I have a 94 vmax 500 and one cylinder is not firing. I have relplaced the plugs, replaced the cable ends and switched plugs but only one cylinder seems to want to fire. It does not matter if I switch the coil wire either. I am getting fuel to the cylinder and I am getting spark to the plug. The sled will run on just the one plug (Which seems odd to me!) but only on the one cylinder. I live 2 hours away from the nearest shop or I would haul it in!Any ideas?
tedgoesfast
New member
did you do a spark test pull both plugs out set them on head pull it over to see if both are firing
compression test time it sounds like if both do not spark sitting on the head. you might be lucky and only have a bad plug cap. the ohm measurement is posted all over the place as it is fairly comon on older sleds.
Both plugs are firing with the same blue spark. If it was the plug it should not run when I switch them. I have not tested the ohms tho. I gues that will e after supper!
tedgoesfast
New member
as maim says compression test time
What would a compression test tell me? I guess I am baffled because it is not even firing on the one cylinder. I would have thought that it would have just run really rough.
Man, what a Christmas present!
tedgoesfast
New member
if you have fire to both cyl one cyl could be down on compression and not firing due to no compression it is a basic test you should do to rule out and engine problems
Thanks for the help. I am going to the neighbors in the AM to borrow a tester. I guess I should be hoping that all is well, but if it is, I will be back to ask what next!
daman
New member
with out comp she no run my friend..grfdave said:
you need 3 things to run, comp, fuel, spark...
a 2 stroke motor will run on 100 ponds of compression. if one cyl is at 100 and the other is at 80 it will still run but should be taken care of asap or during offseason whitchever is closer.
if the compression is good (100lb+ +/- 10% between cyls) i would check the reeds next as it might be time for a new set because they are not closing properly allowing the cylinder to flood out.
if the compression is good (100lb+ +/- 10% between cyls) i would check the reeds next as it might be time for a new set because they are not closing properly allowing the cylinder to flood out.
COmpression test
I did a compression test and the faulty cylinder is running about 60-65 and the other one is running around 110-120. I guess I will haul it into the shop as I am not really up to opening the heads etc. Thanks for all the help guys. At least now I know where I am headed.
I did a compression test and the faulty cylinder is running about 60-65 and the other one is running around 110-120. I guess I will haul it into the shop as I am not really up to opening the heads etc. Thanks for all the help guys. At least now I know where I am headed.
daman
New member
yup you have problems there......grfdave said:
Dont take it to the shop.
Tear it down yourself. Post pictures.. We can save you alot of money guiding you through it. Just post pictures of the tear down.
Tear it down yourself. Post pictures.. We can save you alot of money guiding you through it. Just post pictures of the tear down.
tomseal6 said:
-32 and no shop!! 
I run my own busines as well so I better use my time doing that to pay for the repairs!
Thanks for the advice tho and I will keep you all up to date on how it all goes. My neighbor offered to help so maybe on a weekend we might give it a whirl at his shop.
Yea its not hard at all. Id would take your neighbors offer.
My 2nd sled was a red 94 vmax 500. When I got rid of it, had 90 PSI in each cylinder. Kinda low but I think you have some seious cylinder/piston/ring problems in that cylinder.
My 2nd sled was a red 94 vmax 500. When I got rid of it, had 90 PSI in each cylinder. Kinda low but I think you have some seious cylinder/piston/ring problems in that cylinder.
daman
New member
shipping it to a dealer is going to cost some bread, i'd do it me self...
Is there anywhere online where I can get a step by step rundown on this type of job or should I spend the few dollars and get a chilton/haynes manual?
just make shure whoever does it uses oem yamaha pistons and rings. gaskets and seals can be aftermarket but if you want it to last use the yammy pistons.
heck just do a search here. lots of guys have done this many times.