1967 G15 MKII carb question

oldandmatchless · Post by **oldandmatchless** » Mon Oct 29, 2012 3:50 am

I am currently working on the rebuild of a 67 MKII that has been sitting outside uncovered for the last thirty two years.

The bike is fairly complete and has most of the original parts, but of course is very rusty.

The carbs that are on the bike are Amal Monoblocs 389/236 and 689/236. The parts book shows these as fitted to 1966 Norton Atlas. For the 67 G15 the parts book shows 389/241 and 689/241 carbs. An online Norton website shows that concentric carbs were fitted on all N15/G15's after serial #120XXX, which is after my number.

I am wondering if carbs were switched on this bike at some point or if some left Plumstead with these carb numbers fitted.

Presently it would appear that the slide stop screws are actually touching, making adjustment impossible. Should different slide stop screws be used? Has anyone else encountered this with their G15?

Thanks for any advice.

Regards,

Rick T

Rob Harknett · Post by **Rob Harknett** » Mon Oct 29, 2012 9:49 am

https://www.jampot.com/article_read.asp?id=551
Check out the document I made here Rick.
I have only listed brief details of internals.
There are uk & USA spec's. I note what you say about carb parts touching. Note theres L/H & R/H. Could it be the carbs are fitted the wrong way round or you don't have a matching pair. My list only goes up to 1965, the numbers you have differ by the first digit, so perhaps your carbs are fitted the wrong way round L & R. Something that could had been overlooked being the simple answer.

John Donne · Post by **John Donne** » Mon Oct 29, 2012 12:42 pm

The carb change was after engine and frame numbers 121007, so if your engine and frame numbers are after this number it would have originally used the Amal Concentric carbs. Your Amal carbs should be of the 930 choke size type. The export carbs were stamped L930/7 R/H and L930/9 L/H. Throttle valves 3, needle jets 107, Pilot jets, 25cc, main jet 250 with an air filter and 270 with out. Some main jets were down to 220. The needle clip is in the middle position. See parts book Master Parts List, 1966-1967-1968 and look on pages 9 and 10.

oldandmatchless · Post by **oldandmatchless** » Mon Oct 29, 2012 3:25 pm

Serial # is 119XXX. Should be monoblocs. However my numbers match up with 1966 Atlas numbers. Both carbs have a float bowl and appear to be a matched set.

John Donne · Post by **John Donne** » Mon Oct 29, 2012 4:13 pm

If your engine number is 119*** it could have been built in 1966 and dispatched in 1967, hence the bike would have been sold as a 1967 model year. The 1966 model years would have a left and right handed Amal Monobloc carbs, and not the chopped Amal Monoblocs. For the 1966 models of the G15 Mk2 the carbs are 389/241 for the right hand side 689/241. The Amal 389/236 is for a 1966 Norton Atlas. The parts book i quoted should help sort out your carb problems and also the other parts problems you may or may not have.

John Donne · Post by **John Donne** » Mon Oct 29, 2012 4:15 pm

The Amal 389/241 is for the left hand side.

oldandmatchless · Post by **oldandmatchless** » Mon Oct 29, 2012 5:34 pm

Yes, I think that the bike was manufactured 1966 and dispatched 1967.

The paint scheme is the 1967 paint scheme.

Basically the G15, as I understand it, were Matchless frames with an Atlas motor. Why then was a different Amal carb number shown for the Atlas vs the G15?

Let's say for the sake of argument that I have a Noton Atlas 750. Carb numbers I have are correct for the Atlas. Why then are the slide stop screws hitting?

The parts book shows a slide stop screw number, but for all except P11, P11A and 67-68 Atlas. Does this mean the trottle stop screw was different for the G15? Am I missing something?

RickEdited by - oldandmatchless on 29 Oct 2012 10:19:45 PM

Don Madden · Post by **Don Madden** » Mon Oct 29, 2012 6:44 pm

I looked in Christian's Archives for pics of origina G15 models in the Road Tests, (new bikes) section. The two I looked at both had the throttle adjusting screws on the OUTSIDE as suggested above. Seems obvious to me, but I'm just a Colonial. Cheers, Don.

Rob Harknett · Post by **Rob Harknett** » Mon Oct 29, 2012 11:46 pm

Indeed Don, so as Ricks stops are touching.
the carbs may be just the wrong way round, which is what I hinted at in my first posting.

oldandmatchless · Post by **oldandmatchless** » Tue Oct 30, 2012 12:00 am

Thanks for the replies.

The carbs cannot be switched as they both have float bowls and switching the 389 (Left hand bowl) to the right would prevent a carb from being mounted on the left at all as there would be no room. The 389 is always a LH carb, unless of course it is a chopped 389.

Don, I did look at pics that I could find in Christians Archives and did find pictures of 64 & 65 MKII's with a "chopped" carb on the right hand side. This is correct for 64-65 models as that is what the parts book calls for in those year. In addition, the parts book shows a "chopped" RH carb on the RH side for the CS models. My 1966 G12 CSR uses a 389 on the LH side and a chopped 389 on the RH side. Looks just like the pics you mentioned.

Given that, the parts book shows for the 1966-67 years a 689/xxx for the right hand side. According to Amal (and christians Archives) this is a full bowl (RH side) carb with the throttle stop on the inside.

Given how complete and unmolested the bike is (albeit the rust) I don't think that the carbs have been changed. However that doesn't answer why they (my carbs) have an application number for a 1966 Atlas 750.

I don't know what the difference would be between a 389 & 689/ 236/241 would be.

I did search for photos of 1966 Atlas 750's and found that they show floats bowls right and left with throttle stops on the inside, just as my G15. I would imagine that they would then be afflicted with the same issue am having.Edited by - oldandmatchless on 30 Oct 2012 01:38:41 AM