It has Decent Compression but Still Doesnt Run Right - Motorcycle-Journal Forums

bigE · 09-16-2005, 12:18 AM

Im slowly but surely rebuilding a 1986 RM250 and i know im getting real close to having a decent running bike. Ive installed new reeds, a new piston and rings, and ive cleaned the carb. The bike has 150 psi compression. Not great, but i should be able to get some useable power out of her, right? The bike is incredibly hard to start (i usually have to push start it) and still runs like crap. It has no power in the top end (the bottom end has very little). I did not disassemble the power valve when i had the top end apart because i am not familiar with them and do not really know how they work (I normally ride thumpers). The carb jets have not been adjusted at all yet either. Does anyone have any idea how i could get started on taking care of this problem? Any info on what to do or how the power valve generally works would be greatly appreciated.

Dave2122 · 09-16-2005, 10:28 AM

I believe you have answered your own questions. Look into the Powervalves. Remove and decarbon them, clean all the residual unburned oil and crud out of them. Also jet your carb to maximize your power delivery. 2 strokes are not hard to figure out once you get used to working on them. Actually much easier than a thumper as no valvetrain and cams and timing chain (nothing wrong with that if you like 4 strokes).
Once you get those 2 items up to spec you should be in business. Make sure you also clean up your flywheel and pickup coils under the magneto cover as they may be a bit dirty. Also 150 PSI compression is great, superb, outstanding job on the top end work you did.

bigE · 09-16-2005, 12:27 PM

Thanks Dave. Is there any way to remove/clean the power valves without taking the top end off again? Will they come out if i take the adjustment "knob" for them off? This is my first time doing all this so sorry if this is a stupid question.....

Dave2122 · 09-16-2005, 02:00 PM

From what I remember of that design you can remove them without taking the cylinder off. I suggest you get a shop manual. Either a Clymer's or a Suzuki manual if you are going to do this without any experiance.

bigE · 09-16-2005, 08:43 PM

Thaks again for all the tips Dave. Im using a Clymer manual for a LT250R of the same year i had lying around the house (they have basically the same motor). I cant wait to get this beast running good again!!

cbsz449 · 01-13-2006, 07:56 PM

try putting in new gaskets

bigE · 01-14-2006, 01:30 AM

I put new gaskets in all around and it still ran crappily

It turns out the timing bolt got loose and it was firing at the bottom of the stroke

Dave2122 · 01-16-2006, 08:10 PM

GLad to see it is fixed!

09-16-2005, 12:18 AM	#1 (permalink)
bigE Kickstand Operator Joined: Apr 2005 Bike: 2000 SV650 & 2000 Marauder Location: DFW, Texas Posts: 277	It has Decent Compression but Still Doesnt Run Right Im slowly but surely rebuilding a 1986 RM250 and i know im getting real close to having a decent running bike. Ive installed new reeds, a new piston and rings, and ive cleaned the carb. The bike has 150 psi compression. Not great, but i should be able to get some useable power out of her, right? The bike is incredibly hard to start (i usually have to push start it) and still runs like crap. It has no power in the top end (the bottom end has very little). I did not disassemble the power valve when i had the top end apart because i am not familiar with them and do not really know how they work (I normally ride thumpers). The carb jets have not been adjusted at all yet either. Does anyone have any idea how i could get started on taking care of this problem? Any info on what to do or how the power valve generally works would be greatly appreciated.

09-16-2005, 10:28 AM	#2 (permalink)
Dave2122 Sprocket Pilot Joined: Sep 2004 Bike: Which one of the 9? Location: USA Posts: 887	I believe you have answered your own questions. Look into the Powervalves. Remove and decarbon them, clean all the residual unburned oil and crud out of them. Also jet your carb to maximize your power delivery. 2 strokes are not hard to figure out once you get used to working on them. Actually much easier than a thumper as no valvetrain and cams and timing chain (nothing wrong with that if you like 4 strokes). Once you get those 2 items up to spec you should be in business. Make sure you also clean up your flywheel and pickup coils under the magneto cover as they may be a bit dirty. Also 150 PSI compression is great, superb, outstanding job on the top end work you did. Last edited by Dave2122; 09-16-2005 at 10:30 AM.

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09-16-2005, 12:27 PM	#3 (permalink)
bigE Kickstand Operator Joined: Apr 2005 Bike: 2000 SV650 & 2000 Marauder Location: DFW, Texas Posts: 277	Thanks Dave. Is there any way to remove/clean the power valves without taking the top end off again? Will they come out if i take the adjustment "knob" for them off? This is my first time doing all this so sorry if this is a stupid question.....

09-16-2005, 02:00 PM	#4 (permalink)
Dave2122 Sprocket Pilot Joined: Sep 2004 Bike: Which one of the 9? Location: USA Posts: 887	From what I remember of that design you can remove them without taking the cylinder off. I suggest you get a shop manual. Either a Clymer's or a Suzuki manual if you are going to do this without any experiance.

09-16-2005, 08:43 PM	#5 (permalink)
bigE Kickstand Operator Joined: Apr 2005 Bike: 2000 SV650 & 2000 Marauder Location: DFW, Texas Posts: 277	Thaks again for all the tips Dave. Im using a Clymer manual for a LT250R of the same year i had lying around the house (they have basically the same motor). I cant wait to get this beast running good again!!

01-13-2006, 07:56 PM	#6 (permalink)
cbsz449 Newbie Joined: Dec 2005 Bike: ltz400 Location: south carolina Posts: 13	try putting in new gaskets

01-14-2006, 01:30 AM	#7 (permalink)
bigE Kickstand Operator Joined: Apr 2005 Bike: 2000 SV650 & 2000 Marauder Location: DFW, Texas Posts: 277	I put new gaskets in all around and it still ran crappily It turns out the timing bolt got loose and it was firing at the bottom of the stroke

01-16-2006, 08:10 PM	#8 (permalink)
Dave2122 Sprocket Pilot Joined: Sep 2004 Bike: Which one of the 9? Location: USA Posts: 887	GLad to see it is fixed!

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