compression

[marksdoos]

I HAVE (2) 1998 SEADOO GTX LIMITED. I THINK THEY ARE 947cc I JUST BOUGHT THEM NOT RUNNING 2 DAYS AGO. WOULD LIKE TO CHECK THE COMPRESSION. DOES ANYONE KNOW WHAT THE RANGE SHOULD BE?
THANKS FOR ANY HELP.

 

[voodoo]

Look for 150 minimum, open the throttle and ground the plug cables - then add a spoon of oil and repeat.

 

[Dr Honda]

Look for 150 minimum, open the throttle and ground the plug cables - then add a spoon of oil and repeat.

NO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Never add oil to check compression. I can take a crap engine and get it to read high if I use oil to seal the rings.

150 psi is the factory spec. You should run fine with anything over 135 psi.

How To:

Start with a cold engine.

1) remove the plugs, and ground the wires
2) install the compression tool
3) Hold the throttle open
4) crank until you see a peak reading. (normally 4 or 5 revolutions)
5) repeat for other cylinders.


NOTES:

1) You should not see more than a 10% difference in the cylinders.
2) you may want to put a rag over the other open spark plug hole, or you may get sprayed with fuel/oil.
3) Make sure your battery is fully charged.

 

[marksdoos]

thanks for the help. that tells me i have 2 crap engines. one locked up and one with bad compression.
but only paid $500 for 2 doos & double place trailer.
think i can still double my money.

 

[TheSubwayGuy]

You should be able to double your money easy...

 

[seadooya]

you'll have atleast, 2500 buks, in the motors.

 

[marksdoos]

you'll have atleast, 2500 buks, in the motors.

even though 1 is locked up and the other has lo compression

 

[seadooya]

is the paint, still on the head bolts.

 

[1997sporsterholland]

have a 1997 sportster, turned motor over with carbs pulled, got 115-120 compression on both cylinders. still had other plugs in each time, think i did something wrong or there is a problem. can't believe rings wnet bad in both cylinders at the same time????

 

[Dr Honda]

have a 1997 sportster, turned motor over with carbs pulled, got 115-120 compression on both cylinders. still had other plugs in each time, think i did something wrong or there is a problem. can't believe rings wnet bad in both cylinders at the same time????

If your battery was good... then leaving a plug in the other jug is fine.

Sounds like its time for a rebuild.

 

[got wake?]

even though 1 is locked up and the other has lo compression

you might want to do a leak test. if you are lucky, you might just need to adjust the valves. if one is too tight, it'll lose compression. after i got the heads back for my 4-wheeler from getting P&P, oversized valves, titanium springs, and new cams, one was too tight and was reading 155 psi and the other was reading 210 psi. adjusted the valves to the builders specs and both are right at 210.

if you do a leak test, 0-15% is excellent condition, 16-25% is good condition, 26-40% is fair condition, and over 40% is poor condition. listen for air leaks when it is pressurized. if you hear air in the TB/intake ports means leaky intake valves. if you hear it in the exhaust, leaky exhaust ports. if you hear it in the crankcase, worn cylinders or rings. it might also be shot valve seals, if you still have low compression and the valve clearance is right.

 

[1997sporsterholland]

rebuild carb or engine? this is a 2 cycle engine, no valves- right?

 

[got wake?]

rebuild carb or engine? this is a 2 cycle engine, no valves- right?

ah hell, i'm a dumbass, lol. i'm so used to working on 4-strokes i don't even think about the type of motor usually. if ya'll ever get into can-am ATV's i can tell you how to do darn near anything on them. i've got no experience with 2-stroke motors, though.

 

[marksdoos]

is the paint, still on the head bolts.

yes the engines look great and have not been touched

 

[Wire4Money]

I believe the 951's had 135psi from the factory