all right i got a 660 raptor. it's firing and gettin gas but it won't run. so i pull out my plug and check my compression. It's only got 30 lbs of comression. So i pull my valve covers off and the intake valves look fine, the exhaust valves seem to be workin right except for when they close one of them opens back a little is this normal. Why would it not have much compression. Please help. Thanks

 

It opens back up a little because of the decompression pin. If the quad is not turning over fast enough (IE started) then the pin will keep one of the exhuast valves slightly open to help it turn over quicker while starting.

How long have you had this Raptor? Has it ever ran right since you've had it? Is the parking brake on? Are the wires for the parking brake making good contact at the handlebars?

You'll need to give alot more information about what it is and isn't doing before an educated guess can be made to try and help you out.

 

well i've had it for a few months. It ran when i first got it. I parked it one night then the next morning it wouldn't start. I checked the plug and it wasn't firing. So I ended up replacing the stator which made it fire. but now the compression is low. Wouldn't the parking brake wires keep it from firing. Could it possibly be a stuck valve. or some how got of time. any help would be greatly appreciated. Thanks

 

Check your piston rings and gaskets on the topend.

 

It could be as simple as a valve adjustment or as complicated as a wire grounding somewhere. I believe you need to remove the decompression mechanism before you can get an accurate compression test. If it idles fine but won't rev then I'd check the parking brake wires that connect to the handlebars. If it starts and stumbles all over the place it could be many things but try taking out the CDI, keeping all the wires connected and look at where all the wires plug into it. Mine rubbed through the wires and one or more were touching, making it run real bad. Seperated them,. taped them up and was back in business. Good luck.

 

it is really to just remove the parking brake setup and block off the rear caliper i did this might solve your problem the brake can cause alot of problems if not adjusted right so remove it you can buy a new perch and block off plate on ebay for like 25 bucks