Capri18
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| posted on 17/9/09 at 08:34 PM |
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Vacume advance with bike carbs
What would i need to do to run a pinto on bike carbs using the ctandard dizzy vacume advance? Just curious as i have the carbs and want them bolted
onto the car lol
cheers
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ashg
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| posted on 17/9/09 at 08:53 PM |
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you have to tap each tube on the inlet manifold and run a pipe off each one. you then take the 4 pipes and attach them to one end of a little home
made chamber about the size of a coke can. from the other end of the chamber you take a single pipe to the dizzy.
the chamber is important as it balances out the fluctuations between each inlet. basically dont just join the 4 pipes and attach it to the dizzy as
it will play up
[Edited on 17/9/09 by ashg]
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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britishtrident
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| posted on 17/9/09 at 09:02 PM |
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Simply leave it disconnected and ignore it vacuum advance is an an economy device to allow the engine to run on much weaker mixtures at low throttle
openings it has no effect on power output and bike carbs are not designed to work with it.
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DarrenW
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| posted on 17/9/09 at 09:50 PM |
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As above, leave it off, vac advance doesnt do anything at higher revs.
Try giving megajolt a go, i had bike carbs and mjlj on mine and it went well (ported head and cam too).
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blakep82
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| posted on 17/9/09 at 10:18 PM |
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wouldn't using the vac give better throttle response though? like it does with MJ?
________________________
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MikeRJ
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| posted on 17/9/09 at 10:27 PM |
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quote:
Originally posted by blakep82
wouldn't using the vac give better throttle response though? like it does with MJ?
Better economy primarily, and the difference it makes can be pretty big.
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DarrenW
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| posted on 17/9/09 at 10:50 PM |
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MJ uses the vac as a 3rd input to allow fine tuning of the map. (note map and MAP being 2 very different things). i used mine in 2D mode and it was
better than the std sierra electronic dizzy set up.
Without MAP or TPS connections (hence 2D) you can still set up the map to give the correct advance required at each rev point. Basically you can set
the map up without vacuum to give pretty much the same advance curve as a std dizzy running vac advance..... if you want.
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coozer
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| posted on 17/9/09 at 11:41 PM |
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Drill a hole in each manifold runner tap for an outlet (helps with balancing as well), run each outlet into a 3" long 15mm bit of copper tube -
use 6mm microbore solderd into holes drilled into an end cap, then one outlet at the other end to the dizzy.
This smooths the pulses out from each cylinder and gives just what your looking for.
I'm on the look out for a CB radio
[Edited on 17/9/09 by coozer]
1972 V8 Jago
1980 Z750
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r1_pete
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| posted on 18/9/09 at 07:14 AM |
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Here's how I've done it for megajolt, it also drives a vacuum gauge so no reason it wouldn't work on a distributor.
I used hobby mig tips with the m5 thread screwed into the manifold runners, through undersize holes in the mounting rubbers to ensure a good
seal.
 
Rescued attachment Vacsetup.JPG
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Capri18
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| posted on 18/9/09 at 10:11 AM |
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Cheers for your advice guys, the overall plan is to go MJ using the tps version. I just wanted to get it runnin on the bike carbs quickly so i can see
what difference it has over the standard setup, need to save some pennys for the MJ too.
I'll think il try to keep the vacume advance as fuel economy was one of the main reasons for going bike carbs
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cliftyhanger
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| posted on 18/9/09 at 10:41 AM |
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I would def use vac advance, it will improve light throttle economy and response.
Mig tips are dead handy (I used 6mm ones!), and a small container to smooth the pulses can be made using a bit of 22mm copper pipe, maybe 100mm long,
solder end caps (do one, fit 4 mig tips one end then solder the other with a single tip) I guess you could use 6mm copper fuel pipe as a cheap
alternative to mig tips. Bit of silicone hose, job done. Good for MJ too.
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DarrenW
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| posted on 18/9/09 at 01:08 PM |
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quote:
Originally posted by Capri18
Cheers for your advice guys, the overall plan is to go MJ using the tps version. I just wanted to get it runnin on the bike carbs quickly so i can see
what difference it has over the standard setup, need to save some pennys for the MJ too.
I'll think il try to keep the vacume advance as fuel economy was one of the main reasons for going bike carbs
Just a thought, and i dont know the answer myself, but if you are careful where you position the vac outlets could these also be used as points when
balancing the carbs? Just thinking how you can use the take offs if you do go for TPS MJLJ later.
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