Stromberg Carbs

[glemon]

I promised I would have more questions about my TR250 as I got it running, and run it does (motor, not yet on the road).

My first issue relates to the carb, the front carb appears to be doing its job just fine, but the rear is not. I can lift the piston as much as I want it it doesn't change the engine speed much if at all. If I limit the suction a bit with my hand or restrict the airflow by pushing the piston down the engine picks up speed pretty dramatically.

I am pretty sure the problem is beyond simple adjustment of the needle.

I am thinking maybe float level is off (low, so that it only sucks up fuel when there is increased vacuum) but more of a PITA to take off and adjust on these than on SUs, also I don't pretend to understand the function of all the extra air lines and valves on these things, any thoungts on the problem.

Carbs are cleaned, rebuilt by me, they are from a 74 TR6 but on my TR250.


The Good:

All the guages work, temp, gas tach, amps, oil pressure.

Oil Pressure is very healthy as it should be.

It doesn't overheat or make bad noises

I slipped it into gear and rolled the clutch, reverse and first worked fine, since I rebuilt the gearbox myself I was happy about that, but of course we will have to try the other gears, OK, don't get distracted by all my extraneous comments, start thinking about my carb problem. THANKS

Greg

 

[tdskip]

Sounds like you are way lean on the rear carb. If you restrict airflow like that you are effectively "richening" the mixture, and if she likes it then there you go.

Have you checked for vacuum leaks before you go start pulling the carbs off?

 

[SkinnedKnuckles]

I've not run across the condition where lifting the carb piston has no response. Sure the inlet manifold is tightened down correctly? It may not be seated right at the back carb. See what others say. And the brake booster line is hooked up?

 

[glemon]

The brake line is hooked up, the carbs and manifold all appear to be seated correctly but I will double check, thanks, back out to the hot hot garage, lost 15lbs so far this year working on the car, not diet, just heat and work, much preferable to starving or eating like a bunny rabbit!

Greg

 

[SkinnedKnuckles]

Another thought - you sure fuel is getting<span style="font-weight: bold"> into </span>the back carb? My reasoning is that if there is no fuel, lifting the carb valve will have no effect. The throttle valve (butterfly) is downstream and the ultimate restriction at idle. But placing your across the throat will bring in fuel/air from the other cab via the balance line. Maybe a bad needle valve on the rear? Just guessing.

 

[mtlman8]

WOW! I have the exact same prob. in my 67 tr4a. primary carb is fine, but the secondary carb does'nt change a bit when its lifted.. carbs are rebuilt,new throttle shaft bushings and no vaccum leaks...if I rev the engine it will spit a little smoke out of the carb. I thought that meant too rich. anyway these are 175 cd. any info will help,thanks guys

 

[poolboy]

See if the air valve is actually rising when you rev the engine.

 

[SkinnedKnuckles]

Hey, Poolboy. I just retired last year. You have a leap on me!

Brent

 

[poolboy]

Oh, so that's you, SkinnedKnuckles. Hi !!

 

[mtlman8]

will do. thanks!

 

[glemon]

The piston is rising like the other one, I upped adjusted the float and it seems to be doing much more of what it should, still needs some adjustment, may still be another problem but making progress.

 

[SkinnedKnuckles]

Yep - always has been me. Ya have to make up some login name, but I always follow with my real name, just because.

Brent

 

[mtlman8]

been working on brake and clutch stuff, but decided to fire up the motor and fiddle with the carbs... leaned it out (secondary carb) reved it up... lifted the piston ...no differance... tapped it with the handle end of a screw driver and wah lah!!! lift the piston and it stumbles and falls enrichen it and lift the piston ...she revs. bottom line is,if it don't work HIT IT!

 

[SkinnedKnuckles]

Now make sense of that!

 

[DrEntropy]

Stuck float needle.

 

[tdskip]

tapped it with the handle end of a screw driver and wah lah!!! lift the piston and it stumbles and falls enrichen it and lift the piston ...she revs. bottom line is,if it don't work HIT IT!

My guess is that you may have loosened a sticking valve needle on the float when you tapped it. Corrrect me here guys, but isn't sputtering out the carb typically an indication that your mixture is too lean...

 

[tdskip]

Darn - was trying to beat Doc to this but was too slow....

 

[glemon]

I think I am making progress, but still a ways to go, once again the Buckeye Triumphs site looks like it has some great info on tuning the carbs, I am familiar with pre-emmissions SUs and Strombergs, with adjustment for idle and mixture, but all these additional valves and such on the newer Strombergs are somewhat of a mystery, I can see why people go to webers or SUs on these cars, but it looks like the Buckeye site gives a good explanation of the function of and adjustment of the various control valves.

Greg

 

[glemon]

Yippee, still some fine tuning but I think they are working as they are supposed to now, both sucking gas, still need fine tuning, but got the idle down to 1000 RPM (would not run off choke under 2000 or so before), I think I am down to the fine tuning of the carbs, yippee! Big night, still a ways to go, but feel like maybe there is some end in sight for this project.

Greg