when start enigne it runs ruff, i have a polaris 1987 triple 600 i spark plug tested all of them and they were fine, then pulled each wire off the spark plugs and see how it would run, it ended coming out that number two was not firing at all, it did have spark but no fire,
When you have done all that and still come up empty, try this:
Cut 3 sections of common soda straw (can be stolen from McDonalds, 7-11 or whatever),
Cut them equally 6" long. Pull out all three plugs and stuff a straw in each hole. Rotate any one of them to TDC. Measure each one from the top of the head cover to the end of the straw and record. Stroke the crank to the next cylinder to TDC and measure again and record the numbers. Do the same thing again with the last cylinder and record. When you have done all this, compare your results. The numbers should jibe. What you are trying to do is measure stroke to check to see if your crank is out of phase as in a perfect world the crank stroke is concentric. Its a bit neandrathal to do it this way but it works. If you are several degrees out of phase you should see it in the differences of measurement. It wont tell you how much but it will tell you something is fucked or its ok. The best way is to do this with a TDC finder and a vernier caliper but this meathod will at least tell you if things are really out of whack. Should be within 2 degrees I think, Jon knows for sure. I used this meathod to determine a misdiagnosed crank out of phase on my XCR8.
well i got looking yesterday at my sled and i noticed that a number two carb out of its boot, so i put it back it and tighten the boot up and now it runs good, sept for the drive belt i broke, so got to wait till i get one in the mail. the spare that was on it was to long so i tried just for the hell of it and it broke so i got some coming now tho
well i guys i have the same problem once again, sept its got all new plugs and the carburetors are in the flange boots just fine, but the number two piston goes out of sink when i hammer it or if i try to go over 30 mph so i dont know, i imagine its the carburetor my friend was trying to tell me about some c clamp or something on the bottom of the carb that could have came off and thats whats causing but i have no idea
Heres what had happened to me back in mid 90s, I bought a '95 XCR6 with pipes, heads and trail-ported. I was racing against a friend locally and somehow, I slapped a drivebelt. What I didnt know, it would causes havoc on the crank. Less than 2 weeks later after a night out of riding, it rode home fine. Next morning, when to start it up, the sled wouldnt run, not to mentioned it keeps backfiring. I found that the carb on the clutch side came off the boot - put it back on, same thing, backfired and blew the carb off again. I didnt even understand what was going on. I took it to the dealer and he told me I twisted the crank. I ended up with a new crank and the sled ran good once again. The dealer told me, with the XCR6 I had, the next time the belt snap like that, I should have my crank checked to make sure it stays true before running her again. WL.
My neighbor used to say "The speed that thrills, the speed that kills"
WHITE LIGHTNING RACING ....
Last edited by white lightning : 06-30-2008 at 02:51 PM.
sounds like i might have the same prob with my 89 indy 500 suppose the crank was rebuilt,well the hole motor from the crank up im getting spark,the mag side aint firing though "cold" when its running and it back fires alot.