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Posted By : Barry Higgott, 14-Nov-2004, 11:10am
Hi,
Could anyone help me and perhaps give me a few pointers to what I have done wrong?
I had a fuel leak from the second carb nearest to the bulk head about six weeks ago. I took the carb lid off three weeks ago and today I got around to
fixing it and it wont start very well.The carbs have been empty of petrol for 3 weeks.
I can get it running, but it wont revve up and cuts out between 5 and 30 seconds. It will only start when the choke is out full. When its starts it sound
like its only running on two cylinders.
I replaced the gasket on the float chamber.
I replaced the float chamber lid and float with a second hand one.
I replaced the bottom seal and washed that connects the small pipe from the float chamber to the main jet. This is still leaking very slightly.This may be
the cause, but after five attempts it wont seal.
I have checked the fuel supply at the entry point into carbs one and two and I get a decent amount out every two to three seconds when turning it over on
the starter.
Anyone near Cramlington want to earn a few pennies by fixing it for me?
Thanks in advance
Best regards
Baz
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Posted By : Van Hamlin, 14-Nov-2004,
02:57pm
Sounds as if you are not getting fuel and/or air through the carb itself.
Is the jet moving down when you operate the choke? Compare with the other carb.
Is the carb piston stuck in the down position, this will mean that the needle is blocking the jet? If one piston moves up when you try to start the
engine but the other one doesn't, it it probably sticking. Or you could try lifting it up with your finger while the engine is not running, and see if
it moves freely. It might move a bit and then stick.
Is the jet or the tube to the jet blocked?
Van
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Posted By : Alistair Banks, 14-Nov-2004,
06:25pm
Try checking for a major gasket failure between carbs and the head. I am assuming the thing ran OK before the fuel leak, but it may have been
disturbed as you were working on it. Check the piston moves freely because if it is stuck half way up the bore it alows too much air in and you get
a very lean mixture and therefore bad idle. As for sealing the little supply tube to the jet at the dashpot end, I'm begining to think it is
standard on SU's as my front carb refuses to seal properly. The answer my brother and I think is to fit lovely motorbike carbies, a lame reason but
it works for me. We got two pairs for (4 per pair) for £15 at Newark auto jumble. Once I have made some stub pipe manifolding, I wil
the take it to a rolling road and then let the fun begin.
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Posted By : Barry Higgott, 15-Nov-2004,
03:02pm
Hi,
Thanks for everyones help. I cannot see anything wrong at all. I am going to replace the jet, as the plastic pipe has bent at one end, and this
could be restricting the flow of petrol. Hopefully with the pipe being new as well, this may provide a better seal and stop the leak as
well.
Thanks again
Baz
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Posted By : Tim Willis,
16-Nov-2004, 00:14am
Barry
The main reason the jet leaks from the nut is overtightening. I am pretty sure this is your running problem also.
Even with a new jet the following advice always works.
The plastic pipe has a little brass piece fitted into the end.
Remove this, keep the rubber and washer in place on the pipe just move it back a little.
Now using a philips screwdriver gently open up the end of the plastic pipe, put the brass piece back in so the flared end just sits inside
the pipe, move the rubber and washer back into place and fit the jet. Tighten the nut until the rubber is just nipped, no more or the taper
seat will compress the rubber until it blocks the orifice completely. Doing this stops the pipe pulling through the rubber seal and causing
a leak.
No leaks.
Tim
Willow Triumph
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Posted By : Barry Higgott,
20-Nov-2004, 10:55pm
Hi Tim,
Hope you and your family are well. I didnot see the post until I had fixed my car, due to internet access problems.
I ordered a new jet and it sealed first time .
Question I have got now is......why does my car run better. It starts quicker, and picks up faster than it ever did. I am hoping that
it was the plastic pipe being bend that restricted the petrol. If its some thing to do with metal part that sits inside the carb, I
will be tempted to have all these problems again and I will replace the otherside!
Best regards
Barry
www.myspitfire.co.uk
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Posted By : Andrew Dawson, 14-Nov-2004,
04:51pm
Hi,
Don't know if this helps but I had a similar situation a while back - as I put the power on while coasting it started tho behave like it was on 2
cylinders and I luckily managed to roll into my driveway and began looking at the engine and eventually on to the carbs. A few friends came down and we
kept checking things and trying the engine again.
We took the K+Ns apart and got the running while we could see into the SU inlet. My friend put his plastic-gloved hand next to one of the inlets (the
one that turned out to be ok I think) but got too close and for a second the plastic sucked over the end of the hole and cut off the air to the 'good'
carb - hey presto, the car suddenly idled fine!
Someone might tell you what that means - I'm not going to pretend I know! - but I didn't question it as the car now runs ok... maybe its worth a
try!
Andrew
(Definitely not putting off his carb refurb now)
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Posted By : John Davies, 14-Nov-2004,
09:53pm
Andrew,
Sounds to me like dirt in the jet - the blocked inlet caused max vacuum in the inlet, the piston shoots up opening the jet to the max and the
vacuum sucjs the dirt out. hence it runs okay after.
Baz,
I'm less sure of your cause, see the other posts, but dirt in the jet seems likely.
John
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Posted By : Andrew Dawson, 14-Nov-2004,
11:23pm
John,
Thanks for that, I'm glad someone has enlightened me! As I say, a carb refurb is definitely on the cards at some point - I know they have worn
spindles - though as my car is a daily runner who knows when the refurb day(s) will arrive!!
Andrew