Forks and genernal CB750 K6 rennovation....

[scotia_steve]

Hi all, first post so please be gentle

Last year I was lucky enough to find a pretty immaculate K5 CB750 US import that had been sitting in an enthusiasts garage since the mid 90's with only a few thousand miles done in that time. I got in a van, drove a 600 mile round trip to buy and luckily it was a good one

Couple of things:

1. Forks - I noticed a knocking noise after I'd stripped and replaced the seals, installed missing gaitors and it seems like the two small springs at the bottom of the leg are missing! Anyone else had this? Just ordered some progressive springs too from Hagon....

2. Cold starts. The bike takes numerous attempts to start from cold. When you've used it the day or couple of days before no problem. The carbs are balanced and plugs seem in good nick. Any ideas?


Cheers

Steve

[Voxonda]

Hi Steve,

You really need these springs, they are the rebound springs.
Try open up your petrol tap say 1 or 2 minutes before you start, give it time to (re-)fill the bowls, works for me. Modern fuels seem to evaporate faster then the old ones.

Cheers, Rob

[scotia_steve]

You think that's all it is with starting?


I found the springs after spending

[Voxonda]

You think that's all it is with starting?


I found the springs after spending

[Bryanj]

Modern petrol goes "off" quicker than it used to. If its been stood for over a week drain out the floatbowls and let in fresh from the tank as it stays in better order in bigger lumps as it were/ CX500 and the twin cam750/900 were the first to show this problem back when new but petrol got even worse in the ensuing years

[Dave M]

I don't seem to have any probs with my 550.

I can leave it for several weeks and just for a change I'll start it on the kick. 4 or 5 kicks and she's running.

Must remember to put the footrest back before I ride away...

[scotia_steve]

I was wondering if there was another problem with starting but hopefully that's it

Just noticed the steering head sits in a "notch" straight ahead - just ordered some taper bearings to replace!


Got a feeling the clutch is on the way out too - gears can be hard to engage sometimes, but no slipping....?

[SteveD CB500K0]

Just noticed the steering head sits in a "notch" straight ahead - just ordered some taper bearings to replace!

That's an MOT failure so you're doing the right thing.

[scotia_steve]

Just noticed the steering head sits in a "notch" straight ahead - just ordered some taper bearings to replace!

That's an MOT failure so you're doing the right thing.
[/quote]

I didn't know that! Lucky I'm doing the job. It's a stunning bike - just doing the bits and pieces now that need doing

[Bryanj]

Decent bike Nice car, where are you?

Dave the 500/550 seems more "tolerant" of bad petrol than other models, must be the best to but!!!

[scotia_steve]

Decent bike Nice car, where are you?

Dave the 500/550 seems more "tolerant" of bad petrol than other models, must be the best to but!!!

In Edinburgh. Lot's of nice roads closeby! 

[scotia_steve]

Ok, replaced the head bearings - there is a 1mm difference in height so the forks have to be raised slightly to fit correctly in the top yoke but I figure that cant be too bad... The old races were totally worn out and I needed to use a small blow torch to remove the old race!

Taken the caliper off to paint with heat resistant engine enamel gloss black, painted the top yoke as it was looking a bit sorry for itself and then will rebuild next week!

All this for a fork knock which was most likely the head bearings it seems. Spent the best part of

[Bryanj]

Sorry mate, you can't get much farther from Gloucester so i cant pop round to help!

Careful when tightening the fork tube clamps on the top yoke---there is supposed to be a shaped washer in the gap to stop you over tightening and breaking the ally  but it regularly goes missing.

[scotia_steve]

Sorry mate, you can't get much farther from Gloucester so i cant pop round to help!

Careful when tightening the fork tube clamps on the top yoke---there is supposed to be a shaped washer in the gap to stop you over tightening and breaking the ally  but it regularly goes missing.

I think that's the one that's still there - funny edge to it?

Any idea of torque? This is from a CB550 manual which I believe uses the same fork and stem components....

[BigAl (Alan)]

I have a CB750 K4 (american) I would agree with the starting problem when left for a couple of weeks. Done all the normal things changed plugs/points re-set timing/balanced carbs/check electrics...the problem is the petrol...if its fresh, its fine by week 3/4 problem starting.
Did some research on line and found interesting articles on www.safety-marine.co.uk on petrol problems in boats/canister storage...the upshot is if there is air in the tank/float bowls and the boat (or bike) moves about frequently the octane of the fuel decreases rapidly, you can buy additives to prevent this, but its easier to put fresh petrol in.