01 700 rmk backfire, need sugestions

oilkan · Mar 9, 2009

we've got a 01 700 rmk thats been running great for the last few seasons. on the last ride it blew a belt and since thn it has been running poorly on the low end. it starts great, but off idle acceleration is very choppy, and it backfires when letting off the throttle. it runs good from mid to wot but i noticed a loud uneven idle. the plugs look good, and i've tried different ones with no change. the sled has about 1600 miles on it and i cleaned the carbs back in november. any help is appreciated. thanks, tom.

BB454 · Mar 10, 2009

poor running

Could be the PTO crank seal got damaged when the belt blew. Were any cords caught behind the clutch? If so you may have damaged the seal. When you get it running, squirt carb cleaner or WD40 behind the clutch and see if the RPM picks up. If so the seal will need replaced. Back fire indicated it's sucking air past the seal.

The other thing is that you may have twisted the crank out of phase a little. If it still runs and you have twisted the phase, it will be hard to check. You will need a degree wheel and a dial indicator because it may only be out a small amount. If they are out a lot they won't run and they can be checked by just marking the clutch. Loud uneven idle kind of sounds like a phase problem.

oilkan · Mar 10, 2009

thanks, i was wondering about the crank seal too, it did have some belt cords wraped around the crank, i shut the motor down as soon as the belt blew and removed all the cords, but it seems to co-incide with when the performance issues started. If the crank was out of phase would it still run good through the mid range? I'lll go check the seal right now. thanks for the reply.

NYRIDER · Mar 12, 2009

BB454 said:
Could be the PTO crank seal got damaged when the belt blew. Were any cords caught behind the clutch? If so you may have damaged the seal. When you get it running, squirt carb cleaner or WD40 behind the clutch and see if the RPM picks up. If so the seal will need replaced. Back fire indicated it's sucking air past the seal.

The other thing is that you may have twisted the crank out of phase a little. If it still runs and you have twisted the phase, it will be hard to check. You will need a degree wheel and a dial indicator because it may only be out a small amount. If they are out a lot they won't run and they can be checked by just marking the clutch. Loud uneven idle kind of sounds like a phase problem.

I blew a belt on my old 2000 800 RMK and after that it did back fire, come to find out the crank was out of wack or phase as you say. (that was on my first crank).

polarblu · Mar 12, 2009

On that same note i have a problem with a 99 700 rmk motor.......... It starts and runs great but after a WOT blast i get 100 feet the engine dies then backfires then takes off again???? I tested the stator to Polaris specs and went through the carbs then replaced the CDI/Coil box. I then went to the Alt compensator and still the same WOT die backfire issue!!!

I could use some ideas also!!

Thanks
B

theultrarider · Mar 12, 2009

polarblu said:
On that same note i have a problem with a 99 700 rmk motor.......... It starts and runs great but after a WOT blast i get 100 feet the engine dies then backfires then takes off again???? I tested the stator to Polaris specs and went through the carbs then replaced the CDI/Coil box. I then went to the Alt compensator and still the same WOT die backfire issue!!!

I could use some ideas also!!

Thanks
B

Sounds like you are leaning out. Did this start all of a sudden, or gradually or what? Are the mains too lean? Fuel shut off switch not open all the way? Bad fuel pump? Check the fuel pick up tube laying in the bottom of the gas tank. Is it broke off? That will give you fits when they break off!

jim · Mar 12, 2009

Belt cord in the PTO crank seal...will do exactly that when the seal is blown. It might not be that noticeable but they leak with minimal damage. You can get most shops to pressure test it when they pull it...make sure everything else is sealing well too. And, the crank is most likely fine...they can measure the run-out while they are at it. The 700 cranks are pretty good. Double check primary and secondary for bushings too...make sure that's not the cause of the blown belt. Good luck.

polarblu · Mar 13, 2009

theultrarider said:
Sounds like you are leaning out. Did this start all of a sudden, or gradually or what? Are the mains too lean? Fuel shut off switch not open all the way? Bad fuel pump? Check the fuel pick up tube laying in the bottom of the gas tank. Is it broke off? That will give you fits when they break off!

I had a mag side crank seal go then after the tear down i had this problem i replaced the feul pump already and tested the pick-up tube, took out the shut-off valve. The digitron tells 1200-1300 when it backfires but i was thinking that i had gas burning in the pipe. Have you heard of a stator making these symptoms? I tested it but maybe after it warms up? im grasping at straws as of now riding a stocker Cat cause this engine is in my mod Gen 2.

Thanks for all and any advice

B

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01 700 rmk backfire, need sugestions

oilkan

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BB454

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oilkan

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NYRIDER

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polarblu

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theultrarider

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jim

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polarblu

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