Are Kawasaki Fan Cooled Motor bottom ends interchangeable? - Snowmobile Forum: Your #1 Snowmobile Forum

Joelk · 11-04-2009, 04:58 PM

I have several old Kawasaki FC Twins. Most are out of 71-72 vintage Arctic Cats, but one is a 81 440 out of a John Deere.

I have some 340s, some 399s and some 440s. Having read about the problems with crank seals in these motors I am planning to change them in the motors I will try to get operational again.

I have a couple 440s with very good compression and probably will want to use 440s instead of the smaller motors.

I have a 340 and a 399 with good bottom ends(except for seals), but bad cylinders and pistons. Since these are already out of the sleds and partially torn down I would prefer to reseal the cranks on these motors and then use them with 440 pistons, cylinders and heads.

Are the 340, 399 and 440 cranks and crankcases IDENTICAL. Any reason I can't, or should not, swap the 440 pistons/cylinders/heads onto the the 340 or 399 bottom ends?

What about the 81 440. Aside from the ignition components (it has CDI, other have points) will it interchange?

Thanks, Joel

**RJ Gleason** · 11-04-2009, 05:04 PM

The 399 can be upped to 440 simply by changing the pistons and jugs.
The 340 can only be a 340.

Invader440 · 11-05-2009, 12:57 PM

Quote:

Originally Posted by RJ Gleason

The 399 can be upped to 440 simply by changing the pistons and jugs.
The 340 can only be a 340.

Not true, case is the same for all Cat T1's. If you want to verify it, you can check it out on Browns Leisureworld online parts diagrams. As far as the newer cases in the Drifters/Trailfires, I've only got a parts manual for the 80 Drifters and that shows different part numbers for the 340 and 440 cases so you may not be able to interchange between these two cases.

**RJ Gleason** · 11-05-2009, 02:48 PM

The stroke of the 399 and 440 is the same.
The 340 is much shorter so it is not interchangeable with any of the other engines at all.

I have done this conversion before.

Joelk · 11-05-2009, 03:40 PM

According to several sites which sell pistons for these motors, all three, (340, 399 & 440) have a 60 MM Stroke and the bore is larger on the other engines.

There may be other differences, but it appears the stroke is the same on each.

Invader440 · 11-05-2009, 05:35 PM

Quote:

Originally Posted by Joelk

According to several sites which sell pistons for these motors, all three, (340, 399 & 440) have a 60 MM Stroke and the bore is larger on the other engines.

There may be other differences, but it appears the stroke is the same on each.

Looked it up in my master service training manual and they all have a 60mm stroke.

**RJ Gleason** · 11-05-2009, 06:16 PM

You're right about that, I misread the book. Sometimes I get the stuff backwards that I read.

Invader440 · 11-05-2009, 11:12 PM

Quote:

Originally Posted by RJ Gleason

You're right about that, I misread the book. Sometimes I get the stuff backwards that I read.

Been there, done that lol.