Another 390 Auto Engine

I owned a 390 auto like this and three other auto parts bikes. The 390 auto ran. I didn't want to part with it but a guy in pa called me from Craig's husky sight and offered to buy it. He had only one leg. The auto would be perfect for him. So I parted with all of it. We just have to help others if they have the heart and desire to ride. Do good for others.

What goes around comes around, you're a good guy!

He actually drove to my place from PA and rode the bike. I was impressed. Here's a guy with one leg who rode that 390 auto. His right leg was ok so he had brakes. Sometimes we have to wonder who the handicapped person really is. I gave him one running bike plus three parts bikes.

I would fix the neighborhood kids bikes too. Boring cylinders for them or welding cracks. It's good to give something back.

Just to bring this thread up to date. The new motor is now well and truly run in. So it was time for a proper 2 day timecard enduro. This event was run in the UK by "Vinduro UK". A great bunch of people dedicated to us old farts having fun. It took me a lap or so to work out that I had plenty of time and didn't need to ride like an idiot to keep on time. This was the last lap of day one. Day 2 was run the opposite way round. The gopro decided to quit after about 45 minutes. It did this on previous laps ! no idea why either. I do manage to throw it on the ground too !
The bike rode perfectly for both days. I did change the gearbox oil at the end of day one.

go pro's have a habit of that. sometimes the battery wont take a full charge. I cant turn mine off and on or it locks up and I have to pull the battery and loose the last file (which is always the best bit of the ride)

sometimes I get 20 mins and sometimes 2.25 hours like its supposed to

can i ask why you used Kawasaki little end bearing please ?

Because the new Wossner pistons have a different measurement between the boss faces for the pin.



This means that the alloy shim washers will no longer fit as the gap is smaller. I don't like the idea of the small end bearing wondering about either. So I looked for a bearing with the correct dimensions. Hence the Kawasaki small end !
This fits happily between the boss faces and fits the piston and rod perfectly. I use this bearing on all my Husky motors.

can-am / ski-doo Rotax small end bearings will work also.

What was the piston clearance you ended up with?

I bore mine with .1 mm clearance. The Wossner box says .08mm ! Too tight for me.

Sorry Bill, did you mean the clearance for the small end side float ?

.1 mm is what in thousands? 3.937". Almost .004"

The last 390 I bored to .0045". She lightly seezed. I opened up the bore to .0055" / 006" she ran awesome. The 430 ac specs say .004" so your in the ball park.

oh i see now......... thankyou !

Do you have the Kawie part number for the smaller end rod bearing??

grouty, tell me more about the secret coating, stuff looks great! Is it ultra high temp like 1500 degrees (800 centigrade)? How well does it resists chipping when compared to high temp rattle can paint? How well has it held up for you now that you've got some miles on your rebuild? Which by the way turned out very nice.

Hmm, I wish I could tell you more about the coating ! Rod keeps it a close secret. It is fairly high temp. Certainly more than normal powder coat. After a whole day riding, the coating is not even soft around the exhaust manifold. I recorded cylinder head fin temp of 170 degrees C during the last enduro. So pretty bomb proof there. It seems to resist chipping very well. Far better than rattle cans (IMO). I did manage to chip a tiny bit off the end of one of the fins when I fell off on a load of rocks and stones. Not sure that any paint would have survived that !
I am really happy that after a long day (weekend) with it covered in mud that was deposited on a very hot motor ...... it all washes off and leaves the finish as it was before we went out

I don't have it to hand at the moment Bill. I am sure it was in one of my rebuild posts a while back.

Okay so the secret coating is a powder coating product. That tells me its durable and 170 degrees C is pretty hot for powder coating seeing regular powder is cured around that point. Maybe they have adding ceramic to it.

Getting the color between the cylinder fins like they did with your project would be tough with regular powder. I've seen information about liquid powder coating that allows the coating to be applied in close quarters and a thinner mil thickness. I've always liked regular powder coating for its durability but disliked its thickness on the part. It hides the natural character of the vintage casted parts making them smooth looking. Looks like Rod Spry has a great product on his hands. Wish I could find something like it in the US.