kevin_c

Well I found that one of the intake valves is slightly bent, going to replace. I noticed it while cleaning. It has a slight wobble on the drill. Also the outer springs are out of tolerance, probably not surprising given its age.

Yes it was in the correct way

Yes it was in the correct way

Thanks _Wilson_. I was told that I'm the first to work on this bike (it only had one owner). I did forget to mention that the owner said the electric start stopped working so he just used the kickstarter, and then it froze up. Should I be thinking about the oil pump at this point? The oil path pipe isn't occluded or anything like that. I think I will have a look at the flywheel and the starter. This is what I've ordered so far for the rebuild... Wiseco Powersports Piston Kits PK1015 https://www.summitracing.com/parts/WIS-PK1015 Tusk - Top End Gasket Kit - 1032020077 https://forwardpowersports.com/index.php/top-end-gasket-kit-tusk-1032020077.html

Thanks folks. It turns over beautifully with the top end off. It sounds very smooth (to my untrained ears). At this point I'm almost inclined to replace all the top end consumables and put it back together and see if it runs okay🤷‍♂️ 👍

Yes sir. I haven't taken the rockers out yet. Here's a valve before and after a quick clean, and the lifters, and cam shaft...

Thanks for the questions. The best synopsis I have is that the temp light and fan came on during a cold start. He drove it for ~10 minutes, walked away and let it idle and when he return it had seized up. I didn't try to turn it over myself. I checked the temperature dependent resistance of the oil temp sensor and it checks out fine (10.9 kohm at 75 F and 2 kohm at 187 F).

Thank you all for the welcome and wise questions! Thanks for pointing out the correct model. It is a TRX350A. I did not try to run it - just went with the top end inspection. Compression test is a good idea.

Hi All. Hope someone with more experience has some insight. I was gifted an 86' TRX350 Foreman that is in great shape. The previous owner said one day the oil temp light and fan turned on when he fired it up. He decided it was probably just a bad sensor and ran it anyway. After a while it seized up. He didn't want to work on it so he gave it to me. I was able to free the piston with some penetrating oil in the spark plug hole and a good push on the kickstarter. I decided something was probably really wrong with the piston or cylinder so I took the top end off for inspection. Trouble is, I can't locate the problem. The piston, rings, cylinder, valves, cam shaft, and springs all measure within the service limit. Nothing I can see indicates there was ever a problem (in my limited experience with small engines). I can't "hear" anything that sounds troubling in the crank case but I'm a total novice and new to ATV's. Any thoughts would be greatly appreciated.