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Discussion Starter #1
OK .. got my cylinders back from being measured and honed at a machine shop. They said they are fine; within factory specs so no overbore ( and no Wiseco 810 kit :( ). I've checked the pistons and they seem fine. It seemed low-compression on one cylinder (byt valve clearances were shot on OTHER cylinders too?) and the oil rings look dodgy to me so I'm happy I pulled it down that far.

The pistons have some carbon buildup on the crown, so I'm wondering if it was only valve-stem seals? It seemed to keep smoking regardless of how long it was run, but I suppose that still could be seals?

Anything else I should look for before buttoning it all back up?
 

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Valve stem seals get hard and quit working over time letting the oil go down the valve stem. I believe Ape race parts sell the best. KZ Zone is one of the sellers.
 

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Discussion Starter #4
You had the cylinders honed but didn't install new rings? Did you check valve guides?
Nope .. I bought it smoking. I've pulled it down to the crankcase, sent the cylinders away to be dial-bore checked (OK) and honed. I'll reassemble with new rings.
I'll check the guides next.
 

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It was probably the rings but it is not wise to stay with the old valve oil seals when you are already into the engine. It is normal to have carbon build-up on pistons when it is using oil because that smoking is oil burning.
 

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Quality rings and valve stem oil seals are the best you are going to do, unless a valve guide is travelling with the stem. Then this is a whole new challenge. Do you know fuel sure that it is oil smoke rather than a rich mixture? Some oil smoke that is not to offensive to rearward travellers will preserve your exhaust system. Silver lining.
 

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Quality rings and valve stem oil seals are the best you are going to do, unless a valve guide is travelling with the stem.
I don't understand what you're saying.

Are you saying the valve guides can not cause the smoking?
Or maybe the valve guides are not replaceable? (I think you probably know they are, but I had to ask).

You kind of have me stumped here.
 

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Maybe it is the guide travelling with the stem that I've been unclear about. Sometimes, and for whatever reason (poor fit, butchery, carbon) the valve stem will sieze in the guide and the cam action now reciprocates both the stem and the guide. With the guide going up and down in the head, it acts a bit like an oil pump.
 
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