Forum

[Mark B]

With the 500 Bullet now running, I took it to the MOT station yesterday to see what else was needed to get it fully roadworthy and they gave it an MOT with no advisories! So I went the Long Way Round from Hitchin to Stevenage, and spent a lovely hour thumping around the country roads.

Anyway, being a firm believer in fixing things when they ain't broke, it's now time to swap the Mikarb for the 30mm Mk2 Concentric that I've got. It came off a Velocette Venom and the current settings are: 280 main, 106 needle, 35 pilot and No 3 slide. Are these in the right sort of range as a starting point? (I know that some people will recommend not using a Mk2 anyway...!)

Thanks for any advice.

[papasmurf]

Took my Electra X(ish) in for an MOT this morning, on the way the engine died but I did not pull the clutch in, (fortunately,)a couple seconds later a large bang and belch of flame out of the silencer, engine running again and it has been running OK ever since and passed the MOT, no problems no advisories.

[PeteF]

Change the carb if you like the look of it but it's not an upgrade IMO. There's a chart in the parts book for choosing jets.

[Count Johnny]

If you don't mind me saying so, this would be a retrograde step.



I recently changed from a 32mm MkII Concentric to a VM32 Mikuni and don't regret it even a bit.



Apart from anything else, the MkII has no real means of attaching itself to anything, on a Bullet, so (being quite a heavy carb) is flops about like a limp dick.

[Adrian]

I see the Mk 2 Amals have a lump of alloy just below the screw-on carb top which is drilled and tapped, presumably for attaching a bracket of some sort in order to prevent the very scenario you so colourfully describe. On the other hand the VM32 Mikuni is a splendid carb, which works nicely on tuned BSA B40s as well. How have you secured this one to prevent floppage?



A.

[Tim NZ]

The MK11 is an excellent carb, but its advantages will not be optimised IF you keep the stock Mickarb mounting flange...


Alternate manifold mounting manifold/rubber is advised, I use 142681C. (page 20 in H catalogue) BUT it will also need a 19mm spacer for post 1996 bikes. Dummy the Carb up and you will see how the top of the carb needs to clear the top motor mount and/or the rear tank mounting lugs...


The main jet will need to be dropped in size to 200-220 range. 280 will be way to big unless you have a seriously tuned-up Bullet?


The drilled and tapped screws holes near the top of the carb are for attaching a link-bar, used in multiple carb mounting situations so as to 'join' the carb bodies to allow for balanced choke and throttle operation.

[Count Johnny]

Hi Adrian



We did use the link bar holes to try to locate it - - and the manifold that Tim NZ describes - but it wasn't very satisfactory.



As for the Mikuni, because it is lighter and more compact, it self supports itself on the standard Mikuni flange mount manifold rubber.

[ChrisD]

Hi Mark B
I run a 32mm Mk2 on my 1996 535cc Bullet. I agree with the comment by Tim that you will need to find space for that carb below the tank. I took the easy route and had 2cm of plate brazed onto the rear tank mounting stubs (fill tank with water or CO2!). I also slimmed down the tank fixing nut on the right side to make a bit more space and the carb sits nicely in place. I support the carb on a large cylindrical air cleaner (from Ace Café) fitted to the frame and now it no longer “flops around”.
I run a 220 main, 105 needle and the 2.5 throttle valve (slide) but they will be dependant on testing. I followed the Amal "Tuning your carburettor" guide - still a work in progress now my engine is back together.
Cheers, ChrisD

[Adrian]

Part of the problem is limited under-tank space if you use a separate alloy flange with a rubber connecting piece, though if you use a 90° ferrule for the throttle cable it routes it away from the problem area. The one-piece Mikuni mount moves the carb in a bit so that there is room for the cable to exit and have a reasonable route under the tank. Surrey Cycles offer a similar piece for larger Mk2 Amals using 2.5" stud centres, though with 5 minutes work with a rat tail file these would also fit the Indian 500 Bullet's 60mm stud centres.



I'm surprised that a Mikuni is noticeably lighter than a Mk2 Amal.



A.

[ChrisD]

Hi MarkB. I also had to modify the inlet manifold to angle my 32mm Mk2 concentric away from the petrol tank bracket on my 1996 535cc Bullet. I hacksawed almost completely around the manifold stub leaving a ~5mm long contact. I carefully bent the stub away from the flange until the angle between them was OK for the carb to miss the petrol tank fixings (an offset in this case of 9degrees).
Then I carefully drilled through the flange and into the stub to fix a long 2mm bolt which I tapped into the flange so that once the manifold was mounted with the carb, I could turn the bolt to open the stub-to-flange offset, until the angle was perfect.

Then I drilled two 2mm holes (plus one cock-up as you can see) and located further bolts in them, all fixed with JBWeld. Once that was dry and the stub-flange angle fixed, I filled the wedge-shaped gap around the stub with JB Weld and smoothed the inside. All has been well for the past few thousand km so I guess it works OK. All drilling done with my trusty B&D handheld (hence the odd error).
ChrisD - hope these two images appear OK. If not, please find them in my ChrisD200 photobucket library.