Need some help from the Monobloc experts. Twin 376 Monoblocs...turn on fuel tap, both carbs flood from the center air passage hole at the intake side. I checked the floats and float height..everything is good - they shut off properly and have new viton float needles. I notice the jet blocks are not that tight in the carb body. Would some looseness here cause a floading issue? Looseness is with the jet holder removed. Also noted the screws that are supposed to hold the jet block in place, don't. I can remove the jet block with those screws turned in completely. Those are the symptoms...whaddya think docs?

carbs from '64 BSA Cyclone 376/310

Thanks,

As Commando says on your other thread, be sure you have it built right. If you go to this site and download the page on your 376. http://www.amalcarb.co.uk/downloads.aspx You will get the best info there is.
I am of the opinion that the Viton tipped are not needed and cause inconsistencies running on these carbs the seat comes right out for easy lapping with and old nylon piece and some tooth paste. Just glue an old one on the end of a stick. These are fine carbs work very well. JMO

Hi Norbsa,

Appreciate the reference for 376 Monoblocs. Page 5 under re-assembling might be a fault area for my problem. The "washer" gasket under the jet block is questionable and the comment is if not a good seal will cause rich erratic running....maybe also flooding. I'll pick up some new gaskets at Raber's today and see how it works.

Thanks,

The new jet block gaskets did not cure the problem...still looking. Flooding is coming out of the primary air passage at the intake side of the carb. This is above the fuel level, so don't understand why it does this. The set up is static on my work bench with carb in a vise completely verticle.

hi david,couple of questions ,is this a problem thats justed cropped up or is it something thats hapened after you did some work on the carb,is the problem in one carb or both [im sure the cyclone had two carbs] you say you checked the fuel level ,where did you determine the correct level[on the float chamber cover by the side of the amal logo there is a pip, this is the fuel level mark] have you determined that your floats do in fact float and that they are not leaking,is there a sealing washer under the float needle housing[where the needle seals and the fuel banjos fit] there should be no sealing washer there ,it would raise the needle and the float level

chris plant wrote:hi david,couple of questions ,is this a problem thats justed cropped up or is it something thats hapened after you did some work on the carb,is the problem in one carb or both [im sure the cyclone had two carbs] you say you checked the fuel level ,where did you determine the correct level[on the float chamber cover by the side of the amal logo there is a pip, this is the fuel level mark] have you determined that your floats do in fact float and that they are not leaking,is there a sealing washer under the float needle housing[where the needle seals and the fuel banjos fit] there should be no sealing washer there ,it would raise the needle and the float level

Hi Chris

This is a restoration project that hasn't run in many years.
I know about the float level mark on the bowl cover and the level is correct - the floats do float - the flooding occurs in both carbs. There is not supposed to be a "gasket" under the float needle housing according to the exploded view and I don't have one.

Again with the jet holder and jet block removed, using a rubber stopper at the bottom of the carb, it no longer floods. Indicates the problem is at the bottom of the carb...jet holder or jet block. But...what? One of those problems where you walk away and think about it.


Thanks,

hi david,i agree its one of those problems where you walk away{to the fridge} and get a few cold ones.however going back to your first post regarding the small screws that locate the jet block i think thats all they are supposed to do ,locate it,stop it from turning when the jet holder is tightened up,the gasket under the jet block wont seal until the jet holder is fully tightened,what i cant understand is if the fuel level {not float level} is correct then how can fuel come out of the air passages which are above the fuel level. im off to fridge lol

"what i cant understand is if the fuel level {not float level} is correct then how can fuel come out of the air passages which are above the fuel level. im off to fridge lol"

Exactly! Saturday is coming in a couple of days. Will look at it again after getting the RITA ignition hooked up on the Commando.

I have had this problem and it was the pilot jet,it had not been screwed right home to it's seat in the carb....this may be it or it might not but the symptoms are the same

not-ron wrote:I have had this problem and it was the pilot jet,it had not been screwed right home to it's seat in the carb....this may be it or it might not but the symptoms are the same

Good suggestion, I had not looked here. Checked to see if the pilot jets were loose...they were not. Also cleaned them out with a #77 drill bit. Reassembled turned on the gas tap and they still are leaking. will continue.

Thanks,

May have finally stopped the flooding. To give a good idea of how old this Monoblocs are, they are date stamped 12 63. At some point they must have had considerable contact with water as there was a film of mineral deposit on various parts. I used a de calcifying solution in an ultrasonic clear on all parts then dried and assembled one of the units. It leaked a bit at first, but after tapping with a wooden mallet it stopped and has not leaked again. Hope this is permanent.

Great,

I'm chasing down a carb issue myself that I think I may have found, fingers crossed......

It's nice to hear you got a win, hope for the rest of us!

Now the Commando is acting up. Think it ingested some garbage. It backfires and misses with the choke off, then clears up with the choke on. Think there is some obstruction in the low speed circuit. I already know I'm going to have to remove both Amals and clean them out. It happens every year after doing the winter maintenance. This time I'm going to put in some inline filters on the fuel lines and run the fuel in the tank through a coffee filter back into a gas can. This combat really doesn't like any fuel readily available and being a pain.

David,

Do you have a glass tank?

Changed to steel two years ago. I need to check the fuel tap screens to see if anything is accumulating that might have some particles getting through...such as the tank sealer.

Thanks,