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Sharpthinker

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Posts: 112
Reply with quote  #1 
The Mighty Pred has a misfire.
She starts great
Ticks over great
But when I accelerate she misfires like mad... NO backfire, but also no power
Decelerate and shes fine
Plug has been replaced and has a good colour
Compression test cold...140 psi
Added teaspoon of oil as per manual.... 160 psi
Valve clearances
Inlet left 0.20mm
Inlet right 0.18mm
Exhaust left 0.24mm
Exhaust right 0.26mm
Cleaned air filter
Checked carb "bellow" and cleaned the carb and all good.
If Im honest Im stuck, and before I romove the head and check the valve condition I was hoping you guys could give me the heads up on something slightly easier to sort out.
Cheers
Clive

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2005 Troy Lee, Pro taper bars, 2007 steering mod,CFM airbox,Pure Polaris pipe, Enduro tank, electric fuel pump.
TxOutlawRider

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Reply with quote  #2 
I'm not a preddy expert by any means, but if your compression is that good, I don't think its anything internal causing your misfire.
  Does it only do it when you accelerate?  Might check your plug cap and coil wire (and even test the coil).  Does it make a difference if the engine is warm or cold?  Does it make any difference if you turn on the choke while accelerating?  Do you have any leaks in the intake boot?

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Sharpthinker

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Reply with quote  #3 
I havent checked the intake boot, so thats a good shout.
The plug and gap are fine
How would i test the coil?

She starts and ticks over fine, when shes warm and i use the choke she starts to bog down.
Its when she gets to about 2000 rpm and above she just misfires without any power at all, but never cuts out.

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2005 Troy Lee, Pro taper bars, 2007 steering mod,CFM airbox,Pure Polaris pipe, Enduro tank, electric fuel pump.
TxOutlawRider

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Reply with quote  #4 
I don't have the test specs for the coil but I'm sure someone here will have them, then its just a matter of testing them an ohmmeter.
  Also, do you have the airbox lid on, and is it tight?  Those CV carbs can be finicky about that.  They'll idle ok but start to break up with a little throttle. 
The easiest way I know to test for a leak in the boot is to spray some cleaner or starting fluid around the carb and boot while its running and see if the engine changes speed. 


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2007 Outlaw IRS

"Outlaws are the Chuck Norris of the quad world."
ORION

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Reply with quote  #5 
Ya, I agree with what Tx said. Gotta be fuel mixture problem or its electrical. I wonder if the reverse rev limiter is being triggered somehow. 
LEOGM5150

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Reply with quote  #6 
I have had cdis do that also the dummy lights shorting out can do that maybe that triggers the reverse limiter like orion said.
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2014 POLARIS RZR 4 900 EPS
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Sharpthinker

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Reply with quote  #7 
Good advice guys thank you.
I didn't know there was a reverse limiter, but that does give me another avenue to explore.
It will be the weekend before I get to have a look at her again... watch this pace for updates.

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2005 Troy Lee, Pro taper bars, 2007 steering mod,CFM airbox,Pure Polaris pipe, Enduro tank, electric fuel pump.
Sharpthinker

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Posts: 112
Reply with quote  #8 
Ive checked all the reverse switch wiring, removed the switch and did a visual check... Put it back together and its still misfiring/bogging down. No change.
I also stripped and cleaned connections just to be sure
So, Im now hoping i can borrow a CDI unit to swap and see if thats the problem.
Watch this space.
I have a clutch issue that I will update elsewhere within the forums

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2005 Troy Lee, Pro taper bars, 2007 steering mod,CFM airbox,Pure Polaris pipe, Enduro tank, electric fuel pump.
ORION

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Reply with quote  #9 
Best way to test the reverse switch theory is to disable it. If its shorting out internally, then it would be difficult to tell just by looking at it. If it runs normally with the switch disabled, and it runs bad with the switch re-enabled, then you know that's the problem. I don't have a wiring diagram in front of me, but often you can simply cut one of the wires that goes to a switch and it will stop working. Then just fire it up and see if it runs normally. You would need to identify how the circuit is set up though. Single wire that grounds itself out, or is it a hot wire with a return path and the switch completes the circuit? 
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