RichardW's Velocette rebuild

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moizeau
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Re: RichardW's Velocette rebuild

Post by moizeau »

Splendid news, make sure you gap them without the piston in the cylinder before putting it back together. Use the piston to push them down the bore and gap them at the tightest point, using the piston makes sure they stay square. Good look.

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

With the bike back with exhausts, working on re-assembly. Got the new rings, so have filed them back so they are a tight fit at the entry to the bore, which should minimise the gap further up the bore. You can see the difference in the length of the rings here....
rings2.jpg
After carefully blocking off the crankcase whilst I refitted the gudgeon pin clip, I then unscrewed the nut off the barrell stud and promptly dropped it down the crank case #-o so I had to take the side off to recover it. With the barrel back on, I've put something together wrong as it won't turn over now hmmmm resume that battle tomorrow!

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

Tightening up the outer plate hard presses the inner filler plate onto the end of the crankshaft causing the stiction. Backing it off just a few deg frees it up... With that done it is evident we have a lot more compression, but also that the decompressor is leaking, so I need to sort that out. I have got the saddle springs on but the cover seems to be too long, so I need to make a couple of brackets. Need to try and get it mostly assembled tomorrow. If I can figure out the decompressor, then maybe it will start....🤔

moizeau
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Re: RichardW's Velocette rebuild

Post by moizeau »

Good luck, if you have trouble with the decompressor (kill switch), blank it as long as you can remove the plug safely or wire a switchable ground on the low tension side.

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

After a day spent on reassembly, it's more or less up together now. I've got to put another coat of paint on the tank, fit the chain, put the saddle on (ready, just need to put some additional washers on some of the cover bolts), once the tank is on I need to adjust the gear change.
bikeright.jpg
bikeleft.jpg
It didn't really want to go back together - at least I was working in the garage with the heater on!! Just fitting the rear number plate took about an hour :roll: Not helped by not feeling 100%, and everything I touched fell on the floor, and then disappeared under something!

The throttle is still no good, not sure what to do with that, I may need to go back to the original internal scroll, but I think it's well gummed up. The clutch cable needs making longer.

I've got the lights to put on as well, but I need to get the headlamp re-silvered, and then refurbish it all before putting it on.

I got a quote for chroming the pipes... a grand give or take :shock:

So big question, will it start? Will it heck.... no difference really, still no interest at all in running. Even after quite a few kicks, the plug was still dry, so I don't think it's getting any fuel sucked into the cylinder - it was certainly in the crankcase as it was running out the bottom. Still only showing 3 bar on the compression gauge, but it does come up much quicker than it did (2 kicks).

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

Some more photos of it in action... possibly taken in the winter of 46/47

I think the bike on the right is the Velocette, with my Gran aboard; not sure what the one on the left is, but that's my Grandad.
snow1.jpg
Note the headlight diffuser still fitted on the other machine. Maybe the light on the Velo is so dim it doesn't need one...!!
snow2.jpg
This might be another day, the bike on the right looks like it might be the Velo, the one on the left appears different to the one above as no diffuser.
snow3.jpg

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

I got the info from the factory despatch books. It was shipped in Dec 1928, so sat at the dealers for 7 months before it was registered. Dealer was Auty & Lee in Bury, and first owner was a J Dykins in Potter Street, Bury. Recorded Frame, engine and gearbox numbers match ( although the frame and gearbox nos are transposed in the record). Recorded as a Brown and Barlow carb, but now sporting an Amal type 4 so that's not original.

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

I've ridden it!!

OK, it was only down the hill outside the house under gravity...! My Dad was here so we put some petrol in the carb and tried to bump it - still no interest in running, I'll be working on rebore in the new year!!

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xantia_v6
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Re: RichardW's Velocette rebuild

Post by xantia_v6 »

I still have the opinion that the failure to start is not due to lack of compression. I expect that this engine, being a piston port 2 stroke, and designed to run on 1920s petrol, has an effective compression ratio of 5:1, or even less, so in perfect condition, a hot engine might have a compression test of 75psi.

I suggest that you initially start the engine on gas (propane/butane/acetylene/ether, whatever is available), as these gasses don't require any compression or carburation, just a correctly timed spark.

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

You've mentioned that before Mike - I've got a butane cylinder (4.5 kg ... Ought to be big enough :lol: ) so I could give it a try. Presume just run a tube into the carb throat with the slide wedged open, then crack on some gas and kick it over?

I get petrol in the crank case, but not seemingly in the cylinder, so it looks to me that crankcase pressurisation is not occuring at the right time to transfer the fuel into the cylinder. Pushing down the road at reasonable speed and it makes no effort at all.

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xantia_v6
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Re: RichardW's Velocette rebuild

Post by xantia_v6 »

We used to use an acetylene plumbers torch to produce a compustable gas mix, with the (not ignited) tip of the torch poked into the mouth of the carb.

I believe that the Velocette engine had packing plates in the crankcase to fill the voids around the crankshaft. These are necessary to give the maximum compression ratio in the française for pushing fuel mix up through the transfer port. Are you sure that the correct pieces are present?

RichardW
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Re: RichardW's Velocette rebuild

Post by RichardW »

I could try that with the blowlamp, but it does have a habit of spitting back through the carb, when I've tried Easy Start... Internal baffle is in place as per this post:
RichardW wrote:
31 Jul 2019, 10:32

Hmm, what's that all about, surely that will just blow petrol mix out when it's running? Then I remembered there is this insert to go into the end of the crankcase to reduce the free volume

Image
I will re-check the timing - I'm sure it's BTDC rather than ATDC, but I've been wrong before!!

ekjdm14
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Re: RichardW's Velocette rebuild

Post by ekjdm14 »

Wow what a saga, just got a chance to read through start to finish! My head is not in full working order right now but one thing I can say, the Vito "hand"brake thing... Because Mercedes...