I'm mis firing

I just changed the plugs and noticed that, that the GRiSO is spluttering more than usual on the overrun, giving some gas and it clearly is firing on only one cylinder. I took for a ride and seems to clear up, but the misfire comes back intermittently and then clears up again.
Also noticed that when this happens the idle is too fast and sometimes the revs hunt at idle.
Any ideas?

Plug caps bust.

Bingo!

What do you mean by bust? Should ths h.t. cable be replaced?

yes, eplace them with spme nice NGK SB05Ereplacements

+ 1 plug leeds, same thing happened to me when plugs were last changed. You can confirm it by starting bike in dark and looking for spark around the plug tube. I jury rigged a very temporary fix with electrical tape until I could replace leeds.

When removing the caps did you pull them off the plugs by grabbing the top or levering them under the right angle with a screwdriver? Doing that will cause them to tear and then the spark arcs to earth at the head cover. The correct way is to lever them up off the plugs by sticking a long, thin screwdriver in through the cooling tunnel just above the exhaust and popping them off.

SB05E or F caps can be substituted depending what top electrode you have on the plug.

Pete

Is there any misfiring that could be considered normal? Is the engine supposed to run perfectly smooth?

??? Well it will run as smooth as any 90* Twin can If it's balanced and tuned correctly. If it's missing spark for long periods it'll run like a munter!

What's your bike doing exactly and what year and model is it? I seem to remember it's a GRiSO but an early one you've had rollerised?

Sorry, I have a lot on my mind at the moment and am less than cognisant of your bike but I'll help if I can.

Pete

Yes well, I appreciate your help. My bike is a 2011 GRiSO 8V SE Tenni Green. I recently rollerized it. Love this bike. Although she has given me a little more trouble than I expected when I bought it.

Regarding the misfiring: my motorcycle has always had misfired a little bit usually in second gear when rpms are decreasing returning to idle. It has been that way since I bought it with 10.000 kms. I considered it normal and thought it was due to gasoline quality down here in CR.

Just this past friday I had some trouble with one cylinder shutting down and with the help of these forums, discovered that the spark plug caps are damaged and they were arching. I made some temporary repairs with electrical tape until the new caps arrive. The engine has been working well. But I feel it is misfiring a little more. Around 3000 rpms typically when the engine is returning to idle.

Reading this chat, I guess some of the misfiring is due to the damage I have on the caps. But if some of it remains what other things should be done to assure its tuned and balanced?

I think this is backfiring, and not misfiring. Misfiring happens when plug caps are damaged, backfiring happens when throttling off - which is what you probably have.

Question? What map are you running? Standard or another one? do you have any devices on it like a FatDuc or similar? Are you running a Power Commander? What exhaust do you have? Has the airbox been modified?

Thank you, I think you are right.

Regarding the map, I don't know which one I'm running. How can I know? There are no devices installed on her. I've got the original factory exhaust. An no modification has been done to the airbox either.

Awesome, a "straight" GRiSO. The gurus on mapping may be along shortly to advise. Looks like you have sorted the mis-firing with new plug caps on order - excellent.

Have you done a throttle body balance? This is important!

Yeah, can't mess too much with the standard settings, because I don't have enough knowledge. Regarding the map, not sure if the dealer has made any change on it. But surely if they did, Its a standard map. I'll have the throttle balance in mind, the next time I talk to the dealer, because I do have that little backfiring issue.

When they rollerised it they should of tuned it, it's part of the process. Also it should of been updated to the last factory map.

My suggestion is buy the cables and a manometer, download Guzzidiag and do it yourself. It's not hard.

Pete

Ok. I'll investigate. My main source of information are you guys. So Ill look in the other forums for the cables specs and where to get them. Same for the manometer. Any other information about this you can give me or thread on how to do it, I appreciate.

No need to look elsewhere. Everything you need is right here.

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NGK caps $20 US
Beatle Map $100US
Cables and Guzzidiag donation less than $100 US
3-4 hours and a few beers

Bike will run better than any bike you've ever had. FYI I have an '11 Tenni

Please drink the beers to toast success, AFTER all the work has been done, and a good test ride had. Then drink more beers!

Thanks to everyone. I'll be working on it.