Formula 670 running on one cylinder stalling at 3k - Snowmobile Forum: Your #1 Snowmobile Forum

dsmin · 01-28-2013, 10:41 PM

Hello guys. My sled is alone way out in the woods right now and I'm not quite sure where I need to focus diagnostics so I'm here looking for guidance.

It is a 1998 Formula Z 670.

Took it out this evening, nothing was unusual. Headed down the trails, made it about 10 miles out and slowed to make a bridge crossing. Right after the cross over the sled stalls out on me. Thought it was strange, it was the first time it's ever stalled on me mid-ride.

I sat for a second than gave it a pull and it started right back up but, had a low and weird sounding idle. Gave it a few seconds then went to take off and once it saw throttle it went to about 3k rpm and died out. Now knew something was wrong. Another pull and first pull starts it, still not sounding right though. Go to leave again and it's the same thing, made it to about 3k then stalled.

Took out my flashlight and set of spare new plugs and switched them out on the trail but it didn't help. I pulled one plug out at a time to check for spark and spark was great on both sides. Put the plugs back in started it back up and pulled one plug wire, the PTO side. It died out. Hooked that wire back up started it again, pulled the other wire. There was no change, that side isn't firing..

I than switched the wires to opposite cylinders with the thought that maybe I could make the good side not fire and the bad side fire but it didn't work like that. There was no change, the side that wasn't firing still wasn't firing.

After that I was clueless so I took my key and teether and made the about an hour walk back home. Searched this forum and another but I'm not real informed on what to look for. Only thing I grabbed after searching around was to pull a compression test when I get it back.

**RJ Gleason** · 01-29-2013, 01:54 AM

That would be the first thing I check too.

**smallengineguy** · 01-29-2013, 03:28 AM

Either that or there is no fuel getting to that side.

dsmin · 01-29-2013, 04:42 PM

Last night me and the gf were able to pull it back with my side by side through about 13" of snow. That was pretty fun.

The compression test is done and it's getting 155psi on both sides. Also the plug on the side that won't fire has been wet with fuel when pulling it out so it seems to be getting fuel too.

I'm not sure what's missing.

minisrint521 · 01-29-2013, 10:34 PM

try replacing your spark plug boots,sometimes they go bad.

dsmin · 01-29-2013, 10:45 PM

Tonight with the sled in the garage I had both plugs out and took a look in the cylinders with a flashlight. Looked like the side that won't pop was good and dry compared to the side that is firing. This got me to pull the air box and the mag side carb to give it a cleaning in case it was plugged.

Finished the clean and didn't get much out of it. After getting it back in the sled I took advice from another that thought my mag side crank seal might have been ate. Checked for vacuum pull through that carb compared to the good side and found that it wasn't sucking much at all.

So while it was idling on the pto cylinder I gave the primer a pump or two forcing some fuel to that carb and that was all it took to make it to fire. Guess it isn't pulling fuel after all.

Any advice, tips, possible causes or things to check while replacing the mag crank seal? It was said to be easy and it can be done on the '98 with out splitting the case. But I'll need a how to or manual as I've never been that deep in to a sled motor before.

**smallengineguy** · 01-30-2013, 03:33 AM

Spray carb cleaner into the recoil area while it's running and see if RPM's change. If so, it's the seal. Also, try switching carbs around to see if the problem moves. This will eliminate the carb as a problem for sure.

dsmin · 01-30-2013, 05:57 PM

Changed the carbs over tonight and had no change out of that cylinder. Got the can off then pulled the recoil after it was running. Sprayed in a little cleaner around the flywheel and rev up it did.

Now knowing all this, our last ride out before this all happened I did get warnings that had me ready to turn back. It had a spat of bogging out for a mile or so than we stopped and it ran a high idle for a minute. Talked about turning back than the idle dropped to normal and when we pulled out it was fine and we finished off a short ride.

I was able to get a 1997-1998 midwest manual from a member and should have the seal on order or picked up tomorrow if in stock. Maybe I'll take some pictures and post the operation.

Rczr600rider · 01-30-2013, 06:01 PM

Well, at least you didn't blow it up!

dsmin · 01-30-2013, 06:41 PM

Yes, I'm sure many knew the feel it brought readying for the compression test and getting those first couple pulls done with. For a $26 dollar fix (cross fingers) it is a great relief.

**smallengineguy** · 01-30-2013, 06:45 PM

You'll need a flywheel puller too. They come off HARD!

dsmin · 01-30-2013, 09:38 PM

Thanks for the heads up Seg.

Searched ideas for a bit then went out and pulled the recoil pulley so I could see what I was working with. Looks like I may be buying the Bombardier holder tool at minimum so the crank isn't twisted up. Maybe I can luck out and find some steel around and make one. From there hopefully the few harmonic pullers I have will do the trick.

dsmin · 02-09-2013, 08:52 AM

I am close to getting this running again but it wasn't as easy as just replacing the seal. Made it to The Crank Shop and picked up the puller and holder tools and a new seal. Good people over there. Tools worked great and had the flywheel popped off in about 20 seconds.

I found the stator housing that sandwiches the seal to the case was dangling there by the stator wires, unheld by any bolts. Seems like the previous owner had been into this area before and only put 2 of the 3 bolts back on it. I've made almost 2 seasons on it the way it was. Looks like to much stress there with only 2 bolts as one had snapped and the second the bolt held up but the aluminum mounting ear snapped off around it. This let the housing and seal pull clean away from the case and that's what took the vacuum away from the carb.

Ordered the new stator housing for a hefty price of $59.99, and the stator o-ring which the previous owner also had MIA. Just need to find 3 new M4 allen head bolts locally seeing they priced them at $2.49 a piece and they're likely around for 30 cents.

Should have it running again in about 4 days.