after 300 rpm misfire, 86XJ

My 86 XJ700S misfires after 3000 RPM. Any suggestions anyone can make on how to fix this will be greatly appreciated.

 

mine was doing this. this is what it took for me to fix.

#1 checked the coils
#2 checked the plugs
#3 rebuild the carbs
#4 bench sync the carbs
#5 bought a colortune and used it
#6 sync the carbs with a vacuum gauge.

There could be so many reasons for a misfire however, what have you done to the bike so far?

 

I dissassembled the carbs, let them soak for two weeks and then finished rebuilding and installed them. Then they were synced with carbtune vacuum gauges. The air fuel mixture screws were set back to exactly the same way as at the factory. New spark plugs were installed. The spark plug wires and coils appeared physically fine.

I was wondering if I need a YICS tool for this.

 

probably not related to the misfire,

but the carbs need to be synced and mixtures set W/ the yics tool(or its equal) in place.

I have used nothing more than a cut up cotton t-shirt and marvel mystery oil.

This way also cleans out the yics port too.
Maintnence Free- I Think Not...yamaha, shame on you!

 

You probably need to do some fine tuning on the Pilot Mixture Screws. Factory Preset is generally a little LEAN for the Engine and that will cause rough running.

Read the Plugs.
If the Plugs ate looking a little too clean, right about now, I'd say you have to Bring-out the Pilot Mixture Screws some more.

ColorTuning is the Best Method of finding where the Mixtures should be. Once you do a ColorTune ... Then,, you can add or subtract some Mixture from the Pilot Screws and get your Bike Dialed-in on-the-money!