'96 F3.....

Saturday I was out for about 50 miles on a great, sunny ride. Stopped by my sisters for about 20 minutes. When I left I got about 2 miles and out of nowhere the bike started missing and backfiring out the exhaust. Speaking of exhaust, it sounds totally wimpy now. The nice, mean rasp from the Jardine slip-on is gone. Sounds scooter-ish now. Pulls like a scooter too. Starts every time, idles fine, but I can tell there's something not right in the idle. I'm worried it's something electrical since it was fine one moment and bad the next.

What do you think? Any suggestions.

 

this may be out of left field,but it may be possible that a main jet fell out of one of your carbs and is making the bike run super rich.i hope that isnt it,im sure its a pain to fix.good luck

 

Check to see if you're getting spark to all for cylinders. Pull the spark cap off the plug and stick another plug into it and ground the plug. Then turn the bike over and look for spark. By the way, don't hold the plug while turning the bike over.

 

Yeah my best guess from your description is that you've got one (probably two) cylinders not firing.

Now you need to not run your engine until you solve your problem. If it is a mis-firing cylinder or not firing at all it could bottom out a piston and spin a bearing. Then you're ****ed.

After checking for spark, check your timing marks just to be sure it's not a timing issue. If you've never changed your CCT, your cam chain may have jumped time but you would be the first person ever to have a CCT tensioner fail and not hear it on the top end of your motor.

From your description, you're not getting spark to one or more cylinders.

If you're getting spark form all four cylinders then there is something keeping the combustions chamber from detonating when compression is reached. That could be shot rings (completely shot, you'd have to have noticed this coming on), cracked cylinders or bad plugs.

You describe it as scooterish. Scooters only have one cylinder...

 

i agree with cr3nshaw, I had symptoms that were pretty much the same when i got my bike and it was plugs. But mine was more of a chugging with the "scooterish" power. I could feel when the cylinders would miss each time, but it was only under load. Idle was totally fine.

 

I'll get to the plugs this evening and check for spark. "Scooterish" wasmaybe the wrong description. Powerless & slow (as a scooter) is more like what I meant.

Thanks so far guys. I'll keep you posted.

 

Well, last night I didn't get to work on the bike. So this evening, I got a chance to dig in to it some and MAN am I lucky!

I checked for spark, and everything was good therre. So next on to plugs. First two plugs, no so bad, but the third one, oh crap!

Below is a picture. Plug on the left is the "third" one. Plug on the right is one of the other three. I had a feeling I was in for something when I felt no resistance loosening number three. Also the wire boot was covered in soot, unlike the others. Looks like old number three was backing out over a period of time. I'm glad I wasn't the last to service them at least. I'd hate to know I did that! (Building LS1 RX-7's, breakingcrap can be pretty frequent, whether it be over tightening something, or just to much torque engine-wise!)

So here's the picture. I guess the ground burned up, but that electrode looks like it wanted to fall into the piston.

[IMG]local://upfiles/20414/6282F5A10F484B7BB7BDD0B507A9962D.jpg[/IMG]

 

By the way,a new set of plugs fixed it right up. She runs like, well you know!

Thanks for your suggestions folks!

 

cool deal [sm=smiley20.gif]