Topic: Clutch rattle, spark plugs....

[c15racer]

I think ive got the common clutch rattle with my new CB500,
Its rattling pretty bad on a slow idle and goes away when the revs are increased to 1800-2000rpm.

Pulling the clutch in does make a slight difference but it doesnt totally go. Ive just bought a carb sync tool so im going to set the carbs up and im hoping that makes a big difference.

I have searched on here but i dont understand why the CB's suffer from this problem, is just just wear? as surely when new this wouldnt have gone down well with new buyers? Is there anything you can do to totally ellimate the rattle, im a engineer so i dont mind getting dirty and having to machine parts.

2nd question, what spark plugs are suited for the bike? + whats the plug gap?

Also while i remember is my bike a K2? its a 1974 UK model.

many thanks

[bwaller]

I think you'll find that once you sync the carbs, your rattle will disappear, these bikes are notorious for this when the carbs are out.

For plugs use NGK D7EA set to 0.028"

[Bob Wessner]

I have searched on here but i dont understand why the CB's suffer from this problem, is just just wear?

Here's my guess. When out of sync it means some cylinders are working harder than others and applying differing amounts of force to the crank, etc. causing uneven clutch unit rotation, thus the rattle. Any better, more accurate explanations out there?

[TwoTired]

The rattle you hear may be the primary chain whip, and the trans gears "clacking" with the speed changes.
Carb sync should, at least, improve this, as all cylinders firing with the same strength should keep the crank at constant speed.  With the crank changing speed the primary chain alternates which side is in tension/slack.  There is no tensioner on the 500/550.  Then the trans gears alternate which face is in contact.  It makes quite a racket at low RPM.  The clutch basket/clutch plate tabs can make noise too, with rotational speed variation.  But, this noise changes with with clutch engagement.

Cheers,

[c15racer]

many thanks for the replys guys.

Ill hang fire and wait for my carbtune to get here (shouldnt be long as im in the uk anyway) and then ill get the carbs sorted and ill report back with the findings.

On a similar note how do you go about getting the middle 2 cylinders plugs out? My plug socket wouldnt go past the webbing on the heads. Ive bought a plug key from david silver in the hope its the correct tool for removing them but i was wondering if anyone else struggles?

[hymodyne]

a deep well 18mm socket and an extension have worked for me.

hym

[TwoTired]

On a similar note how do you go about getting the middle 2 cylinders plugs out? My plug socket wouldnt go past the webbing on the heads. Ive bought a plug key from david silver in the hope its the correct tool for removing them but i was wondering if anyone else struggles?

I find the plug socket that comes with the tool kit works best.  It has a bell mouth that fits over the plugs' hex, and narrows above it to clear the interference.  Straight walled sockets, need to be at least thin wall design for any hope of clearance.  The worst danger is during insertion, as a straight walled socket will tend to cross thread the plug in the softer aluminum hole.

Cheers,

[c15racer]

cheers, i went into my local town but i couldnt find anything so i ended up grinding a socket i had down. Turns out ive a duff plug which wasnt helping matters

[mystic_1]

The worst danger is during insertion, as a straight walled socket will tend to cross thread the plug in the softer aluminum hole.

I always try to spin my plugs in as much as possible just using my finger tips, to avoid this very thing.

When access is hard, slip a piece of rubber tubing over the plug's insulator and use that as a handle to spin in the plug, then just pull to pop it off once the plug is in.


mystic_1

[c15racer]

great tip! ill give that idea a go in the future 

[750K2]

i've got a 750 k2 that also has given me fits while inserting spark plugs.  with a deep drive socket i could set the plug tight but couldn't remove the socket.  so i took my deep drive socket and chamfered the top edge on a stationary belt sander to get more clearance.  works great.