Hey , I have a 99 Grizzly 600. I've had nothing but good luck with it until last week. I changed my oil and spark plug. Since then it backfires when I let off the throttle , and I get blue smoke ( only when driving in gear). The plug is the same as what I took out as is the oil. I'm thinking maybe the carb needs some work. Any replies would be appriciated. Thanks.

 

Check your oil level. That blue smoke makes me think you may have overfilled it.

~HoundDog

 

Thanks ,HD , but my oil level is a little under if anything. Thanks for your reply !

 

Have you performed a compression check yet?

 

The back fire on let off, is a lean condition in the idle circuit.
Look for exhaust leaks, .....or vacumn leaks, in the intake.
If that checks out ok, turn the mixture screw 1/4 turn richer.


Does it smoke with the throttle on, or when it is off?
What other stuff did you do, when you changed the oil and plug?Did you clean and reoil the air filter?

 

Yes I cleaned the filter ,but I didnt re-oil it. I did just notice that there is a screw missing on my intake cover though. Maybe to much air ??? Smokes with the throttle on . Not a very heavy blue color , but enough to concern me. Other then these two problems, the bike works great. Compression is good. I've run Honda most of my life so I dont know a whole lot about troubeshooting the Grizzy. Appriciate all replies, Thanks.

 

did you tell it that the surgeon general has found smoking to be harmful to air filters and may cause carbuerator failure, j/k lol

 

Did you perform both a wet and dry compression checks? If you have your reading from a dry test, a second wet test can be done. By removing the spark plug and squirting a few squirts of oil in the cylinder, then checking the compression to see if it raises pressure from the dry test, you can see if there is small amounts of leakage of combustion gases between a piston and the cylinder wall into the crankcase in the engine.

 

If the filter isnt oiled, it wont do much good. The oil is what traps and holds the dirt and dust...the filter just holds the oil. This could also be the reason for the lean, the unoiled filter wont have much resistance to air flow, and will be leaner than an oiled filter. Use the proper air filter oil, its much stickier than motor oil, and wont drip to the bottom of the air box.
Which screw is missing?heres a diagram....picture