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Post by snagglpussping on May 28, 2020 8:18:41 GMT
hi everybody i have a 1981 cb250nb it hasnt been moved for ten years . inside tank nice ,the two smaller jets were blocked put fuel and goes ok. redonr front brake m cyl and piston .rides good .has a chain like noise so took rocker cover off andloosened tension bolt and pushed it out from top and retightened still same . the tappets were about 4 thou all round .maybe to tight? or maybe ballancer chain  open to ideas here in australia hynam sa 5262  |
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Post by pierre on May 28, 2020 10:05:42 GMT
The tensioners blade may be worn out ? Or it could be the counterweight chain. I just rebuilt the engine of my CB400 and it's also making some chain noise. Still need to investigate.
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Post by stevegbr on May 28, 2020 10:09:41 GMT
hello and welcome to the forum.
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Post by Deleted on May 28, 2020 20:01:03 GMT
How many miles has the bike done? I found the cam chain to be very loose on my high-mileage bike and making a lot of noise.
The chain tensioner would not take up the slack. I replaced the chain by using one with a rivet link so I did not have to dismantle the engine. Not an easy job but well described in the Technical section of this forum.
If your chain is not too worn the tensioner might take up the slack. Contrary to the workshop manual, you should not loosen the cam chain tensioner bolt with the engine running. Warm up the engine, stop the engine and loosen the bottom not of the cam chain tensioner. If it is working, the tensioner should move inside the engine and take up the slack in the chain. Re-tighten the nut and listen to the engine running again. If there is no change you may need a new cam chain and or tensioner. I am not sure if you can replace the tensioner without dismantling the engine.
It is probably worth checking the tension of the balance weight chain as well as this can be done without taking the engine apart.
Dennis
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Post by snagglpussping on May 28, 2020 22:08:38 GMT
cheers will they run without ballancer ?
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Post by pierre on May 29, 2020 7:12:01 GMT
It could probably run without balancer but you need to disassemble the engine to remove the chain. So at this point, you could simply replace it. You should first check the balancer chain tensioner which you access from the right side cover behind the cap. You may need to rotate the stopper on the shaft.
About the cam chain tensioners, on model C and above (>82) you can replace from the top but I believe it's not possible on earlier models because the rear tensioner is captive in the crankcase.
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Post by buster on May 29, 2020 8:42:20 GMT
hi welcome along.
always difficult to diagnose a noise without hearing it in person. the balance chain is easy enough to adjust, just take the little cap off the clutch cover, back the nuts off a few turns and pull the adjuster forwards a little on its splines then push it against the spring and release and it should 'flick' itself into position, then firmly nip the nuts back up, job done. cam chains a different set up as others have said. I'd guess if its a jingle type noise its probably the cam chain, if its more of a ticking noise (from the top end) then it could be a valve issue.
pierre's right about the cam chain tensioner on my na model its clamped in with a bolt and part of the balance chain guide inside the crankcases, I think your nb will be the same set up.
hope this is some help
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Post by na44superdream on May 29, 2020 9:46:37 GMT
When you have the rocker cover off (and definitely the spark plugs disconnected, and absolutely nothing around to fall in the engine~) Since the cam chain should be tensioned statically. you can do an adjust, and push down on the tensioner , just in case the spring has lost a bit of its mojo.....  Does it look like all the adjustment on the balancer quadrant has been used up? looking through the inspection cover.  |
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Post by snagglpussping on Jun 5, 2020 10:24:32 GMT
awsum cheers for that . stay covid free NO 5G
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open to ideas here in australia hynam sa 5262
