Check the bushing on the rod where the piston pin goes - take the piston pin and try to slide into it: it should feel more or less like pushing the back of a syringe: you should feel no appreciable axial play. If it does have play then you have to replace the bushing, which has to be done by an experienced mechanic AND it has to be machined to the proper clearance... You are getting ahead of yourself, take the cylinder out along with the piston and get them measured to check if the celarance is right (you can find them on the workshop manual). If it is, then it's not a piston problem and you should look into other things, like the connecting rod. I'd highly recommend to not make any assumptions. Numbers don't lie - get the stuff professionalyy measured.
I got the head and cylinder off yesterday. The piston is cracked and the wrist pin was sliding out. One of the circlips was missing. I knew for sure that I installed them both so I searched for quite awhile with a magnet down into the crank and finally found the missing circlip. Thankfully it wasn't to hard to get out. The bore was scratched up from the piston. 350 dollars for a new OEM cylinder isn't the end of the world, but this Wossner piston has sure cost me a lot of money and headache. I will check the bushing play when the new OEM piston/wrist pin come in the mail. I don't mean to talk bad about a company, but I personally do not trust the piston Wossner made for this bike. I am hoping to have better luck with the OEM.
I don’t see any signs of damage to the crank and their is no up and down play at the rod. It turns over smooth. Will know if the bushing is ok when OEM wrist pin arrives.
I don't know how deep those scratches are. Is it posssible to replate the cylinder of our 610s?. I had it replated in my 2 stroke Yamaha... . When installing circlips, it is suggested that you orient them like this guy explains @1:14: (Link in case the player doesn't work: youtu.be/qpP6WXxLmXI?t=1m14s) because in that way the momentum generated by the little mass of the circlip will bend it less when the engine will be running and therefore the probability of a circlip exiting by its seat will be lowered.
I will definitely install with that orientation. I had the gaps pointing towards the exhaust. The cylinder could probably be re-nikasil plated, but I doubt it would be cheaper then 350. I'm super excited to get the parts and put the bike together. I'll take pictures of everything for you guys.
Jesus that's quite some damage. You are probably better off with a new cylinder price wise, but i'd look into re-nikasiling it just to get the full picture. I wonder if the crack on the piston came first and then the circlip fell out or the other way around. How deep are the grooves on the cylinder surface? Can you feel them with your fingers? I can't tell from the picture, but if the scores aren't too deep MAYBE you could reuse the cylinder. Glad that you found the culprit!
300 seems like the going rate for a repair/re-plate for single cylinder (no shipping included). So all things considered pretty similar in pricing, but I already ordered new cylinder. I can definitely feel the groove on the cylinder wall. I’m not sure if the piston cracked first or the circlip came out first, but I know for sure both clips were installed completely. The clips were not orientated with the gap pointing up, but that isn’t an excuse for the piston to fail in my opinion. I also personally don’t think a brand new piston should only get 70psi without a cap of oil in the cylinder (this was the case before the failure). In retrospect the only reason the bike didn’t work on my first initial build was due to low compression from the piston/rings and not the timing. I didn’t know to put a little oil in the cylinder so I messed with the timing and bent valves. Then after getting valves fixed compression was still low (due to piston) which prompted me to try oil. Finally the bike had good compression and started, but the piston failed and the noise started. Long story short I think this 100 dollar Wossner piston is going to cost me about 1,000, but I learned some things at least.
Oem cylinder came in today. Their is a small divot in the wall I can just barely pick it up with fingernail. What do you guys think, should I try and return it?
Not sure on that one. Mine has one scratch i can barley feel but i think im going to go with it and rehone with new rings. Where did you find a new OEM cylinder for 350 btw?
I took the cylinder to a local machine/engine shop that has a good reputation and the owner told me that the imperfection is so smooth/small and low in the bore that he wouldn't worry about it. He said anything I would do with a scotch bright pad would make it worse. Since It's near the bottom of the bore the pressure on the rings is at it's lowest. It is pretty smooth and I have to scrape from the side not up/down to barely pick it up. If anyone disagrees with this guy please let me know because my plan right now is to use the cylinder currently. I still have to wait for at least another week before my head studs to arrive so if anyone sees this later on and thinks it's crazy to use this cylinder please let me know.
I would use that cylinder without reworking it: When I got my 250 2 stroke cylinder replated, I pointed out that there was a small cavity in the cylinder at the workshop and they made me notice that it was neither on the exhaust side, nor on the intake side, where the cylinder is mechanically stressed the most. According to them (a reputable shop here in Italy), since the connecting rod moves along the exhaust-intake axis and not sideways, the left and right sides of the cylinder do little to support the piston and therefore a cavity there would be less problematic. In the schematic picture attached I show the cylinder seen from the top, with the cam chain slot drawn to give it an orientation. The red zones are the exhaust and intake sides, where, according to this theory, a cavity would be more serious than in the orange zones, which would be worse than the yellow zones. According to them, though, those imperfections are common and negligible in any zone and we shouldn't worry about them. My 250 surely didn't feel like it didn't have compression afterwards. I also remember that I browsed a little about cylinders imperfections at the time, finding out that they are common indeed. You can also quickly install the cylinder in the crankcases just to check whether the rings touch that zone, which looks quite low. The surface of the cylinder, AFAIK, has a cross-hatched pattern which should make it hold the oil better and BTW the pattern is visible in your pictures, so probably using hand operated abrasives is inadvisable.
Café husky is finally back up. Good news! Got everything working and have 150 miles on rebuild. The bike runs and looks better then it ever has. Woohooo so happy. Thank you guys for sticking with me.
Great job Luke! You DM'd me a while ago on ADV Rider and I just wanted to mention that I had exactly the same problems you were having (low compression, not being able to start) after rebuilding the head and installing a Wossner piston. The only difference is my cylinder was not scored at all, but I bought a OEM cylinder and piston kit, just as you had done. A couple of things to add about the Wossner vs OE Piston... I finally disassembled my 610 yesterday (after sitting for a yr or so) and actually measured them both, along with looking at the differences. Here are my conclusions... 1) The OEM piston uses 2 compression rings, while the Wossner only uses 1 compression ring. Not sure if it makes a difference, but maybe/hopefully the OEM design will help seal everything up better. 2) The Wossner piston is 1mm (.0393") higher than the OEM piston. The distance from the top of the Grudgeon pin to the top of the piston is the same on both, but the Wossner is definitely higher/longer. The wossner also has a raised center section in the middle that measures approx. .015" higher in that area. Not sure why it is designed that way, but there was no piston/valve contact to the Wossner piston after disassembly, only low compression. Attached pics from left to right are: Damaged OEM Piston (from failed valve spring retainer bouncing around in the combustion chamber), Wossner piston designed for the 06-08 TE610, New OEM Piston. I'll update my thread with this issue as well and hope your bike is still running well!
Hi BenM and thank you for your report. I'm afraid that in the future it will be harder and harder to find OEM parts for our bikes, so it's nice that people review and also measure the alternatives.
