KDXRIDER.NET

I wonder if a PTFE ring could be made to fit? Would probably need to be split at an angle to get it over the shaft and into the groove I came across these on McMaster Carr, I think they are for a hydraulic cylinder.
https://www.mcmaster.com/products/packi ... ng-seals/

Has anyone been able to solve this issue?

When I get around to putting my engine back together on my 99 that's been retired for several seasons (while I ride my 97), I definitely planned to give this some attention.

I'll be tearing the engine down here in the next few weeks, but sending the crankshaft out as well as the cylinder, so it might be a bit before I put it back together, unless I pull apart and alleged good condition bottom and that I have just for inspection, cleaning, and fresh seals. If that's the case, I will be looking into this sooner.



Apparently Jeff Fredette has an o-ring size that he uses for it although it apparently fits a bit tighter than the original packing seal. If someone wanted to call him and ask him, I'm sure he would be able to lend advice. http://www.theoringstore.com is where I got two bulk o-ring kits in a multitude of metric size is, I'm sure they would have whatever size is closest.

IIRC its a 6mm ID x 2mm CS, but it has been a while since I've had my engine apart.

I've almost given up on the custom seal route. Done a bunch of looking and reaching out, there is no product that will work for a guy trying to build a mould at home. It's an industrial process to work with a proper material like Viton or HNBR. I will send a drawing to a seal shop we use instead. The dimensions fall just outside their smallest capability to manufacture in their CNC, but ya never know. Other plan is build a new shaft with the groove sized for a standard 106 oring, making sure it has the correct squeeze (about .010") for a dynamic application, as you're stretching it a bit. Might be able to build em for a reasonable price if I build 10........... will keep ya posted. But it's a problem that needs to be properly solved........

bufftester wrote: 02:58 pm Feb 12 2025 IIRC its a 6mm ID x 2mm CS, but it has been a while since I've had my engine apart.

I measured 2.5 c/s but I sure could be wrong, will double check. Issue is that the seal is a thin profile with two humps, but wide. So the groove depth is shallow compared to a standard oring. But yet too wide for a standard oring, both metric or imperial. I have the parts on my desk at home waiting for me to finish up some measuring. Sounds like I should sit my arse down at the PC with the vernier tonight!

Molly's 70 wrote: 12:43 pm Jul 17 2024 Well, the 2 packing rings I ordered from partzilla was a no go. They just gave me a refund.

Thanks for sharing this info. It's important to know.

Wonder if a quad/X-ring or square ring might work?

https://www.bing.com/images/search?q=qu ... RE&first=1

https://www.mcmaster.com/products/quatt ... ttro-seals

https://www.mcmaster.com/products/o-rin ... pe~square/

bufftester wrote: 02:58 pm Feb 12 2025 IIRC its a 6mm ID x 2mm CS, but it has been a while since I've had my engine apart.

If this is the actual size, looking up Viton, theoringstore.com has both 75/80 durometer and 90 durometer offerings in this exact size...

$3.50 for a quantity of (50) of the 70 durometer versions, at 7 cents each...
https://www.theoringstore.com/store/ind ... ts_id=2808

If it is a different cross section than 2.00mm, the 75/80 durometer listings have more variety of cross sectional dimensions than the 90 durometer, at 1.8mm, 1.9, 2.0, 2.2, 2.4mm etc
2.2mm cross section x 6mm i.d.:
https://www.theoringstore.com/store/ind ... s_id=41088


The 90 durometer 2.0mm CS is quite expensive in comparison to the 75 durometer lol, $10.50 for a minimum quantity of (50), at 21 cents per o-ring...
https://www.theoringstore.com/store/ind ... s_id=41920

Their Viton material: "Heat Resistance Up to 400°F (204°C) and higher temperatures with shorter life expectancy."

They also had the standard universal Buna-N Nitrile (NBR) Metric O-Rings – 70 Durometer, but these are only rated for up to 250 degrees Fahrenheit. This may potentially compromise this packing o-ring in the cylinder jug if one got stuck in the mud on a hot humid summer day and overheated their KDX, and I'm not sure how hot the hottest portions of the cylinder jug get, but the hottest I typically see my KDX under hard use in the summer is 205 degrees coolant temperature at the radiator cap thermometer I have installed.

The Viton Flourocarbon-resistant composition o-rings are good for 400 degrees Fahrenheit, well above what we need to be concerned with as best as I could tell, although this IS in fact on the exhaust side of the cylinder... so maybe I'm underestimating this?
EGT's at wide open throttle hard abuse heavy loads at around 1200 degrees F means your jetting is set for optimum power if I'm understanding correctly, but obviously the engine temperature is never near that due to water cooling and atmostpheric air cooling even on the exterior of our water cooled engines. On diesel engines, that's considered really good as well, but 1600 for any long duration pulls is melting pistons territory.
The cylinder jugs on our bikes are water cooled and have a bit of air cooling effect as well, as our expansion chambers on the outside never glow red hot except at AMA Vintage Motorcycle Days standing still holding WOT in the burnout pit at the corner party - I watched a guy boil over his CR500 in this exact scenario lol... and I am guilty of once ruining my valve stem seals "finishing off" my bald tire on my street bike, '77 GS750 Suzuki big bore, with a guy lighting a cigarette off my 4-into-1 header, in the exact same scenario, maybe a different year though lol... standing still, the actual EGT has a chance to heat up the pipe a lot closer to the Exhaust Gas Temperature... moving even at slower speeds, the air cooling keeps things significantly cooler.



There's also the JIS, Japanese Industrial Standard automotive and industrial standardized o-ring sizes, but also only available up to 250 degrees max temp:
https://www.theoringstore.com/store/ind ... _1965_1967


Additionally, there's silicone o-rings, which are good to 450 degrees F, and rated for oils, but I'm not sure if they're capable of handling gasoline exposure for the long term? It doesn't list gasoline in the "Not compatible with" section, but I'd be cautious and research this. Compatible with oils, but not Automatic Transmission Fluid...??? Interesting. Viton is definitely the more chemically resistant material of almost the same heat range.
https://www.theoringstore.com/store/ind ... s_id=25102

Kawibunga wrote: 03:06 pm Feb 12 2025

bufftester wrote: 02:58 pm Feb 12 2025 IIRC its a 6mm ID x 2mm CS, but it has been a while since I've had my engine apart.

I measured 2.5 c/s but I sure could be wrong, will double check. . Sounds like I should sit my arse down at the PC with the vernier tonight!

I should have scrolled down before I replied to the first promising post that I saw! I believe theoringstore.com has a fair bit in that 2.5mm CS size as well. 6mm i.d. still? There's a 2.5mm CS x 6mm i.d. and a 5.5mm i.d. version as well as many others, again in 75 durometer Viton, there are far more options than 90 durometer Viton.
https://www.theoringstore.com/store/ind ... =368_65_67
Please do measure yours since you have it apart, and let us know! I love finding solutions to problems like this...

Kawibunga wrote: 03:06 pm Feb 12 2025
Issue is that the seal is a thin profile with two humps, but wide. So the groove depth is shallow compared to a standard oring. But yet too wide for a standard oring, both metric or imperial.

Is the cross section too thick/wide to have two of these i.d./o.d. o-rings stacked side by side? Perhaps undersizing them just a hair to get them to squeeze in but be slightly squished side to side will deform them in our favor to still seal on the o.d. properly?
If all else fails, I'll just chuck up the shaft in my lathe and widen the groove to stack two standard metric viton o-rings if the appropriate size exists to do so.
Otherwise, a metric viton quad ring or x-ring would be the way to go... Google search that!
https://www.oringsandmore.com/x-rings-6 ... um-10-pcs/
https://www.oringsandmore.com/x-rings-5 ... um-10-pcs/
(less size selection in an x-ring, but perhaps we could get lucky?)

inch and metric sizes listed side by size with industry standard numbering system:
https://www.allorings.com/x-ring-seal-sizes

https://www.revataengineering.com/xring-quadrings.htm

JimmyB wrote: 07:24 pm Feb 12 2025 Wonder if a quad/X-ring or square ring might work?

https://www.bing.com/images/search?q=qu ... RE&first=1

https://www.mcmaster.com/products/quatt ... ttro-seals

https://www.mcmaster.com/products/o-rin ... pe~square/

Absolutely, a viton x-ring would be the best possible solution to this if we could find one in the right size. I'd settle for a viton o-ring or two stacked side by side though if that's all we can find.
It may likely need to to be a metric size unless we got lucky and something crossed over to fit well. All those are inch sizes, but they do have them in several Viton offerings though.

It's coming, still more to do ( the rest of the teeth etc) and a couple anomalies in what I measured when compared to to the 3D model, but I'm getting there.

Reverse engineering and copying something this small is a pain. I picked up a RevoPoint 3D scanner a few months ago that I haven't fired up yet, guess it's time! That hopefully will answer some questions that the Vernier just can't...........

Very nice work!
But before you get too far...
did you get a better measurement on that packing seal? There's a chance I might have one in a box of engine parts here, I'll have to check...

https://www.cmsnl.com/products/packing-nas_430491076/

Here's a photo of the NLA KIPS shaft packing seal. Sort of like a quad ring / x-ring, but with only two lips on the outside portion, the rest is basically a rounded corner square o-ring seal.
I also used CMS Netherlands to look up the part interchange, and unfortunately the H series and 220 are the only engines these packing seals wherever used on, unfortunately. So many parts for our bikes, when looked up on interchanges, may fit 50 or 200 models even, but not this one...all 27 models/model years are just the entire run of the KDX200H/220A(R). I'd imagine a website that lists the international '94+ KDX220B (KDX220SR) would also include those models in the interchange, but those models are even more scarce anywhere that we are concerned with in general.

Has anyone been able to measure this yet?
@Kawibunga ???
I might be able to dig late tonight or tomorrow and see if I have a spare that's not installed in an engine.

Busy weekend, but got a bit more into it....... it's amazing how good one's camera phone actually is........
The seal groove is pretty much size on size with seals ID and seals width. The most important thing is the OD once installed. Assuming it's an 8mm bore (I don't have PIN gauges to properly check it) there isn't much squeeze on that seal. Likely to keep the actuation friction as low as possible. The measured OD is what I measured with the seal installed on the shaft. I'd want to shoot for .317" as your min, and probably no higher than .325" as you max OD with a seal installed (my two bits anyways)
These are the best numbers I can get. Dimension in {} are in mm. Will keep working on it though. As stated, my goal is to get a standard sized Xring or Oring to fit a modified groove if at all possible, resulting in the same squeeze.......

Looking at the numbers in a bit more detail. One should be able to get a 007 or 008 oring to work (same size xring would be preferred) BUT the cross section of a 000 series oring is thicker, so I'll have to make the groove slightly deeper to make sure there's not too much squeeze/interference. A 100 series oring is just too thick (.103" actual cross section)........... reason I'm pushing for standard SAE #'d orings is that they will be easier for most people to find vs a metric seal.

I'll 3d print some sample shafts that I can doube check fits on before I go and machine the actual part. Will update as I finalize geometry........ but this should be a solution that works that everyone can do.

kawibunga, really appreciate your efforts with this subject. You bring capabilities that this old dog is too old to learn. Thank you.

Kawibunga wrote: 04:46 pm Feb 18 2025 Looking at the numbers in a bit more detail. One should be able to get a 007 or 008 oring to work (same size xring would be preferred) BUT the cross section of a 000 series oring is thicker, so I'll have to make the groove slightly deeper to make sure there's not too much squeeze/interference. A 100 series oring is just too thick (.103" actual cross section)...........


reason I'm pushing for standard SAE #'d orings is that they will be easier for most people to find vs a metric seal.

I wouldn't necessarily push for SAE simply for greater availability, as most of us are going to order them from a specialist like McMaster Carr or the O-Ring Store websites anyways... better fit is best really. I doubt someone is going to be trying to find a high temperature gasoline resistant o-ring at the corner hardware store on a whim... they'll be doing a full engine teardown and sourcing parts that aren't typically stocked at a local bike shop anyways, so please consider the metric options as well if they are a slightly better fit than SAE!
Viton seems a much better choice than BunaN as well, unless of course the sizes we need aren't found in any close fitment in Viton or similar.

Kawibunga wrote: 03:00 pm Feb 12 2025 Other plan is build a new shaft with the groove sized for a standard 106 oring, making sure it has the correct squeeze (about .010") for a dynamic application, as you're stretching it a bit.

So when you say the correct squeeze of around 0,010" compression, I assume you are referring to the cross-sectional compression, and not referencing the entire o.d of the o-ring be 0.010" larger than the i.d of the shaft bore? One way of reading that is double as much as the other! Thanks in advance for your clarification!
The well used worn out leaking seal measurements may also reflect dimensions of smaller o.d. than was original to this material due to age, heat, and being compressed for 20+ years, so if we know the amount of compression or squish intended, + the i.d. of the shaft bore in the cylinder, this might be a more accurate way to approach this.


This o-ring seems to fit the bill on everything if "8.05mm + .010" cross sectional squeeze" beyond the dimensions listed is what we're after:

https://www.theoringstore.com/store/ind ... ts_id=2937

and... that's considered a JIS standard size even!
1.5mm X 5.5mm V75 Fluorocarbon FKM O-Rings 75/80 Durometer Black (JIS S6-V75)
I should look through my o-ring kits, as 1 of the two is all JIS o-rings, like 500 of them! The other is all exclusively metric as well, but not the standardized JIS Japanese Industrial Standards sizing. This would be 8.50mm o.d. vs your drawing of the old seal (shrunken with age????) at 8.05mm, assuming your 0.010"/0.254mm squish factor added to the cross sectional dimension (this could be a total misinterpretation or your intent though, perhaps 8.05mm was your final dimension prior to squish but after considering aging and permanent compression of the existing old packing seal).

The other issue is, the cross section being a round o-ring and not a rectangular dimension x-ring, we would have extra space next to it...
Having the groove machined slightly deeper would of course be best for the seal fitment, as then we could just use a larger o-ring cross section that fits the width of the groove. *OR*... since cutting the groove deeper would weaken the shaft technically, perhaps we cut the groove wider instead, and run two of these o-rings side by side? That right there sounds like a very viable option to me and is a simple mod with no reduction in the structural soundness of the shaft (if it ever even was close to it's maximum allowable forces working against it in the first place...)

Assuming the above added .010" sectional squish above the 8.05mm o.d. worn in dimension, this first ring applies, but if 8.03mm total uncompressed o.d. is what we're after, the second is a great candidate:

Metric X-Ring:
https://www.oringsandmore.com/x-rings-5 ... um-10-pcs/

X Rings 5.28 x 1.78mm Minimum 10 pcs
$0.05
That's a bit more required compression than 0.254mm as stated (0.010"), assuming that was cross sectional compression, and not total diameter compression.

if machining the shaft groove down in diameter/depth slightly, this one comes out to listed dimension of 8.03mm o.d., whereas your drawing shows 8.05mm as the actual size of the (well used worn out?) original

https://www.oringsandmore.com/x-rings-4 ... um-10-pcs/

X Rings 4.47 x 1.78mm Minimum 10 pcs
4.47 ID x 1.78 CS X Ring X Rings
$0.05

EDIT - this size converted to decimal inch sizing equates to exactly the standard "-008" SAE size.



Or this perhaps, inch side, but perhaps it would stretch and compress? The closest "SAE" sizes I can find in any format o-ring x-ring etc are all seeming to be listed as size standard "-009" - although you mentioning a dash 008 makes me think the 8.05mm dimension you list was total and not with .010" / .254mm sectional squish added.
https://www.mcmaster.com/6540K119/


*OR* your -008 size in an x-ring, these are both Viton Fluoroelastomer x-rings, a much better choice for an engine cylinder:

McMaster-Carr -008 X-ring Viton 6540K118 https://www.mcmaster.com/6540K118/


Lastly, if a fatter o-ring or x-ring could not be sourced to fill the width of the shaft groove, why not leave the depth alone and modify the width slightly to fit TWO o-rings of the actual cross sectional requirement or close?

I think the friction and compression / squish fit is critical, as we know our KIPS actuator pins can be dislodged with force from their pressed in fitment onto the shaft engaging the KIPS governor timer assembly, so we don't want to introduce too much resistance in this assembly, so the installed o.d. is a sensitive area to get just right, just enough to seal but not add significant resistance. I may zap my KIPS pin with a MIG welder as a precautionary measure anyways, but more force required will still wear down all components involved more readily, which we do not want...

Chuck, a bit of background info with regards to my thought process with regards to Oring sizing What we have here for me is what I think is called "confirmation Bias" unfortunately. In my day job I design downhole tools for the oil and gas industry (mechanical engineer). The tools that go in the ground when they're drilling and fracking etc oil & gas wells. Sealing hydrocarbons and other stuff at 10,000 psi / 300°F - in this industry we primarily used SAE standard seal sizes, thus that's what I'm most familiar with. We'll use metric seals in odd applications where there is no other choice. But it's easier to find SAE seals in the higher end elastomers that these applications demand. High end VItons and HNBR etc.......

With regards to Viton/FKM vs BUNA/Nitrile - viton is great chemically but weak mechanically. Much better chance of actually just tearing and breaking this seal during installation and wear and tear vs a BUNA/Nitrile seal - But standard Buna/Nitrile is not near as chemically & heat resistant as Viton, but the super duper version of Nitrile, Hydrogenated Nitrile (HNBR or HSN as it's called) is pretty much as good everywhere as viton, but way better mechanically. Hence my choices are HNBR/HSN - VITON/FKM - BUNA/NITRILE in that order.......... and you always want them Black, that means carbon filled and way stronger, any type of seal.

WIth regards to the squeeze - that number is on the cross section. So for instance for a 008 seal - they call it a 1/16" cross section. but it's actually .070" c/s - Standard recommendation is .010" - .018" squeeze on that cross section for dynamic sealing applications. So your overall radial height from groove bottom to the bore surface would be .060". As you mentioned we're concerned about friction, so I'd error on the lower side of this range (.010" instead of .018"). Ideally I'd have some beauty nice Mitutoyo pin gauges to check the exact bore size, but I recently changed jobs, so would have to buy my own! But think I can use my 3D printer to make some gauges.

With regards to widening the groove for two seals. It might work, but in most applications what happens is individuals seals can roll, and the wider groove will increase our seal friction. Not best practice, but as I said it sure might still work, just not my preference from my experiences.

We absolutely don't want to machine the groove down too far like you say - but it wouldn't concern me going down from .217" to .176"+ - this shaft doesn't see a bunch of tension so there is no way we'd pull it apart. (but don't quote me!)

The McMaster part 6540K118 - the 008 Xring or Quad ring is EXACLTY what I want to try to get to work. It's slightly narrower but nothing I'd be worried about (instead of about .001 clearance per side on groove width, we have .004" - means pretty much nothing) My plan is to 3d print some parts and install this on it and measure the final OD with the seal on. Make sure I'm in the range, then machine the shaft groove deeper but leave the width the same, and try it!

My my last concern - which you don't have - is all though I love McMaster, they don't ship up here to Canada unless it's a corporate account. But as they are so awesome and handy, pretty much every company in my line of work does have a corporate account, so I'll get some via that (thanks for the leg work!) but our other Canadian/international members will have to go to a local seal supplier (not your local hardware) and get a 008 Xring directly from them (assuming this works)

So thanks again for the leg work on the McMaster Carr xring. My plan is to get that one, then see if my local seal guys can source one in HNBR as well, and then get to some measuring and testing done and let everyone know where I land. Probably way too much of a deep dive here and Jeff Fredette would read this call me some dumb arse nerd engineer! Job hazard I guess :)

I believe it was McMaster that has a minimum quantity, so you might end up buying a large quantity of them, 25 or 50 for $16, so you could probably turn around and sell them to members for $10 to cover mostly your time and a small fraction just to help out with the initial purchase.... The problem is having members find someone to cut down the shaft groove diameter very slightly. I can see some DIY'ers finding some way to do this by chucking it into a drill clamped into a vise!