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Discussion Starter · #1 ·
Hey Folks,

still trying to figure out the lean cylinder on my sled.
question is, what are crank seals? where are they? how do you replace them? and how do you check if they are bad?

Is there one on either end of the crank? I know there is one on the clutch side which can be replaced by just pulling the clutch. Is there one on the mag side? Do you have to pull the flywheel off and such?
The mag side is the lean one.

Thanks.
 

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Which cyclinder and how do you know its running lean?

There is a complete process to check for leaking seals. It takes a few special tools to complete the diagnostic work. You should check with your dealer to see if they have the tools.

It is not a complicated process by any means (similiar to testing your cooling system on your car for leaks) but you do need some special tools and you also have to know what the recommended crankcase pressures are otherwise... if you dont have a blown seal and you exceed the recommended pressures.....you will!

Hope this helps with your question.

And yes there are PTO, Mag and Centre seals in a crankcase fed two stroke as each cyclinder must work independently of the other.

Ben
 

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Discussion Starter · #3 ·
It's the mag side.
The plug is white.
see here for the details
I thought there might be a simple way to check, kind of like checking for vacuum leaks on a regular motor (spray water, wd40,unlit propane and see if the idle changes). But then again it would be hard to get any of that behind the flywheel.
I have a part for the float coming in sometime this week, and if that doesn't fix the problem, I figure crank seals are next (if I don't park it in the bush first).

Thanks.
 

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Crank seals get hard with time / mileage, if your sled is older and or has a few miles on it yes it's time...................not hard to do but yes is a bit time consuming as it requires your splitting the crank case. AC now suggests using a special silicone they sell instead of the motorcycle products we've used in the past.
 

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Before you decide to start tearing down your motor, have the seals leak tested! Yes you can check your PTO seal with propane and see if your idle changes and you are also right, it is difficult to check the mag side and the centre seal.

It will cost you about an hours labour at a shop to have your seals checked by a dealer with the right equipment.

From there you can make an informed decision as to whether you need to go deeper into the engine.

If you have to do crank seals, you will probably be encouraged to do the bearing as well, and then it goes on from there! Its just like a renovation... you know your already there so you might as well do this and that.

Ben
 

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Its like turning your flywheel and putting your old clutch back in because its still has 50 percent of its service life left.

You might do this if your going to sell the car right away but if you are planning to keep it a while well....

New bearings are a cheap investment if you have to be there anyway (and you plan to keep the machine a while).

Yes, those bearings can probably do another 8000 miles if properly cared for.

My point was, you can, with the right equipment, perform a very simple diagnostic check first and see if you need to go there at all.

I would do the diagnostic work before I started tearing things apart.

Ben
 

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Get a can of starting fluid and while the engine is at idel spray the motor at every place a leak could be present. The cylinder base behind the drive clutch in the mag hole any place you can get it. When you find the leak the RPM of the motor will change and most of the time it will act like you flooded the moter with fuel.
 

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Followed both you posts and I see you had fuel or oil in the exhaust. In my experience I have only seen this happen 2 ways although there may be more. 1 is the choke not seating causing cylinder not to fire and just blow oil and fuel through the cylinder unburnt. 2 happened just a few weeks ago. A buddys sled was bogging and smoking like crazy. We found stator was defective after installing a backup stator we had, it ran great. I've never had a crankseal go, but I guess its possible. I would go over carbs and fuel lines again first though and set everything to the specs in the manual and switch them around to see if condition follows a carb. I would also check for a head gasket leak or waterpunp leak.
 

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Discussion Starter · #10 ·
Hey thanks for the info guys.

Lots of good info here. I'll check for leaks the best I can or bring it away. Don't really plan on keeping the sled but with everything i've done to it recently I almost should.

buuutttt, thundercat900 has reminded me again. I know part of it is the float in the mag side (the lean one) 's carb. I got the part yesterday and will install in tomorrow to see if the keeps the float from draining.
Next is the choke. I got a new cable this year and follow someones instructions to set it in another post. Sled still runs real rich on one side and real lean on other...while smoking like cwazy.

Any new tips on eliminating the choke cable from this?

Thanks.
 
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