Advance/retard VB600

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bevanclark
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Re: Advance/retard VB600

Postby bevanclark » Sat May 08, 2021 11:28 pm

Mark,
Herre's a clip of my VB in case its of inmterest:
https://youtu.be/322FrPzSdbM

It splutters a bit until warmed up, but idles smoothly after that on full advance and when retarded.
Cheers,
Bevan

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Re: Advance/retard VB600

Postby nevhunter » Sun May 09, 2021 2:04 am

The idle at full advance should stumble a bit or it may be a bit retarded and reduce the power and blue the pipe. The exhaust valve life may shortened also. Consider increasing the exhaust tappet clearance by about .002". Nev

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admin
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Re: Advance/retard VB600

Postby admin » Mon May 10, 2021 2:22 pm

If you are just checking the timing, then all you need to do is check the position of the piston vs the opening of the points.
Depending on your approach that's a stick and some thin paper or a TDC gauge and the TDC buzzer for magnetos.
Takes about 5 mins and tell you if it's close or far out - don't forget to set the lever to advance.

Incidentally, the carburetter is usually set for the right idle speed at full advance on a warm engine. i.e. you adjust the slide/throttle screw and the mixture screw for those conditions. Bike dependant, it may start on choke or flood (or both) and then take a while to reach that point.
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simon.holyfield
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Re: Advance/retard VB600

Postby simon.holyfield » Mon May 10, 2021 2:40 pm

admin wrote:Incidentally, the carburetter is usually set for the right idle speed at full advance on a warm engine. i.e. you adjust the slide/throttle screw and the mixture screw for those conditions. Bike dependant, it may start on choke or flood (or both) and then take a while to reach that point.


Is this how most folk set up the carburettor? I know it doesn't really matter, but (for example) my son is getting his head around manual ignition and I'd like to have the bike set up as conventionally as possible.
cheers

Simes

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Re: Advance/retard VB600

Postby admin » Mon May 10, 2021 3:21 pm

worn carbs aside, it's the conditions the bike will run at 95% of the time.
My experience is that if you set it when the bike is too cold or too hot (esp on an air cooled bike) then it won't be quite right.

I always set the idle slightly high, on a single especially, as sometimes they will stall if you set it for "impressively slow". You can always knock the timing lever back, if you're sat there stationary and want to impress.
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Re: Advance/retard VB600

Postby MarkOgden » Thu May 13, 2021 4:49 pm

Chaps

Many thanks for all the useful advice. I found a procedure for timing from John Nash ages ago and followed that - with 5/16 BTDC, set at full advance, and a marked up straw in the bolt hole OPPOSITE the spark plug. My newly purchased TDC tool was hopeless - it's a side valve dummy! I had completely forgotten about that minor detail. I had marked up the points opening position on the contact breaker body previously though, and I could (just about) see the points open by eye.

Anyways - timing now seems better. Definitely now has an increase in revs at full advance after starting from a little retarded, and what seems to be a crisper exhaust note.

Not cleaned up the commutator just yet, nor ridden it, but battery now at 13V post charge.


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