New Race tour piston gone for a burton

[clubbook]

Help please.

Recently siezed my modified/tuned cast barrel with new MB race tour piston (ouch!) at about 45 to 50 mph, (this was after 300 or 400 miles) at reasonably high speed with no problems.
I.ve just changed to a TS1 and no matter how i jet it, currently up to a 350 main jet!!! it still runs very hot with a greyish/light brown plug brown. Engine continues to run when exhaust blocked off and small amount of oil seeping from breather plug.

Set up with a TMX 30 and JL3 Had all new good quality oil seals on both recent rebuilds.

Know it suggests an air leak but buggered if we can find any when cold.

Could it be the carb or exhaust?

Any comments / advice / direction greatly recieved

Thanks Paul

[drunkmunkey6969]

what is rest of carb spec.......air screw turns, pilot, needle, clip etc etc......

[Stampede]

sounds more like an air leak......

[clubbook]

Is there anyway to test for an air leak other than full engine strip, and visual isnpection?

[J1MS]

Is the engine case ported? As they can crack on the mag side middle of the transfer feed out to the mag gasket face, depends on how deep the transfer feeds have been cut and themschining for the mag as it can get very thin here if it hasn't been reinforced with weld first.

Could be many other causes just thought I would mention this as I've seen it many times on other peoples engines over the years.

[J1MS]

I've leak tested around the parts you can see by spraying WD 40 and looked for bubbling on or near the gaskets with the engine running.

There is probably somthing better than WD40 that you could use but it's all I had at the time.

[clubbook]

No mods to engine casing. Thanks for input

[Mel K]

Fairy liquid will show up an air leak by blowing bubbles.

[Stampede]

try brake cleaner - when you spray it on the air leak, the revs should suddenly go high or down (have forgotten which way exactly, but something happens! )

[drunkmunkey6969]

Recently siezed my modified/tuned cast barrel with new MB race tour piston (ouch!) at about 45 to 50 mph, (this was after 300 or 400 miles) at reasonably high speed with no problems.

So........main jet cools efficienntly at wide open throttle, you have done 300-400 miles at high speed with no problems......but in the mid range 45-50mph (so 4000rpm-5000rpm??) it seizes.........as i say.......what are the rest of your carb settings?