How to check/test for bad crank seals? - Snowmobile Forum: Your #1 Snowmobile Forum

Joelk · 10-31-2009, 09:59 PM

I have several older Kawasaki FC engines. Some in sleds, and some not, and want to try to figure out which ones are best, and swap them into the best sleds.

I can get a general indication of the compression by how hard it pulls and can also do compression tests, but I'm not familiar with how to check for bad crank seals with engines out of the sleds.

How would you recommend checking for bad crank seals with engine/s out of sled?

If in sled, (if it will start/run) I have read to check by spraying carb cleaner etc around the seals to see if it changes speed. Is this a good test? Any other/better tests.

Have heard the Kaw FCs had a lot of issues with crank seals. Can they be changed W/O seperating crankcase? Any tips?

What about the center seal. Do these often fail and it imperative that they be replaced if bad? How would you check to see if they are bad?

Thanks, Joel

YamahaSS440 · 10-31-2009, 10:52 PM

All i know is how to test the clutch side seal. Idle the engine and spray a small amount of starting fluid on it and if the motor revs up, its got a bad seal.

**BC_Dan** · 10-31-2009, 11:00 PM

With the engine out, about the only way would be a leak-down test using a tester...

Here's a link to some info on leakdown tests...

Pressure Testing - - ATV at Off-Road.com

Invader440 · 11-01-2009, 10:51 AM

Quote:

Originally Posted by Joelk

What about the center seal. Do these often fail and it imperative that they be replaced if bad? How would you check to see if they are bad?

Thanks, Joel

Only ones you have to worry about are the 71-73 engines with the old style center seal and those can be updated with the 2 piece center seal with O rings. 74 and up had the new style seal with the O rings.

Joelk · 11-01-2009, 07:14 PM

BC Dan, thanks for the link. It should work for end seals, but what about the center seal. Any way to detect if it is bad.

I have about 8 of the 71-73 Kaw FA motors.

Is there a way to test for the center seal being bad and what effect does it have on how the engine runs? I assume it would not make the engine run lean (at least not like an end seal would) but what effect does it have when it is bad?

Can the end seals be removed and replaced without seperating the cases?

If the seals are fairly cheap and can be replaced W/O teardown. I may just change them if I don't have to split the cases.

**RJ Gleason** · 11-02-2009, 09:32 AM

The F/A engines were not so much the problem with the center seals as the fans were.
To test the center seal, you would only pressurize one side at a time.
You can change the end seals without splitting the case, but you must use some sealer when you put the new ones in.

Joelk · 11-02-2009, 04:44 PM

I typed FA when I meant to type FC. All of the Kawasaki motors I have are Fan Cooled.

I tore one down today to see what I was dealing with. The prior owner had already removed the scored pistons and cylinders.

The crank, rods and crankcase appear to be in good condition, but the seals were definately bad. It looked like they were loose on the crank, and the one on the clutch side also had corrosion around the outside of the seals where they sealed to the case. Probably would have leaked in both places.

The center seal also appeared to be very loose and had corrosion around it.

The way it looked, I think I will probably want to change ALL the seals in any of my Kaw FC engines before running them.

Looks very easy to change the outer seals, but not so easy to change the center seal.

How do I change the center seal? I may be able to cut it off the crank, but how do I get a new one back on.

I heard that they redesigned the seal on later Kawasaki engines. Can the new seal be used in the older engines and can it be installed without pulling the crank apart?

**RJ Gleason** · 11-03-2009, 10:48 AM

The new replacement is a two piece with O-rings that you have to get on it.
You will not have to split the crank to use these.

Joelk · 11-03-2009, 09:40 PM

I think I have seen a photo of one of the "new style" center seals. Appeared to be an aluminum circle, cut in half and had two O rings around it.

It makes sense how it will seal to the case, but not clear how it will seal to the crank.

O rings there also? If so, how do you get them over the assembled crank?

What keeps the seal from moving side to side?

Joelk · 11-04-2009, 04:38 PM

It appears something is wrong with my system. I got an E-mail indicating RJ had replied, but don't see the reply when I get to the thread.

Some additional ?s

What seals the inside of the new style seal to the crank?

I removed an old center seal by cutting it with a die grinder, then twisting till I got it off. I got it off OK, but am wondering if there is any better way to do it, as I have several more to do. Any suggestions of a better way to get them off?

**RJ Gleason** · 11-04-2009, 04:56 PM

There are flat rubber half rings on the inside and the O-rings hold it in place on the outside and make a tight fit between the case halves.