-F only to prefer a 99 KX125/200 hybrid track or trails.

I ended up doing a port job on the cylinder and opening the exit of the exhaust port up to the size of the inner diameter of the Pro Circuit pipe. Then I opened the rest and blended in the corners of the boost ports. I polished the kips valves with 1500 grit sandpaper and the entire exhaust port nice and shiny. I slightly raised and widened the exhaust port and matched the center powervalve so everything was flush and raised it slightly. I left the intake rough and the 3 ports under the reed cage I opened. Who ever installed the liner did a porting job of their own with the intake ports abs transfer ports. As far as the head I sanded down the corner of the dome slightly and sanded off the sharp edges around the outside of the combustion chamber and resurfaced it on emery cloth on glass. Then I polished the dome in the head with 1500 grit and rubbing compound but left the squish area a rough texture. I added a spacer on the left kips valve, I have a 36.5mm pwk #6 slide cek needle. Jaguar's CDI box paired with a 08 CRF450R coil and Accell high performance coil wire. Pro Circuit H-series Platinum 2 pipe and 99-02 KX250 Pro Circuit shorty.
...Seems to run great dont think I need much more.

You're definitely making me really want to start looking out for a 96-98/99-02 KX 125 chassis, even more so than my curiosities already had me looking for one...
I can't afford taking up any more space here though otherwise I'll be filling my entire basement with bikes as well as the garage! I keep saying I need to sell 1 or 2 old Suzuki GS street bikes and maybe 1 of my 2 vintage dirt bikes, but it's a tough thing to part with any good bike!

[Kx200x]

Well James Stewart smoked everyone on a 99 kx125. He ran a PC linkage. I bought a kouba link which is similar geometry lowering the rear. I raised the fork legs as well. It's a smaller bike then my 350 and I'm 5 foot 7 140lbs so its a win win for me. Now that it running real nice ill probably tear it down over the winter and paint everything nice and put some fresh plastics on it. Im in the same boat. Dumping off the street bikes trimming down the stable to 2 steeds. I'll say tossing the air forks and remapping th ecu made me like the ktm much more.

[KDXGarage]

"trimming down the stable to 2 steeds"

Hey, man. Watch your language. There are adults around here.

[Kx200x]

Can you go into more detail with what you said about adding a spacer to the left KIPS valve?
Are you talking about making a spacer for the KIPS subport resonator chamber on the left hand side of the engine?

I've got a pretty heavily ported cylinder although the timing was not altered drastically, intake side was opened up quite a bit although the transfer ports have knife edges on the wrong side of them, that was the old school way to do it, the way that the mixture flows should hit a rounded edge and not a knife edge, same way air flow goes over an airplane wing. The knife edge should be at the air-exiting side & not the air-entering side.
Since that cylinder was bored out to 70.00mm for a Wiseco oversized 223cc piston, & I don't have a head to match it, I'm going to attempt to taking a KDX220SR head with its low end and mid-range torque profile completely different from the 220r head, and open it up 1.0mm by taking 0.50mm off of the gasket surface edge of the squish area to match, and then I will work with that head and maybe do a couple different reshaping operations and test runs. I'm going to send out my other cylinders for more professional cording of known porting and engine building gurus versus this current one that came from Canada (shop formerly called CV Tech did the work and it has low hours since then from previous owner).
I'll have to compare the port timing but I don't think it's drastically altered, and this is going to be my experiment to build a tractor engine... Although how much the ports are opened up might not work well with the low RPM focused head profile. The 220SR has something like a 13.5mm wide squish band platform vs the RB head being closer to stock at maybe 9.5mm wide squish band with 1.0mm total squish clearance as installed with head gasket included.

After I finish rehabbing my old house and sell it I'll have some money to play with and will be sending some cylinders out this winter to Tom Morgan Racing Engines (cylinder and head) and to Ted Boyko @ Boyko Racing (cylinder-only, to work with an RB'd 220 head).

yea its just a spacer that is idk 7mm wide spacing out the chamber. I bought the bike a 1999 KX 125 already with the kdx engine installed and have been racing a 21 red 350 ktm xcf( GASGAS ex350f) and thought the kdx was slow. He had some weird airbox thing on it and figured if I had to rebuild the top end it wouldn't be a big deal. Then I took it apart and there were no powervalves at all in the cylinder, it was broken, and had a terrible porting job done to it. Then I found it difficult to source parts not like when I was 15 working a the kawasaki dealer in 2000. So i found a cylinder on ebay that looked complete and payed $500. When I got it one PV was broken and part of the inner exhaust port past the PV was broken and pressed in toward the center of the port. I then found a dismantler on ebay and bought a complete running engine with video of the bike together ripping wheelies. It ran ok for a while but I bought a pro circuit pipe for and h series and a PC silencer for a 99-02 KX250. I pulled the PC pipe off to get the silencer to fit better and noticed scoring and the PV overclocked. Pulled the head and found the nikasil peeling. The wiseco piston was supposed to be 65.94mm but was closer to 66mm as mesured by the machinist. I now had all the powervalves so I took the ebay damaged cylinder to a welder and he said he would have a diffucult time welding it and to just remove the part cracked and bent into the exhaust port. It had a sleeve and needed a .25mm larger piston so I thought might as well port this thing. Worst case I lose $100 bucks and Im sending the nikasil damaged cylinder off to be reconditioned. I found IMD in england selling cast pistons which I prefer. They also had a taller dome. I used to hot rod cars and forged pistons were used for nitrous and forced induction and have different expansion rates. Not really neccessary on a dirtbike. I had 3 cylinder resonator covers and thought Id just cut one down and add it but found the original cylinder had one already. I dont know if it did anything. Idk If it does anything because of all the changes made like porting( you can really open the exhaust port.), switching to a CEK needle, clocking the PV correctly, relieving a little tension on the PV spring( my beta 300 had a screw and Id run it with little tension so it would get on the pipe faster), polishing the combustion chamber and cutting the head a little, Installing a crf450r coil, and Jaguars CDI(Jaguar who sells the CDI recommends a CR coil that it produces more voltage) So honestly I have no Idea If it helped. I also used the original bottom end because the main bearings were making a racked and I was losing tranny fluid and the original bottom end had a tight connecting rod and recent hot rod bearings and seals. Before I was running the engine with overclocked PV I could clear the biggest jump at the local MX track. It much faster now. It has great power right off idle and almost flipped backwards in 3rd when I went up the street! I have a 36.5mm PWk and need to perfect the jetting. Ran good with a 158 main. Went up to a 160. Not sure if I should go back down was very humid today. Cut my slide to a #7. I have a boyeson 14x with new dual stage fiberglass reeds also. However I bought a used v force delta 3 reed cage but didnt have a boot. I bought a broken 14XA reed cage for 40 buck and cut the reed cage off and ported it to match the v force 3 opening. Im gong to try it out soon. I love the hybrid because its a smaller chassis then newer bikes and its more fun to ride a two stroke around ripping then my 350 that I can get out of 2nd in the woods. After chasing more top end power If your cylinder is ported for top end I wouldnt worry about bottom end loss like you were saying. Also on a side note if you have 2006 kdx you have a 20 year old cdi box. Transistors, resistors and capacitors are much better quality these days. Also they would allow for + - 10% difference in performance of these parts so one cdi box may have a completely different ignition curve then another. Jaguars box has brand new, new age electrical components. His also have tighter tolereances he states on his website. It has two sets of switches to alter the curve. 1 set has two switches that advance the entire curve. If you leave them both down is like oem. The second set of switches work after 6k rpm and retard the timing to increase over rev. The CDI box increased the spark so much I have to hold the kill switch down almost twice as long or the bike will start back up. It really helped the performance of the bike including the low end. I could be crawling at very low rpm and open the throttle full and the bike picks up. It revs out further and I find myself in 3rd when I would be in 2nd before. The CDI box and PC exhaust were the best money I spent on it and if your after low end the cdi is best. I know TMI

[Kx200x]

"trimming down the stable to 2 steeds"

Hey, man. Watch your language. There are adults around here.

You"ll have to enlighten me I'm not sure what was offensive? I should be in a support group for people that can't stop buying broken motorcycles to fix. I just need 2. 1 MX and 1 Woods. Retiring from the street. Tax season comes around and a new bike enters the garage. Jk gonna put my resources in the KDX hybrid. SSS forks on the horizon?

[KDXGarage]

I was just kidding. I would get cold shakes if I really had to narrow down to just 2.