717 & 787 compression

[ezekielguy86]

Ok Ive never done a compression test on my own until today. Watch may other do it I just never had my owed my own. So I picked up one at Harbor Freight since it was only $20 I figured what the hell. My question is are my numbers bad?

95 XP 717 pulled 120-121. I bought this ski last year and it runs great. I just did all my fuel lines today and let it run for 15min no problems.

97 GSX 787 pulled 131-131. Just bought this ski and haven't had a chance to ride it yet but it runs great hooked up to water on the trailer. Still need to replace the grey lines and do some little things.

Also on a side note. Like I said I did my xp's fuel lines today with all 1/4 hose is that ok. Someone said 5/16 but everything I pulled looked like 1/4.

Thanks

 

[ocod]

They are low and I would confirm with another gauge.
Healthy motors are at 150.
It will start and may run but for how long.

 

[AdamXP800]

If the gauge is reading 8-10 psi low, they are both okish

Both cylinders being that close to each other, I would assume they are fine

 

[Seadoobuddy]

I might retest them with a good gauge. WOT while testing.

Did you run it 15 minutes on the hose or in the water?
Hopefully in the water....no more than 2-3 minutes on the hose.

 

[ezekielguy86]

It was on the hose and was more like 3-5min. Is running it on the hose bad for it.

Also I didnt do the compression test WOT does that make a difference?

 

[kicker]

WOT test, most of the time will give you a higher reading. XP should be in the 135 range and the GSX 155.
If you run on the hose to long you can burn up your carbon seal on the driveshaft. I spray water on it with a squirt bottle if I need it to run linger then a minute.

Sent using Tapatalk

 

[LouDoo]

Both ski's should be in the 150 range, 120 is way low, but before you get too excited do the compression with a know good gauge. AutoZone and Advance both loan tools, borrow one and check it against yours. Compression should be checked on a cool or cold engine, with the throttle wide open, remove both spark plugs, ground the spark plug leads, turn over the engine until the gauge peaks.

Lou

 

[Seadoobuddy]

Lou is correct......but anyone who gets on the forum at just after 6am before work is addicted to it

150 for all rotax 2 stroke motors up to the 787, 135psi for the 951 motor.

 

[ezekielguy86]

Alright guys I'll give them another go tonight hopefully. Thanks

 

[Matt Braley]

Lou is correct......but anyone who gets on the forum at just after 6am before work is addicted to it

LORD KNOWS THAT'S TRUE! I'm guilty :seeya:

 

[digvid]

I had the HF pressure gauge and my numbers where way low, I then used a craftsman and a snap-on set and the numbers where normal. I took the HF one back.... its junk don't trust it...

 

[Seadoobuddy]

I had the HF pressure gauge and my numbers where way low, I then used a craftsman and a snap-on set and the numbers where normal. I took the HF one back.... its junk don't trust it...

YUP, I have a thread about the HF tools.
http://www.seadooforum.com/showthread.php?56995-HARBOR-FREIGHT-Tools&p=322186&highlight=#post322186

some like them and some don't. I'm not thrilled with them.

 

[Robj]

HF tools are junk. But sometimes that is all you need. I have some of their tools and they work fine, but they are still cheap junk. Like the saying goes, you get what you pay for.