Welcome to our resource for MG Car Information.



TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - Early Stromberg Adjustment

I have a 68 TR250, but seeing as that board is a howling wilderness I'd thought I'd inquire here first. I beleive very early TR6s had the same Stromberg as the TR250, so thats my tie-in. Anyway, heres the question.
My TR250 has the stock Strombergs which have a large brass hex plug (or bushing as the books say)in the bottom of the float bowl that contains the jet assembly. The carb has a fixed metering needle which canno tbe adjusted. On the TR4A there was a nifty knurled knob that allowed you to move the jet up and down like the SU carb. The knurled knob was threaded into the bushing assembly in contact with the spring loaded jet, and had an o-ring to prevent leakage.
I can see that the jet is also spring loaded inside the bushing assembly of my TR250, and the only obvious way that it got in there was that in went in from the bottom, the opening of which is sealed with a brass plug resembling a tiny freeze plug. Can this plug be safely removed and left off without causing a fuel leak, and will I find an adjustment screw under the plug?
I can buy a used one and experiment, but I hope someone here knows the answer. The Archives had little to offer.
Regards, Andy

Andy Blackley

Removing that plug will empty the bowl of fuel...inside that bowl is the float and shut off valve. If you have ZS carbs then they are adjusted via the very top when the black or white plastic knob is removed, you then need a special tool to adjust the mixture.
Also the jet assembly is in the upper section of the carb
Do you have a MOSS book or the Bentley one handy ? I think the pictures will explain it better.
Charlie B.

Charlie: The early ZS used on the TR250 does not have a plastic plug in the float bowl and does not adjust from the top, which are features found on the ZS carbs from late 1969 onwards. I have the pictures you mention and they do not apply. The TRF TR250 catalog has a nice exploded view of this carb, but it doesnt answer the question. I sent a similar email to Joe Curto, perhaps he can clue me in. Thanks for your interest.
Andy Blackley

Yes indeedly doodly, the TR250 carbs are different, even want to go so far as to say that the earliest ones have fixed needles and adjustable jets, but the later ones have spring loaded adjustable needles with fixed jets (even though they look very similar to each other with the hex nut instead of the round plug at the float bowl). My TR250 is a rather late one, but there is a set of early TR250 carbs sitting on shelf in the shop. I will try and remember to get a look at them tomorrow and report back.

I stand corrected......that's what great about this site...I learn something almost every day.
Charlie B.

Joe Curto replied to my inquiry:
"Andy that is an elusive jet, I think we can fit the early TR4 jet which is adjustable, leaving the plug out may give you a leak. I do have samples of it and was going to make some but that will not be for a while.

Joe "

My TR250 is fairly early (CD2051L) and I can confirm that the needle is fixed, and the jet appears to be very similar to the earlier TR4A. In the back of the Moss catalog amoungst the Tech Tips its says that by removing the brass hex plug the jet adjuster is exposed. Not on my car it aint. The jet is INSIDE the brass hex bushing, which extends all the way through to the bridge, again, very similar, but not identical to the TR4A carbs.
Andy Blackley


I looked at three sets of carbs. The first was the set off of an early TR250 (serial number semi-close to yours). It was just as you described, so to that one, yea, it's what you and Joe said.

Next up was my later TR250 (CD6050), carbs are on car so this was done with light and mirror for the bottom side viewing. It was something of a hybrid in that the needle was not adjustable but was spring loaded, the jet looked to adjustable in a painful sort of way. Another thing is that unlike the earlier TR250, it had a round plug at the bottom that was similar in appearance to the one on the TR6.

Next up were the ones pulled off of my 1971 TR6. I already knew this from work on them, but wanted to see what the subtle differences were. The jet is fixed, no adjustment. The needle is adjustable. I can't say for sure that this would be true across the entire range, but the quick and dirty visual clue on adjustable vs, non-adjustable needle was at the top of the piston oil reservoir on these three sets of carbs.

If the needle was adjustable, there were small slots in the reservoir wall at the top where the pins in the needle adjuster sleeve fit. This allows you to keep the piston from turning when adjusting the needle. No slots for the sleeve pins meant there was no adjustment at the needle.

This thread was discussed between 24/05/2005 and 27/05/2005

Triumph TR6 index

This thread is from the archive. The Live Triumph TR6 BBS is active now.