I have run accelerator pump Dell'Ortos on my Bullets for more than 20 years and they are excellent devices once set up properly, far better than a Concentric MK1.
BUT: they are a pain in the ass to fit under the tank. I actually had to lift my tank up by about 30-40mm.
You will have to make up your own adaptors as there is nothing available from the shelf to fit to your Bullet.
And Dell'Orto parts are far more expensive than Amal.
The best choice for performance and ease of fitting is probably the Mikuni VM series (effectively a big and better Mikcarb). You can choose 28/30/32/34/36/38mm and so on.
But again:
be prepared to spend considerably more money on top on jets etc. to set it up.
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For Royal Enfield owners and enthusiasts
- Thu Sep 24, 2015 9:42 am
#51274
Opinions will always vary, but, for me, where permitted [ie not in pre '62 racing for instance], it is an Amal MK II over anything else, every time and closely followed by the Monoblocs - their only downside being they are not always large enough for some applications. Cheers, Paul.
- Fri Sep 25, 2015 1:38 am
#51278
Bullet Whisperer has a way with the Mk2 and I know he posted the jetting for a Mk2-fitted Fury a little while ago - was it on here or on the MBR forum, Paul? Phil might like a note of it!
Nico, you're right about being out on a bit of a limb when it comes to using Dell'Ortos on a Bullet, one of the problems being that they are bulkier than the Amal 276 or Monoblocs the bikes were originally designed to run with, though depending on the type of carb mounting used the same can apply to the Mk2 Amal! The problem is that if you use a mounting that puts the actual carb too far back the throttle cable fouls the tank. In your case you chose to raise the tank. I was having concerns over this with my NotaFury, but I found the answer was to use a 90 degree cable ferrule from Dell'Orto to route the cable away from the underside of the tank, together with careful attention to the alloy mounting stub I was using. That way I got everything to fit neatly.
The stub was originally from Watsonian Squire in their days as the UK Royal Enfield Importer, and was part of their performance kit for the Electra-X, which used the Dell'Orto PHF32 carb. As our hosts bought out all the W.S. RE spares they might have one or two left. This has the same 60mm stud centres as the Indian 500 classic Bullet's Mikarb mounting so should be suitable for experimentation. Malossi also sell compact one-piece flange rubber mountings for the Dell'Orto PHF and PHBE carbs with 60mm stud centres, AND a version with 2" stud centres for 350 Bullets and Redditch 500s.
Phil, another carb you might try is the Mikuni TM36-31 flat slide pumper carb, it gave very good results on my tuned Electra-X, the only problem being (apart from conversion to push-pull throttle) is that it's also a bit bulky under the head steady rear mounting. A little work is needed! The mounting rubber to use is the one intended for the SR/XT500 Yamaha, with the 70mm centre stud holes elongated inwards to match the inlet flange on the Fury head.
A.
Nico, you're right about being out on a bit of a limb when it comes to using Dell'Ortos on a Bullet, one of the problems being that they are bulkier than the Amal 276 or Monoblocs the bikes were originally designed to run with, though depending on the type of carb mounting used the same can apply to the Mk2 Amal! The problem is that if you use a mounting that puts the actual carb too far back the throttle cable fouls the tank. In your case you chose to raise the tank. I was having concerns over this with my NotaFury, but I found the answer was to use a 90 degree cable ferrule from Dell'Orto to route the cable away from the underside of the tank, together with careful attention to the alloy mounting stub I was using. That way I got everything to fit neatly.
The stub was originally from Watsonian Squire in their days as the UK Royal Enfield Importer, and was part of their performance kit for the Electra-X, which used the Dell'Orto PHF32 carb. As our hosts bought out all the W.S. RE spares they might have one or two left. This has the same 60mm stud centres as the Indian 500 classic Bullet's Mikarb mounting so should be suitable for experimentation. Malossi also sell compact one-piece flange rubber mountings for the Dell'Orto PHF and PHBE carbs with 60mm stud centres, AND a version with 2" stud centres for 350 Bullets and Redditch 500s.
Phil, another carb you might try is the Mikuni TM36-31 flat slide pumper carb, it gave very good results on my tuned Electra-X, the only problem being (apart from conversion to push-pull throttle) is that it's also a bit bulky under the head steady rear mounting. A little work is needed! The mounting rubber to use is the one intended for the SR/XT500 Yamaha, with the 70mm centre stud holes elongated inwards to match the inlet flange on the Fury head.
A.
- Sat Sep 26, 2015 4:02 pm
#51298
@Adrian
I have my Dell'Orto as close as it can get to the Big Head cylinder head (you can just turn the bolts between carb and adapter) and I always run the 90° ferrule, still had to lift the tank. Might be the choice of parts that I use (English frame from 1952, big Twin tank from around 1953).
Good to know about Malossi, that could help me in the future.
@Bullet Whisperer
I understand about the Concentric MK2s which indeed are good carbs (way better than the MkI). But they get more difficult to get in the bigger sizes and fairly expensive, too. Also, quality wise the Mikunis are just way better, so I might settle for the Mikuni for my next project.
I have my Dell'Orto as close as it can get to the Big Head cylinder head (you can just turn the bolts between carb and adapter) and I always run the 90° ferrule, still had to lift the tank. Might be the choice of parts that I use (English frame from 1952, big Twin tank from around 1953).
Good to know about Malossi, that could help me in the future.
@Bullet Whisperer
I understand about the Concentric MK2s which indeed are good carbs (way better than the MkI). But they get more difficult to get in the bigger sizes and fairly expensive, too. Also, quality wise the Mikunis are just way better, so I might settle for the Mikuni for my next project.
- Mon Sep 28, 2015 12:49 am
#51324
Nico,
exactly which Dell'Orto carb are you using? The PHF is a little smaller than the PHM, and there are also various mounting options, onto or into the adapter. The choice of tank does have a lot to do with it, I have seen pictures of older twin tanks which have a lot less underside clearance than the single cylinder bikes' tanks. Even then it might still be very tight, I quote from our hosts' catalogue entry for their Big Heads:
"Please note: That the standard Indian tank will need some small modification to the underside to give the required clearance."
One style of tank which does seem to fit with the PHM Dell'Orto (with the provisions I mentioned earlier) is the smaller Redditch-style tank with the chrome side panels, as fitted to the Fury models. Not everyone's cup of tea as range is limited. Our hosts sell Indian copies of these (92674A).
As far as I can tell the tank used on the roadster Big Head 500s looks a lot like the Constellation tank, could anyone with a genuine factory Big Head bike confirm?
A.
exactly which Dell'Orto carb are you using? The PHF is a little smaller than the PHM, and there are also various mounting options, onto or into the adapter. The choice of tank does have a lot to do with it, I have seen pictures of older twin tanks which have a lot less underside clearance than the single cylinder bikes' tanks. Even then it might still be very tight, I quote from our hosts' catalogue entry for their Big Heads:
"Please note: That the standard Indian tank will need some small modification to the underside to give the required clearance."
One style of tank which does seem to fit with the PHM Dell'Orto (with the provisions I mentioned earlier) is the smaller Redditch-style tank with the chrome side panels, as fitted to the Fury models. Not everyone's cup of tea as range is limited. Our hosts sell Indian copies of these (92674A).
As far as I can tell the tank used on the roadster Big Head 500s looks a lot like the Constellation tank, could anyone with a genuine factory Big Head bike confirm?
A.
- Mon Sep 28, 2015 6:38 am
#51326
Hi Phil/BW
I have a tuned 535 1996 Bullet with a 32mm Mk2 carb (Mr H’s performance cams, 200180), and I am having difficulty getting the jetting right after retiming the cams (inlet retarded 1tooth and exhaust advance 1tooth to match Ace Café’s 535 setting, measured with dial gauge and clear of piston). Where could I find those jetting suggestions of Bullet Whisperer or the ones you used on your 535, Phil?
Currently I find bogging at full throttle means I have to use a 220 main jet, seems a bit small, but I’ve tried all others up to 260 - I just want to be sure that is in the correct ballpark. I find plug chops with our 95octane unleaded fuel (Cape Town) are only effective if the mixture is wildly wrong – badly sooted and wildly lean are obvious with my twin Iridium plugs, but in between I always get medium brown centre electrode but slightly sooted on the ends of the threads.
BTW I twin-plugged my head after TimNZ advice. Mounted the decomp in the centre of the head with a 2mm port into the chamber. Magic!
Thanks, ChrisD
I have a tuned 535 1996 Bullet with a 32mm Mk2 carb (Mr H’s performance cams, 200180), and I am having difficulty getting the jetting right after retiming the cams (inlet retarded 1tooth and exhaust advance 1tooth to match Ace Café’s 535 setting, measured with dial gauge and clear of piston). Where could I find those jetting suggestions of Bullet Whisperer or the ones you used on your 535, Phil?
Currently I find bogging at full throttle means I have to use a 220 main jet, seems a bit small, but I’ve tried all others up to 260 - I just want to be sure that is in the correct ballpark. I find plug chops with our 95octane unleaded fuel (Cape Town) are only effective if the mixture is wildly wrong – badly sooted and wildly lean are obvious with my twin Iridium plugs, but in between I always get medium brown centre electrode but slightly sooted on the ends of the threads.
BTW I twin-plugged my head after TimNZ advice. Mounted the decomp in the centre of the head with a 2mm port into the chamber. Magic!
Thanks, ChrisD
- Mon Sep 28, 2015 8:09 am
#51329
Chris,
the theory with the added decomp sounds OK, though with the Big Head's different design it would need double checking. The valve seats are pretty close together, though you probably could get a 2mm drill between them. With the relevant section of centre finning milled away, how deep is the metal that's left? How far do you drill and tap for the decomp valve, assuming it's the normal Bullet item? You can get smaller decomp valves for chainsaws too. What I'm saying is SKETCH PLEASE! The only time I added a decomp valve to an engine where there wasn't supposed to be one was on my AVL hybrid, there was just about room to drill and tap through for the normal valve.
Final question, how many degrees ignition advance are you running?
Thanks.
A.
the theory with the added decomp sounds OK, though with the Big Head's different design it would need double checking. The valve seats are pretty close together, though you probably could get a 2mm drill between them. With the relevant section of centre finning milled away, how deep is the metal that's left? How far do you drill and tap for the decomp valve, assuming it's the normal Bullet item? You can get smaller decomp valves for chainsaws too. What I'm saying is SKETCH PLEASE! The only time I added a decomp valve to an engine where there wasn't supposed to be one was on my AVL hybrid, there was just about room to drill and tap through for the normal valve.
Final question, how many degrees ignition advance are you running?
Thanks.
A.
- Mon Sep 28, 2015 6:28 pm
#51333
Adrian,
The head has at least 20mm aluminium in the top centre so there’s ample space for the stub that you screw into the head (grind away the few fins and mount it in the centre) and into which the standard decomp screws. Not my idea – a mod devised by TimNZ. Been there for ~5000 kms so far and all is well. See the pictures and fitting details in my photobucket account, Chrisd200 (in the twin plugging library). Lots of other data there too.
Today out on the bike testing the carb jets, I couldn’t understand why it wouldn’t rev smoothly or go above ~60kph until I realised I’d forgotten to reattach one plug cap after the plugchop. I am beginning to realise I need a 0.105†needle jet to go with the 220 main jet. Sounds like it should be weak, but doesn’t appear to be.
Static advance is ~5-7degBTDC (~8.0:1 compression) and full advance has been tested at varying amounts between 28-35degBTDC, amounts proven by strobe. The variability is gained by sequentially removing the metal epoxy fill from the worn slot in the advance retard mechanism. This variability had no effect on the misfiring at revs above ~3500 – not surprisingly either. The engine will rev to 5000rpm in 3rd gear easily and once (by mistake) 6000rpm on the stand (cue comment on the breakable conrod).
Hope this helps
ChrisD
The head has at least 20mm aluminium in the top centre so there’s ample space for the stub that you screw into the head (grind away the few fins and mount it in the centre) and into which the standard decomp screws. Not my idea – a mod devised by TimNZ. Been there for ~5000 kms so far and all is well. See the pictures and fitting details in my photobucket account, Chrisd200 (in the twin plugging library). Lots of other data there too.
Today out on the bike testing the carb jets, I couldn’t understand why it wouldn’t rev smoothly or go above ~60kph until I realised I’d forgotten to reattach one plug cap after the plugchop. I am beginning to realise I need a 0.105†needle jet to go with the 220 main jet. Sounds like it should be weak, but doesn’t appear to be.
Static advance is ~5-7degBTDC (~8.0:1 compression) and full advance has been tested at varying amounts between 28-35degBTDC, amounts proven by strobe. The variability is gained by sequentially removing the metal epoxy fill from the worn slot in the advance retard mechanism. This variability had no effect on the misfiring at revs above ~3500 – not surprisingly either. The engine will rev to 5000rpm in 3rd gear easily and once (by mistake) 6000rpm on the stand (cue comment on the breakable conrod).
Hope this helps
ChrisD
- Tue Sep 29, 2015 6:49 pm
#51341
Thanks Chris,
the compression ratio on my project's engine is still fairly conservative, so the squish band on its own should take care of improved combustion, but I will have a good look in case it needs to be increased. I suspect your con rod will survive for a while longer, though you can save up for a steel one if you're worried. Mine was built with a steel con rod and needle roller big end to go with the lightened and balanced 350 crank as well as the other tuning work. One less thing to worry about, though quite a faff to get done, according to B.W.!
A.
the compression ratio on my project's engine is still fairly conservative, so the squish band on its own should take care of improved combustion, but I will have a good look in case it needs to be increased. I suspect your con rod will survive for a while longer, though you can save up for a steel one if you're worried. Mine was built with a steel con rod and needle roller big end to go with the lightened and balanced 350 crank as well as the other tuning work. One less thing to worry about, though quite a faff to get done, according to B.W.!
A.
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