Yzf valve replacement

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Yzf valve replacement

Post by curl666 on Thu Feb 04, 2016 7:31 pm

I recently picked up a yzf 250, assured by the owner it just required the valve clearances to be shimmed.

Upon starting work on the bike, all bolts were loose, I thought looks like someone has had the engine open and just decided to f@ck it off.

I set the engine to TDC, timing lined up via stator side case and camshaft markings.

The yzf spec inlet at 0.10-0.15mm and exhaust at 0.17-0.22.

I had 1 tight inlet valve, which could probably be shimmed back to spec.
Other inlet valve I could slip a 0.6mm feeler gauge under Smile

The exhaust valves 1 was super tight, the smallest feeler gauge I had wouldn't even go under think it's 0.04
Other exhaust valves were huge 0.6mm

Any thoughts?

The bike doesn't owe me a great deal, I could break it for spares and make my money back but was fancying the engine as a little project rebuild.

If the valves have to be replaced, can the new valves just be lapped into the head or are new seats/inserts required? Anyone know a price for valve seats?

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Re: Yzf valve replacement

Post by steve on Thu Feb 04, 2016 8:17 pm

Titanium valves in them Shocked ££££££££££££
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Re: Yzf valve replacement

Post by curl666 on Thu Feb 04, 2016 11:32 pm

steve wrote:Titanium valves in them Shocked ££££££££££££

Yeh I had a quick look on eBay around £60 each valve!

Found stainless steel valves which are cheaper and have good reviews, but apparently as the valve is heavier you need to replace the valve springs etc and the saving on valves soon disappears.

I've got a spare yzf engine in bits in the garage, but sadly the valves are scrap on that too Sad

I didn't go any further than checking the valve clearances, but I could see the cam shafts looked rough. I'm wondering whether this maybe causing the crazy valve gap I've got.

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Re: Yzf valve replacement

Post by steve on Fri Feb 05, 2016 6:39 pm

I read on thumper talk when I had mine if its been ridden had as in reved the bollox off it all the time the valves can stretch to.
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Re: Yzf valve replacement

Post by JTM525 on Fri Feb 05, 2016 6:48 pm

Can titanium valves be lapped or do they need the seats reground?
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Re: Yzf valve replacement

Post by phil990 on Fri Feb 05, 2016 7:26 pm

Yamahaha's valve clearance gets tighter, not looser with age.

More likely to be no oil. Measure hight of cam on both bikes.

Engine is FBAPD... Rolling Eyes
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Re: Yzf valve replacement

Post by curl666 on Fri Feb 05, 2016 10:09 pm

FBAPD?

will inspect engine further when I'm next at home. They Haynes manual claims the valve seats/replacement is beyond a DIY job.

Just goes through strip down, take head to get valves cut and rebuild

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Re: Yzf valve replacement

Post by dai 530 on Sun Feb 07, 2016 9:02 am

The 1st thing to do is take the shim out and measure it and then try a smaller shim
the valve could be bent
the valve seat could be worn
Its a easy job to do but if it needs valve guides or the seats to be cut your better off sending it off to be done
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Re: Yzf valve replacement

Post by phil990 on Sun Feb 07, 2016 8:22 pm

FBAPD = F@@ked beyond all possible doubt.

You could do an engine compression test or as the Americans call it a leak down test to check valves and rings...
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Re: Yzf valve replacement

Post by curl666 on Sun Feb 07, 2016 9:06 pm

Thanks for updates.

Will class it as FBAPD until further inspection. Hoping to look at it tomorrow.

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