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1982 Rm 250

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I know odd question, but im running this engine on my shifter kart.

Problem is it doesnt feel as fast as i think its supposed to, low end is alright top end is slower im running a 300 main jet with 40:1 fuel mix carb needle at the stock position.

Clutch is new, previous owner said he re did the top end and didnt run it long. Piston is real clean cylinder walls look ok no real grooves to catch my fingernail. Spark plug was a dry black in color(changed it when i bought the motor), did a compression test and got 70psi not sure whats normal and im also not sure if my gauge is working right. Bike starts up on the 1st or second kick without the choke.

If it matters im running a 14t front sprocket and a 27 rear with 5 inch rims and 11 inch tires

Sorry if this is in the wrong area, heres a video of me riding maybe you guys can hear somthing i cant. Thanks for the help

ImageUploadedByThumper Talk1401542569.130955.jpgImageUploadedByThumper Talk1401542589.130259.jpg

Edited by Assy

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Compression can't be 70 psi, it wouldn't even run.

 

Did you test with the throttle wide open, and continue kicking until the gauge stopped moving?

 

The plug should be tan, not black.

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Good point i forgot to open the throttle, noob move lol. Whats black mean? Rich? Also i didnt do a actual plug chop just removed the plug and looked at the insulator. Thanks for the reply.

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Even with the throttle closed it should at least read over 100. What size back sprocket r u running.

27t rear 14 front

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When you do a compression check kick it over 4 or 5 times with the throttle wide open, basically once the needle stops going up that's what you have.

 

Power wise, with a motor built in 1982 any number of things could be wrong.  Did you ever have it running like you felt it should run?  If so, how long ago was that?  How much practice time and number of races do you have on the motor?  And have you always run the same fuel, carb settings and engine package?

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When you do a compression check kick it over 4 or 5 times with the throttle wide open, basically once the needle stops going up that's what you have.

Power wise, with a motor built in 1982 any number of things could be wrong. Did you ever have it running like you felt it should run? If so, how long ago was that? How much practice time and number of races do you have on the motor? And have you always run the same fuel, carb settings and engine package?

I just got the motor, iv drove it 10 times about 2 mins per after warmup. Its never been in a real race.

40:1 is the ratio iv been using with same carb setting other then recently upping the jet, its always felt this way since i had it.

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Just put the motor back together and re tested i got to 90psi anyone know whats normal?

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I think your tester is broken. An engine won't even run on 90 psi compression.

I would expect at least 150-175.

Possibly ill have to snag another one and re test.

Does anyone know how to check ign timing? Want to also rule that out while im at it.

On a side note what year did suzuki start coating the cylinders vs sleeving them?

You should have a lot more compression than 90 psi, pull apart the top end and measure all the clearances. Something's definitely wrong with that motor.

what am i mesuring?

Thanks for the help guys!

Edited by Assy

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Is the carb jetted for 40:1?

Noob when it comes to dirt bikes, but when i googled what was the best ratio for an rm250 everyone said 40:1 so thats what i mixed it at lol. Edited by Assy

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Noob when it comes to dirt bikes, but when i googled what was the best ratio for an rm250 everyone said 40:1 so thats what i mixed it at lol.

Yeah, alot of people are idiots haha. 

Pick a ratio, 30:1, 40:1 20:1 doesn't matter. Jett the bike for your ratio. 

I pick 32:1 because its easy to mix 4oz per gallon.

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Read what it's supposed to take. Then check the jetting to see it it's stock. And if it is. Go with that ratio

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Had a chance to compression test again with a different tester im at 150psi is that good?

Also does the water pump thats on the motor have the piwer to transfer the water from 3ft for feed and 3ft for return? Or should i get a external one also?

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Took the kart out for a run today, sadly to say i think the ring started to melt onto the cyl walls ImageUploadedByThumper Talk1403571062.035478.jpgImageUploadedByThumper Talk1403571070.835028.jpgImageUploadedByThumper Talk1403571086.701349.jpg

Kart stalled out and locked up the wheels in the back until i put it in neutral. Any ideas why?

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Sounds like you seized your motor and judging by those pics the plating has worn thin the rings scuffed into the plating you can see fresh metal streak patterns in the walls

Edited by 78SuzyQ

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