Dropped Valve and Holed Piston

[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.

[rockTJ]

Ahh bollards! Sorry to hear that mate. Saturday morning I just tipped a 3HE cylinder head and a load of valves, camshafts etc etc as I had no takers.......

Not worth getting an OE piston/ring set and getting the barrells re-honed??? I hope you get it sorted soon.

Chris

[Clanky]

Damn, the Devil farts in my general direction yet again

But yeah, thinking I can get possibly fix this with a second hand head and as you suggest if the bores are good enough new rings and a hone. That would be a very good result.

Thought about a second hand engine but you never really know what you're getting. At least this way I'll know its been done right and should be good for a lot of miles.

So, I may just need a standard piston and rings are these easier to find than oversize parts?

[Evilchicken0]

You might find the rings but the pistons will be difficult.

Really the engine is toast, getting a secondhand engine would be easier, give it a topend refresh and you have your "known" engine.
Or fit a 600 3HE.

[dobbslc]

If you go for the rebuild you should take the sump off first to see what's in there, also you can then clean the gauze filter out too.
If you let the engine run for a long time it will probably be full of swarf!
If the oil looks clean you might be ok.
Dobbs

[Taggyd]

ive got a head, well one and a half and a set of pistons (no barrels) from a previously running engine i bought for race spare. infact ive got nost bits! let me know if any use!

[Clanky]

Thanks everyone for the advice,

Just weighing up my options but the 400 was supposed to be my daily ride and the quickest/cheapest fix would be a replacement engine to get it back in use.

Taggy, thanks for the offer to help with parts. I still fancy having a go at rebuilding the original engine (never done one before) so I'll PM you if there are any bits I need

[laminator]

Thanks everyone for the advice,

Just weighing up my options but the 400 was supposed to be my daily ride and the quickest/cheapest fix would be a replacement engine to get it back in use.

Taggy, thanks for the offer to help with parts. I still fancy having a go at rebuilding the original engine (never done one before) so I'll PM you if there are any bits I need

I'd never stripped a bike engine until recently, but managed to sort the head/etc on mine without any problems.

I had a thread running on the strip and rebuild -viewtopic.php?f=37&t=33678

I'd guess the issue is cost vs speed. You could get another engine and hopefully it's a good runner, but won't be the cheap option. If the bikes required to be running in a short amount of time I guess this is the easiest way. It will also give you time to work on fixing the problems with your existing engine without any presssure. Good luck whichever route you take.

[CMSMJ1]

While we are talking engines - does a 3EN clutch basket fit in a 3HE?

It is the barrels that are the difference innit?

[Clanky]

Hi Laminator,

Followed your engine rebuild thread (good read) and I've read plenty of others and they sort of leave you thinking "I wanna try that". I just didn't expect to have the opportunity come round so quickly.

I have managed to find and buy an engine off ebay with low mileage, at a reasonable price, collecting it today before work then I have two days off to get it fitted and to try it out.

I will go ahead and rebuild the original but like you say if I have a running bike it takes the time pressure off so I can take my time and enjoy it.