XL 500 RC rattling help

[ninjakev]

Having bought a 1984 XL 500 RC it rattled very noisily from what sounds like the top end. I disconected the decompression cables to eliminate the lifter from touching but it made no difference. Next I removed the unit and set the tappets correctly (which were also rechecked by my brother in law) and checked timing marks were correct. The timing chain had good tight tension. Last night after refitting the unit I fired her up but the rattling is still exactly the same.
Any body got any ideas as this is frustrating and I don't want to ride it in case I do any serious damage to it.
Any help would be greatly appreciated, Kev.

[catteeclan]

Common prob with this bike was the camshaft wearing into the head. There's no bearing as such just the cam running on the head alloy.
Think you'll have to have the top off and check out the followers first though.

[ninjakev]

Hi Catteeclan, when I had the unit out I pulled the top off to check the timing marks, the camshaft and followers looked fine with no scoring or discolouration. I did not take the cam out but the bearing surface looked perfect on the cam and the cam carrier, Kev.

[catteeclan]

Like I said the cam wears into the head. You need to get the cam chain off, put the cam cover on with a few bolts and adjust the tappets so none are in contact with the valves. Get your finger in the hole where the rev counter normally fits. It's still difficult to feel as it's mainly the rear most that suffers.

Does it sound worse untill the oil gets round when first started?
More light knocking than metalic clicking?

[ninjakev]

Hi catteeclan, have removed engine and stipped off barrel and head. Have done as you said and yes there is movement on the cam in the carrier.Any suggestions where I go from here ?
Thanks, Kev.

[AlanH]

A few options...
1) Machine out the journals and put a set of shell bearings in there.
2) Pre-heat the head and TIG weld the journals to build them back up. Machine back to standard size.
3) Replacement head - probably rare to find a good used one.

Maybe the best thing to do is let a few specialist engineering shops have a look. Hopefully someone will have a suggestion for one local to you.

[catteeclan]

Mine has been bored out and a bearing made out of bronze fitted. Not done by me, I purchased the bike with this already done.
Think AlanH has the right idea, try a few machine shops.

[ninjakev]

Thanks for the advice Alan and Catteeclan, but think I am really in the brown stuff now as after cleaning the carbon in the head have found that both exhaust valves don't sit square in the seats (can see light through them both) and It also has a lovely crack from the edge of one inlet seat to the spark plug hole !!!!!
Now I'm really stuck !!!!

[catteeclan]

Thanks for the advice Alan and Catteeclan, but think I am really in the brown stuff now as after cleaning the carbon in the head have found that both exhaust valves don't sit square in the seats (can see light through them both) and It also has a lovely crack from the edge of one inlet seat to the spark plug hole !!!!!
Now I'm really stuck !!!!

Oh crap. The crack isn't uncommon either. How do the valves not sit square with the seats? Seats burned?

Sounds like you're going to need another head anyway.

[ninjakev]

The Valves look as if they are slightly bent but the seats don't look burnt.
Have put a search on partfinder but haven't had a call.
Any ideas for a source or alternative head? ie FT500 XR500 are they the same ?
Kev.