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Carburettor Metering Needles

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Simmo

Simmo

Jedi Hopeful
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Lookig for some advice please.

I have my TR3A now rebuilt with a standard engine except for the Feruson Pistons. I have installed a new set of HS6 Carburettors with TW needles.

Now I have some running problems.

When the engine is idling at around 900RPM it seems just fine. Not rich or lean and it revs up fine too.

Under load it seems very reluctant to rev in the 1200- 2000 RPM range. When it gets going its fine but very hesitant after you have slowed down and foot back on the gas it tends to not want to regain revs.

Im wondering if this is a needle problem or maybe even vacuum advance, which is installed and set as per book.

Any suggestions would be apreciated
 
Should rev just fine, even without the vacuum advance. Did you have the line disconnected when setting the timing?

1200 rpm is pretty slow to be applying a load, not much power down there. Maybe you just need to drop a gear?

What do you have in the carb dampers?

Have you double-checked the cam timing?
 
Randall,

Didnt have the line disconected and the bellows etc are working properly.
I mean I do drop down gears but even starting offf in 1St it is rough getting the first few hundred revs going but when I get to say 2000 its just fine.
Cam timing. No what do you suggest.
Singer Sewing Machine oil is in the dampers.( very light 3 in one I think they call it in the US)
Cheers
Ian
 
Try a heavier oil in the dampers, such as whatever engine oil you're using. If the oil is too light, the piston will fly up too quickly. The oil in the damper slows and smoothes the movement of the piston. On hard acceleration, vacuum that would otherwise quickly lift the piston is redirected to quickly suck more fuel out of the jet. As the piston slowly continues its rise, the mixture returns to a more normal ratio.
 
You could replace the "3 in 1" damper oil with mineral oil for even more of an accelerator pump effect.
 
Thanks a million Guys! The change from "3 in 1" to 20-50 engine oil did the trick. I can now accelerate away, in top gear, from 1000RPM without any coughing or spluttering.
The idea seemed far too simple to work but how wrong I was!
 
Most manufacturers recommend using the same oil you use in the engine. I know there is a lot of opinions, but all thru the years the manuals all said use the engine oil.
 
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