speedyxjs
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 posted on 2/9/08 at 04:11 PM |
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Small (Midget) Question
If ones engine were to sputter and nearly die before regaining consciousness every time you try to accellerate (only when cold) what would the cure
be?
I have changed plugs, ht leads, air filters, fitted new (used but cleaned) points and tuned (hopfully correctly) carbs.
How long can i resist the temptation to drop a V8 in?
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D Beddows
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| posted on 2/9/08 at 04:15 PM |
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You haven't got the choke out?
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speedyxjs
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| posted on 2/9/08 at 04:17 PM |
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Yes i have. She runs fine on tickover until i touch the go faster (or even just go) pedal
How long can i resist the temptation to drop a V8 in?
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tegwin
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| posted on 2/9/08 at 04:20 PM |
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Sounds like on of the progression jets is blocked or something in the carb is not right....
My pinto was doing that badly so the guy at the RR soldered up one of the progression jets and it improved a lot!
------------------------------------------------------------------------------------------------------------------------
Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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r1_pete
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| posted on 2/9/08 at 04:23 PM |
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Assuming you're on the standard SU's a sticking throttle piston will cause that, if its stuck just off fully seated in the tickover
position. Or if there is no damping oil in the dashpot.
[Edited on 2/9/08 by r1_pete]
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speedyxjs
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| posted on 2/9/08 at 04:27 PM |
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So lets pretend i have only just learnt how to tune SU's but dont know much else about them. Do i need new carbs?
How long can i resist the temptation to drop a V8 in?
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DRC INDY 7
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| posted on 2/9/08 at 04:27 PM |
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Dashpot oil
https://www.facebook.com/groups/462610273778799/
Puddle Dodgers Club
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Peteff
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| posted on 2/9/08 at 04:32 PM |
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Undo the black plastic thing on the top of the carb, it unscrews like a bottle cap and fill the hole with engine oil. Now push the damper back in and
screw it back on.
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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speedyxjs
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| posted on 2/9/08 at 04:33 PM |
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I had a look before i tuned the carbs and it looked like there was oil in there How much should there be?
How long can i resist the temptation to drop a V8 in?
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mr henderson
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| posted on 2/9/08 at 04:44 PM |
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Try lifting the dashpots with your finger (have to take the aircleaner off first, of course) and see if they rise smoothly and drop down on their own
slow but smooth, and without sticking anywhere
John
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speedyxjs
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| posted on 2/9/08 at 05:02 PM |
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Yep they both drop smooth not too slow though
How long can i resist the temptation to drop a V8 in?
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austin man
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| posted on 2/9/08 at 05:36 PM |
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I though the oil used in the dashpot was quite a thin oil ? not necessarily engine oil. It is possible that the the carbs have glazed over with oild
expires petrol this can cause a bit of a sticky residue that requires cleaning, one of the needles may be slightly bent ?
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speedyxjs
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| posted on 2/9/08 at 05:56 PM |
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quote:
Originally posted by austin man
I though the oil used in the dashpot was quite a thin oil ? not necessarily engine oil. It is possible that the the carbs have glazed over with oild
expires petrol this can cause a bit of a sticky residue that requires cleaning, one of the needles may be slightly bent ?
Im pretty sure the handbook says to use the same grade as the engine.
How long can i resist the temptation to drop a V8 in?
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britishtrident
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| posted on 2/9/08 at 06:33 PM |
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The carb dampers require a fairly thin engine oil say a 10w/40 or better still 5w/30 or Auto transmision fluid.
Using anything thicker ie 20w/50 causes poor throttle response in cold weather.
Thin oil like 3 in 1 or Redex will just evaporate.
Don't over fill the damper dashpot.
When everything is correct the piston should fall smoothly without sticking -- to check if everything thing is correct remove the damper lid lift the
piston up and let it return it should fall smoothly and hit the end stop with distinct "click".
Midgets and MGB will splutter from cold if the airfilters have been changed to performance items without changing the carb needles to richer ones.
[Edited on 2/9/08 by britishtrident]
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Peteff
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| posted on 2/9/08 at 06:35 PM |
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Thin oil lets the damper rise too quick so the mixture weakens and you get a flat spot. 20/50 was always the oil of choice but any engine oil should
do the job. Fill them to the top and push the damper back in slowly so you don't splodge it out.
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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britishtrident
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| posted on 2/9/08 at 06:42 PM |
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With nearly 40 years experience of SU carbs I can say that 20w/50 is a very bad idea in the UK climate nothing thicker than 10w/40.
[Edited on 2/9/08 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Mark Allanson
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| posted on 2/9/08 at 08:01 PM |
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The problem is almost certainly the carbs, cure as listed by peeps above.
If the problem still persists, just check the weights in the dizzy are free moving. Partially seized or sticky ones can give similar symptoms.
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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owelly
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| posted on 2/9/08 at 08:06 PM |
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If the car only does it when cold, "that's what they all do sir"!!!
http://www.ppcmag.co.uk
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zetec7
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| posted on 3/9/08 at 04:55 AM |
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I agree on the use of lightweight oil in SU piston dampers - thinner was always better, in my experience. I used to use 3-in-1 oil (or ATF,if I
didn't have the former handy) with great success, both on the street and on the track. Anything heavier and it would bog off-idle. And when
you reach in and lift the piston, it should drop with an audible "clack" sound. If it doesn't, the jet isn't centered on the
needle, which will cause running problems. Make sure that the dropping sound is the same on both carbs...
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