Compression numbers and carb help

[mikey12]

I just picked up a 99 gtx with the 951 in it and 166 hours. It had been sitting a couple years with no stabilizer. I was able to fire it up with old gas and a little starting fluid to help. It ran and idled no problem. I am going to run some fresh gas and seafoam in it. Any other suggestions? Should I go ahead and clean the carbs or do you think since it idled ok, to just run it?

I checked the compression after i ran it for 30 seconds. One was 105 and the other was 100. I know this may be low, but will it still operate in water ok? I am new to these type of engines/machine so any help or suggestions would be good.

Also, there is a tube coming out the back top left of the prop. Looks like you can connect a hose. Is this where you can start it with water in your driveway?

How you check to make sure the oil pump is working ok? Does anyone just premix the gas to be safe?
Thanks!

 

[Seadoobuddy]

Welcome to the forum.
Nice ski.
The compression should be close to 135 on a 951motor. So yours is way low....did you check it at WOT position?
Yes, that is the flush connection in the back...see my thread and also Dr Honda's one on a fuel filter.
change out any grey fuel lines for black auto lines and YES clean the carb, esp the little filter inside....I sent mine to Dr. Honda.

I wouldn't use Seafoam or any other detergent additive on a 2 stroke motor.

give me a minute to find the thread links.....

http://www.seadooforum.com/showthre...e-adapter-pics&p=296896&highlight=#post296896

http://www.seadooforum.com/showthread.php?33749-How-To-Adding-an-in-line-filter&p=276813#post276813

 

[Minnetonka4me]

Compression sounds low should be near 130. Your tester usually test low?

I recommend redoing the carbs and fuel lines if you dont know the history. #1 killer of seadoo motors.

Yes that hook up is for the hose.

 

[mikey12]

Thanks for the info! I did not check it at WOT, so i will recheck it. How easy is it to do a top end? And should the bottom end be redone as well?

 

[RodInEscondido]

There are a number of threads regarding compression testing on this forum ... common advice is to use another compression tester to verify readings ... and a third one if necessary to find 2 readings close to the same before making serious decisions.

Enjoy the forum ... lotsa good stuff and knowledge here.

Rod

 

[Robj]

I would take it for a run and then recheck the compression, especially if it has been sitting for a while.

 

[mikey12]

Yeah I will probably just clean things up and try it before I tear it apart. Hopefully it just needs to clean up the cylinders and rings to get a better reading.

 

[Minnetonka4me]

I just realized your in CO...if you are in higher elevations it might be about right.

 

[mikey12]

I am at mile above sea level. Will that really make a difference on a compression test?

 

[Spimothy Leary]

I would take it for a run and then recheck the compression, especially if it has been sitting for a while.

agreed,
if it makes it back to the ramp on the first run, its a positive sign !

i wasn't aware that elevation impacted compression #'s..

i've been sitting around 8ft since 1977 so what do i know...

subscribed ...

 

[Robj]

In Denver the atmospheric pressure is about 12.1 psia, according to google, whereas at sea level it is 14.5 psia if I remember correctly. So yes it will make a difference in the measured compression. Roughly your 100 psi at mile high would be about 125 psi at sealevel. Unfortunately the lower atmospheric pressure will also effect engine output as well.

 

[Spimothy Leary]

In Denver the atmospheric pressure is about 12.1 psia, according to google, whereas at sea level it is 14.5 psia if I remember correctly. So yes it will make a difference in the measured compression. Roughly your 100 psi at mile high would be about 125 psi at sealevel. Unfortunately the lower atmospheric pressure will also effect engine output as well.

neat... learn something every day... or in my case with seadoo's, about every 45 minutes

 

[SabrToothSqrl]

Tough call. Being the rodent 951 guru: it sounds like it will run. 166 hours is most the life of a 951. It's not always a sudden death, usually HP is lost year after year. Part of me says run it as it. Part of me says rebuild it since summer is a ways off. DO NOT premix "just in case". That's pointless. DO run the correct oil. Do swap the fuel lines. Do clean the carbs. If you don't do this for fun/a living, have a shop do your engine. You get back a basically whole new engine with a no fault warranty. If you replace the top end and not crank on a 14 year old engine.... Your gonna have a bad day.

 

[mikey12]

Thanks for tips. What is a reasonable price to pay for an engine rebuild on this 951?

 

[Spimothy Leary]

Thanks for tips. What is a reasonable price to pay for an engine rebuild on this 951?

depends on what needs rebuilt.
a complete rebuild will cost upwards to $1000

if you just need to rebuild/replace the crank, your looking at $3-400 for the crank, gaskets, and labor costs, which essentially will be dam near the same amount, in reality you can safely expect 300 as an absolute minimum on labor costs for a tear down, replace crank, rebuild.

the other option (assuming those comp numbers are right for your elevation) is to just run it....

if you decide to run it 'as is' the only downside is if it gives up on you, it might blow a hole in the cases or crack them, which is quite common... which will increase the rebuild cost by about $300.

the crank is definitely on the tail end of its lifespan based on the hours, but it might run just dandy for another 40-80 hours trouble free and for many riders, that's a full season, if not two or three.

 

[Minnetonka4me]

Man I love noticing things other people do not. Is it cuz I'm a left paw?? LOL

Ill let the other guys fill you in on prices; if it was built from my guy with an OEM rebuilt crank, and not skimping on pistons and bearings it would be in the $1500 range.

 

[Spimothy Leary]

Man I love noticing things other people do not. Is it cuz I'm a left paw?? LOL

Ill let the other guys fill you in on prices; if it was built from my guy with an OEM rebuilt crank, and not skimping on pistons and bearings it would be in the $1500 range.

true...

but SES $1K, (plus shipping)

SBT $1200 (plus shipping)

but i'm ONLY ordered one SBT engine (for my personal use) and that was two weeks ago, because the ski i'm putting it in will be my 2nd ski for about a month or two, then listed at top dollar prices, and I figured an engine with 10ish months left on the warranty would be a selling point. a vast majority of the time for me i'm ordering a crank and or a top end and nothing more, and if my cyl's are bore-able, i'm usually boring locally and just ordering wsm's.

with that said,,, yes,,, if you don't cut corners and it will be a ski for either my personal use or for somebody I know, it really does cost more to do it yourself, but its done RIGHT ! Its a concern to have it done right for me, because I expect to put a minimum of 100 hours on in a season.

 

[mikey12]

I ran it a few times yesterday with fresh gas. It idled just fine. Both cyl were about the same. I then tried another gauge, and one was 110 and the other 120. Both of these compression testers are 20-25 years old. I will borrow a newer one from a friend and give that a try. The motor was also warm, but I feel a little better about those readings. Thanks again for your help everyone. It is awesome how so many experienced people are willing to chip in their 2 cents!