Engine Overheat - Help!

markbano · Post by **markbano** » December 15th, 2007, 9:58 pm

Well, it looks like the season has ended early for one of my boys.

Our 1991 Kitty Cat overheated today. It was an odd situation. It looks like one of the posts that holds the airbox on the carb broke and the airbox fell off. Of course we didn't know it had fallen off and it was obviously running too lean. Ultimately, it started clanking and finally stopped. When I took the plug out it was smoking. When it cooled, I put a new plug it. It starts and idles fine but there are a bunch of "clanging" noises in the engine now so I'm afraid to run it further. Obviously something is seriously wrong with it. Does anyone know what the likely failure would be in an overheat situation like this? I have rebuilt snowmobile engines before - how hard is this one to rebuild? Is this a common problem with these? I spent many years around snowmobiles and never have I had the maintenance problems that I've had with these two Kitty Cats. Thanks for any insights you might have!

Markbano

markbano · Post by **markbano** » December 16th, 2007, 5:19 pm

Well... I removed and tore down the engine.

The clanging appears to be a result of excess play where the connecting rod attaches to the crank. I assume the bearing is bad.

Do most people just replace the entire crank and connecting rod all as one or can I push out the pin that holds the connecting rod to the crank and replace that bearing?

Thanks for any help you can provide!

Markbano

snodaddy · Post by **snodaddy** » December 17th, 2007, 1:39 am

Ah another rod bearing failure, Arctic Cat makes a slit rod for these things and that should fix the problem. check out obups and call Jonn he was able to get us one. Our kitty cat still has the same crankshaft and my boy smoked the engine twice, of course I was playing with jetting combinations when this happened. Got it figured out though and no problems since.

Snodaddy

markbano · Post by **markbano** » December 17th, 2007, 9:54 am

Yup - used a press and heat to remove the lower rod pin and pulled out a completely toasted bearing. I've already ordered a new bearing and a new set of gaskets and seals for the engine. Some night this week all the parts will go in the parts washer and I'll begin reassembly over the holiday weekend.

I've got two of these machines - an 87 and a 91, and neither of them runs well no matter what I do. They get hot and bog (or, in this case, burn up).

I'm getting tempted to scratch this and go to something bigger for my older boy, and then let me 7 year old daughter use this Kitty when I get it fixed.

What did you discover on the jetting? I'll check the jetting before I put the carb back on. Thanks!

Markbano

snodaddy · Post by **snodaddy** » December 17th, 2007, 11:42 pm

I can't tell you my jetting combination because we race ours and I don't want people setting theirs up like ours, but some people go with a 2.0 needle and seat and #70 main jet as a starting point, this combination works well, if you go any lower on the main jet then you risk burning up the engine. I also know that those junk idler wheels without the bearings in them need to be greased regularly or they will not spin easily, and this will cause the engine to bog down. Good luck.

Snodaddy

markbano · Post by **markbano** » December 18th, 2007, 9:50 am

Great. Thanks for the tips!

kidsperformance · Post by **kidsperformance** » December 18th, 2007, 2:16 pm

should never use heat to separate the crank..if the crank jorunal is discolored....it's junk.....word of caution when you get your new rod the lower pin and bearing and id of the new rod is still too tight....it will need to be honed out till you get .0013 to .0015 clearance....if you don't you will burn it up again.....to press a crank apart you need to make up a U plate and bolt down the jorunal with the hole that is provided in the crank...your bogging is a fuel issue.....as the piston top is getting hot and the fuel is coming in through the transfers some of it is hitting the piston top and sizzling away...plus it getting so hot it burning down the transfers and basically making things very hot in the crankcase.....a good pump gas 93 is only the best thing you can do.....and good luck fitting good 93 pump gas without all the crap in it....2.0 needle and seat with a #70 jet is a good start for a set-up with the governor tied....

markbano · Post by **markbano** » December 18th, 2007, 4:22 pm

Thanks for the help! It is very much appreciated.

We used a piston/rod press to push the pin out. Used only very mild heat. Sounds like we shouldn't have done that, though. That's what we do w/ aircraft engines so I may have picked up a bad habit.

We were not going to replace the rod - just the bearing. The rod and pin seem just fine.

Where is the best place to get the No. 2 needle and 70 jet? Dennis Kirk, or one of the vendors listed on this website?

Another good idea for me might be to just get bigger machines for my boys. I like the limited speed of the Kitty but with these machines going full throttle (sans governor) all the time, they take a beating.

Thanks again!

kidsperformance · Post by **kidsperformance** » December 19th, 2007, 7:26 am

Fox Dist.....talk to Bernie.....630-513-9700

snodaddy · Post by **snodaddy** » December 19th, 2007, 12:20 pm

Jonn Olson from obups has the 2.0 needle & seat and #70 main jet. His number is 1-888-999-3211. Enjoy the winter.

Juston

markbano · Post by **markbano** » January 27th, 2008, 9:49 pm

As a follow-up, I did rebuild the engine and it has run fine ever since.

However, I have a second Kitty Cat and it got hot today and you could hear the squeel of the bearings. I put some oil in through the spark plug hole and cooled it off, pull it a few times, and then it ran fine again.

I noticed that the airbox was loose. Could this have made it run too lean and caused the overheat? Also - it was about 33 degrees. Maybe too warm? These things seem to tend to overheat easily, which then damages the bearings. Does anyone else have this problem? I've got two of these and this seems to be a theme with them.

THX_138 · Post by **THX_138** » January 28th, 2008, 1:13 pm

Are your problems air boxes... or fuel mixtures?????

Have had a few of these sleds and never a problem like yours in all the years...I don't think it's common

markbano · Post by **markbano** » January 28th, 2008, 3:50 pm

Hi

I mix 2.3 oz of 2 stroke oil to 1 gal, 4 oz of gas - that should be 50:1, right?

I'm not sure what the problem is. I will say that we have the governors disconnected and the kids ride these things wide open around the yard so maybe we are just exceeding the design limits of this little engine. I had not heard anyone suggest that taking the governor off could do this, though...

THX_138 · Post by **THX_138** » January 28th, 2008, 9:15 pm

Disconnecting the governor and NOT doing further mods can possibly cause problems
When revving over the normal limits for the float level and the jet sizing, it will starve for fuel and run lean...
Lean is no good for your piston or the lubrication of the bottom end of a 2-stroke
An aftermarket exhaust or no more exhaust then just a pipe can create the problems you're having also

markbano · Post by **markbano** » January 28th, 2008, 9:29 pm

I've never changed the inlet needle and jet so maybe I should do that.

A needle and jet were recommended by someone on this thread. I'll try that unless you have something else you would recommend. Thanks for the help!

Kitty Cat Snowmobiles

Engine Overheat - Help!

Engine Overheat - Help!

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