1998 Suzuki RM 250 Help

[mdavidso]

This bike is begining to aggrivate me. I bought in in pieces. I have rebuilt both top and bottom end. I have cleaned the carb and did everything for the first start and ride. I noticed when I bought it a fairly major dent in the pipe, something like the person before hit a pole or something hard enough to bend the rim and dent the pipe. Well anyway, I kick the bike and it starts right up. Put it in gear and try to go, it doesnt go. it has barely enough power to lug itself around. you can shift through the gears and get some speed built up. But thats it. Feels lean, spits and chugs like a seriosly lean bike does. Tried changing timing because Ive had a simular problem on a different bike. nothing. changed jetting, it had a 42/152, put a 165 main in it. Made no difference. Changed spark plug, hotter, no difference. I Pulled the plug it looked brown, a little dark but brown. does it have something to do with the dent in the pipe or is it the carb still?

 

[2strokerfun]

Carb clean? Getting gas? Air filter clean? Muffler unobstructed?

 

[arnego2]

Hi there
sorry to hear that, how is the clutch, a bike that old you need to see if the bike's clutch is still in spec. I think the friction plates have to have at least 2.8mm of thickness.

 

[mdavidso]

Getting gas to carb. Brand new clean air filter with filter oil on it. Thought muffler might have been plugged. Took it off still no help. it acts like its not 2 cycling? Could the dent be big enough to cause airflow to be obstructed and the expansion chamber to basically be bypassed? Another note: the dent is where the pipe mounts to the frame to almost the other frame.

 

[mdavidso]

What about the clutch plates? They are all brand new. How does the clucth have anoything to do with my problem?

 

[arnego2]

If the clutch slipps that could be your problem. If new and nothing changed you can exlude it for your list. When doing the top end did you see how much squish the piston has? Is the silencer clean or is it full with old caked oil? New packing? Also powervalve can have an influence at least.

 

[_JOE_]

Just a shot in the dark......piston in backwards?

 

[mdavidso]

I followed wiesco piston clearance/ ring clearance precautions. I also just undented the pipe. and it is better but still not running correctly. Also, this carb is not one ive saw before, it has the electronic selonoid? hooked into the CDI box, and some sort of electronic thing on the powervalve. Does anyone know what it is?

 

[mdavidso]

Haha nope. piston isn't in backwards.

 

[arnego2]

That is for the Power jet system. No Idea if the 1998 RM250 has that. A picture would be nice. How is the silencer? Clean?

 

[mdavidso]

Mine has it. I cant get a picture, no camera. What does it do exactly? and I unplugged it and I'm close with the jetting. Its real lean on the bottom end lean in the middle but good top end. So im going to change the needle clip position and maybe a richer pilot.

 

[_JOE_]

If you're having to go way off stock on the jetting you have an issue elsewhere. A leakdown test would be ideal in this situation. You can spend countless hours guessing and screwing around trying to figure out something that takes a few minutes to pinpoint with a leakdown check.

The power jet helps to fill in the jetting curve. Carbs tend to have natural lean spots in the midrange, the power jet helps fill them in to make smoother power. If it's malfunctioning it shouldn't make it run horribly.

If it's lean it should idle erratic and be surgey with steady throttle. The plug should also be light colored. Have you ridden it long enough to get it warm?

 

[mdavidso]

What is stock jetting for this bike? What does a leakdown test do and how to do it? I've never heard of that test. I have never had this problem, I have several bikes and none have had any sort of jettin problem like this. This bike is strange, It starts first kick and idles perfectly, put it in gear and it sounds and feels rich. Then once it starts moving it spits and surges like its abnormally lean, then it richens up and runs alright. If you let off the gas and try to hit it again it surges like its lean. I pulled the plug its golden brown. Have I ridden long enough? most likely, the pipe is hot enough to burn, the head is warm all the coolant lines are warm as well as the radiators. Current jetting is 152/42 n3wk needle, 4th clip position.

 

[arnego2]

Some airleak somewhere? 4rth NP is quite rich. How is the bottom end? Is there a play on the flywheel. Up and down?

 

[mdavidso]

no freeplay. brand new crank seals and everything.

 

[_JOE_]

I don't have a clue what your stock jetting is. Are you sure you're lean? Rich can cause sputtering and sluggishness too, however if you are that rich your fender should be pretty black, lol. When you say 4th clip position you mean from the top right? That seems really rich for a stock motor/pipe.

A leakdown test basically pressurizes the lower end to check for leaks. You can buy kits a few places.... http://www.harborfreight.com/automotive-motorcycle/diagnostics/cylinder-leak-down-tester-94190.html

That's a cheap kit but SHOULD be useable with some plugs for the intake/exhaust. You just have to keep the pressure low.

 

[mdavidso]

Im fairly certain its lean. theres no spooge or real thick smoke from the exhaust. yes from the top down. Its not quite stock. FMF pipe, 2.1mm oversized piston. MCR work done on the cylinder, no clue what was done. Has a cast iron sleeve though.

 

[killer454]

sounds like a power valve problem
not opening up,or sticking on the new sleave you had put in.

check to make sure the power valve is moving freely and working.if it stays closed the bike will not open up on throttle.
you said the bike barly pulls itself! check the power valve operation.

i had a cr125r and had a steel sleeve put in and the company that did the work did not clearance for the power valve and when i got it back together bike did what your saying yours is doing.i took it back apart and clearanced on the power valve (NOT THE CYLINDER)with a dremal and then it was better.

still had a bog though fixed that by jetting the carb and engine to 50/50 mix of 110 race fuel and 89 octain unlead at 32-1 on good oil.
the piston that i bought for the rebuild was a domed instead of the stock flat top,so i raised the octain up on my mix with the race fuel and 89-91 ratio and good oil to finish the mix.

BIKE SCREEMS NOW

 

[arnego2]

Jetting?

As Joe said the powerjet help the jetting curve. I looked up the RM jetting in another forum 162 main, 38 pilot and needle N1ED on second clip is someone running over there. I found that people running a Fatty had to go leaner one or 2 sizes on their pilot as it started and went straight into bogging.

At the carb cleaning did you change the float height?

I used a Suzuki needle once in my YZ250 and had a sputtering in the upper range. I misinterpreted it as being to lean, the plug showed grey but in the end the needle was it. As you have no torque in the lower RPM it could be the pilot or you rings are not sealing. Did the piston have a lot of play?

Another thing, which way you placed the oil seal clutch side when rebuilding? Open towards crank or opposite?

 

[mdavidso]

Powervalve isn't stuck, I fiiled it down myself. I might have to add some race fuel, I used to run it with 93 in my Yamaha. I had adjusted the float height several times. At first gas would pour out of the overflows, I adjusted it slighty until the gas stoppped flowing. Right now I don't remember which way I put it in.. I know for certain that I put it in the way the old one came out.

 

[arnego2]

Rm250 98

If nothing works: Make a check list. Go by that point after point.
Carb settings, adjustments done one after one and first step float high (stock being 16mm I read somewhere) Also have a look on the needle set. If worn it'll be impossible to dial her in. And read through this > click me

Clean the contacts of the flywheel magneto do exclude lack of current.
Last I'd look at the oil seal the correct way of tyhe suzuki oilseeal is open opposite crank i.e clutch side.

If you are sure the float is correct try a 38 pilot. If the bike runs under low RPM correctly but midlevel sputters go to the 3rd level. It is important that you do one step at the time so you can exclude slowly everything else.

 

[mdavidso]

Just put a different carb on. a standard PWK 172 main 45 pilot, DJG neede 3rd clip position. Helped a little but still not quite right.

 

[mdavidso]

Im definatly making a list, I'm slowly making progress. the bike seems to run alright at low rpm right now, but stutters and has a little power at high rpm.

 

[arnego2]

Put the needle on clip higher.
Good luck

 

[mdavidso]

Well I got it all figured out. I put the old carb back on and decided that I was going to make it run or break it. 152 main 42 pilot n3wk needle 3rd clip position. I took offf, it spit spat made all sorts of weird noises and started running. Made it about a city block or two, turned around pinned it and it wouldn't go felt lean, felt rich then it took off like a bat outta hell. Picked the wheel up and ran great. Still running great, and sold it!