QuestionQUESTION: I installed a rebuild Stromberg 150 carb. Car starts, idles
and accelerates fine...going downhill. As soon as a load
is put on the engine going uphill, it bogs down, sputters
and won't run over 2,000 rpm. Is this a mixture issue that
I have to buy one of the Triumph special tools?
ANSWER: Possibly, especially if you didn't rebuild the carb, and you didn't set the needle yourself
Check you timing as well, it may be too retarded.
Was the car running OK before the carb swap?
---------- FOLLOW-UP ----------
QUESTION: Yes, but the carb was old and unable to keep a firm idle.
Accelerated OK but bad fuel economy. I adjusted the
valves, set the timing to factory specs, adjusted dwell and
point gap. I also noted that the car pulled fine going up
hill if the choke was slightly pulled. I guess that the
mixture is too lean. I need the adjusting tool. Any tips
that I should look out for when adjusting the mixture?
Thanks.
AnswerYour choke test would confirm that there is likely a mixture problem, or the float isn't set to keep enough fuel in the bowl.
The adjusting tool is only needed if you want to adjust the needle without pulling the air valve. If you are willing/able, you can pull the 4 screws off the dashpot, and the air valve body & spring can be removed. Then with a long allen screw adjust the needle in or out as needed. Pulling the needle up in the valve body richens the mixture across the entire RPM range.
Some CD150s are a fixed needle, and other (older) ones are adjustable jets. The adjustable needle and fixed jet are the most common.
The "driving" test is the best way to set the mixture if you don't have an 02 sensor or machine to measure the AFR.
-Set the mixture.
-Clean one or more spark plugs so you clearly see the white insulators.
-Drive the car for a few minutes at wide open throttle with a load (like uphilll)
-While still at WOT, turn off the ignition and coast to a stop (don't idle the engine)
-Pull a spark plug and inspect the color of the insulator; black too rich, white too lean, brownish/grayish just right.
COnversely, you can just adjust a 1/4 turn at a time, do a run up the hill, timing yourself between two points. When you feel you have enough power, no pinging, and the shortest elapsed time, you are probably at an optimum mixture for normal cruisng.
You'll then have to go back and set the idle mixture, timing, fast idle and regular idle
Setting the carb is a repeated process between setting timing, setting mixtures, checking performance, repeat until you get the best settings. The factory timing settings, for example, are not always the best timing settings for economy or power. They were generally set for emissions.
Hope that helps.
