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Sorry for the double post, but my other thread in the sub forum wasn't getting any hits.

Long story short, I put a new top end in my 220 fearing the stock piston failure. Everything went well and bike seemed to run fine other than a slight hanging idle symptom. Did not have this feature before the top end rebuild. I've been trying to find the source without any luck and built myself a leak down tester and found I was losing about 1 psi every two minutes. Not good. Could not source any leaks around the head, intake, plug, exhaust or base gaskets. I also took a worrying photo of my new piston through the intake a few days ago.



So I tore it all apart yesterday to find it wasn't in as bad a shape as I thought. Piston looks ok and there is some wear but I can't feel it with my fingernail at all. Exhaust side looks fine.









I am pretty sure my crank seals are the culprit due to process of elimination. Unless somebody thinks otherwise. What would I be looking at to have a shop split the cases and replace the seals and bearings with the motor out of the bike? Not confident I can tackle that job myself.

Any other thoughts appreciated.

hanging idle/ high idle usually means intake leak, bad boot, stator crank seal. i would bet first of all on intake boot/leaks. the transmission side would mean very rich condition, lots of smoke, and oil loss. what you have isn't that.

pull the stator cover and stator.
pressurize the case again and spray with soapy water. don't go crazy with the pressure, 4-5psi should be enough to see a leak.
same deal for the clutch side, but more involved to expose the crank seal over there.

your piston looks like a '4 corners seizure' which usually happens when an engine is run too high of an rpm, before the engine has warmed. the piston swells faster than the cylinder, so blamo, seizure.

Thanks. I agree it does look that way, but what's odd is the exhaust side of the piston is perfect, so only two of the 4 corners seizure. I will button it back up and pull the stator and spray soapy water in there to verify.

I just had my lower end rebuilt but my buddy did mine. The kawi dealer wanted 80.00 an hour. They wanted 544.00 to rebuild the bottom. That was parts, labor and fluids. Hope this helps.

That is helpful, thank you. Was that price with the motor in the bike, or out?

That was the motor in. If you take it out and the guy your taking it to knows what he is doing it would only take a couple of hours. I didn't put a new crank in it. I just did the seal and bearing kit and a rod kit.

Millenium tech did my motor rebuild for $300. Came back clean as a whistle too. Of course there were other expenses - I had them case match, port and polish, and replate the cylinder, rebuild the bottom end, and shipping, and I bought the seal and gasket set separately and sent it with. But I thought their engine building price was reasonable, and it arrived ready to put in the bike.

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Thanks Chilly and Friedom. I did see that millennium offered the service as well, and honestly I could use a replate too, but I just am not sure I want to pay for shipping there and back. My plan right now is to pull the motor, pull the flywheel and do another leak down test to verify my left crank seal is the issue. If it is, I'm going to try to find somebody local to split the cases and replace the crank bearings and seals. I am kind of debating trying it myself but its riding season and I just want this thing back together.

Should've just left it alone with the stock piston in it!

I didn't have this issue before I redid the top end and added the RB mods. Would those things have caused the ~20 year old crank seal to fail?

When my seals leaked it showed zero signs of it. My horse power dropped a lot and I noticed that my oil level dropped only after riding for a half hour. So if you check your level now take off on it and see if the level drops.

Mnmonster wrote:I didn't have this issue before I redid the top end and added the RB mods. Would those things have caused the ~20 year old crank seal to fail?

I cant see how those things would cause a crank seal to fail. So either it is just really weird timing or the leak is coming from something related to the work you did. I know you checked out the other sources of a leak, but I would double check them.

I did a pressure test on an engine that clearly had bad seals and it passed. I figured I screwed up the pressure test. Later I read that sometimes a seal will hold on pressure but leak on vacuum. Maybe if I did a vacuum test I would have gotten a different result.

It's always a good idea to do a pressure test and pull a vacuum test. 6psi or so only. Don't need to blow out the seals, just see if they hold over a time period.

Thanks everybody for the responses. I will update when I have time to dig into it more, hopefully this weekend. What's the consensus on my piston? Usable or not?

Mnmonster wrote: What's the consensus on my piston? Usable or not?

If I am remebering correctly, you dont have much time on that piston. I would definitely reuse it. I personally would replace the rings since they dont cost much.

Once you get it back together I would suggest letting the bike warm up a little longer. I start my bike, put on my gear and by that time the radiators are warm/hot (depending on time of year). I then take it easy out of the parking lot and then ride it as usual.

I finally had some time to check the left side crank seal. Could not find any signs of a leak pressurizing the cylinder and using the soap and water method. I decided to replace both the base gasket and head gaskets just to rule out everything. After I did so I noticed a large leak at the base gasket at the very front of the cylinder under the exhaust outlet. Pulled the cylinder back off and noticed there is a a slight height difference between the case halves.





I found a thread where a guy had a similar issue and he used a large file to carefully even up where the two halves meet. Might try this unless there are any other suggestions. Don't really want to pull motor and have it machined/milled flat.

Also found another smaller leak in a weird spot an not sure how to cure it.



It is at the end of one of the reed block screws threads into the cylinder. Not where the surfaces meet. Suggestions?

woah, that's crazy. Is there a crack there that you can see or feel?

Julien D wrote:woah, that's crazy. Is there a crack there that you can see or feel?

At the case or the cylinder by the reed block? Both answers would be a "no". I could not see or feel any evidence of a crack.

Mnmonster wrote:I found a thread where a guy had a similar issue and he used a large file to carefully even up where the two halves meet. Might try this unless there are any other suggestions. Don't really want to pull motor and have it machined/milled flat.

Did you happen to use an aftermarket base gasket when you discovered the leak?

Taking a file to the cases would be my last choice. I could see myself doing my damage than good.

Tedh98 wrote:

Mnmonster wrote:I found a thread where a guy had a similar issue and he used a large file to carefully even up where the two halves meet. Might try this unless there are any other suggestions. Don't really want to pull motor and have it machined/milled flat.

Did you happen to use an aftermarket base gasket when you discovered the leak?

Taking a file to the cases would be my last choice. I could see myself doing my damage than good.

I agree, the filing idea does make me nervous I would just make it worse.

Yes, it was an aftermarket gasket. Do you think I would have better luck with an OEM gasket? When I initially redid my top end (and also used an aftermarket gasket) the leak was either not there, or much much smaller. I could here this one leaking as soon as I pressurized the cylinder.

Looking at your pictures, it appears that one case half was changed. From what I understand, the two cases are matched at the factory so you do not have a step like that. I bet that is what is happening at the rear of the cylinder under the reed block; there is a step in the case also.

Mnmonster wrote:Yes, it was an aftermarket gasket. Do you think I would have better luck with an OEM gasket?

OEM base gaskets definitely fit better than aftermarket. I'm not sure if an OEM gasket would seal up that difference any better, but it is the easiest solution to try at this point.