Motorcycle Repair/Intruder 800


QUESTION: I recently changed my OEM exhaust for Cobra slash cut. Sounded great and ran great first ride. It now runs rough and back fires. One exhaust does not fit tight as the gasket was damaged when removing. I did order another one, but has not arrived yet. I know sometimes they have to be rejected for best performance

ANSWER: Anytime your Modify the Exhaust Pipes it removes Restriction form the exhaust and moves much more Air through the Carburetors.
Then it is necessary to Increase the Fuel in the AFR. (Air to Fuel Ratio)
Often the Mixture Screw will not be enough adjustment to acquire the needed fuel to the AFR.
This is why Re-Jetting may be Necessary.
Often a Dynojet Jet Needle kit can Resolve the Issue.
Contact me at: if you need more assistance.
I am very Good at Installing Dynojeyt Kits and Re-Jetting..

---------- FOLLOW-UP ----------

QUESTION: Thanks for your quick response!
Would it be normal to run good and then start running rough. Also, would a loose fitting muffler cause any issues.

Yes a loose fitting muffler can cause issues.
I would install the new gasket before doing anything else.
The noise from modified exhaust isn't a backfire but more of a popping
or back rapping through the exhaust. This is due to a Lean Fuel Mixture.
A backfire is more a valve and Timing Issue.
You can Increase the Fuel in the AFR (air to fuel ratio) by turning the mixture
screw counter-clockwise.
You can check your AFR by checking the color on the spark plugs.
Black plug is to rich. Turn the screw in (clockwise) to lessen the fuel in the AFR.
White Plug is to lean. Turn the screw out (counter CW) to Increase the fuel in the AFR.
Be careful as running an Engine with a Lean AFR can cause your Pipes to turn color.

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william joseph stack


I specialize in Virago carburetors. Internal parts sizes, Needle and jet sizes for each and every year and model. Hitachi and Mikuni. I also can give tech support and Tech Support for carburetor problems and issues. Carburetor tuning and syncronization. Carbburetor rejetting and dynojet installations for engine modifications. I know every needle and jet size for every Virago made. I have done over50 Virago carb Salesand Rebuilds in 2012. I have over 50 sets ofVirago carbs in stockright now. I Build, Ride and Breath Virago. I have both the 1983 Midnight Virago's. The XV750MK and the XV920MK. 1 of my 1981 XV750H is is Premier Cycles, Billy Joel's Bike Museum.... I am an Honest and Fair man. I am also a Finicky Perfectionist withmy carb work. Ihave all the obsolete hardto find carb parts. I have new diaphragms, new floats, I have the float level setting down to an art. I have fabricated transparent bowls for both version 1 and version 2 carburetors.


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