Seadoo engine shop rebuild problems 951

[nickelz]

A week or so ago i had a post stating that i got a freshly rebuilt 951 from seadooengineshop.com. The compression after a proper break in was 120psi in both cyclinders. I asked why the compression was so low and was told because the head i sent was chopped. He also sent these pics for a reference.

The first pic is OEM and the second pic is what he said my head looked like.

Will this affect the compression and drop it down to 120 psi?

All opinions will help.

 

[LouDoo]

I'm not sure exactly what a chopped head is. Looking at the pictures it looks to me that picture no. 2 is the stock head and picture no. 1 has been polished. I'm suspecting that the head has been shaved in other words milled down to take out the imperfections. Generally this would raise the compression and you can compensate for the higher compression by using a thicker head gasket. Maybe SES used too thick of a gasket, IDK?

I'm not a professional and therefore I cannot say if this is good or bad, but if you had purchased the rebuild from a larger shop you would have received an off the shelf motor most likely not the motor that you had previously, and wouldn't have had this problem.

Lou

 

[Dr Honda]

I'm right with Lou on this one.

If the head was shaved/milled... then that would raise the compression. Also... why wouldn't they have said something before rebuilding your engine? And finally... why wouldn't hey have corrected the problem? If that head was cut too thin... then they would have never gotten the squash band set properly.

Actually from the pic... I can't tel. Personally, it just looks like someone hit it with a wire brush.

Sounds like this shop is a little on the shady side.

 

[Dr Honda]

I just checked their web site, and you have a warranty. I'd be using it. BUT....... how can they give a warranty if they aren't properly building engines?


OK... before we form a lynch mob... have you run a tank of fuel in that engine yet? Have you double checked the compression, and the gauge? A 951 will only be about 135 PSI on a fresh rebuild. So... a small leak in the O-ring on the gauge, or a weak battery will show up as low compression.

 

[SabrToothSqrl]

Heads

The 2nd photo has a better 'lip' on the top of the combustion chamber.
I'd find 951 heads similar to the first photo all the time on Ebay, and my other engine guy refused to use them... said they would not run as well.

But he didn't have a shop to work with, just his garage...

I've used red lines to identify the lip difference between the heads.

 

[Dr Honda]

I'd find 951 heads similar to the first photo all the time on Ebay, and my other engine guy refused to use them... said they would not run as well.

Well... at least your guy has a brain in his head. The reason you find cut heads on eBay for the 951 is because people cut them, and then kill the engine. The 951 really is at the peak of it's available power... and trying to add more to that engine normally ends badly. Heck... the first year of the 951 had massive failures, and they basically de-tuned them for 98.

As I said before... if that head was questionable to a rebuild shop... it should have never been used.

With that said....

Nicklez: did they send those pictures to you during the build, or after you questioned them on the low compression? If it was after... I would be suspect if that's even your head. The reason I say that is... if they thought something was wrong enough... and they stopped to take a picture of YOUR parts... then they shoudl have stopped the build until they talked to you about the potential issue.


Second... I would check the squash band right now, to see where it's at.

 

[SabrToothSqrl]

I'm curious to know the actual, on water performance of this engine... Mine says 120 as well, but starts, idles, and will shoot to 7k from idle without issue. I'm guessing it's the 220+ hrs on the starter or my $20 compression gauge... the 951 in my 02 GTX with 32 hrs on it shows a perfect 135, but the starter is much newer.

 

[Dr Honda]

I'm curious to know the actual, on water performance of this engine... Mine says 120 as well, but starts, idles, and will shoot to 7k from idle without issue. I'm guessing it's the 220+ hrs on the starter or my $20 compression gauge... the 951 in my 02 GTX with 32 hrs on it shows a perfect 135, but the starter is much newer.

Absolutely... a weak starter, or battery will show up as low compression too.

 

[xstalian]

i bought the same engine from the same guy you did and the way i checked my compresson was pulled out the plugs and cranked it , but other on here say have a charged battery pull off the injectors plugs if its a DI and hold the gas wide open and test it mine shoed up as 115 and also ground the plugs, so when i get home im going to do it see if it changes from 115 is low for a brand new motor

 

[mikidymac]

Ok, the head in the first picture is a stock head that has been hit with a wire wheel. The secont picture has had the squish area cut and that is the lip you are seeing. This cut of the squish area has increased your combustion chamber volume and thus reduced your cranking compression. The issue is not that your compression will be a little low but the big issue is that now your squish clearance is much more than the factory range and will provide noticably lower performance. If any engine builder saw this and even took a picture he should have called the customer and told them they needed a new head. This was not rebuilt to factory spec because like I said the squish can not be within spec with it cut unless he decked your cylinders too. The only way you will know for sure is to check the squish and see if it is within spec. BTW: 120psi on a new engine is not within factory spec either......

 

[xstalian]

well if my compression is low and if i sent ti back if they dont know what the heck there doing he is going to sent me the same kinda crap back

 

[xstalian]

what about all the labor there

 

[LouDoo]

If you bought the engine through a re-seller, and they installed it, I would think you would also have recourse on the installation. If you purchased the engine direct from SES, unless they will make a deal I would guess your on your own.

We've hijacked this thread from the original poster, if you have more questions please ask them in your thread or start a new thread.

Lou