Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: toucheturtle on April 24, 2010, 07:07:11 PM
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Hi all,
Decided on a little routine maintenance today but as per usual I seem to have just created a whole world of misery for myself. Adjusted tappets on my CB500K1 and fitted new plugs, before running the bike again thought I'd re-tension the cam chain adjuster.
When I fired the bike up it made a horrible rattling sound on idle and low revs which seems to go away as you increase the revs. The adjusting screw slot is in the horizontal position, is it supposed to be vertical? See photo
Have tried turning the screw but doesn't seem to want to turn more than 45 degrees clockwise. Went through manual procedure of setting crankshaft advancer assembly at 15 degrees ATDC but seems no movement in adjustment screw. I am not aware of damaging anything but does sound like a bag of nails now.
Any advice greatly appreciated,
Andy
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That screw is NOT an adjuster! To adjust the can chain tension, all you do is looseb the locknut, with the crankshaft turned to a partcular position, and then re-tighten the locknut (the cam chain tension is automatically adjusted by a spring within the mechanism.
To find the correct crankshaft position, rotate the crankshaft so the T.14 mark aligns with the timing mark on the crankcase, make sure that the number 1 cylinder valves are closed (slack in both #1 cylinder tappets) - if not rotate a full turn and check for #1 tappet slack again. Then rotate the crankshaft a further 15
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Here's a link to Bryan Jones' patented cam chain adjustment technique.
Not quite by the book but the result of (30?) year's experience...
http://forums.sohc4.net/index.php?topic=369.msg315851#msg315851
Steve
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Not quite by the book but works perfectly.
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Thanks for the advice, I have followed the procedure you describe honda-san, however I have an old Honda 500 manual which describes the engine disassembly process. It advises to:-
"Loosen the lock nut of the cam chain tension adjuster Leave the wrench on the nut), turn the screw fully Approximately 90 degrees) clockwise, and then tighten the lock nut. In this condition the cam chain tensioner is not applying tension to the cam chain."
The diagram shows the adjuster screw slot in the vertical position being turned through to the horizontal position. I'm not aware of moving the position of the screw but now I have noticed it's position I just am not sure if it's in the right position.
Having slept on the problem will check all feeler gaps again, I think it may just be firing on three cylinders as it wont tick over below 2000 revs and klunks over till the revs are raised.
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When disassembling the engine you don't want any chain tension, hence locking it off in that way. For running the bike the tension needs to be on and right, the sping in the tensioner sets that if the locknut is loosed off and cam is in the prescibed position. The slotted screw has a cog on the other end that works against a 'rack' on the tensioner mechanism and I'd not worry about the angle the slot assumes, other than that it might help indicate wear in the tensioner blade if there was a dramatic shift after between adjustments. Other factor to look out for is when setting the tension, that the slotted screw can turn when tightening the locknut after setting tension, so hold the screw where it ends up after tensioning just while you tighten the locknut.
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That screw is NOT an adjuster! To adjust the can chain tension, all you do is looseb the locknut, with the crankshaft turned to a partcular position, and then re-tighten the locknut (the cam chain tension is automatically adjusted by a spring within the mechanism.
To find the correct crankshaft position, rotate the crankshaft so the T.14 mark aligns with the timing mark on the crankcase, make sure that the number 1 cylinder valves are closed (slack in both #1 cylinder tappets) - if not rotate a full turn and check for #1 tappet slack again. Then rotate the crankshaft a further 15
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Solved problem almost straight away, the 2 and 3 points were closed, must have knocked them when turning the crank. bike is back to it's old self again now.
Many thanks for all the advise