340 trailfire Center Crankshaft Seal

KCG646 · Post by **KCG646** » Mon Nov 03, 2008 1:53 pm

How can you tell if a center crankshaft seal is bad on a 340 trailfire? What exactly does the center crankshaft seal do?

JoeRainville · Post by **JoeRainville** » Mon Nov 03, 2008 2:38 pm

The center seal on all Kawi powered Deere's doesn't wear out. It's a 'non-contact, dynamic seal' that used aerodynamics and close tollerances to work. Kawi motors in 71-75 Cat's had center seal issues that was handled by a two piece aluminum seal kit.

The outer crank seals on ANY vintage sled should be replaced if they are still original. I've seen seals as new as 10 years old that were shot. Even NOS motors need the seals replaced as the rubber hardens and takes a set.

I hope this helps,
-Joe Rainville

Deere Daze · Post by **Deere Daze** » Mon Nov 03, 2008 2:41 pm

Chances of your center seal going bad is almost impossible.The center seal on the JD kawi powerd trailfires is a "Non-Contact Laberinth Seal".In order for the center seal to be bad, your crank would have to be bent.The center seal never comes into contact with your crankshaft.Now the outer crank seals do come into contact with your crank,these seals should be changed if they are cracked,stiff,leaking or your not sure when they were changed last.

Another thing to keep in mind is that cheap aftermarket seals only have a service life of a few years if your lucky, like everything else, you get what you pay for and if you buy a cheap $2 aftermarket seal, dont expect a lifetime of service out of it.

:thinksnow:

Deere Daze · Post by **Deere Daze** » Mon Nov 03, 2008 2:43 pm

Well i guess Joe can type faster than me! lol

KCG646 · Post by **KCG646** » Mon Nov 03, 2008 2:47 pm

I was wondering if the center crankshaft seal was bad because of an issue I am having but can't seem to figure it out. MY 340 starts on the 1st or 2nd pull everytime. It runs really good for about 15 minutes and then if you leave it idle or run at lower speeds, it seems as if it starts to flood itself out. You have to keep it floored and it will spit and sputter for a minute or so and then take off like it is suppose to. I have check the float and it is sealing, I have replace all the seals on the motor, check for air leaks @ intake, new pistons, adjusted the choke to make sure it is sealing (New choke), what other possible situations would cause it to flood itself out? Is the jetting possible wrong? What size jet should I be running in it? Where can I purchase the correct size jet for the carb? I have also tried 2 different carbs and the issue is the same on both. Any help would be appreciated.

hardware440 · Post by **hardware440** » Mon Nov 03, 2008 9:28 pm

funny thing my 440 trailfire does the same thing i have new engine .my teck said but new main jet and needle and seat.mine runs great for 15 minutes then fowls the plugs .what is your air mix screw turned out to0 my manual says 1 turn. 340 is 1.5 turns .my teck said for me to try 2 turns then go from there

JDT · Post by **JDT** » Tue Nov 04, 2008 1:48 am

Without a center seal you will have no impulse to operate the fuel pump and very poor transfer of fuel to the ports.

400brian · Post by **400brian** » Tue Nov 04, 2008 2:18 am

Several years ago, we had a list member who was adamant that his Kawi center seal was bad ( I do not recall who it was now ).

As I recall, his crank end play had become excessive, damaging the center seal area, and rendering it non-functional. I believe he had to replace the case to make things right.