720 motor compression?

[digvid]

Hey all, I'm still working on my 2000 gti project. Thanks to a few on here I'm starting to get closer to the water ....
I was just wondering if I should rebuild the motor or get another motor to drop in. Mine isn't seized but I'm sure it was ran hard and def. Not taken care of. I havent even started mine yet so I don't even know how it is yet ( the way it looks I don't have high hopes) I found a low hour motor for $500 it's still in the seadoo and he will run it for me , supposedly only ran in fresh water and the compression is 132 lb & 140 lb is that normal for the 720 and is that a fair deal or should I try and get it cheaper or stick with mine... ahhhhhhhn so many questions lol

Thanks

 

[smc0922]

Eh I'd rather see 150 in each hole, but bring your own gauge and compare.

 

[Seadoobuddy]

I would get a rebuild one (SBT) or get yours rebuild by SES and get a warranty with it. The used one will need rebuilding with in a year or so & you don't know anything about nhow it was ran.

 

[LouDoo]

For $500 no way. Besides what are the chances of a freshwater ski in FL?

You can get a fresh rebuild with a warranty for around $750.00, SBT in Clearwater, just go pick it up. What's the compression of your engine?

Lou

 

[digvid]

Lou, I'm not sure what my compression is right now. The motor is out and the starter is bad , I did try and turn it over with my ratchet but I just couldn't turn it fast enough. I was only able to get each cyl. Up to around 45 by hand... if my motor is bad I will prob. Do the SBT thing since its only about 2 hrs away I was just hesitant after reading a few posts on here about SBT .

 

[LouDoo]

Well I can't speak for others, I've got a SBT motor in my 95XP 800, this will be the third season of hopefully trouble free riding.

Lou

 

[LouDoo]

I would get a rebuild one (SBT) or get yours rebuild by SES and get a warranty with it. The used one will need rebuilding with in a year or so & you don't know anything about nhow it was ran.

Is this reverse universe day? SDB and I actually agree on something......hmmm.....

Lou

 

[Robj]

SBT builds a good product. Being so close to them I wouldn't hesitate to put one of their engines in my ski. If you have any problems you are covered by a no fault warranty.

 

[Robj]

Buying a used motor is a crap shoot. Kinda like buying a condom, I would never buy a good condition used one. Much better off getting a new or reman engine for slightly more than a used one.

 

[digvid]

OK so I just check the compression on my motor and both cyl. Are 100 each.
So what I have read so far that is way to low correct, so should I just do a top end build on mine?

 

[kicker]

Sorry to hear that it is that low.
IMO it is not worth just doing a top end. If your doing the rebuild yourself you would want to at least open up the case and check the crank, seals and bearings. I am going to guess that it will be ready for a rebuild as well.

If you plan on sending to a shop like SES or SBT then get the full rebuild so you know it is going to be good for a few years and get the warranty. There is no warranty on a topend rebuild.

 

[digvid]

OK one more question on the compression, I have the compression gauge from harbor freight and it reads 100 x2,
I also have an older one from snap-on and it reads 140 x 2 the biggest difference in the two are the one from HF has a hose almost 2 ft long and the snap-on is only about 7 in. long. Which one do I believe?

 

[LouDoo]

I would tend to believe the Snap-On, do you know the last time it was calibrated?

Lou

 

[68ragtop]

I agree with Lou. If both cylinders are within a few LBS of each other, check the gauge. There are so many POS gauge sets out there that I believe some people have already condemned good engines. I have a snap on as well, ITs very accurate. I have seen cheap gauges read more than 20 lbs less than mine. Some gauges don't come with all the correct adapters to fit the plug hole entirely. The adaptor needs to screw all the way down to the bottom of the threads just like the spark plug. Then the check valve on the tester needs to be at the bottom of that fitting where the electrode of the spark plug would normally be. If your gauge has an erector set of adaptors, I wouldn't trust it. Just My $.02

 

[digvid]

I have never had the snap-on adjusted but then again it doesn't get much use. The HF gauge has a long hose, the part that goes into the spark plug hole is open with no check valve. The check valve is 20 " away on the bottom of the gauge I'm leaning towards the snap-on.... now I get to try and get the flywheel off, I've already broke one puller lol

 

[Robj]

I broke a el cheapo puller too. Get a better one and it will work.

 

[68ragtop]

The HF gauge has a long hose, the part that goes into the spark plug hole is open with no check valve. The check valve is 20 " away on the bottom of the gauge

There's a big part of the problem. Everything on the cylinder side of the check valve, basically becomes part of the combustion chamber volume when your testing it. The more volume, the lower the compression reading will be. Not to mention the possibility of the gauge being inaccurate on top of things. If your hose is 20 feet long thats ok, as long as the check valve is at the very end of the tester. That would take longer for the pressure to build up in the long hose, but it would get there. Better testers will not only have all the spark plug thread sizes, but they will have different lengths of each thread too. Each of them with the check valve on the very tip.

Snap-on, mac, Matco, none of those are cheap, I know. But as an alternative, consider looking at the Craftsman kit. Its not bad & about half the price.

 

[68ragtop]

This one is only $60.00 Something to think about... http://www.sears.com/craftsman-compression-test-kit/p-00947089000P

 

[digvid]

i think i might get the craftsman it looks good.
on a good note i did get the flywheel off, i borrowed my friends craftsman puller. i had to really crank down on it but it finally popped off...