Engine noise

[burger uk]

Hi all i was wondering if anyone has any enigne knowledge at all. i have a little and i have a problem as follows

I bought a 2000 burgman with an engine noise, its a loud tap come knock from the top end, the engine starts but the noise is so loud i switch it off instantly, i bought the bike like this so i have no idea how the noise come about. i am planning on stripping the bike to repair and i assume the noise is either a valve ar the cam, i intent to remove the rocker cover and see if the chain is still ok and look at the valve clerances. if this all seems fine then i have to delve deeper and split the chain and open up the engine, is there any help anyone can give, (constructive please) and i lso need a repair manual so i wondered if any one had a link to download or an idea to how i can come about one, the bike has done 25k and seems in good condition, it has oil in and it look clean the belt look goos to, i have no history what so ever.

many thanks

[nexusmaximus]

I hope you got it at a bargain basement price, fella, with a sound like that coming from the engine?...doesn't sound good.

...best of luck with your endeavour, mate.

[TmaX9]

It will be a 250 at that age won't it?

Before you do all that have you checked to see if the spark plug is fitted properly, nipped up and not got a loose helicoil or anything?
The noise is definitely an internal sound?
I'd whip the cam cover off first with the engine in situ, and check that there isn't a broken rocker arm or displaced cam follower/shim/bucket or something that simple. It may even be that the valve clearance adjuster screw has come loose and there is a massive clearance developed.
Always eliminate the simple/cheap options before delving into the more complex/expensive options.
There is a 400 manual on http://www.wotmeworry.org.uk/manuals" onclick="window.open(this.href);return false; but alas no 250 one.

[burger uk]

Thanks for your advice the best so far, i have checked the plug, that was my first port of call as its definatly internal and definatly top end but the plug even tho black was ok and it nipped up fine, so next i will check what you suggest in your post and hopefully its something simple, it is a carb 400 model not a 250 by the way so ill click the link, many thanks, as i progress ill update the post, but i have to like many find the balance of kids,work,household diy,wifetime etc but im desperate to fix it as if your like me it keeps niggleing away in the back of my mind to fix it. the noise is loud and clacky

[burger uk]

I have stripped out the carb and rocker cover and all looks normal  i have yet to check valve clearances but no broken rockers i will look to see if i can turn the engine over and see if it looks like its working properly. I'm a little green on engine internals and more so fault diagnosis in this area. So if anyone has any more advise. Please feel free to post, many thanks 

[pikey]

Id take variator off as well so its just the engine your listening to.If its starting and running Id of thought valves are ok or near enough.Julian

[nexusmaximus]

Thinking about it, my old yammy made a loud clacking/banging noise before it stopped moving, and the mechanic that looked at it said that the piston arm had snapped...cost too much to fix, so i sold it, as was.

[TmaX9]

While you have the cam cover off, set the crank to TDC, there will be a plug on the crankcase somewhere so you can align a mark, then check that the cam TDC mark is also aligned. If no mark shows turn the engine another full turn.
I'm thinking if the cam adjuster has been removed at some time and the timing chain jumped a tooth, the piston may be slightly contacting a valve as it get to TDC as the cam timing is a few degrees out. The worst thing is if it's bent the valve although not too difficult to repair.

[pikey]

The timimg mark is on back of engine exhaust side theres a plug you take out and turn engine by hand until you see the mark thro the hole.Julian

[burger uk]

That was my next move, I was looking for the crank Plug so I can see the tdc mark. Now I know where it is I'll check the two. There is a other clue, with the Plug out if I turn the variator shaft with a 10mm spanner anti clockwise the piston moves to the bottom and then the whole thing seems to lock up and I can't seem to complete a revolution.. In my mind this is not good as I know you get a little resistance as the compression builds up but with the Plug removed i think I should be able to turn the motor over via the variator shaft correct me if I'm wrong. Still my glass is half full and I will fix it. Thanks for all your help it is really appreciated, I can't wait to get her on the road.