high compression damage?? Rebuild advice too

[ksnowdog]

Hello everyone, I've always gotten good advice here, so I'm back for more!!

I did a compression test tonight on my 95 200. My compression was at 200 (with an automotive tester, is that OK?) at WOT. I assume it is from carbon build up on my piston and hopefully the cause of poor perfomance. It always runs good, there is just no punch or real power in the bike, although the low end torque is still good.

Am I going to do any damage running the bike right now??

My winter project is to rebuild the top end, FMF torque pipe, Boyesen Power Reeds (607), carb cleaning with new (42/45 pilot, R1174K jet needle, 152/155 main jet). Any other advice? I ride mostly woods 2nd-4th gear, at 1000 feet elevation in temperatures that range from 40 to 105 degrees!!! Any other advice/corrections??

Should I go ahead and just replace the piston (are they expensive??) and any cheap parts while I have it torn apart? This is my first rebuild, other than a ‘minimally standard’ tool set and a ring pliars thingy, do I need any other tools? Do I need to buy the piston puller??

Once again thanks in advance for any help

 

[andrew]

200 psi does sound kind of high, but I don't know if that alone would cause damage.
Your poor performance in the mid and top range sounds like the KIPS may not be working properly. It could be gummed up with carbon, which fits in with your observations about carbon build-up causing your high compression...
If I were you, I'd strip it down and completely clean and de-glaze your top end, make sure the KIPS is clean and functional, inspect the bore and perhaps give it a quick hone, and replace they rings (they're cheap enough). Pistons will generally last a while - inspect yours, and measure the bore-piston clearance and only get a new one if it's outside spec.
I have always found my piston pin easy to get out by hand, but if yours is jammed in (usually due to overheating) you can make a puller from a nut & bolt and a bit of pipe.
If you haven't got a workshop manual yet, do yourself a favour and get one.

Hope this helps,
Andrew
96 KDX 200

 

[Fred T]

Excuse me but he said this is a 1995. It's what, 8 years old? He shoud lay his old piston to rest before it cracks or something and put a new OEM piston and rings in it. Get a gasket kit, new circlipsand wrist pin bearings too. Check the bore to make sure the nikasil (SP?) is still in good shape. Take the kips apart (check www.bryankimsey.com for a nice step by step pictorial) and clean your kips. Take your time and do it right and she'll run for a long time.

 

[canyncarvr]

Check this out:
http://dirtrider.net/forums3/showthread.php?s=&threadid=66888&highlight=alpha+AND+designation

For information regarding piston sizes and such.

If you have to replate...make sure that whoever does it (us chrome, langcourt for example) has the piston to match their replate TO.

Don't confuse pro-x with pro-lite. The former is oem, the latter wiseco.

Get a wrist pin bearing! They don't generally come in 'kits'.

No 'special tool' required. Well...check out a motion-pro tool for torquing the cylinder nuts. No 'math' required if you keep the adapter at 90º to your torque wrench.

...not that there's anything wrong with a little math!! ;)

Any questions, please ask. This is considerably shortened from its original form due to a posting 'issue'. If you don't know where to get a pro-x, where to get replate done etc, just ask.

I do run on...............

Cheers!

 

[andrew]

Originally posted by Fred T
Excuse me but he said this is a 1995. It's what, 8 years old? He shoud lay his old piston to rest before it cracks or something and put a new OEM piston and rings in it.

He didn't say his piston was 8 years old! Of course, if it IS, then maybe he should replace it. But they ARE pretty tough and if it measures up OK and hasn't been rattling in the bore then it's probably got plenty of life in it still. If money were no object one could replace everything, but to me that's a lot of money, so I evaluate the necessity of every dollar I spend on it.
I know what you're gonna say: Is your engine worth the fifty or sixty bucks for a new piston - well, it's a calculated risk isn't it, no matter how old the piston is. I haven't stuffed it up yet, touch wood!
Just my opnion...

Andrew
96 KDX200

 

[canyncarvr]

I put the first topend in my oh-oh at close to the 2 year mark.

The piston removed was a 'C' tolerance designation. It measured 2.592".
A new out of the box 'B' piston measured 2.597".

With the difference in alpha markings being about .0004", the .005" difference in the above measurements gives a bit of an idea of how much a piston can wear in a pretty short period of time.

Certainly, 'If it measures up...' is the correct way to do it. Don't assume that just because the piston doesn't appear damaged, it's ok.

 

[ksnowdog]

Thanks for the replies.

As far as I know the motor has never been opened. Do I have to wait to get the thing apart before I order pison/rings to see what size??

Also what comes in the 'kit'? Should I get this from the local dealer? price? Or should I get online cheaper? Where?

 

[ksnowdog]

Very ignorant question (one more!). Re-plate, do you mean the cylinder itself? And just if it is out of spec, does that happen often?

I appreciate the replies

 

[canyncarvr]

Yes you should wait. You can't order a piston for an unknown cylinder size. Not if you want it to fit better'n half-fast.

Piston kits commonly include piston, rings, circlips and pin. But (again) usually NOT the wrist pin bearing.

If you order a piston from a kawi dealer, you'll probably get a 'B' piston (65.95mm). It would probably work...but the CORRECT alpha designation (at the least) would work better. You can get the other alpha designations Pro-x has from sage, I believe. He has an ad running on CDave's site:

http://justkdx.dirtrider.net

Click on <links>

Last price I heard for Pro-x was $130. You'll need a gasket set. The motion-pro adapter that will allow you to 'reach' the cylinder nuts with a torque wrench is very handy. They're hanging on a rack at a local bike shop. Motion-pro is on the web, too.

 

[70 marlin]

All I'll say is Eric Gorr! If your not sure on your sizing or the shape of the bore or the condition of the platting. Send it off to him and while he has it. Pay a little extra and let him do your kips valve and a little porting! It’s cheap @ twice the price! He’s done it for me twice.

 

[canyncarvr]

$400 (last I checked...doubt it's changed) Includes porting of your choice (bottom, top, moh better everywhere), a bore to make your 200 a 225, head machining as required, replate, gaskets, all parts and cleaning/machining your KIPS to fit the new bore.

If you have to do a replate, it seems kinda silly to NOT go the big-bore route. DO make SURE the fuel of your choice is a KNOWN issue. That'll make a big difference in the work done on your head.

My nikasil™ is off in a couple of spots. An EG big-bore is on my wish list for sure!

***edit***
Yes, 'replate' refers to the cylinder. They are 'coated' with a super-d-duper hard layer that makes them 'virtually' indestructible.

Which is not to say such cylinders NEVER go away. Like I said...my plating is off in a couple of spots, thanks to one tank of BelRay H1R (HR1, whatever it is) oil!!

Get yours checked by someone that has the correct tool. You can't determine out-of-round using piston-to-cylinder clearance numbers you get from a feeler guage.

 

[chiro972]

I'm a newbie here and I'm picking up a 2000 220 in about a week. The current owner says the engine has been rebuilt, but I want to make sure exactly what he did. I have read through the justkdx site and can't find answers to some questions.

1: It sounds like these bikes don't use sleeves? When the piston is shot does the cylinder need to be rebored? and then rechromed? How often does that need to be done?

2: I'm hoping he at least has a manual, but I haven't asked yet. If not, where do I get answers to basic questions like what ratio of fuel/oil to use and other basic stuff?

Thanks guys. If there is another website to look at, or if I am missing this stuff on justkdx, please point me in the right direction.

 

[canyncarvr]

1. They don't use sleeves. They can BE sleeved, but they don't 'come' that way. Just because the piston is replaced doesn't mean there needs to be any replating, unless the plating is damaged or the bore is damaged. More often than not the piston will wear beyond spec before the cylinder is damaged. Of course, unless things are let go TOO far. It's not chrome, but a hi-nickle plate, hence the name nikasil. Also referred to as nicosel, nicosil and such. The first is the trademarked name.

2. Kawi recommends 32:1 fuel/oil. That, like the oem jetting, is on the safe side. More commonly, 40:1 is used. Oil mfgs like maxima recommend 40:1. That's not based on it being a kdx, but size of the engine. You can find that @:

http://www.maximausa.com/

You can get a manual from any kawi dealer.

Do bookmark (and check out) CDave's site:

http://justkdx.dirtrider.net

A lot of info on basic mods, carb theory, links to good spots etc.

You might ask if a wiseco piston was used. If you've been looking around this site much of late, you've read about the 220 oem piston. It's got problems, and should be replaced certainly during anything called a 'topend' job.

If you have some other questions, please do ask. Better to start another thread, though. Something that will contain responses pertinent to your particular question.

Have fun!!

 

[chiro972]

Thank-you. Yeah the piston talk is what got me wondering just what he did when he "rebuilt" the bike.

 

[canyncarvr]

Forewarned is forearmed....caveat emptor and all that stuff.....