1989 Honda TRX250R Fourtrax, Super Clean, low hrs and original ( SF Bay Area)

Hi guys. I have a problem where the quad will start and run well for about 5 minutes and then it dies. On inspection the airbox has oil in it (quite a lot). The oil is pumping through the cylinder head breather hose. This problem first happened suddenly. I have since done the top end including, piston, gaskets, rings and valves. I have also done the carb (not that I thought that this was the problem). The compression seems normal. The only thing that I can think of, is that I did not grind the valves well enough. Anyone experienced this? If so, how did you fix it? Any other thoughts?

I Ran across this video today comparing an aftermarket to OEM Carb on Suzuki Vinson, thought it might generate some interest, it is quite long but informative.
 

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View File 2006-2011 Honda Rincon TRX 680 FA/FGA service manual
2006-2011 Honda Rincon TRX 680 FA/FGA service manual
Submitter Admin Submitted 04/09/2024 Category Honda ATV  

Hey all back again with my 1989 moto 4 250.
After putting a new carb on it it's really sputtery, it has new gas and I'm wondering what to tune on the carb to make it idle better. I've attached a video to describe the issue more. The bike is still work in progress but I think the video gets the point across. Thanks!
Snapchat-1142015191.mp4