The 199a I'm restoring has evidence of a cold seizure so a full top end overhaul is in order.

I'm looking for any information or advice on conducting a rebore. Not sure if it's a plated bore or if a straightforward rebore will suffice.

Any help welcome!

A straightforward bore depending the oversize you need is from +0.25 - 1.25 in 0.25 steps. Luckily the barrel inside the cylinder is not plated.

That's great. I'll let the engineer have a look first before ordering a new kit. The piston is marked T2+ on the crown and 83K5 inside.

The T2+ indicates final cylinder diameter after boring. If using a Mahle piston (oem) , then these markings are critical as they need to be used to get the proper final bore size. If using a wiseco piston then follow their specs...... And then add another 3 thou to prevent cold seizure.

Steve

Hi Steve ve

Thanks for replying. It is the original Mahle piston. I bought the bike when it was 1 year old from a chap in Oban. I'll buy the new kit from Inmotion. Is there anything in particular I need to advise the folk doing the rebore?

John

Original bore clearance is 1.7 thou I'm told (by the gents at inmotion) that's all the rebore shop should need to know.

Sounds quite tight to me, I'm having mine done to that spec but need to warm up gently....

I'd have to look at my manual to determine the final size but 1.7 is in the ball park. The mahle pistons work just fine at that clearance and so long as they are properly warmed up there won't be an issue. Wiseco pistons have to be run quite loose to prevent cold seizures and even at that they'll still seize at some point. In 25 years of being a professional mechanic I've never seen a wiseco piston not seize. Stick with mahle always if you can

The difference being Mahle are cast, wiseco forged. The italkit pistons are cast and seem good..

Hi i have 2 barrels in the shop now being rebored 1 piston is a italkit the other a new Mahhle i was told 2 thou i bought another brand new Mahle by mistake.

I always bore mine to 1.5 thou and have never had a problem, always very careful during run in. A friend had his bored and thought it was nice and quiet until we went riding together and then realized his brand new rebuild was quite noisy. To cut a long story short, he pulled it down and got the piston ceramic coated [cost about $40]  The ceramic coating people can alter the thickness of their coating to suit, and after reassembly the motor was a lot quieter and ran great, fairly cheap solution.

Cheers Greg

Very useful information here, as my 159 might need a rebore.

Nothing new for me to add only my own  opinions, Mahle whenever I can get them, nice that 350 pattern

pistons work wherever, we have at present 85mm piston well worn in M199.

Mahle pistons @ .0015 thousandths clearance, (finding a good bore man very important).

When forced to run a forged piston .003 thousandths and let her rattle until warm , then OK but not as nice 

as a Mahle.

Sadly getting near impossible to source a Mahle here anymore.

Larry

I bought 3 Mahle pistons

not long ago from spain. I still have 1 84.45 brand new in box.

Edited September 22, 201510 yr by bondy

I'm hoping just to go to the first oversize for now but thanks for that Bondy. I take it Mahles are like hen's teeth now? Anyone know what Inmotion supplies?

Inmotion ones are very good iv'e just put 1 in a 199b