Posted By : Ed Lannen, 30-Dec-2005, 07:00pm

Hi All,
I have just replaced the carbs on my GT6 and it is now running like a dog! It starts okay but when you give it some throttle there is a few second delay before it picks up and when it does it sounds pretty rough. I set the mixture up as per the manual - all the way in then 3 turns back out. I have not played about with the mixture set up yet but was just wondering if the above symptons suggest something simple such as the mixture being too rich or weak? I will get it tuned properly but at the moment I dont think she would make it to my local garage!! Any thoughts would be greatly appreciated.

Cheers

Ed.

Followups :

Carbs set-up too rich ???

Posted By : Ed Lannen, 31-Dec-2005, 03:52pm

Took the RH carb off and re-set the float and gave it a general spring clean and that seems to have sorted it. However, the carbs still seem to be running rich and even with the mixture screws fully in I cant seem to weaken them off. The needles are 6E but the ones in the original carbs were 6AC - is this where my problem lies?

Ed.

Carbs set-up too rich ???

Posted By : Chris Taylor, 31-Dec-2005, 06:02pm

While the differences between needles seem small, they can make a big difference. You need the right needles for your engine set up, and the right spring above the air valve (although some Stromberg carbs had no spring at all).
If your engine is standard,then you need the standard needles. If your engine is modified, then you need the guidance of others who have dne the same mods as to the most suitable needles, or a trip to a rolling road to set up the carbs correctly.
It's very hard to work out from the end of a keyboard, but I'd be tempted to say that your mixture is too weak; the hesitation when opening the throttle suggests that to me.
It could however also be just a lack of oil in the dashpots!
If your engine ran properly with the other needles in, then try refitting them and see what happens; it won't take long to swap them over. Also, make sure the jets are properly centred, and the needles correctly and firmly located in the piston.
Have you tried the "lift the air valve 1/16" and note the engine response" tuning technique? That is pretty accurate IF YOU HAVE THE RIGHT NEEDLES installed. Are there other signs of running rich like hunting at tickover (like leaving the choke out too long) and black smoke from the exhaust? Once the engine has warmed up, it's worth taking out 2 spark plugs, one fed by each carb, and seeing what they tell you about mixture strength.
- Carbs set-up too rich ???
  
  Posted By : Ed Lannen, 31-Dec-2005, 06:15pm
  
  Cheers Chris. I have been using the lifting the air valve technique and even with the mixture screws right in the engine always gains speed rather than dies. I sorted the hesitation problem out by giving the RH carb a spring clean - I dont think the cylinders it feeds were getting any / enough fuel. I think I will swap the needles over tommorow and give it another go.
  
  Thanks again for your help.
  
  Ed.

Section : Carburettors

Carbs set-up too rich ???

Followups :

Carbs set-up too rich ???

Carbs set-up too rich ???

Carbs set-up too rich ???