RM250 Still runs like crap - Motorcycle-Journal Forums

bigE · 08-03-2005, 05:40 PM

I finally had time to install a new piston and rings on my 1986 rm250. It had almost no power before the new piston and there is basically no change in power delivery after the new piston was installed. It has brand new reeds too. I dont know what to do now.... Could it be the carb? Also, the bike is still incredibly hard to start (i usually have to push start it)..... Any ideas? Im getting desperate....

digipoi · 08-04-2005, 03:40 AM

Did you replace the piston and rings with stock sizes? Did you do a compression test? Your cylinder could be worn and may need a larger diameter piston/ring set (of course after the machine work). Did you clean your exhaust valve thoroughly when you replaced the piston? Hows the pipe? Is there carbon buildup near the exhaust port side?

I would definitely give your carb a good cleaning too while youre at it.

bigE · 08-04-2005, 08:50 PM

The piston and rings are 1mm oversize. The bore job was previously done.... Havent done a compression test yet, I dont have a tester.... I never actually removed the exhaust valve and honestly i have no idea how its adjusted (this is my first bike with one that ive ever had problems with).... Could this make that much of a power difference? There is no top or bottom end power.... The pipe is "well used" to put it nicely. It does have one or two small cracks in it....

ALLEYCAT50 · 08-05-2005, 11:23 PM

clean the carb well. brake clean is good, better get one of the bigger cans. after that check the float, make sure it is seating. check the float height. with the cracks in the pipe it will not run very well. if you know someone that can weld, get them to fix the cracks, it won't last a long time but you will know if that is the problem. oh yeah, while you have the carb apart check the needle for bends. spark plug is a B8EGV 0.024 gap. try the small things that don't cost much. good luck.

bigE · 08-06-2005, 11:38 AM

Thanks for all the ideas Guys! I'll tear into the carb and see what happens!

08-03-2005, 05:40 PM	#1 (permalink)
bigE Kickstand Operator Joined: Apr 2005 Bike: 2000 SV650 & 2000 Marauder Location: DFW, Texas Posts: 278	RM250 Still runs like crap I finally had time to install a new piston and rings on my 1986 rm250. It had almost no power before the new piston and there is basically no change in power delivery after the new piston was installed. It has brand new reeds too. I dont know what to do now.... Could it be the carb? Also, the bike is still incredibly hard to start (i usually have to push start it)..... Any ideas? Im getting desperate....

08-04-2005, 03:40 AM	#2 (permalink)
digipoi Seat Tester Joined: Sep 2004 Location: Honolulu Posts: 84	Did you replace the piston and rings with stock sizes? Did you do a compression test? Your cylinder could be worn and may need a larger diameter piston/ring set (of course after the machine work). Did you clean your exhaust valve thoroughly when you replaced the piston? Hows the pipe? Is there carbon buildup near the exhaust port side? I would definitely give your carb a good cleaning too while youre at it. __________________ 2004 RM250 2004 DRZ125L 2006 TTR-90E 2004 JR50 1993 RM250 1990 KDX200

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08-04-2005, 08:50 PM	#3 (permalink)
bigE Kickstand Operator Joined: Apr 2005 Bike: 2000 SV650 & 2000 Marauder Location: DFW, Texas Posts: 278	The piston and rings are 1mm oversize. The bore job was previously done.... Havent done a compression test yet, I dont have a tester.... I never actually removed the exhaust valve and honestly i have no idea how its adjusted (this is my first bike with one that ive ever had problems with).... Could this make that much of a power difference? There is no top or bottom end power.... The pipe is "well used" to put it nicely. It does have one or two small cracks in it....

08-05-2005, 11:23 PM	#4 (permalink)
ALLEYCAT50 Seat Tester Joined: Jun 2005 Bike: 2008 YZ450 Location: NOVA SCOTIA Posts: 70	clean the carb well. brake clean is good, better get one of the bigger cans. after that check the float, make sure it is seating. check the float height. with the cracks in the pipe it will not run very well. if you know someone that can weld, get them to fix the cracks, it won't last a long time but you will know if that is the problem. oh yeah, while you have the carb apart check the needle for bends. spark plug is a B8EGV 0.024 gap. try the small things that don't cost much. good luck.

08-06-2005, 11:38 AM	#5 (permalink)
bigE Kickstand Operator Joined: Apr 2005 Bike: 2000 SV650 & 2000 Marauder Location: DFW, Texas Posts: 278	Thanks for all the ideas Guys! I'll tear into the carb and see what happens!

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