MTC-piston clearence question

I have a question about MTC piston to cylinder clearence.
MTC says the clearence for street pistons (10,5:1) is only
0.0005 to 0.01 ".
This is only 0.0127 to 0.025 mm (I´m from Germany ),Kawasaki pistons have 0.04 to 0.07 mm.
Are the MTC clearence specifications really correct ?

the mtc pistons are incredible,the alloy's they use in their pistons expand at roughly the same rate as the cylinder, that is why they can run their clearances so tight. the first set of mtc pistons i put in years ago told me the clearances i thought it was a misprint, so i called mtc up the next day to double check and those were the right clearances.i was so used to stock cast pistons or wiseco forged with quite a bit looser clearances it was quite a shock to see some that were so tight. one note of warning as they are so tight be very careful installing them in the block.

Good Luck..I own the very same pistons. And 3 exhaust valves and 1 Intake valve later and 2 base gaskets(stacked) and after sending them back to MTC and paying them 150 to remachine them down they are GREAT!? I know prostock bikes use them...but we are not prostock bikes, we are looking for reliability on the steet. Use them as ashtrays and buy WISECO! Just a thought...

had your block been decked.

JDScherz wrote:

Good Luck..I own the very same pistons. And 3 exhaust valves and 1 Intake valve later and 2 base gaskets(stacked) and after sending them back to MTC and paying them 150 to remachine them down they are GREAT!? I know prostock bikes use them...but we are not prostock bikes, we are looking for reliability on the steet. Use them as ashtrays and buy WISECO! Just a thought...

did you check the deck height before final assembly of motor?how about valve to piston clearance?theres more involved to engine building than just bolting a bunch of parts together

Anyone that runs with .0005" piston to cylinder clearance has a lot bigger balls than I do :woohoo:

steell wrote:

Anyone that runs with .0005" piston to cylinder clearance has a lot bigger balls than I do :woohoo:

Big ol balls. :ohmy:

Perhaps we're comparing apples to oranges. .002-.004 inches is pretty typical piston to cyl tolerance. and allowing for advances in metalurgy, half that is understandable. valve to piston clearances however haven't changed that much.in the day, race motors (decked heads/surfaced cyls/big valves/stroked cranks/hi-comp. pistons/high lift cams, etal,)usually came with the recommedation of @ .020 inches clearance for valve to piston. (checked by assembing with lead or clay attop piston, rotating crank, dissassembly and measuring squished remains)... signs of insufficient piston to cyl clearances would be siezure, broken rings, broken piston lands. whereas kissing valves could easily be the product of worn rods/crank/rod bearings/insufficient clearance/high revs, again etall. especially in the case of 30 year old roller cranks. just points to ponder,G

Is it possible the MTC pistons are cast and the Wiesco are forged, thus explaining the difference in clearance requirements? Seems I remember that forged ones required more clearance as they swell more coming up to temperature. Something about the material grain structure inherent to both processes. On the other hand I could be full of schiet. Happy Friday and ride safe, Steve

if you run .0005 clearance, I think you are going to gauld the piston real fast, .002-.004 sounds more like what it should be, dont forget to check the ring end gap

MTCs are forged and are a very good piston. We are an MTC distributor.

Jay

shighley wrote:

Is it possible the MTC pistons are cast and the Wiesco are forged, thus explaining the difference in clearance requirements? Seems I remember that forged ones required more clearance as they swell more coming up to temperature. Something about the material grain structure inherent to both processes. On the other hand I could be full of schiet. Happy Friday and ride safe, Steve

Since Jay says they're forged, we'll take his word, he's the man. But I'll add my $.02. You're right about microstructure. Maybe MTC uses a different alloy with a different thermal expansion coefficient, or a different heat treatment with the same results. They wanted tight clearances, and engineers can do this. I'm sure I could with a but of time, a materials lab like the one at my school, and the Aluminum volume of the Metals Handbook. And as for galling the piston, I would venture to say that smaller clearance would reduce it, not increase it. Greater moment arm for galling against the cylinder wall if you have more clearance.