Knocking from crappy 125 bike

[timbrell]

After I stopped laughing at him and giving him the compulsory 'grow some balls and buy a proper bike' jibes I offered to have a look at my skint mate's Kawasaki Eliminator 125 (very fitting name for a homo-erotic wannabe cruiser).

He said it was making a knocking sound that started a little while after he crashed it, so he stopped riding it to prevent it getting worse. After I got it over to mine I took it for a cheeky ride up the road and back, and sure enough it makes a horrible knock when you close the throttle. It doesn't do it in neutral and if you pull the clutch in as you close the throttle it doesn't happen either. It is a single heavy knock from the engine.

In my not so infinite wisdom I thought it must be the gearbox or a clutch mechanism problem as the engine runs fine, it changes gear smoothly and the clutch doesn't seem to be slipping (it only has 12bhp!). I think it may be a gear shaft bearing or thrust washer that's knackered so it knocks when the engine unloads quickly but sounds fine under constant load.

So come on you garage geniuses, anyone got any ideas? He can't pay to have the engine stripped at the moment (he couldn't even afford the gaskets and oil!) and I haven't got the time or space to do it for him on the cheap right now, and a replacement engine is about the same as he paid for the bike so not worth it.

[lorenzo]

Stick it on its side stand and take the clutch cover off, you might lose a litre of oil but not much more, and you might be able to get away with reusing the gasket (doubtful). I'd start with the easy stuff, has the main bolt come off the clutch, or is there something funny going on in there?

It has to be said, if he can't afford to pay for a £5 gasket then the bike's pretty much a write off for all intents and purposes as far as he's concerned. How does he fill it with petrol?

[timbrell]

He doesn't! His lack of cash is temporary in theory, he hasn't been working and used the bike to get to work. I would have thought the main clutch bolt would make a bit more of a racket, or at least some judder. It sounds fine and runs smoothly except for that very specific knock. Definitely the logical place to start though.

I'd delve deeper but I'm getting another bike to break tomorrow and the garage is full already. I'll be getting it back in when I've finished that and he has some money for the essentials, will definitely need new gaskets, he seems to be allergic to hoses and sponges so they'll be screwed. The poor lad's a bit of a dunce, the guy he normally goes to wanted him to book it in for a rebuild at 500 pounds without even seeing/hearing it!

Wondered if anyone has come across this sort of problem before, try and narrow down the options when I do look at it properly. If it's a terminal problem it will be a write off unless anyone has a cheap engine for a ............. just remembered, this is PB forum.

[Gregorious77]

could it be the chain rubbing somewhere? if it got bent in the crash!

[Tomfoolery]

Awesome bobber material, there.

[timbrell]

Found out a little more when I dropped it back off to him last night, just after he crashed it he ran out of petrol going down a big hill and tried to bump start it at 60mph, it started after he did that. Considering that's probably it's top speed I'm thinking that's gonna have done something nasty internally!

It certainly isn't the chain rubbing anywhere, it's a heavy mechanical clunk from the engine.

Tomfoolery, you can make him an offer for it if you like that sort of thing!