Topic: Front end rattle?

[38rudge]

Not had my CB750K2 that long but I find that when going over sharp ridges or a series of road irregularities that I get a rattling/jarring sound from the front end a similar sound to something slapping against the front mudguard?

Thought it might be the speedo cable, so I removed that  and went for a ride but still the same problem? Are these bikes known to have this sort of problem? Is it likely to be the front fork springs rattling?

Negotiating normal undulations does not cause any noise only sharp bumps. Has anybody else experienced this and found the cause and a cure? 

[dave500]

check those head light support tube/ears,they can slide up and down the forks and rattle.

[38rudge]

Thanks for the reply and suggestion.

The headlamp brk's and rubbers are all new and very firm if I try to move them, so not sure that they may be the source?

Has anybody else any suggestions or know if this may be a fork spring problem?

[dave500]

yeah ok,i have one soggy rubber and it makes an annoying rattle the same way as yours,youve looked at and adjusted the steering bearings?if they are the stock ones they may have a dead or flat spot in the race where you cant really adjust the slack out without going too tight?they can be upgraded to tapered roller types if that's the case,kits are quite cheap for these if needed.

[my name is nobody]

In addition, check the caliper hinge for vertical looseness/wear.Ttry applying front brake when going over bumps and see if noise goes away when caliper is applied.

[dave500]

good call nobody!i had wear in that spot and managed to wrap some thin shim around the pivot,not perfect but stopped a little rattle and the fingernails down the black board #$%*ing squeal!

[my name is nobody]

good call nobody!i had wear in that spot and managed to wrap some thin shim around the pivot,not perfect but stopped a little rattle and the fingernails down the black board #$%*ing squeal!

Yup, it can absorb vibration (which sets up noise) in some cases too. Lubing helps as well. There was a fix for
that condition in a TSB from Honda, and a shim with a part number. Came up on this board a looong time
ago posted by the late Raul Guellego(sp?). Terry knew him well.

[Dunk]

In addition, check the caliper hinge for vertical looseness/wear.Ttry applying front brake when going over bumps and see if noise goes away when caliper is applied.

^ This.  You can make a shim with feeler gauges. Measure the vertical slop and use a feeler a couple thou smaller than the gap. Punch a hole in it and trim to size, lightly grease and install.

[38rudge]

Thanks for all the replies and suggestions.

Bike already has tapper bearings fitted, but will check their play. No apparent play on the brake caliper arm but will try applying the brake to see if that makes any difference?

The noise is fairly loud and as previously expressed producing the sound like something banging/chattering  against the mudguard or something in the front of the bike. Can't find anything loose?

[TwoTired]

I can't hear your noise.

But, on the off chance the sound is misdirected...
Have you checked the drive chain tension?

I had a noise during braking from down below.  Checked front end for bits in contact under compression. Found nothing.

Eventually....

Fricken chain was too loose and smacking the chain guard during decel.  Sound bounced off of something up forward.

Why didn't I find that sooner? 

[Don R]

 Both of my K0's do that, I'm interested to find it also. It's for sure in the fork area. I'll check my brake for play too.

[disco]

My K2 does it as well. K6 does not. I have a new set of PROGressive springs to install. They have a small plastic ‘preload’ that comes with kit. I’m thinking that’s the problem with mine. No preload is allowing the springs to rattle slightly over corrugations.

[my name is nobody]

Also, check the rubber grommets inside the bolt holes of the fender braces for rot/wear.

[Old Moe Toe]

My K2 made a noise just like that.
Ended up being the little rivets that attach the front fender/guard to the mounting brackets had worn loose.
Couple of taps with a hammer to the rivets fixed it.
Might not be your problem but you never know.

[ilikepinkcrayons]

Maybe the bird's nest of junk in your headlight bucket? Long shot, but it's a thought...

[38rudge]

Also, check the rubber grommets inside the bolt holes of the fender braces for rot/wear.

Mine is the earlier K2 without the rubber bushes on the stays.

[38rudge]

My K2 does it as well. K6 does not. I have a new set of PROGressive springs to install. They have a small plastic ‘preload’ that comes with kit. I’m thinking that’s the problem with mine. No preload is allowing the springs to rattle slightly over corrugations.

I have also fitted  progressive fork springs that came with a couple of aluminium pre-load spacers. However, when refitting the fork caps the whole lot is under tension, so dont believe that it is due to no preload?

[38rudge]

I can't hear your noise.

But, on the off chance the sound is misdirected...
Have you checked the drive chain tension?

I had a noise during braking from down below.  Checked front end for bits in contact under compression. Found nothing.

Eventually....

Fricken chain was too loose and smacking the chain guard during decel.  Sound bounced off of something up forward.

Why didn't I find that sooner? 

I will certainly check the chain play. But it is a new chain and sprockets which I do check and adjust regularly.

[dave500]

don't forget these are old bikes,even new they wernt exactly perfect?its been years since cars had a manual choke,lotta guys expect to push the button and have it idle straight up?the art of having a feel for the fueling has gone away in that reguard?sure your not being fussy?

[disco]

My K2 does it as well. K6 does not. I have a new set of PROGressive springs to install. They have a small plastic ‘preload’ that comes with kit. I’m thinking that’s the problem with mine. No preload is allowing the springs to rattle slightly over corrugations.

I have also fitted  progressive fork springs that came with a couple of aluminium pre-load spacers. However, when refitting the fork caps the whole lot is under tension, so dont believe that it is due to no preload?

OK well that just blew that theory! 😜 I don’t know where to go with my front end now. I’ll have to keep an eye see how this pans out.

[Jerry Rxman Griffin aka MuthaF'er]

Be sure you have the correct volume of fork oil.

[BobR]

 Have this too. Been that way since I got the bike in 98 and fixed it up. Recent renewed interest in riding it has me finally looking to fix the annoying clunk. Might be a stupid question but are there any internal "bumpers" to soften full fork extension? Seems to me that's when I get it. Bob

[Don R]

Both of my K0's do that, I'm interested to find it also. It's for sure in the fork area. I'll check my brake for play too.

 They both have vertical travel in the caliper arm. Now I know what mine are doing. Next up, how to tighten them up a bit. ? I'll try dunk's suggestion first. I have a whitney punch, let's see if it will punch a feeler gauge.

[BobR]

 I just checked my caliper arm. Decent bit of up/down movement. Going to make a small shim and try it. Bob

[BobR]

 Upon inspecting the caliper pivot arm assembly I realized the two top bolts (the ones that also attach the fender) only need to be loosened slightly , and while holding downward force on the upper pivot holder re-tightened. Virtually all play is gone. The upper mount bolt holes allow small up and down movement so if they are removed to mess with the fender or whatever a lot of play will be introduced into the caliper pivot arm unless downward pressure is applied when tightened. HTH Bob

Update: It should be noted my assembly is different than the one shown in the manual here. (See next post with pic)