Motor Compresion Help??

[yamahaman101]

I have a 1993 GTX and ran the compression yesterday on the heads and got the following: Cylinder 1= 100 and cylinder 2=90 Does this mean the engine is on its way out?? I took it out on the lake yesterday and the cooling system is flowing, oil flowing and seems to run fine with a little shake on idle. Can someone advise? Thank you for your help.

PS this website has helped me a ton and I can't say thank you enough.

 

[timmyboy76]

run it til she goes (dies). That "rough" idle could be, carb/s need cleaning/rebuilt, or just turn idle up some.

 

[yamahaman101]

Life Left

How long do you think it will last till it blows? I just cleaned the carbs and put them back on as the ski sat for 5 years till I hit the lake last week. I also noticed that the gas had a separation with some kind of clear stuff floating at the top. I know that water is heavier than fuel so not sure what this could be?

 

[kustomkarl]

The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. I hope this helps you.


Karl

 

[popasodatastie]

Not yet but Soon

if its rough idleing you could still have a lot of life or a little it just depends on how you ride. You can always turn up the idle jet to smooth it out but 100 and 90 arnt bad but deffently not good you may get by this summer but over the winter i would look into a rebulid and then you'll be ready for next spring I also have some rough idleing in my 96 but i have 150psi in each cylinder i tuned it and now it runs like a champ! Hope it helps Good luck! :cheers:

 

[Cid6.7]

Drain that gas & change plugs
Let'er Rip

 

[Josh6t_97xp]

Agreed gas and plugs cheap to do.

hopefully you can make it through the summer.
You got a winter project on your hands

 

[yamahaman101]

What If

Hey Guys:
I was told today by a friend that you could maybe reseat and improve compression on the cylinders by putting a little Mytery Marvel Oil in the cylinders and let it set for a day. He did this on a two stroke dirt bike and his compression increased by 10 psi per cylinder. Have you guys heard of this or tried it on a motor that was low on compression and had been sitting for 5 years prior to this year?

 

[yamahaman101]

Spark Plugs Answer

I have replaced the spark plugs and gas to 96octain. I have also replaced the gas lines with new hoses and cleaned the carb. Boy were they nasty and brown inside.

 

[kustomkarl]

That seadoo is designed to run on 87 octane. Unless its pinging your just wasting you money. The marvel mystery oil might help if it's been sitting around for a while...it helps to reduce the corrosion and sticking rings...Let us know if we can help out any more.

Karl

 

[ski-d00]

I would expect your compression to increase after use. After sitting for 5 years, I'm sure the cylinder walls have some rust no matter how well it was winterized/fogged. Marvel Mystery oil is a pretty potent detergent/additive and can some times cause more harm than good. I would ride it for at least 5-10 hours before checking the compression again. The idle will also improve when the compression improves but you can turn it up a little if it wants to stall.