GP 1200 COMPRESSION QUESTION

[HONEDOUT]

CHECKED THE COMP ON MY 98 GP 1200 TODAY AND FOUND #1 95PSI #2 110PSI #3 115PSI 188 HRS ON STOCK ORIGIONAL MOTOR. CHECKED IT COLD WITH THROTTLE WIDE OPEN. IS THE NORMAL OR A LITTLE LOW. SKI RUNS PERFECT. BOUGHT IT NEW AND RUNS LIKE THE DAY I BOUGHT IT.

[dank]

How long has it been sitting and was it fogged after last use? It is low on compression on #1 and #2. they should not be that far apart.

[Mpeavler1]

TO ME...sounds like your just time for a top-end prolly getting the rings worn down some and not building the same compression as it used to....I aggree with Dank tho something is amiss...is could be anything but the only way to tell is take the thing apart and see....I bet you will find the rings are just worn out and the cylinders need bored .25-.5 mil over and new pistons rings and bearings and clips and a few new gaskets and you will back up to par!
188 hours is a lot of time on a single set of rings if you ask me..../shrug [img]/graemlins/winkanim.gif[/img]
Cheers,
Mike

[Technical Support]

Correct diagnosis.

[HONEDOUT]

THANX FOR THE REPLIES. AS FAR AS SITTING UP IT RARELY DOES. RIDE 2-3 TIMES A WEEK YEAR ROUND. FOR AT LEAST AN HOUR AT A TIME. I GUESS I WILL THINK ABOUT A TOP END IN THE NEAR FUTURE.

[Technical Support]

With that low an hour count, on that engine, I can say almost certainly, if your gauge is accurate - it was at least partially seized sometime in it's past - perhaps someone ran it with the fuel switch off for a short time, or overheated it...maybe you didn't know about it. It may hold that compression for a long time, but it will eventually get worse. I would say if you didn't have a recent problem with it, just keep an eye on it. If it starts declining further, stop running it and tear it down.

[99gp1200]

It could be my gauge but the compression on my '99GP1200 was 115 on all three cylinders
when it was new with 0 hours.

[Technical Support]

Then you are 20, and 5 low on two cylinders.

[Mpeavler1]

I WOULD STOP RIGHT NOW....and tear down the thing before you ruin that crank and see whats going on!! IT could be rings worn...at your hours from hard riding....but something is wrong with it bro.....a little time now can save you big later!

Mike

[jaafallon]

I understand most of this post... But:

Is the problem that the lowest compression is on the #1 Cylinder?

What tells you that the engine "probably seized" in the past?

You said: "perhaps someone ran it with the fuel switch off for a short time."

How would I know that happened?

Regardless, thanks for all the help you guys have provided me (and many others).

Man! I like these skis!

jim

[Technical Support]

You won't know what happened until you tear it down for inspection.

The fact that all three cylinders are low, tells me that it has some scuff damage, from seizure. It should be 120-125 on all three cylinders, using a good gauge.

[MACKZILLA]

Re: GP 1200 COMPRESSION QUESTION

First of all I would look at the cylinders through a borescope and see if she had some scaring on the cylinders and how bad,if crank is ok then a top end job could prove to solve this for a few seasons or you can pop a fresh SBT in there for a few more bucks and make sure you go through those carbs you could have leaned out some on two of those cylinders,if you are still running a oil pump then check to make sure you are getting the correct amount of oil to each cylinder,this is a MUST!!!! the only drawback to pre-mix is a bad carb,but should run crappy when this occurs,myself I like to pre-mix ,gives me peace of mind,,,,,,Goodluck...