ANY IDEAS WHY?

Tuned up my 900 one day and showed my brother. He said sounds like its gonna blow up. It was klakity and it wouldnt idle very well. Turned out it was the inner two pistons had broken rings. Any time a cylinder does not have enough gas or too much on these bikes the engine will sound clacky at idle. My bike doesnt have a primary chain. Something is wrong and it wont get better by driving it I never read the beginning of the post toastie so bear with me. Have you checked the compression? My guess (always good ones) is if tis not compression tis carbs/vacuum. These are the things that cause the noise your hearing. The fact that it didnt misfire while driving tells something here. check the plugs colors and that should nail it.

I just read the rest of your post. Sounds like the timing is way too advanced. If you have it set to fire at the fire mark it is way too advanced. That's why you have to use 93 or whatever. With the piston kit it now has faster flame front and the timing needs to be backed down to increase power and stop the pinging and that god awful vibration through the handle bars. Mark the timing where its at and loosen the screws and turn the plate clockwise one eight of an inch and fire it up. shoud be a world of diff. If its too advanced like I think it is, it should be kicking back on u when u start it. Its running rough simply because it isnt getting enough fuel at idle. That's also the reason it hangs up before it idle back down again. You do not have a vac leak been tested for that. Might have to look into the carbs and double check the idle circuit, pilot jets and needle heights in that order. If it was me i'd check compression before u even go there. Seems odd that it's not popping at all, so this would be the time to tell the truth about that.:lol:

nads.com wrote:

I just read the rest of your post. Sounds like the timing is way too advanced. If you have it set to fire at the fire mark it is way too advanced. That's why you have to use 93 or whatever. With the piston kit it now has faster flame front and the timing needs to be backed down to increase power and stop the pinging and that god awful vibration through the handle bars. Mark the timing where its at and loosen the screws and turn the plate clockwise one eight of an inch and fire it up. shoud be a world of diff. If its too advanced like I think it is, it should be kicking back on u when u start it. Its running rough simply because it isnt getting enough fuel at idle. That's also the reason it hangs up before it idle back down again. You do not have a vac leak been tested for that. Might have to look into the carbs and double check the idle circuit, pilot jets and needle heights in that order. If it was me i'd check compression before u even go there. Seems odd that it's not popping at all, so this would be the time to tell the truth about that.:lol:

thanks.....i m going to recheck timing one of these nites.......and no, she aint a poppin....

If not already done, would double-check valve clearances.

Cold compression figures may be good, but marginally too tight valve clearances may cause loss of compression at normal operating temp.

Good Luck!

I had this exact same problem. It eluded me for days... then I got it.

It was the bolts that hold the starter clutch assembly to the stator magnet.

The bolts loosened themselves off so far that they were causing the bike to make a klanketing random sound anywhere below 1800rpm, and closer to idle, it would just stall out.

Got some new bolts and lock washers. Proper torque, and problem solved.

Goodluck my friend!