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Gearbox woes

Submitted by kevin_bell on Wednesday, 26 April, 2017 - 01:00
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Heavy Twins

Hope somebody can help please.

I had an oil leak through the kickstart shaft seal and so I took off the outer cover, replaced all of the seals and the pawl spring for the gear selector. The gears changed fine before I took the cover off and seemed to be alright after I had refitted it - checked up and down and it was good. I'm in the middle of a major engine refurb and so the gearbox just sat until recently when I was refitting the primary drive. When I tried to put it into 4th, I could only select 1st, neutral and second.

I looked at the previous threads about selector problems and my symptoms match the spring "wind-up", but I haven't replaced that spring. I got the Mick Hemming article and found that I should have selected 2nd gear before fitting the outer cover (this isn't mentioned in the Haynes manual!) but I had also fitted the pawl spring upside down. Hurray - I thought - solved! However after fitting the pawl spring correctly with the straight leg on the top, and checking that every gear selected using a screwdriver, when I put the outer cover on, only two gear again!

I'm at a loss now. I have taken a couple of photos and wonder if anyone could tell me if the pawl/ratchet plate assembly are worn? I see that my pawl has part number 04.0123 cast onto it, but this isn't a recognised part number on Andover or Norvil lists. The listed pawl looks a lot different to mine, but Norvil say that it fits all models from 1957 onwards - my bike is a 1965 SS so I would have thought it would have been fitted already.

Any help would be greatly appreciated.

EDIT: Sorry, it's the pawl CARRIER that has the number cast onto to, not the pawl itself. Have examined the pawl more closely and it does seem to be worn so I'll get a new one as a matter of course and hope that cures the problem!

Attachments
Pawl-detail.gif
pawl-overview-gif

Submitted by david_comeau on Wednesday, 26 April, 2017 - 01:02

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I see from your pix the ratchet spring is touching the gearshift pawl. This is an absolute NO- NO.

Just installing the spring in position and correctly oriented is only the first step. Second step is to tweek/bend the legs so they DO NOT touch the pawl, and yet restrict the movement to NOT fall into the ratchet plate until called for by shifter action.

Looking at the old brits pix "Correct spring fitment" you can not discern the clearance needed. It can be small, but if it touches both sides, gear shift rarely works reliably.

Submitted by kevin_bell on Thursday, 27 April, 2017 - 01:00

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Previously john_holmes wrote:

Go to

http://www.oldbritts.com/gearbox_a.html

scroll most of the way down and check you have the ratchet spring bent correctly as detailed in the instructions.

Thanks John, that was a great link. My photo didn't show it correctly, but there IS a small gap on each side of the pawl. Hopefully the new pawl will engage more easily when I get it.

Submitted by kevin_bell on Thursday, 27 April, 2017 - 01:03

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Previously David Comeau wrote:

I see from your pix the ratchet spring is touching the gearshift pawl. This is an absolute NO- NO.

Just installing the spring in position and correctly oriented is only the first step. Second step is to tweek/bend the legs so they DO NOT touch the pawl, and yet restrict the movement to NOT fall into the ratchet plate until called for by shifter action.

Looking at the old brits pix "Correct spring fitment" you can not discern the clearance needed. It can be small, but if it touches both sides, gear shift rarely works reliably.

Many thanks for your reply and assistance Dave. As mentioned in my reply to John, there actually is a small gap on each side of the pawl - just a rubbish photo of mine! - so I will polish up the pawl post and fit a new pawl - mine has worn on the ends.

Submitted by kevin_bell on Sunday, 30 April, 2017 - 01:00

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Just as an update - the new pawl arrived from Andover Norton and was duly fitted. I noted that there was a lot more 'meat' on the engagement lugs of the new one, I suppose after 52 years you can expect a little bit of wear!

So far, the gear selection seems to be working alright and I'm hoping it will be even more positive when I get the engine running.

Thanks to David and John for their help.

Kevin

 

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