98 Form Z only idles on one cylinder - Snowmobile Forum: Your #1 Snowmobile Forum

**smallengineguy** · 11-04-2012, 05:35 AM

Posted for someone else:

I have a 1998 Formula Z 670 and when i got it it ran fine 50km latter i blew the mag side piston, i rebuilt the top end but after rebuild it didnt run right, however the side that blew ran like a champ but the clutch side wont run at idle. ive swapped carbs around and it runs the same so i know both sides are getting fuel, both sides are getting spark and both sides have 145 psi. I was always told spark fuel and compression means combustion but not in this case. Also the side that wont run has coolant leaking from the head bolt closest to the RAVE. if you can help me that would be great.

**RJ Gleason** · 11-04-2012, 08:52 AM

Prolly the problem, coolant leaking into the cylinder.

Beandon422 · 11-04-2012, 12:38 PM

ive torn the top end apart again, drained the coolant flushed the bottom end like i was told to do, changed the plugs and re-cleaned the carbs, still the same problem. The pistons rings and cylinders are all good. It wouldnt be getting coolant as i have not put any more in it.

**smallengineguy** · 11-05-2012, 03:53 AM

Dose it kick in at higher RPM's?

**RJ Gleason** · 11-05-2012, 05:06 AM

Also, does the exhaust have a sweet smell to it?

IRONDOG · 11-05-2012, 08:46 AM

Quote:

Originally Posted by smallengineguy

Posted for someone else:

I have a 1998 Formula Z 670 and when i got it it ran fine 50km latter i blew the mag side piston, i rebuilt the top end but after rebuild it didnt run right, however the side that blew ran like a champ but the clutch side wont run at idle. ive swapped carbs around and it runs the same so i know both sides are getting fuel, both sides are getting spark and both sides have 145 psi. I was always told spark fuel and compression means combustion but not in this case. Also the side that wont run has coolant leaking from the head bolt closest to the RAVE. if you can help me that would be great.

You do know that the headbolt over the RAVE valve is shorter than the other bolts, right? The two short headbolts must go in their proper location over the RAVE valve. Also the four bolts that hold the cylinder to the crankcase have to go in their proper locations. The two longer bolts go on the front of the cylinder, the two shorter on the rear. If you get any of these mixed up you will have water leak problems.

Beandon422 · 11-05-2012, 03:38 PM

IRONDOG - yes all head bolts and cylinder-to-crank bolts are all in proper spots. and all torqued to 21 foot pounds as per manual states.

RJ - No there is no sweet smell, the exhaust smells like normal 2-stroke exhaust

SEG - It seems to kick in at about 4500rpm. atleast thats the rpm its at when i can pull the plug on the mag side ( side i know runs) and keep it running. however once i have the clutch side going and mag side with out a wire, full throttle gets about 2500 rpm and sounds really boggy.

Could this issue be a crank seal on clutch side? out of everything ive been told this seems to be where it may come down to. I have no problem tearing down the motor and getting the crank redone but i want to make sure 100% this is the issue before i do it.

**smallengineguy** · 11-06-2012, 03:50 AM

How does the plug look? If it's really light colored, it's lean, which would point to an air leak. Sounds like that's the issue. Spray carb cleaner around the clutch seal while it's running. If the RPM's change, that seal is bad.

Beandon422 · 11-06-2012, 11:15 AM

is it possible to change the seal without taking the motor apart?

**smallengineguy** · 11-06-2012, 07:05 PM

You need to separate the crankcase halves to do it, but you don't have to take the top end apart.

Beandon422 · 11-06-2012, 08:13 PM

thanks, but found a guy with a 670 that works and is willing to trade me motor plus 200 for his working one, i figure this is my best option.