79 Jag Bogging down - Snowmobile Forum: Your #1 Snowmobile Forum

BLinindoll · 01-25-2005, 05:21 PM

My friend has a 79 Jag. It will run fine for a while, then it will eventually start to bog down. Sometimes you can keep it running by pumping the throttle, then it will be fine for another minute or so. Sometimes it will just die when pumping the throttle. Thought it might have been the fuel filter so we changed it but it does the same thing. Then we thought it was the fuel pump. Changed it and it does the same thing. Changed the plugs, eventually will do the same thing. Figured it might be fouling them, so we changed them AGAIN. Was fine for a few minutes and bogged again. We eventually ran out of plugs, so for whatever reason we decided to just switch them around. Was fine for a little while and again, bogged down. If we just waited without doing anything with the plugs, it would not fire up. If we played with the plugs, it would fire, but not run for long. A Shop told him it is a bad crank seal. If it were, wouldn't the engine just rev out of control from too much air? or would it just bog down because it was pulling too much air instead of an air fuel mix, causing a lean situation? He is running about 32:1 mix. Hes gonna try 40:1. Any ideas anyone?

kingmort · 01-25-2005, 08:38 PM

I have seen one do excactly that from a bad crank seal before.

I'd stay with the 32-1 ratio.Too much oil is alot safer than not enough and Ive never seen an engine die from too rich an oil mixture.I used to always run 20-1 in everything.

**smallengineguy** · 01-25-2005, 09:38 PM

How do the plugs look? Is one different from the other?

BLinindoll · 01-25-2005, 11:22 PM

actually at first, the right cylinder gets greyish and the other is fine for a little bit longer, then it gets grey as well... like a dark grey. If it were the crank seal, what would cause it not to start unless it sits for a few minutes. I dont think playing with the plugs actually does anything besides take time.

Another question while im at it. What exactly does a fouled plug look like and what is it cause by usually. It's weird how i know a lot about some areas, but completely clueless about others. I have a feeling none of my frirends that I have talked to actually knows what one looks like. I honestly think they have been throwing out some perfectly good plugs.

**smallengineguy** · 01-26-2005, 06:45 AM

Fouled plugs can be describes, as wet, black and oily when removed. Brown, gray or whitish aren't fouled, but gray/white is a sign oof a lean condition.

BLinindoll · 01-26-2005, 12:07 PM

well then it would make sence to be a crank seal. thanks.

void · 01-28-2005, 04:24 AM

I have the same problem with my Pantera –80. Let me know if you get it running…

BLinindoll · 01-30-2005, 10:06 AM

turns out to be one blown cylinder... hes having a new piston a rings put in.

kingmort · 01-30-2005, 07:11 PM

If he's going to all the trouble, tell him to get a new set of crankseals put in at the same time.There has to be a reason that it took the piston out.