xr400 cam chain

[gav03]

Hi,

Finally got around to stripping down my XR400 engine that suddenly expired on me a couple of months ago.
On removing the valve cover, it was apparant that the cam chain had broken. Unfortunately it was jammed lower down in the engine so the cylinder head, cylinder and right hand engine cover were removed to allow access.

The chain was eventually extracted and no other damage appears to have occured. So, I have some questions for you guys who may have done this work before:

I presume a new chain will come already joined. If this is the case, what is involved in putting into the engine - does the primary crank gear need to be removed to allow the fitting? Having already tried to remove the 27mm nut on the end of the shaft unsuccessfully, what is the best way to do this and lock the drive gear in place while it is done. All I am doing is spinning the whole engine over. My workshop manual makes no mention of replacing the camchain.

Whilst flushing out the crankcase to ensure there were no flakes of metal lurking around, If found a piece of orange plastic tube, about an inch long and half inch in diameter. Any ideas where this may have come from?

While everything is apart I've cleaned and measured the various components to make sure everything is in spec according to the manual. Is there anything else that you would recommend I can do while the engine is stripped down?

Many thanks

[jasonbc]

Hi,

Finally got around to stripping down my XR400 engine that suddenly expired on me a couple of months ago.
On removing the valve cover, it was apparant that the cam chain had broken. Unfortunately it was jammed lower down in the engine so the cylinder head, cylinder and right hand engine cover were removed to allow access.

The chain was eventually extracted and no other damage appears to have occured. So, I have some questions for you guys who may have done this work before:

I presume a new chain will come already joined. If this is the case, what is involved in putting into the engine - does the primary crank gear need to be removed to allow the fitting? Having already tried to remove the 27mm nut on the end of the shaft unsuccessfully, what is the best way to do this and lock the drive gear in place while it is done. All I am doing is spinning the whole engine over. My workshop manual makes no mention of replacing the camchain.

Whilst flushing out the crankcase to ensure there were no flakes of metal lurking around, If found a piece of orange plastic tube, about an inch long and half inch in diameter. Any ideas where this may have come from?

While everything is apart I've cleaned and measured the various components to make sure everything is in spec according to the manual. Is there anything else that you would recommend I can do while the engine is stripped down?

Many thanks

I did mine a couple of months back easy job. Chains can come sealed or open ended i bought an open chain as its easier and quicker as you only need to break the old chain join the new one to it and then rotate the crank until the new chain is all the way through. With a sealed one you can take the right hand engine case off and drop it down and place it over the bottom sprocket, if your handy you can do it with the engine case on and use a telescopic magnet to push the chain over the bottom sprocket. Check your bottom strainer to see if thats clear, i'm surprised it let go and did not do any damage, can't think what the orange tube is and i don't remember seeing one in my motor ( thats not to say it doesn't have one)unless some one was using it on a funnel when filling the oil and it fell down through the frame but that unlikely as the frame strainer would have stopped it going any further

[sheep911uk]

Gav i have a brand new sealed genuine Honda cam chain for sale if your interested.
Nick

[gav03]

Thanks for the advice, and thanks for the offer Nick, but parts have already been ordered.

I'm hopeful that a new cam chain and gasket kit will be all that is need to rebuild the engine. This has been a job I had been dreading for some time, but it's (so far) not been too bad. Fingers crossed, nothing else is damaged!

Gav

[walesxr]

You have a 99% chance of bent valves if you cam chain broke, this is easily checked as you already have the head off, by tipping some petrol down into the ports and seeing if it sips past the valves, I bet that it will rush past a couple of them.

[gav03]

Thanks for the tip. I'll try it at the workshop tomorrow.

There was no visual sign of contact between valves and piston. The bike has a 440 big bore kit and the piston has valve recesses machined into the crown. Fingers crossed there has been no valve/piston interface! I'll report back on the test results.

[gav03]

Petrol through valves test completed - looked ok, went ahead and rebuilt engine. Bit of a ******* getting the new chain over the cam sprocket, but a bit of 'persausion' did the trick.

Also had an issue with getting the kick start mechanism back together - my manual is a bit ****e to say the least so it took four attempts to sort it out.

Finally got everything together, adjusted the valve clearances and went for it. Started after the third kick which was a pleasant surprise!

Full off-road test this weekend!

This was the first time I've been so deep into an engines internals, so I'm a bit chuffed with my spanner work to say the least. It would have been easier with a proper workshop manual, but thank you to those that offered advice.

Gav

[TRANSPORTER]

Good effort on the fix, makes you wonder sometimes why some people take their bikes into bike shops to have the work done on them, I bet now after you have done this major surgery on yours you will think twice about paying someone else to do any more work on your bike for you.

[walesxr]

Petrol through valves test completed - looked ok, went ahead and rebuilt engine. Bit of a ******* getting the new chain over the cam sprocket, but a bit of 'persausion' did the trick.


Gav

Good news on your valves, I think you were very lucky. But I have no experience of the 440 conversions, so maybe they do have more clearance. Anyway well done on sorting it out yourself.

[Nigel Rees]

Gav i have a brand new sealed genuine Honda cam chain for sale if your interested.
Nick

Hi, do you still have the cam chain, or any exhaust valves for sale
Thanks