I have a 1966 Triumph Bonneville T120 in the U.S. with twin Amal monobloc carburetors. Neither my service shop nor I can figure out why gas pours out of the tickler valves. We don't think that the floats have failed, but it seems that gas must be filling the float chamber and then leaking out the tickler valves on top of the lower part of the carbs. So far, I haven't been able to find parts in the U.S. for these carbs. Any thoughts on fixing the problem and/or finding carburetor overhaul kits? Thank you in advance. Kimpopper
The needle valve in the banjo housing will be the problem, remove the float bowl covers and fuel inlet banjos and then you can get to the float and needle holders to check it.
Darkman: Thanks for your advice. I'm awaiting the arrival of a carburetor rebuild kit and will let you know after we check it out. The old needle valve seems to be fine, but maybe the needle seating in the banjo housing isn't letting the needle valve seat correctly.
kim, does your shop work on very many older british machines? try dave at the bonneville shop for amal parts https://www.thebonnevilleshop.com/?s=amal&post_type=product&type_aws=true&aws_id=1&aws_filter=1
Speedrattle: Sorry for my delay in replying. No, my shop doesn't work on many older British machines. They did good work on my 2016 Bonneville a couple of years ago, though. Unfortunately, I haven't been able to find anyone in my area who really knows the old British bikes. As to parts, yes, I was able to order Amal carburetor parts and an overhaul kit and front-fork parts from The Bonneville Shop. They are a great source for old Triumph parts. I had gotten parts from them before Covid and am really glad they survived. Thank you for your thoughts. Kimpopper
i dont have any suggestions either, although chicago would surely have someone. the reason im asking is because a tickler flowing fuel like that is instantly identifiable as a float needle issue, and is often an easy fix. but only if you know what youre looking at. its not so easy if your expertise is in fuel injection, which is the norm these days. so even though your shop must be the go-to place for your new machine, i would suggest doing some looking for someone who has experience in the old stuff for the older one. just a suggestion.
as Speedrattle: Sorry -- it's been several weeks. The shop completely rebuilt both carburetors with kits from thebonnevilleshop.com and the leaks stopped. I'm not sure if they figured out the underlying cause of the leaks. Everything looked good. They test drove it, though, and found a crack with a leak in the right carb. We finally found a shop who could weld aluminum and agreed to weld the crack. I'm hoping to get it back this week. If that doesn't work, I'm planning to replace the carb with a new or used one. Kimpopper
Unfortunately the older brits don't like the fuel if it is the unleaded. Usually you need to replace the inlet needle or adjust the float to the correct position. Hope the weld works but not sure on welding alloy. Do let us know.
Thanks, Joe. One shop that welds aluminum wouldn't tackle this as he said it probably had pot metal in it and would not take a weld. Another shop has it now and hopefully will be able to. If not, thebonnevilleshop.com sells new and used ones. Kimpopper
the monobloc is a very competent carburetter, but is also quite expensive. for less than the cost of one monobloc, you could replace both of them with VM or TM mikuni carburetters, which will fit right on and work more efficiently. the only glitch might be their total length. i dont know offhand how long the monoblocs are, but the VM mikunis are definitely longer than the concentrics. the TMs are shorter because they are flat slides.
