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Webber Alpha carbs
scoop - 20/9/10 at 08:02 PM

Just been out in a very nice orange Westie out my way for a blat after looking at his webber carbs. Having looked at them and not being that familiar with them i was surprised to see that there isnt much to adjust but now have a couple of questions about them.
Firstly the metal gasket between the carb body and the inlet manifold is loose dispite the nuts being tight. Is something wrong there?
Secondly the carb for 3 and 4 flows more air at idle and at 2000rpm the difference is even greater.How do you adjust that and is that normal?
Cheers, Steve.

interestedparty - 20/9/10 at 08:52 PM

I don't know a lot about Weber carbs, but I do know the bits you are referering to are called "Thackeray Washers" or something similar, and are there to stop the carbs being affected by the vibration of the engine.

The difference in air is sorted out by adjusting the throttle linkage.

scoop - 20/9/10 at 09:28 PM

Thats good news on both points then. The throttle linkage was the only thing that made any difference for us but it was very sensitive. A quarter turn was too much!

Xtreme Kermit - 20/9/10 at 10:05 PM

Webers are sensitive creatures

1/4 turn can make the difference between being sweet and mahoosive pops and bangs... (don't ask me how I know)

This I what I have for the mountings.

http://rallynuts.com/motorsport/MISAB_Plates_2323/



[Edited on 20/9/10 by Xtreme Kermit]

scoop - 22/9/10 at 08:37 AM

I cant believe so few people on here have webers or are willing to help out on this one, unless 'interestedparty' is correct

interestedparty - 22/9/10 at 10:24 AM

quote:
Originally posted by scoop
I cant believe so few people on here have webers or are willing to help out on this one, unless 'interestedparty' is correct


What is the actual question, maybe people are missing it, (I certainly am)?

Generally speaking though, if you don't know a lot about Webers in general, and that particular set-up, the best (only) answer is a rolling road that does. It might well cost £150 ish for a couple of hours, but it will be worth it.

Barksavon - 22/9/10 at 08:12 PM

I had twin Dellorto Dhla 40's on my engine which are similar to twin webers i believe. I had Misab plates fitted between carbs and manifold which are metal plates with a circular rubber gasket, it is intended to stop the carbs vibrating which can result in the carb bodies cracking or the fuel frothing. If you hve thackery washers fitted then they shouldnt be tightened to the point that the 'coils' of the washer are completely closed up but i dont think the misabs should be 'loose' either i would think you will be risking sucking air into the inlets if they are. As far as airflow is concerned i think ive read that you should take the readings from the inner choke of each carb, that would be 2 and 3 i think, and get them balanced up.......

MikeRJ - 23/9/10 at 04:17 PM

quote:
Originally posted by scoop
Having looked at them and not being that familiar with them i was surprised to see that there isnt much to adjust


There are numerous parameters to adjust on Webers, but most are adjusted by replacing jets with different sized ones rather than twiddling screws.

Carb balance is adjusted by the linkage between the two carbs, and yes 1/4 of a turn will make a big difference!

The gasket between carb and manifold will probably be a Misab plate. There are supposed to be gently clamped in order to create a good seal but still allow movement, which is why there will either be spring shaped washers (Thackery washers) or rubber bushes and steel cups between the carb flange and the manifold nut. It's a good idea to check the Misab plates if you suspect any leaks; I have seen cheap copies where the bonded O ring has parted company from the plate and caused a leak.