BritBike Forum logo
BritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike Sponsor SteadfastCyclesBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorHepolite PistonsBritBike Sponsor
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Member Spotlight
Smackinthemiddle, NJ
Posts: 480
Joined: April 2011
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
a word from..
Manuals on DVD (Shipping included)
Previous Thread
Next Thread
Print Thread
Rate Thread
Amal Monobloc 389/95 1 3/16 Carb settings
#744401 08/04/18 6:28 pm
Joined: Jun 2016
Posts: 87
Britbike forum member
OP Offline
Britbike forum member
Joined: Jun 2016
Posts: 87
1966 T120TT 650 E.T ignition. Twin carbs are now running well but I did need to do quite a bit of tuning to my original AMAL Momobloc 389/95 1 3/16 to get them just right.

Both carbs were sent off to Lund Engeering for a bore and slide re-sleeve.

2 Triumph NOS Gauze filter Pancake air cleaner/Filters offset with the hump/dome back plate. Not paper filters. Just enough space to fit with no rubbing on oil tank or side cover. No switch gear in the side cover.

Elevation is 3200 feet ish (Boise, Idaho)
3.5 Slide (4 is stock)
310 Main Jet (330 is stock) ( Might go to a 300. The 310 is just a tiny bit rich but just at full wide open throttle)
25 Pilot Jet (Stock)
106 Needle Jet (Stock)
"D" needle in 2nd to top notch.

I spent most of the time testing different jets and needle positions but I always came to the conclusion that 1/4 throttle to full throttle was always much to rich with the default settings. In all positions really except full lean (Top notch and 300 main) then it was not ride-able.

This frustrating issue was finally solved with the purchase a new 106 needle jet (Default size). New main jets and needle were purchased new during my trouble shooting and tuning. I just never though it could be a well well worn needle jet and that it had to be the other things that AMAL speaks about in its tuning guides for the AMAL Monobloc. Those guides are here -> -> Amal Monobloc tuning guide and parts diagrams

If i was to give one thought of wisdom when endlessly tuning a Monobloc to no avail i would say.... Its the needle Jet dummy.....


Last edited by ToolBox Dave; 08/04/18 7:28 pm.

1961 BSA DBD34 Clubman
1966 Triumph T120TT
1972 Rickman 250MX

Support Your #1 BritBike Forum!

Check out British motorcycles for sale: British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Re: Amal Monobloc 389/95 1 3/16 Carb settings
ToolBox Dave #744833 08/08/18 12:02 am
Joined: Dec 2002
Posts: 3,298
Likes: 15
Britbike forum member
Britbike forum member
Joined: Dec 2002
Posts: 3,298
Likes: 15
I learned that also, Dave. Since then I've maybe replaced some that didn't really need it. Some years ago there were some bogus Monobloc needle jets in the supply chain, defective or counterfeit I never knew which. That was a hair puller to figure out, and I've bought direct from Burlen since.

Moderated by  John Healy 

Link Copied to Clipboard
Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | DVD- Manuals & Parts books
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.7.4