Fishface
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| posted on 23/1/06 at 01:23 PM |
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carbs not sucking
Still struggling with my engine running. It seems now I have one pair of carbs ok and one the dont seem to be working. The pair on the left suck and
when i put my hand over them suck and then stall the car. The pair on the right do absolutely nothing. I took the jets out and blew them through, no
sign of blockages. Any ideas. Im wondering now if it could be a problem with the aldon dizzy that i brought off ebay, but it seems stange that it
fires 2 and not the four?
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jambojeef
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| posted on 23/1/06 at 01:30 PM |
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Just a thought but is the linkage to the second set of carbs free and moving properly?
Geoff
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02GF74
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| posted on 23/1/06 at 01:44 PM |
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for carbs to suck, then need an oriofice to suck through. For example try sucking air trhough you mouth with your mouth closedd, you can't do
it. the same will happen if the air passage to the carb is blocked and this is usually done by a throttle disc.
Have you checked the disc rotates and opens the passage? Is there anything else blocking the carb such as incorrectly fitted gaskets, unlikley....
Isthe engine in good condiotn i.e. the valves and cam lobes are working as they should?
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rusty nuts
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| posted on 23/1/06 at 02:09 PM |
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Sounds like you haven't got the second carb opening , slack or broken linkage or even missing ? you say one is sucking but not the other, in
order to suck you need a vacuum, suggest a compression test as sticking/burnt valves could be a problem especially if engine history is unknown .
check for blockage in inlet ports it wouldn't be the first time rags etc have been left in? Unlikely but possible and easy to check . What
engine /carbs etc have you got ? may help with diagnosis. Have you a spark at the plugs for the cylinders that are not working? have you got an air
leak into manifold ? could be missing servo connection bung or similar ? Check all the simple things first before condemming any thing . Should give
you enough to be going on . HTH
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rusty nuts
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| posted on 23/1/06 at 02:11 PM |
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Where abouts in Ely are you?
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RazMan
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| posted on 23/1/06 at 03:44 PM |
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Are your valve clearances ok? If they are dramatically out then they might not even be opening - that would give you loss of 'suck'
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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Fishface
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| posted on 23/1/06 at 04:24 PM |
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thanks for the response guys. Im actually in downham market now.
The engine is a recon tuned engine from Lyndales in Peterborough so it should be ok. It does have second hand 40's which i was told were ok and
the guy who sold them to me seemed honest enough etc.
My biggest worry was that I had a slight backfire from the carbs onto a petrol rag which i had to extinguish (what a prat) which left powder around
the carbs. It all cleared up ok and even ran just as it had before. It wasnt until recently someone said it seems to be running on 3 cylinders and
removed one of the leads without it making any difference before I relaised something was up. As it sits in my father in laws garage at the moment it
a bit hard to get to it but this weekend when i looked it didnt even to be sucking through either of the carbs. However although it runs lumpy im
surprised that its running on two I would of thought it just wouldnt turn over. It seemed easy building the car up but boy im certainly no mechanic.
Could a faulty dizzy cause a problem? I brought an aldon dizzy and igniter of ebay which i noticed the copper bits under the cap seem coated in
something or is this normal?
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garyo
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| posted on 23/1/06 at 05:10 PM |
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As some people have already suggested, the engine might only be running on three cylinders while it's idling. At idle the throttle butteryflys
are *barely* open, so even a tiny misalignment between the two carbs could be causing the symptoms you're seeing. Have you tried turning the
balance screen on the linkage between the two carbs? What happens?
Another problem that sometimes happens is people run the carbs without a throttle stop, and over the years all the stamping on the throttle causes the
shaft to twist, causing the butterflys within the same carb to go out of alignment with each other. There's not too much you can do about
this...
Gary
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wment
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| posted on 24/1/06 at 12:18 AM |
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Sounds like a good adjustment is in order. Both carbs should flow the excact same amount of air at idle, or anywhere through their range. I have use a
device called a Uni-Syn to adjust car and motorcycle carbs. FI systems that have multiple throttle bodies need to be adjusted so they all flow the
same amount of air. There are other devices you could use also.
[Edited on 1/24/2006 by wment]
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Peteff
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| posted on 24/1/06 at 10:57 AM |
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Could a faulty dizzy cause a problem?
A faulty distributor cap always causes a problem. Replace it and the rotor arm at the same time.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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