sledy99600
New member
All,
This is my first post. Bought a 99 vmax 600 twin (stock?) after 30 years without sledding. Only 3000K - 1800mi that should have told me something ... I did not notice it had a fresh top (new gasket).
Pulled hard and ran fast but backfired a lot when I got it - that was a bad coil. Then ran great but burned 4 quarts oil per tank and occasionally bogged after sustained high speed. Carb rebuild seemed to solve bogging issue and the plugs looked clean and dry after I worked with oil pump and cable to get it down to 1.5 quarts per tank by mid season ... then it died with no spark.
Bought new CDI, coil - nothing. Replaced stator and it lived again! Pulled hard up to about 75mph (as before stator) which is all I need ... ran for about 3 hours made a funny air sound running down a lake at 75mph for about 4 minutes. I stopped and checked boots etc - looked fine. Ran ok for an other hour then died all at once coming down a hill on a trial.
Got it home. I have spark, but I find compression is only 104 in #1 and 50 in #2
No glow in the headlight when I pull it over.
I don't know where to start. I have tried to find a service manual online.
I think I should check the reed valves before tearing the engine down. How do I access the reed valves and what do I look for?
Another stator is $175 from the distributor.
I have a spare unused CDI I paid $200 for in the Yamaha part bag (8CR-00) - tested it works as does my original (8CR-10) I could trade it for new pistons/rings if I find I need them.
Any ideas would be appreciated
This is my first post. Bought a 99 vmax 600 twin (stock?) after 30 years without sledding. Only 3000K - 1800mi that should have told me something ... I did not notice it had a fresh top (new gasket).
Pulled hard and ran fast but backfired a lot when I got it - that was a bad coil. Then ran great but burned 4 quarts oil per tank and occasionally bogged after sustained high speed. Carb rebuild seemed to solve bogging issue and the plugs looked clean and dry after I worked with oil pump and cable to get it down to 1.5 quarts per tank by mid season ... then it died with no spark.
Bought new CDI, coil - nothing. Replaced stator and it lived again! Pulled hard up to about 75mph (as before stator) which is all I need ... ran for about 3 hours made a funny air sound running down a lake at 75mph for about 4 minutes. I stopped and checked boots etc - looked fine. Ran ok for an other hour then died all at once coming down a hill on a trial.
Got it home. I have spark, but I find compression is only 104 in #1 and 50 in #2
No glow in the headlight when I pull it over.
I don't know where to start. I have tried to find a service manual online.
I think I should check the reed valves before tearing the engine down. How do I access the reed valves and what do I look for?
Another stator is $175 from the distributor.
I have a spare unused CDI I paid $200 for in the Yamaha part bag (8CR-00) - tested it works as does my original (8CR-10) I could trade it for new pistons/rings if I find I need them.
Any ideas would be appreciated
Last edited:
Throttle Junkie35
New member
Take the carbs off and clean them and look for a possible clogged main jet or other dirt issues. Then pop off the flywheel and inspect the crank seal for leakage. If there is, it would be time to replace them. Sounds like you have other issues if your only getting 75mph wide open. Should be more like 90-95mph.
braindead1684
Member
if you dropped to 50 psi you need internal work plain and simple. pull the head and inspect I would bet you have a bad ring if lucky you will just need new rings.
Check your plugs and piston wash based on some pics you can find with a search on here, this will give a good indicator of rich/lean to decide how much further you need to dig in.
Check your plugs and piston wash based on some pics you can find with a search on here, this will give a good indicator of rich/lean to decide how much further you need to dig in.
sledy99600
New member
Thanks for the info.
I live in the Toronto area, but spend weekdays 4 hours north so there will be a delay for the repair and any updates.
So I guess no point in looking at reed valves?
I found a service manual online - it arrives in mid April from the US.
I will pull the carbs, flywheel and head off next weekend and look for pics for comparison.
Thanks again.
Too bad I am missing the end of the best sledding year in the area in thirty years
but it was fun while it lasted.
If anyone is interested sled conditions are still great north from Barrie, but it can't last long with the sun - likely another 2 weeks which is very unusual for this area from what I hear.
I live in the Toronto area, but spend weekdays 4 hours north so there will be a delay for the repair and any updates.
So I guess no point in looking at reed valves?
I found a service manual online - it arrives in mid April from the US.
I will pull the carbs, flywheel and head off next weekend and look for pics for comparison.
Thanks again.
Too bad I am missing the end of the best sledding year in the area in thirty years
but it was fun while it lasted.If anyone is interested sled conditions are still great north from Barrie, but it can't last long with the sun - likely another 2 weeks which is very unusual for this area from what I hear.
Throttle Junkie35
New member
At the very least you need a piston and rings in the bad cylinder. My first post was to find out why you burned it down. Your reeds are probably fine and you can inspect them when you tear the motor down. If you have bad reeds the sled would be very hard to start and sound like its running on one cylinder until you get the RPM's way up there. Either way, low compression is a bad piston/rings.
biglsells
VIP Member
x2 on what Throttle said, if you have 50 psi or even 104 in a cyl your problems are bigger than bad reeds. I've burned down these twins a couple times, once was from a bad pto seal.