I have a 1985 ATC 250r with top end issues. I ride the big dunes at St. Anthony Idaho and cannot keep the motor from falling on it's face. Even in 3rd or 2nd gear. It pulls from the bottom pretty good. About 1/4 up any large dune it just absolutely quits on me. It's like the tires are in wet cement. The motor was in need of a tune so here's what I've done. Went from stock 250 to .010 over. All Honda OEM parts. Same issue. Put in new lightly oiled filter. Same issue. Checked compression, Max I got was 155 psi. The Honda shop manual states that compresson should be 170.7 - 199.1 psi? Is 155 bad? Is 170-199 real? Rebuilt carb with jetting according to honda manual for altitude. Once on the dunes I went even lower to get a nice golden brown color. Same issue. Cannot climb anything. Next changed to V-Force3 reeds and removed and repacked pipe and silencer. Same. If I stay on flat ground it runs like a champ. Under any load it absolutely acts like I have a 50 lb. anchor tied on. Any help would be appreciated. Thanks

 

mice nest in your intake!!!!!!

 

No mice in intake. I wish it were that easy. Could there be blockage anywhere else causing my issues?

 

if it is hard to climb up something or a hill as u said , might wanna try or look at ur clutches and clutch basket.

 

Mine was doing that and come to find out I was running really lean....what fuel ratio are you using and also I would look at getting an 86 r stock carb....made a world of differnece on mine

 

Low float level in the carb?

 

I will try to answer all the questions in one shot. I always thought of clutch problems as slipping with higher engine rev. It is definitely not slipping. Is there a chance the clutch is loading the motor down? I have ran at 32:1 and 40:1 on the last trip. No difference. I set the float level according to the Honda manual. It is not starving for fuel. There is no backfiring or higher rev lunging like running out of fuel feels. Can anyone clarify the compression. Is 155psi valid? Also, I have heard that you can loose some compression in the crank case. If so how would you check? At this point I am almost convinced to go through the whole motor and give it a once over. New clutch, check the cylinder, replace the rings, replace all seals and gaskets and see where I am.

 

Just my 2 cents worth, but have you tried a new plug? (Proper heat range)

I have seen plugs that are fine until they are placed under a heavy load.

 

I have gone through a few of them now. All NGKs D8EA. I'm thinking of trying a champion. Other than that I am kinda back at square one.

 

Well first of all 155psi is a little on the low side. A fresh stock 250r engine should be pushing out a solid 170psi. When you were compression testing it were you holding the throttle wide open? Not holding the throttle open can affect your reading. Does it make any difference running with the head light on or off? Are you running the stock exhaust and intake?