Hey guys-
I just got my cylinder back from getting bored to fit a 40 over Wiseco. The guy at the shop told me I have about .0035" clearance. The piston measures 3.304" and the bore measures 3.311" with a dial caliper. Does this mean I truly have .0035" clearance, or is it .007" clearance? I'm wondering because my ring end gap is .022" and the piston feels pretty loose in the bore.

 

I hate to be bearer of bad news . But it's not bored right.

That cylinder if it is stock it should be bored to 3.307". Piped and modded cylinders need a little more .

The ring end gap gives away the problem. The end gap should be around .013" or .010". If you are at .022". The clearance is not right . Ring end gaps grows by the amount of .00314" per additional thousands of piston to wall clearance . If the bore was at 3.307" (where it should be) , the ring end gap would be back down where it should be . (Do the math)

Sorry to give you the bad news . The quad will run no problem - but I am sure it angers you to know end knowing that it is not as it ought to be .

Rick

PS --> the dial caliper is doing a good job on the piston - thats what they measure . Are you sure you are being accuratte on the bore - mikes work better . I find it odd the shop gave it back to you - when honing a cylinder to fit it you know what the hole size is when you are done.


Rick

 

Rick-
I took the cylinder to a snowmobile performance shop that's been in business for 7 years. I asked for .003" clearance, and when I picked it up, he said he had a mistake on the measurements and the clearance was closer to .0035". What I'm trying to find out is if I need .003" piston-to-bore clearance, shoud the cylinder measure .003" bigger or .006" bigger than the piston?

Also, I know the dial caliper is not the best tool for measuring bore size, but I don't have a bore micrometer. I measured at the skirt and the top of the cylinder both front to back and side to side. All measurements were 3.311".

 

Depending on mods that cylinder should measure 3.307" - 3.308" .

.003 to .004 over the diameter of the piston .

 

Thanks Rick.

That's not what I wanted to hear, but thanks for the truth. I will call the shop tomorrow morning to see what they are willing to do to fix the problem. The guy that did the work told me the clearance was "closer to .0035". He then went on to say that excessive clearance is the main cause of skirts breaking off. Well, enough venting. Rick, I may be giving you a call for a 50 over Wiseco and a bore job.

 

Disregard this thread. It turns out my rings were mispackaged and I had received rings for a 20 or 30 over Wiseco.

Also, a dial caliper is not the right tool for measuring cylinder bore. I was getting incorrect readings with my dial caliper. It turns out the cylinder was bored correctly to 3.3075".

 

What was the part # on the ring pack ?

20 over rings = 3287TD

30 over rings = 3297TD

40 over rings = 3307TD

30 over rings will have a much bigger gap than .022".

~Just trying to help ~

Rick

 

Rick-
The rings are packaged "3307TD, 84.00 MM RING SET". I can only assume they were packaged wrong since the cylinder was bored correctly.

Another thing to add is when talking to the guy at the snowmobile shop, he mentioned that these rings may have been seconds from Wiseco. The other numbers on the package are 082905/5/5/1998. Would that mean these rings were made in 1998?

 

A couple more things came to mind: Did Wiseco ever have any issues with their quality control? Also, when was that great Wiseco Piston Famine?

 

The Great Wiseco Piston Famine was in 1997 or so . The tooling for the 400 piston was broken . I got a heads up on it back in the day . I called every wiseco distributer in the country and bought them all . I didn't run low - I had it covered . Wiseco even called me looking for a piston back then for a Dirt Wheels article . I wrote the whole story and didn't get a lick of credit - so it goes - I wasn't upset about it but I was suprised that after saving their asses and boring a cylinder and getting it to the magazine boys , I at least should have gotten on the *good guy list * .


I have seen one wiseco piston that did not have ring locating pins once . The pistons themselves are machined perfect - or at least identical for batches anyway .

I have never seen rings mispackaged .

It would be nice if I could measure your cylinder , not accusing anyone of BSing you , but this is very unusual .

Why not send it to me ? I'll check it out , if the clearance is not right I will let you know - and just to show I am not trying to pick up a $$$ I will exchange your piston for a new 50 over and just charge you for a bore ($40 ) if needed . This is way to fishy .

Rick