118 psi too low? - Snowmobile Forum: Your #1 Snowmobile Forum

sschne62 · 10-13-2009, 10:18 PM

im reading 118 psi at WOT in my zr600 is that too low?

Mrdman2442 · 10-13-2009, 11:06 PM

That is about mid range, 100 is usually the min while 120 - 140psi is great.

JheLrey · 10-13-2009, 11:43 PM

No... its fine...

**kccats** · 10-14-2009, 08:22 AM

Yes it's abit low! Everyone complains that the Cats come apart! But they expect to go 5000 miles! Freshen the motor at about 3000-3500, before it needs it! The performance starts to fall off fast as compression drops! Good time to do it, as well as some porting!

JheLrey · 10-14-2009, 09:59 AM

Are they both right on or close to each other in numbers? Is your compression tester a screw on or a push in the plug hole? Engine hot or cold? How many pulls? These things can cause it to change....

**RJ Gleason** · 10-14-2009, 10:06 AM

Quality of the gauge will also have bearing here too.
If the engine starts easily and idles well with no other issues when running, leave it alone.
Use the same gauge for subsequent testing, the current reading can be your base line.

I do suggest that you retest with the following procedure;
remove both plugs, leave ignition off, hold throttle wide open, pull the engine over as fast as you can not less than 5 times.
You may find that you get a higher reading (125-130 or better).
Do this either warm or cold. Warm engine readings will be slightly higher.

Blaine1 · 10-14-2009, 01:07 PM

Quote:

Originally Posted by RJ Gleason

Quality of the gauge will also have bearing here too.
If the engine starts easily and idles well with no other issues when running, leave it alone.
Use the same gauge for subsequent testing, the current reading can be your base line.

I do suggest that you retest with the following procedure;
remove both plugs, leave ignition off, hold throttle wide open, pull the engine over as fast as you can not less than 5 times.
You may find that you get a higher reading (125-130 or better).
Do this either warm or cold. Warm engine readings will be slightly higher.

The only thing I'd add is that you also do a "cold vs hot" test. 118 may seem low, but like previously mentioned it depends on the gauge. If in doubt, find another motor or two like yours and check them with your gauge for comparrison. Also, if you're at 120 lbs cold and 118 lbs hot, that is also good. If you're at 118 lbs cold and 100 lbs hot...well then "Houston, we have a problem."

**kccats** · 10-14-2009, 03:31 PM

How many miles? Try adding a bit of oil and retest! If it goes up, go threw it! Remember a set of gaskets and rings is only about 100 bucks!

justmytailights · 10-14-2009, 11:53 PM

sounds a littlel low,but,when you did the test did you have the throttle wide open and pull the rope until the gauge read it's highest which should be around 5 - 6 pulls. other than that the test was invalid.
justmytailights

sschne62 · 11-04-2009, 06:21 PM

thank you for the help everyone yes i tested it warm with throttle wide open and pulled it 6 times got 118 in both cylinders i have a set of gaskets on the way and will hone the cylinders and might order some rings too

polaris rider · 11-04-2009, 07:16 PM

Whats the miles on her?

kingston_rider · 11-04-2009, 08:31 PM

If the cylinders are nickasil coated, don't hone them unless your a pro as I am told they can be easily damaged. Mileage as stated earlier is a big factor on deciding on a rebuild. I bought a sled last winter, it started and ran great, within 300 miles a ring turned on one of the old kimpex pistons inside, took out one of the jugs when it did. If you aren't sure of the miles and condition of the top end, take it apart. When I tore mine down I found the piston on the side that was still intact was cracked, this sled was a time bomb waiting to go off with me having zero indication until it did.

sschne62 · 11-05-2009, 05:42 PM

4500 miles

polaris rider · 11-05-2009, 05:44 PM

although compression aint really all that low, sense the mileage is up there, id say go ahead and rebuilt... at least do rings and gaskets

sschne62 · 11-05-2009, 05:59 PM

well the main reason i want to do it is because it doesnt have good acceleration it starts and idles fine but when given gas it tends to bog and i pulled the plugs and they looked fouled they had oil on them and i read somewhere that oil on plugs indicates bad rings

**BC_Dan** · 11-05-2009, 07:14 PM

Oil on plugs usually means too much oil is being injected. Black plugs could mean the main jets are too big and you are jetted too rich.

Hesitation on acceleration, especially if it's better if you have the choke at 1/2, usually indicates the carbs need to be cleaned. Pay special attention to the pilot jet and the air screw settings. The air screw should be 1 turn out from lightly seated as an initial setting. You can turn the air screw in 1/8 of a turn at a time on each carb and see if your hesitation goes away. I have had carbs that ran great at 1/2 turn from lightly seated.

Waters88 · 11-05-2009, 09:32 PM

I would give strong consideration to rebuilding the engine if its a 'cat. I do not know why, but every other company you hear of sleds that have super high miles on engines that are not touched, but with Arctic cats, I dont hear of any of those. With how they like to blow up, i would go for a rebuild....

sschne62 · 11-05-2009, 09:40 PM

Quote:

Originally Posted by BC_Dan

Oil on plugs usually means too much oil is being injected. Black plugs could mean the main jets are too big and you are jetted too rich.

Hesitation on acceleration, especially if it's better if you have the choke at 1/2, usually indicates the carbs need to be cleaned. Pay special attention to the pilot jet and the air screw settings. The air screw should be 1 turn out from lightly seated as an initial setting. You can turn the air screw in 1/8 of a turn at a time on each carb and see if your hesitation goes away. I have had carbs that ran great at 1/2 turn from lightly seated.

it is an efi setup

600BlairMorgan · 11-06-2009, 12:46 AM

Check the ground on the elect system. if its dirty she'll give you the same issues you are describing. And don't hone your cylinders they are coated so get them done professionally or you'll have more issues than just hesitation. Did you check your clutches?

SkiDooFormulaMX · 11-06-2009, 09:41 AM

Quote:

Originally Posted by Waters88

I would give strong consideration to rebuilding the engine if its a 'cat. I do not know why, but every other company you hear of sleds that have super high miles on engines that are not touched, but with Arctic cats, I dont hear of any of those. With how they like to blow up, i would go for a rebuild....

ive had cats my whole life with 5 or 6k plus miles and 125 plus pounds on both sides. never blew one up or towed out of the woods, did plenty of towing with other lower mileage newer sleds tho. 5k id redo any top end, any sled, but not always dire.