Question about Wiseco Pistons

[Jiggz]

"Ignore the warning to provide extra clearance--this is for racing only. I use Wiseco exclusively on my engines. They are forged, which is stronger than stock. They are easier to assemble, and they come complete with wrist pins and rings."

This is comment from Frank A from previous thread. My question is if these pistons with wrist pins (& rings) are pressed type or uses circlips. Also, does that mean the existing rods and caps with bearing can be used with these pistons?

My '89 125HP started misfiring on the way home but made it the docks. Upon flushing it was not idling properly. Did compression test and #3 is reading 60 PSI compare to the 125's on all other cylinders. Took the head off and the cylinder walls are in perfect shape. There is a little ding on #3 piston around 11:00 but it looks like it's been there for awhile. I have yet to remove the carbs and inspect the reeds. But from the look of #3 piston it looks like I might as well replaced it if I already decided to work this far. Can anybody give me an idea what causes such a ding? Here's some pics.

 

[Jiggz]

Re: Question about Wiseco Pistons

Never mind about the ding. After searching the forum come to find out this is a broken top ring pushing against the crown. So I guess it's time to order wiseco pistons complete with rings and pins and their bearing kits.

 

[pnwboat]

Re: Question about Wiseco Pistons

Yeah looks like maybe the ring caught the edge of the exhaust port opening. You can minimize this by chamfering the edge of the exhaust port opening and also the intake openings with a small dremel. Don't have to take off a lot, just enough to get rid of the sharp edge on the opening. Just be aware that this will throw a lot of abrasive grit around so you want to either block off any critical areas with some rags (if you're doing it without dis-assembling the block), or wash the block out thoroughly if you have a bare block.

 

[Jiggz]

Re: Question about Wiseco Pistons

Chamfering the ports is a good idea at least on the vertical sides of each hole. Time to break out the ol' dremel tool and some grinding stones. Thanks for the advice.

 

[Frank Acampora]

Re: Question about Wiseco Pistons

Wiseco pistons are made to attach to stock rods. However: Since there is more aluminum inside at the wrist pin bearing surfaces and since the wrist pins are held with circlips, you MUST buy and use the bearing kit Wiseco offers for their pistons.

The stock semi-keystone top rings seem to tend to break for no reason at any RPM. I have never had a problem with older style square top rings or Wiseco 2 degree tapered rings. Yes, there is a slight taper and yes, the rings are marked "top" for correct orientation upon installation. Anyway, because of the way they are ground to clear the locating pin in the piston, you can not install them upside-down.

Even though the engines seem to be prone to breaking the top ring, there is no guarantee that it will happen again on a different cylinder. So, if you have the money and time and it offends you aesthetically to have one different piston, by all means, replace all four. If on the other hand having one different piston will not bother you, simply replace the one bad piston.

Me: I tend to be just a little anal/obsessive-compulsive and a single different piston would bother me to no end. I would know it was in there even if no one else did. I would either replace all four, or two in a pattern --like #1 and #3 or #2 and #3. Yeah--It sometimes makes my life a little difficult. Just last night I was food shopping with my wife: She picked up three boxes of tea bags, added them to the cart and walked on. I HAD to go back and add a fourth to make it an even number. Of course, she stuck it to me about that.

 

[Jiggz]

Re: Question about Wiseco Pistons

As per your recommendations I ordered the wiseco and the wrist pin bearing kit. Removed the piston yesterday and as expected top ring caught up with the lower side of exhaust port. It's way out of the compression area but will need to hone it and deglazed the entire cylinder.

The cap screws (1/4" 12 point), during removal felt like they are loctite'd, is this correct? I also found during removal of the cap and bearing, tilting the entire engine a little forward (around 30 degree from vertical) helped to recover those loose rollers. As they fall off, they tend to roll out into the reed opening. I had a clean rag at the front of the engine to catch 'em instead of letting them fall of the lower cowl which is a big no no. Only one roller fell and stayed into the CC but was able to drag it back to the reed opening using a magnetic tip screwdriver which was not strong enough to magnetized the roller.

As for losing sleep with one different piston? A 6 pack of beer will fix that sleeplessness in a heartbeat at a much cheaper cost, LOL. Joking aside, not at all especially for a highly tightly budgeted person like me. Now I need to identify all those gaskets for the reeds, intake mani and carbs.

Thank you again.

Jiggz

 

[Frank Acampora]

Re: Question about Wiseco Pistons

The factory does assemble the rods with some sort of a locking/filling compound. It does fill in the gap in the big end of the rod--the hole is slightly larger than the screw diameter. It is friable and I usually break it off at disassembly since it does make it more difficult to start the screw.

For various personal reasons I have never used locktite to reassemble and if correctly torqued to 190 inch pounds, (for the 1/4 X 28 bolts) the cap bolts will not loosen without it. If you want to use it, it couldn't hurt.

 

[Jiggz]

Re: Question about Wiseco Pistons

Thanks. If it couldn't hurt then I can use at least the semi-permanent loctite just to be on the safe side.