1989 Force 125 Wiseco piston

[Imgonefishing]

1989 Force 125 8V9B

Had a ring break on bottom piston and it ate the piston. Compression was 138/140/140/60 The cylinder walls look good and I think a little dremil work on the exhaust port and honing will be fine there. Reading here I have picked up that Wiseco Pistons are easier to get back in than the stock one. My question is. Can I replace just the 1 with a weisco and leave the other 3 stock? Or do I have to feel the pain in my wallet and replace all 4?

 

[Frank Acampora]

Re: 1989 Force 125 Wiseco piston

Yep! You can replace only one--even if you overbore. All sizes are balanced to factory weight and look exactly like the factory stock pistons. Only difference is that they are forged and thus a bit stronger.

I absolutely HATE those semi-keystone stock top rings. For no reason, they seem to catch in the ports and break.

Wiseco pistons also have a better set of rings on them.

 

[Imgonefishing]

Re: 1989 Force 125 Wiseco piston

Thanks Frank I will get a piston on order. Clymers shows a special tool needed to get the wrist pin out. Is this absolutely necessary? Or is there a man on a budget alternative?

 

[Frank Acampora]

Re: 1989 Force 125 Wiseco piston

The special tool is absolutely necessary if you are going to re-use the wrist pin needle bearings.

Since you are going to buy a new piston complete with wrist pin and since it will require using the Wiseco bearing kit, you don't care about damage to the piston, needles, or wrist pin. SO: Use a press to push out the wrist pin without the tool. If you don't have access to a press, then hammer it out, BUT-- that won't be easy to do.

Before you disassemble, note the position of the con-rod; it is usually oriented one way. There are numbers forged into the web on one side. I forget if they go up or down--that's the kind of thing I note when disassembling then forget after assembling. Keeps my brain from getting too crowded and hurting.