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Fuel Starvation

Posted: Wed Jun 20, 2007 6:48 pm
Author: uk kev
what would be the symptoms out on the road of fuel starvation?

and does fuel starvation happen at all rev ranges across the range, or does it come in at higher revs?

Posted: Wed Jun 20, 2007 7:11 pm
Author: Rich
It all depends what type of starvation.
If it is flow through the jets it will start missing and hunting at revs and changing main jets up to bigger ones won't make any difference - eg needle jet restricting flow.
If it is fuel flow it may effect it at all rev range but it is unlikely. Usually it will effect high revs and when you shut off may seem like you are running out of fuel until the fuel reaches the pilot jets again
If you do suspect it, check the breather system on the tank as this could be the cause. Are you running twin feeds or a single middle feed? What carbs, jets, filters, pipe are the air jets / passageways clean. what is the fuel height, you are better to do it by fuel level than float height.
Before bothering with the carbs chack cam chain / valve clearances / ignition and the power feed to the ignition are all Ok.

Posted: Wed Jun 20, 2007 7:37 pm
Author: uk kev
My bike is not right, that's all I know for sure right now.

It starts, and sits at idle perfectly, quiet, no searching, just doing it easy, revs well at stand still.
But out on the road she gets real lumpy, missing, almost drying up, then as the revs drop, and I change down a gear, she starts to pick up again.

26mm carbs, fully rebuilt, twin feed. through vacuum tap
Electronic ignition of unknown age/use

Posted: Wed Jun 20, 2007 9:17 pm
Author: bunnysZ
ukkev
if u want bring the bike over to my place , swap the carbs over for a set of my carbs, take it for a ride see if that makes a difference , you will know then if its the carbs,
i should be in most of sat during the day

Posted: Wed Jun 20, 2007 10:08 pm
Author: uk kev
Thanks Paul, but not sure I want to risk the M25 the way she's running at the moment. so little time to get things sorted, I will make the rally, but maybe not the ride out :roll:

Posted: Wed Jun 20, 2007 10:40 pm
Author: paul doran
so many time's lately I have seen similar problems from other members
firstly are the needle height's right
there are five notches on the needle
a standard set up requires the needle to be set in the middle
mixture is crucial as the slighest adjustment is critical
recommended setting is one and a half turns out but I find an extra quarter turn is needed
but balance is also crucial
good luck it's a bloody minefield

Posted: Wed Jun 20, 2007 11:34 pm
Author: big green bus
make sure the fuel tank breather is clear. i had loads of prob's and found the tank at fault after a paint job

Posted: Thu Jun 21, 2007 7:50 pm
Author: Rich
When it's misfiring do a plug chop, if they are wet you have problems with your ignition/charging system. black and sooty too rich - speckled white too lean.
Drain fuel so the tank is half full, when it happens undo fuel cap - if it gets better your breather is at fault.
You say you have a vacuum fuel tap onto 26mm carbs - where have you connected the vac pipe to? post a picture of them with the connection.

Posted: Thu Jun 21, 2007 8:36 pm
Author: uk kev
As the replacement carbs I have had fitted don't have a vacuum take off, the vacuum for the fuel tap comes from one of the manifold vacuum tubes.

Posted: Fri Jun 22, 2007 8:40 pm
Author: ROZZER
Check fuel tap is flowing at correct rate, my bike was fitted with a new pattern tap (shitty chinese copy that wasn't cheap :evil: ), when I checked fuel flow into a measuring jug it was only running @ 50% of required rate and on reserve was even worse. Lobbed it in the bin (seal inside was blocking outlet, tried cutting out hole in seal to clear but just kept distorting when assembled, hence the bin) and bought NOS Kawasaki - voila no further problems with fuelling. :D