Tacho worm drive removal/installation

[beemsquar]

Hi guys,

I need to replace the worm drive in the rocker cover as it is worn, but can't for the life of me see how to remove it. I've looked online for the answer with no avail.

Obviously I turned to you guys here for the answer.

I have spare rocker so will have to do this twice and fit the better one.

If anyone has pictures of there removal that would be helpful too.

Cheers

Andy

[Bryanj]

You talking 750?

[AshimotoK0]

Think he means CB350/400 four Bryan.

[beemsquar]

Yeah for the 400 four.

[Bryanj]

Looking at the parts list there is a circlip on the bush inside the cover, remove that at I think the gear and bush come out as an assembly pushed out from the inside

[Drew400]

Hi Andy,

I gave up on mine. Circlip out, no problem, but the rubber bung resisted all attempts! The word b%%%%%d sprang to my lips a few times.

Good luck with yours, but if it's any consolation, mine was vapour blasted in situ and barely leaks after the rebuild!

Cheers, D.

[beemsquar]

I think I really need to get it out, it's worn and also I can't get the new oil seal in correctly as the PO has squished the metal flange inside and the seal won't seat properly.

I also have removed the circuit and tried to push it out, but you have to give it way more force than I'm willing to put on it to push it out, which is why I thought I would check if there's something else that needs to be removed first.

So close to getting this engine together now.

[beemsquar]

Can anyone else offer any advice please?  I really want to get this all together now and don't want to force it out.

I dont think you can buy the bush part anymore from DSS or CMSNL

[Clem2112]

These things seem to defy removal even after extracting the seal and circlip.
From memory I got the the seal out by screwing in 2 small screws and extracted it with pliers.
The circlip is a plain one and is fiddly to prise out.
I filled the cavity where the gear sits with plus-gas to ease the bush which is a tight fit.
Left that for a day or two to soak in warm conditions ... Might have put the whole thing in the oven ...only 100 C or so to be safe.
Next bit was a bit brutal but I saw no other way......
Got the shaft to move a bit by tapping the gear with an ally drift to protect the hardened teeth.
Then I  used a blunt flat bladed screwdriver as a wedge once the end was free of the blind hole
tapped that until there was enough gap to get the drift in. Then the side of the drift can be
hammered to drive the gear out.
 As mentioned thecgear comes out complete with its bushing.
Probably the trickiest engine part to dismantle so it's nice when it finally comes out !

[beemsquar]

Thank you so much, this is vary helpful!  Do you know if you can fit a used bush inside or does it have to be replaced with a new one?

[Clem2112]

I don't think (sure?) the bush is available separately and probably never was?

Come to think of it , the bush may remain in the casting when the gear is driven out.
I think the OD of the teeth is slightly smaller than the ID of the bush (and gear shaft plain dia)
so there is a clearance..... You will see either way.

[Chris400F]

Looking at the parts manual the setup looks very similar to the G5 models.
I have an engine for those in bits so could have a look at the parts.
The shaft diameter is quite a bit smaller than the gear so you won't get one out without the other.
P/N for the bush (parts list calls it a collar) is 12435-377-000.
I don't think you'll find a new one (although you never know ....), found a S/H one and doubtless there are others:
http://www.ebay.co.uk/itm/75-Honda-CB400F-Supersport-Tachometer-Drive-Gear-Collar-OEM-Bushing-Cylinder-/400936697439

[beemsquar]

Cheers guys, thats what I thought Chris. Looking at it from inside the rocker the gear looks larger than the collar, so I didn't want to force it.

The main problem other than the gear is that the collar itself is damaged and and new seal wont seat against the bush, the old seal I removed looked like it had been cut down and siliconed in place, but I don't fancy bodging it.

I have a spare rocker with an intact bush and screw, so If I could remove it I will swap them over, thanks for the link though, good to know I can possibly get a spare if needed.

[Clem2112]

That picture of the bush in the ebay ad explains why it was so hard to drive out !
Over an inch of engagement in the alloy casting.

[beemsquar]

At last I managed to get the little bugger out! I removed the one from my spare rocker cover easily by removing the circlip and gently tapping the worm drive with a piece of cut down acrylic so not to damage the splines.

The reason it wouldn't come out of the rocker I was using was because there were remains of the old oil seal in there still, once I had carefully picked it out, it came out as easily as the first one. It also explains why my new seal wouldn't seat properly! Panic over.