Club 80-90 Forums

Just rebuilt my t25. I left the carb untouched and in start up it was very erratic.
I have a twin choke Weber on it and found the main jet was blocked.
(Very) stupidly have mixed up the main jets for the first choke and the second choke. They are different bore sizes and have different drillings. (The jets are in a line of 4 with the two main jets in the middle)
I can’t find any literature and my Weber carb ID tag is missing.
Now cleaned, it now runs evenly and accelerates without splutter and coughing. So apart from swapping the 2 jets and seeing which way runs best, and maybe a plug chop while just using the first choke, how might I best work out which jet should be in which hole?
Any ideas most welcome

As an idea would I be right in thinking that the larger jet with the biggest hole would go with the larger choke diameter?

Really need to identify which Weber you have then go from there.

This may help if it’s a 34Dat

Attention happy weber 34dat owners ht ... source=app

Thanks for reply. I have looked up an image of that carb and it’s not a 34 dat. I will at some stage try and find out what it is!
In the meantime I have swapped jets a couple of times and decided it runs much better one way round and plug chops are generally good colour so sorted for now. I also found a wooden splinter in one of the main jets so running overall much improved!

What's a plug chop?

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Reckon he just means cutting engine mid revs while driving, coast to stop and pulling spark plugs to look at colour.

An undercooked pork chop?

Sorry.. that’s what I meant by a plug chop.. pre color tune.. you can probably buy a good electronic analysis tool nowdays

As it was running fairly well with the right jets in the right holes I decided to check ignition timing. I found the vacuum retard diaphragm was broken so have replaced that. Timed it to the Haynes manual with vacuum pipe disconnected at 900rpm. With vacuum pipe reconnected it now affects the timing but it has made the engine less responsive/less torque at low engine speeds.
I remember having a Weber carb on another vehicle and the advice was to disregard and not connect the vacuum pipe. Has come across this advice for a down draught progressive twin choke Weber on a Vw boxer? (Still haven’t identified Weber carb model)
I guess the original instructions on fitting aftermarket Weber to a waterboxer have long since been lost?