Dropped Valve and Holed Piston (Update - Back on the road)

[Clanky]

Hi,

Recently took the bike (3EN1) for a run and it suddenly developed a buzzing noise which passed quickly but it lost power and the exhaust was very smokey. I initially thought it was maybe a ring that had gone.

Got a chance to take the engine out today and I found that the head of an exhaust valve on number 3 cylinder had snapped off. It had danced around around a bit and ended up lodged on its side in the valve seat (or what was left of it). The piston itself is holed so god knows what may have got into the crankcase. Remarkably the bore is undamaged but the head is knackered.





I'm going to look for a new head, pistons/rings and strip it down slow time. Any suppliers of oversize pistons/rings, I know they're hard to find but worth asking.

[SouthendChris]

http://www.ebay.co.uk/itm/221036125199

Might provide lots of usefull parts.......


http://www.ebay.co.uk/itm/120920937119
Chris

[Clanky]

Cheers Chris,

Ebay is the way ahead I think. Might get a replacement motor if its cheap enough so that I can use the bike over the summer and slowly rebuild the bust one, I quite fancy having a go at this. The bores look good so it may be I can get a standard piston to replace the damaged one have it honed out and fit new rings all round.

[zed]

as a matter of interest, what mileage did your motor have on it when the valve went? were you riding it hard at the time? I'm a newb on bike motors...

[Clanky]

Hi Zed,

It was not a high mileage engine about 16k. The valve clearances were very tight when I got it so a did an adjustment. It ran fine and I don't ride the bike overly hard, well within it's limits. The day it went I was only doing about 50 mph having just accelerated away from a stop at some lights.

I know I got the valve clearances right when I adjusted them because I checked and re-checked (It is always possible I screwed something up but I don't think so). I had put just under 1k on it after the valve adjustment and would have thought that it would have gone a lot sooner if something was not right.

I've just put a replacement engine in (similar mileage) and first impressions are good. I will hopefully give it a test ride later today or tomorrow.

[zed]

where did you get your valve shims? if I'm reading off the right model in my manual, you need a selection of shims to get the valve clearances right?

[Clanky]

Hi Zed,

The only down side to adjusting the valves is that you won't know the number or size of the shims you'll need until you measure the gaps and then you need to order them. Having a wide enough selection of spare shims available to cover any eventuallity is just too expensive. You can often save money by swapping some shims around.

There was a guy who created a programme called 'shimulator' that worked it all out for you after you input your current shim sizes into a table but it seems to have been taken down by the creator. Shame really but not too difficult to work out using the tables in the workshop manual.

Heres a link to an excellent guide on valve adjustment, read it in conjunction with the manual and it really is very helpful and clear

http://www.fzrarchives.com/ipb/index.ph ... opic=44645

I am running the UK shim swap scheme for Fzronline. Basically you buy the shims you need at a discounted price if you trade in your old shims. Other places to try are ebay, usually cheaper than most dealers. Off the top of my head the shim diameter is 7.48mm.

[zed]

thanks mate

[Clanky]

Good times

Got a low mileage engine off ebay and fitted it over the last few days. Test ride today was a total success runs really well, bike is up and running again so I won't be missing out on the summer rides.

Also found some +1mm pistons and rings to rebuild the old engine later on.

[yamaha_george]

Clanky,
good news indeed, glad it all went in smoothly.

[loganlexow]

I just had something similar happen today. Now I am scared.... I got as far as removing the tank, airbox, and carbs and found this:



UGH....

Oh, and sorry for thread jacking. Just frustrated and venting. Cheers

[Clanky]

Sorry to hear that you have a problem there. Hopefully the damage wont be too bad and fairly easy/cheap to fix (fingers crossed)

Let us know what you find when the head is off.