14 replies to this topic

[bsw]

HI I am about to get the barrel of my 175 rebored.The engineering firm asked for the working clearence,
I am taking the barrel to 2nd oversize.Where or can anyone give me this info.

[yamty175]

TY175 Owners Manual: Piston clearance 0.040-0.045mm or if you're watching in black and white 0.0016-0.0018 inches. This is as new, it doesn't give a minimum or maximum
Jon.

Edited by yamty175, 19 January 2012 - 10:57 PM.

[majesty320]

http://www.tytrials.co.uk/ ring these people they will tell what clearance to bore to, they did with mine but I cant remember as it was a while ago

Edited by majesty320, 19 January 2012 - 11:27 PM.

[Dadof2]

I would be a bit suspicious of a firm that had to ask, are they familiar with oring two strokes ?

Pistons are usually tapered being less diameter at the top to allow for more expansion - if they measure it and calculate bore size from there it will probably seize. I agree with 0.0016 inch clearance but that is probably front to back on the piston skirt.
Cheers

[yamty175]

Good point Dadof2.
TY175 owners manual: Cylinder taper 0.008mm or 0.0003 inches (new) maximum (allowable) 0.05mm or 0.002 inches.
Maximum (allowable) out of round 0.01mm or 0.0004inches.
Jon.

[bsw]

Thanks for all replies,I should have mentioned i need to bore this to suit a 2nd oversize weisco piston,

[fergie]

One thing you should know about wiseco's is that you need to let the bike warm up properly before riding. They also seem to rattle alot when they are cold.

[feetupfun]

There should be piston clearance info on notes that came with the Wiseco piston. Wiseco need different piston clearance to what is in the Yamaha book due to the composition of the piston metal having a different thermal expansion rate compared to pistons like Yamaha and Pro-X. The Wiseco is not the best piston for the TY175 for trials use because they are made for race applications rather than trials so will rattle a lot more than others as has already been mentioned.

[B40RT]

I know a couple of TY175 owners that have tried Wiseco pistons without success, and changed quickly as there is no power. (don't shot the messenger)

[Guy53]

I would read carefully the previous 3 post BEFORE sending my cylinder for a rebore, you might just '' waste '' an o/s, unfortunatly the saying '' you can pay me now or you can pay me later but you gonna have to pay me anyway '' is right in this case. Maybe the guy's at the shop that you chose are aware of the potential problems therefore asking you for specific tolerances. Of course it's just my opinion.

Guy

[B40RT]

Dadof2, on 20 January 2012 - 04:49 PM, said:

I would be a bit suspicious of a firm that had to ask, are they familiar with oring two strokes ?

I think I would be even more suspicious if they didn't ask !

[bsw]

To avoid a rebore i only need a new 1st oversize piston kit as the bore is ok ,the bottom ring is siezed
on the piston.I could not source a piston kit for the bike anywhere so i purchased a 2nd oversize from a TY specilists in the UK.
Anyone here know who has one in stock?

[B40RT]

bsw, on 21 January 2012 - 03:47 PM, said:

To avoid a rebore i only need a new 1st oversize piston kit as the bore is ok ,the bottom ring is siezed
on the piston.I could not source a piston kit for the bike anywhere so i purchased a 2nd oversize from a TY specilists in the UK.
Anyone here know who has one in stock?

You couldn't pick out the bottom ring and clean up the piston, and try and source a replacement ring ?

[Guy53]

Is 443-11610-20 the part number you are looking for?
If so pm me

Guy

[mattylad]

Hundreds of pistons on ebay, especially from US