Super Jet Stuck piston pin!!

[ticega306]

Short version
Piston pin bearings rusted and crapped out with lack of use. Removed cylinders and pistons cant move. Best case scenario i'd need to replace pin, bearings and clips. Pins however are stuck, I can't get them to budge in either direction. Any recommendations on how best to remove stubborn pins without damage to the pistons?


Long version
My ski has been sitting with little/no use for a while (5 to 6 months) after a fresh top end rebuild about a year ago. The last time it was ridden engine ingested water. All the water was drained out and spit out with the spark plugs removed. The engine was fired up with new plugs and ran on the hose for a while. This was about 5months ago and it hasn't been ridden since.

Not surprisingly the egnine wold not turn over when I tried starting it last week. The engine was not seized but very difficult to turn over even by hand. I removed the engine from the hull and put it on the bench. I removed the cylinder head to have a look and all looked ok. Kept trying to turn over by hand, it turned but was stiff and started to feel obvious signs of failed bearings. Removed cylinders and lower rod bearings (crank side) look good and are smooth. Piston pin bearings however are shot. With the cylinders removed there is no way I can pivot the pistons about their pins. I removed the clips on both sides of the pistons and tried to press the pins out with no success. I tried tapping lightly but they won't budge.

I'm now trying to find the best way to remove the pins without damaging my pistons. The are fairly new pistons and don't want to have to buy new ones. Any and all suggestions are welcomed.

 

[fx1mark]

how about buying a c-clamp, and grinding down the rotating end so it fits into the side of the piston. then use a piece of wood on the other side of the piston go you don't damage it. if it moves the pin all the way flush with the side of the piston and you need to push it more, drill and hole in the wood for the pin to through and place something between the clamp and the hole like a metal plate. the you can push the pin into the hole in the wood.

 

[Waternut]

I'd be more worried about bending a rod hammering on the wrist pin...

 

[Seanc]

HEat and a GOOD penetrating oil will be your friend. When hammering on it make sure to support the rod some how as to not bend it.

 

[fx1mark]

you can also search on ebay for "piston pin puller" and buy one, or fabricate one using a long threaded bolt, with a piece of pipe large enough for the pin to go into, and a stack of washers. tighten the bolt and pull the pin into the pipe.

 

[Joker]

HEat and a GOOD penetrating oil will be your friend. When hammering on it make sure to support the rod some how as to not bend it.

X2 take a piece of sturdy wood (I use oak) and cut a notch in it big enough for the rod to slip into it. Turn the coupler by hand until it runs the piston down hitting the wood. That should be enough support for you to heat and PB Buster the pin to get it out.

 

[Kny21]

Cut the rods and work on each piston separately. While free from the crank you can set up in a vise and go to town.

 

[Seanc]

Cut the rods and work on each piston separately. While free from the crank you can set up in a vise and go to town.

Except then you toast a perfect crank possibly. Aluminum expands much more than your steel piston pin. All else fails cut the piston up around the rod then go to town. And if all, all else fails dasa 1200cc PV motor will bolt up

 

[ticega306]

Thanx for the input guys.

First thing im gonna try is a DIY "piston pin puller". An image search on google got me the following pics. Pretty sure I've got enough lying around the garage to put together something like these.

I don't like the idea of hammering or banging on the pins. My rods, lower bearings and crank are fine and don't wanna risk damaging any of them. worst case scenario I'd accept to loose the pistons and cut them out like seanc mentioned.

 

[Kny21]

I guess I'm the only one going out on a limb here with the thinking that if your wrist pin bearings are that F'd your crank isn't going to be much better. :jester: Even so then wrist pin journals are probably pitted to hell and it's going to negate everything.

Go ahead, cheap out and save the precious pistons and reuse that bad crank. Expenses are going to go up when you need a complete motor, cases and all. :smashfreakB:

 

[fx1mark]

Well. he will probably find out shortly. the pins might come right out, or not.

 

[Tyler Zane]

she looks a tad lean to me.. :shrug: zero piston wash and plenty of carbon on the underside of crown. this might be why your piston pin is hard to get out.

looks to be some scuff marks on the skirt in that first pic too.

 

[BruceSki]

I guess I'm the only one going out on a limb here with the thinking that if your wrist pin bearings are that F'd your crank isn't going to be much better. :jester: Even so then wrist pin journals are probably pitted to hell and it's going to negate everything.

Go ahead, cheap out and save the precious pistons and reuse that bad crank. Expenses are going to go up when you need a complete motor, cases and all. :smashfreakB:

I was going to type out a long winded response like this too but he seems to have it covered. Why did you tell him otherwise?!!!!

That crank will be mint!!!

 

[ticega306]

was able to work on the engine over the weekend and got both pins out with much less effort than i expected. twice last week and again this week i had sprayed WD40 generously under the pistons and let it sit till this weekend. i took some crappy cell phone pics that i'll post later.

i used a 3/8" threaded rod about 12" long passed through the piston pin. had a long 1/2" socket on one end pushing the pin and a peice 1.5" pvc on the other end to recieve the pin. put a nut and washers on either end and started tightening to put pressure on the pin. using a heat gun i heated the pistons till i had to wear gloves to hold them. continued tightening and very easily the pins just pushed right into the pvc peice.

there was thin rust all over the bearings and the needles would not spin easily. i sprayed them with WD40 and they cleaned up well and the needles now spin easily and smoothly. the pins look marked but are smooth to the tuch. the running surface on the rods is also smooth, there are some marks but no pitting.

with the piston removed i could inspect the rod bearings on the crank again and they are good. they spin smoth with no vertical plan and the usual lateral play is within tolerance.

so far looks like ill only be needing new pins, bearings, and circlips

 

[fx1mark]

Cool, I was wondering if you ever got the pins out. I am sure you are happy the damage wasn't too bad.

 

[Tyler Zane]

You still might want to check your tune. That carbon build up on the underside of the piston is a result of the piston crown getting to hot (lean mixture) and burning the fresh gas/oil charge entering the crankcase.

 

[ticega306]

You still might want to check your tune. That carbon build up on the underside of the piston is a result of the piston crown getting to hot (lean mixture) and burning the fresh gas/oil charge entering the crankcase.

Thanx for the concern tzane but those are not my pistons. I pulled those pics straight off a google image search. I posted them to show the ideas I was gonna use to try to pull the pins.

 

[motoman96]

Your crank is toast. When the yfz450 first came out I had this problem. Got the pin out, reassembled, then the rod snapped destroying the entire motor. Yamaha sent a complete drop in motor which is unheard of, don't risk it.

 

[Tyler Zane]

Thanx for the concern tzane but those are not my pistons. I pulled those pics straight off a google image search. I posted them to show the ideas I was gonna use to try to pull the pins.

Oh, I just assumed those where yours. Good thing they aren't! :biggrin:


Unfortunately you did mention rust on the pin bearings, and the crank bearings are exposed to the same elements, so like a few others have said, your crank is most likely done. Even if it appears fine, its pretty risky to run it.