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Just installed kms stage one kit, and went up three jet sizes like instructions said to. Now after a short open throttle down the road it backfired on decel. Any suggestions on what carb adjustment needs to be made now?
 

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I believe it is a 40 :dunno:
 

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Captain Zoom Sand Pirate
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and you may need to ruchen the idle mixture.
 

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If by back-firing you mean rapid popping the moment you let off the gas that is lean idle a/f...

If it backfires like a shotgun one time as the motor settles down that is...

Idle rpms too high...
Needle set too high...
Rich idle a/f...

That is assuming you have no mechanical reasons causing your problem...

like cracked header...or carb loose in boot...intake vacuum leak...there may be other possibilities as well such as...

crap stuck in float needle causing carb flooding...

see the jetting sticky...fully tune the carb and verify the header is not cracked behind the collar inside the head...you have to take it out to tell...
 

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If by back-firing you mean rapid popping the moment you let off the gas that is lean idle a/f...

If it backfires like a shotgun one time as the motor settles down that is...

Idle rpms too high...
Needle set too high...
Rich idle a/f...

That is assuming you have no mechanical reasons causing your problem...

like cracked header...or carb loose in boot...intake vacuum leak...there may be other possibilities as well such as...

crap stuck in float needle causing carb flooding...

see the jetting sticky...fully tune the carb and verify the header is not cracked behind the collar inside the head...you have to take it out to tell...
Hello tyrap,
I have been working on this rhino for months to get it right. Thanks to this forum, I was able to get the help I have needed in most cases and I thank all who participate for your help.

I am down to one last issue and have read posts on this until my eyes cross, and have been replacing and adjusting until I have this thing running like a top, except for one thing, the shotgun blast out the tail upon deceleration.

First off, it's a ‘07 660 Sport, I’m at approx 5000 ft.

I have new:
Fuel pickup, fuel line, fuel filter, out of the box carburetor with a 45 main jet, airbox removed and K&N air filter attached directly to the carb intake. Valves adjusted, new spark plug, Idle set to 1500, carb boot looks good.

One thing I have not checked yet is the header for crack due to the fact that I have to disassemble everything to get to it (roll cage, etc). Trying to eliminate all other possibilities first.

I conducted an experiment today and wanted to share my results in case it may be relevant to my issue...I got up to top speed, decelerated, and pulled out on the choke as I slowed and no backfire. What does that tell you, if anything??
 

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Check out this YouTube video to see if it helps solve your backfire issue:

Spraying something like WD40 around your intake area looking for RPM increases is a method I used years ago looking for vacuum leaks - it works but may take a little trial and error to decipher results - like a little RPM gain is normal but if the engine speed picks up significantly then you found a problem. On the exhaust diagnosis I used a stethoscope - I would pull the metal attachment out of the stethoscope hose (usually 1/4" clear hose) then insert a piece of copper tubing (10"-12" long) into the hose. With engine running I would listen for exhaust leaks by positioning the copper tube in the area of the header pipe or exhaust manifold and continue to move it around until I found the leak - you'll know when you find it - it will about blow your ears off even though, without the scope, you may not hear anything at all. In fact you really don't need a scope - just get an appropriate length of 1/4" tubing and insert it into a piece of vacuum hose with the rubber end at your ear, just move the tubing around till you locate the leak.

Old guy tip #78..
 
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