low compression

[djkorn1]

yeah go ride it. i'm at 168 and 154 in my ski still starts and runs great until it doesn't i'm not touching it.

That ski is ticking...... KA-____!

 

[chrisdoc0608]

Same head with new rings,new head gasket. Then a complete top end from another boat, including head and cylinder.

new base gasket? I wonder if the base gasket may be thicker than it needs to be. Check your squish

 

[Naples]

The base gasket I used seemed really thin. Ive got a spare in my hand that seems to be thicker than the one im currently running. Could this be the problem? Or would the thinner gasket make the compression higher?

 

[chrisdoc0608]

a thinner base gasket would reduce the squish so compression would raise

 

[Naples]

Im ing lost...

 

[Waternut]

hmmm... Sounds like the only things that weren't changed were the crank, case, and reeds. Since the cranks should be the same, I can't imagine it'd be any of those. Maybe your starter is going bad or the wires are corroded and not giving the starter enough juice to turn over fast enough.

Are you checking the compression the same way on both? Is the throttle wide open and a disconnected spark plug in the other cylinder? Is it actually the same battery?

 

[chrisdoc0608]

Im ing lost...

CHECK YOUR SQUISH then you can determine if it is a thinner gasket you need, or if there is another component like a weak starter (i doubt it) that is causing the problem

 

[Waternut]

Since he didn't understand how porting affected compression, I doubt he'll understand how to check his squish.

I started explaining it but figured a guide online would work better and I found this... http://www.seadoosource.com/squishgap.html

 

[chrisdoc0608]

you can also check out the tech faq, It shows step by step. make sure you use the non acid core solder, and if I recall your squish should be somewhere around .045-.055 but you need to double check that

 

[agua]

get a head put on it if its a stock one. i put one on my 650 and it has 185 even

 

[Algonquin]

Porting doesn't matter, since he pulled a topend that had 150/150 then put it onto another lower end and now it has 135.

Do a leakdown test, you could have a leak somewhere. I would guess bad reeds. When less air is being forced into the combustion chamber there is less to compress, yielding lower numbers. Or as mentioned a weak starter, or battery.

If the same thickness of gaskets were used squish will not be affected, if different gaskets used, then yes your squish should be checked.

Also for the other post, 168/154 is only a 9.1% or 8.3% difference, depending how you look at it. Just run it.

 

[Naples]

Thanks for the replies everyone. I'll let you know what happens.