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ok i have a 91 with a 90.5 weisco piston. it is a super freash rebuild. it has no relief on the bridge and no holes in the piston. it does appear that the piston has a bit of side play. what is the max play side to side and what would happen if you dont relief the bridge? and if i have to relief how deep do i go? also it has no scallops and i might want to have them machined in where do they go and how deep and how tall. is there any directions? havent ran the motor just wanta make sure it's right the first time. also i check my cylinder and came out with 90.5 id. and it's a 90.5 piston. still seems to have a few thousands play.

updat piston number is 636m09050 all i know is that it is 90.50. i did mic it and it came out to 90.00 so all i can guess is taht 90.50 is with rings. it is not drilled. so should i take the cylinder to the machine shop and have them drill the piston and relieve the bridge. and if so while im there should i get the scallops put in or is it borded too much over. where is the directions for all of this. thanks and : bling : guys. boy im coming along fast for a 4 stroker. hahah

Scallops are for eating, not putting in engines. (I dont even like eating them)

Scallops exsist in the stock bore, and end up getting honed away when the cylinder is refinished. They allow for less compression when starting the bike. Have a good engine builder do them, GSS would be a good choice. If you send him the jug, piston and head and tell him to make your bike fast and streetable, he will set you up right.

You don't need the scallops, those are for pussies, do the holes and bridge relief yourself, it's simple stuff, wiesco's come with complete insrtuctions how to do this, I'm sure someone here can scan and post for you.

ou812 wrote:You don't need the scallops and holes, those are for pussies, do the bridge relief yourself, it's simple stuff, wiseco's come with complete insrtuctions how to do this, I'm sure someone here can scan and post for you.

Fixed it.

who is gss?

aloha450x wrote:who is gss?

http://bannedcr500riders.com/board/viewtopic.php?t=606

ok got the directions on relieving the bridge and scallops. what is the cons of scallops? alos could i run with no bridge. i have read of few people that just machine that shit out. remember this is a street bike that will be seeing lots of revs and being beat up like a hooker. lol

If the exhaust bridge isnt relieved and you have no holes drilled in the piston expect to squeek it within the first 5 gallons of gas.. You need to relieve the bridge properly and or have the piston drilled. My bridge was relieved properly and i didnt drill the holes in my piston.. Been goin great since my last rebuild

aloha450x wrote:ok got the directions on relieving the bridge and scallops. what is the cons of scallops? alos could i run with no bridge. i have read of few people that just machine that shit out. remember this is a street bike that will be seeing lots of revs and being beat up like a hooker. lol

Removing the bridge is for full on race. Not a good idea for the street.

k gonna take the cylinder to the machine shop tomorrow. should i put the scallops in or not?

Dont bother with the scallops, they decompress the cylinder during starting. Have the bridge PROPERLY relieved per the manual. Drill the holes, they hurt nothing and could save the motor.

If you havnt had the motor ported for mid/top end revving the snot outta it is only gonna make you go SLOWER and over heat. Oh ya, and look stupid...

what needs to be ported

aloha450x wrote:what needs to be ported

Ported??

shit nevermind thanks for the help. im gonna drop it off in the morning. and ill drill the piston myself.

aloha450x wrote:shit nevermind thanks for the help. im gonna drop it off in the morning. and ill drill the piston myself.

Use a spring loaded center punch, the curve of the piston makes it real easy for the drill bit to "walk"...

Here is a good pic of the holes you need to drill

Those are pretty big...

AlisoBob wrote:Those are pretty big...

Don't be scared.........

Nodge wrote:Scallops are for eating, not putting in engines. (I dont even like eating them)

pstoffers wrote:

AlisoBob wrote:Those are pretty big...

Don't be scared.........

I'm not scared, but I think their defeating the thought..

Smaller holes allow lube onto the majority of surface area.

Bigger hole reduce the amount of surface area, increasing load on the remaining area.

Also, primary compression is going out those holes too.

I know Glen drills em' big, but I dont agree with it.

the diagram does show smaller holes...i didnt even put any holes in mine. I could tell there was a good relief on the bridge...no problems and I have put 20-30 hrs on it.

Caseys500 wrote:the diagram does show smaller holes...i didnt even put any holes in mine. I could tell there was a good relief on the bridge...no problems and I have put 20-30 hrs on it.

With proper relief you "shouldnt" need the holes. They are a "back-up" and dont hurt anything to have. Can you say FREEBIE!!

Rick, those things are HOOOOOG!! I thought that was a picture of a pen/pencil holder at first!! HAHA

AlisoBob wrote:

pstoffers wrote:

AlisoBob wrote:Those are pretty big...

Don't be scared.........

I'm not scared, but I think their defeating the thought..

Smaller holes allow lube onto the majority of surface area.

Bigger hole reduce the amount of surface area, increasing load on the remaining area.

Also, primary compression is going out those holes too.

I know Glen drills em' big, but I dont agree with it.

I think the reasoning for the bigger holes is better "cooling" from the raw fuel contact on the bridge. But I think that greater contact area with the piston may offer better cooling??