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KJK_JR

installing new piston should I do anything else?

26 posts in this topic

I am currently installing new piston/rings and cam chain on my 09 and was wondering if I should do anything with the head (valve seals, springs,etc). The bike has 3 seaons of use with unknown hours. Only two intakes and one exhaust valve have been adjusted once and haven't moved two seasons later.

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Since you are going to have the head off, I'd pull the valves and inspect them. The valve 'face' (the angled part that contacts the seat) will have a bright line where the valve contacts the seat. The edge of the bright line should not have a detectible step. If you can feel a step when you run your fingernail across it, it may be time to replace valves and re-cut seats.

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Okay i guess disassembling the head is a good idea. If everything looks good and measures within spec should i just replace the valve seals and clean everything up? What are good methods of cleaning the valves? Anything I shouldn't do...Obviously not use sandpaper.

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Okay i guess disassembling the head is a good idea. If everything looks good and measures within spec should i just replace the valve seals and clean everything up? What are good methods of cleaning the valves? Anything I shouldn't do...Obviously not use sandpaper.

You can use #000 or #0000 steel wool or some broke-down green or white Scotch Brite to clean the valves. You can also use a wire wheel on a bench grinder if you are very careful.

Make sure you use some good moly paste on the valve stems when you pur everything back together.

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You can use #000 or #0000 steel wool or some broke-down green or white Scotch Brite to clean the valves. You can also use a wire wheel on a bench grinder if you are very careful.

Make sure you use some good moly paste on the valve stems when you pur everything back together.

The easiest and I believe is the best way is to make sure the valves are closed and spark plug is in the head. Turn the head upside down and fill up chamber with WD40 and let it sit at least over night. Pour out WD40 and wipe all carbon away with a rag. Works awesome.

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The easiest and I believe is the best way is to make sure the valves are closed and spark plug is in the head. Turn the head upside down and fill up chamber with WD40 and let it sit at least over night. Pour out WD40 and wipe all carbon away with a rag. Works awesome.

Oven cleaner also works good too. Just keep it confined to the valves.

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disassembled the head...not sure if pics are good enough to say anything

Exhaust valves:

Left

DSCN0498.jpg

Right

DSCN0500.jpg

Intakes:

Left

DSCN0502.jpg

Middle

DSCN0505.jpg

Right

DSCN0503.jpg

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Some pics of the head....again don't think the pics are good enough to say anything

DSCN0509.jpg

DSCN0508.jpg

DSCN0507.jpg

DSCN0510.jpg

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Aside from the carbon build-up on the valves, they dont look too bad. Clean them up good and post new pics.

Try runnung come Chevron Techron concentrate or BG 44K on a regular basis and you shouldn't have any carbon build up.

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You lack a good clean seating surface. The carbon buildup is likely holding your valves open a tad. be sure to clean all that stuff from the head and valve.

You didn't mention replacing your valve stem seals. They are cheap and they are easy to replace.

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You lack a good clean seating surface. The carbon buildup is likely holding your valves open a tad. be sure to clean all that stuff from the head and valve.

You didn't mention replacing your valve stem seals. They are cheap and they are easy to replace.

yes I'm gonna clean everything up really good. Yes I will replace the valve stem seals. Should I replace the springs even if they are within specification?

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well its looking like im just gonna replace all the valves with pro-x stainless steel ones. Of course i'll use the appropriate springs and have the valve seats recut. The cylinder is in questionable conditions as well. Almost looks like the plating is worn through at the top.

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so looks like i may have other problems as well. The area in the cylinder head where the valve lifters reside appears to have scratches and wear marks. According to the manual if these scratches exist it says to replace the cylinder. So before I start panicking what do you guys think?

DSCN0511.jpg

DSCN0521.jpg

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For one thing, that's not the cylinder. Minor scoring in the lifter bores is not necessarily something bad enough to warrant replacement of the head. If the lifter fits well, has acceptable clearance, and moves freely in the bore, it's serviceable. You may want to knock down any high spots with some fine sand paper (but CLEAN it up if you do), but that doesn't look like a deal breaker to me.

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