Hitchcocks Forum

Hi.

I have a 2006 classic with a 535 conversion 28mm micarb and free flowing exhaust and boyer mk 4 ignition, I would like to fit a bellmouth to the carb and was hoping someone out there has a similar setup and could give me an idea of what jetting you are using .

badger man.

TRY THESE FOR SIZE, MAIN JET 125 ,NEEDLE JET P2, PILOTJET 30,SLIDE2.5.HOPE THIS IS HELPFUL

Thanks for that Jonesy , will give it another try, I have that set up but seems I may need a p4 needle jet as its not pulling cleanly mid range, is it permissible to place a washer or 2 under the needle to lift it further out to see if that helps before I get the p4?

badger.

With the proviso that all Enfields behave differently, my free-flowing 500 greatly benefited from drilling the main jet out to 1.5mm as has been recommended by others here. If you have a smaller mainjet knocking about why not try it, worst case is it could run too rich at middle to top end.

Hi Midge.
Yes I do have the original main jet 110 I think, any idea what approx size you end up with by drilling out with 1.5mm drill. How much effect does the main jet have for mid range running ie half to three quarter throttle ? the reason I thought of the washers under the needle was to see if I was heading in the right direction before ordering a p4 jet but don't know if lifting the needle up beyond the bottom grove will help richen up the mixture or have an adverse effect on the carb.

Hi badger man I have fitted the bellmouth to a 28 mm Mikcarb (500 cc iron barrel, tuned head, 8:1 piston, free flow exhaust). Jettings are: 130 main jet, 30 pilot jet, P4 needle jet, 2.5 slide. It's not perfect for my bike, because the overall carb size is too small, but it's the best carb jetting for the bike set up. The P4 and 130 main jet helped a lot in this direction... good luck with the jetting... Jacob

Hi Badger, I think all are in the ball park here but all are in a slightly different state of tune, e.g. compression, gas flow, maybe even timing..

No two motors are the same as you know so plug chops are the way to go, no short cuts..

Careful of running too weak as will overheat your 535 piston so stay rich side..

Raising needle may give a clue as you say but you may have to P4 the jet to get enough flow. if hesitant off tickover you may need number 2 slide.

Two answer question drill to 1.0mm = approx 130cc/min…. 1.127mm= 170cc/min…. 1.223mm=200cc/min… and 1.5mm is approx 305cc/min..

Note jet size is equivalent to cc's passed.. Have fun and post your results.. cheers gwilly..

Jacob,

thanks for your info I think im going to try drilling out my spare mainjet to 1.5mm that is assuming 1.5mm is larger than the 125 main jet I have in at the moment I will obviously check this first, then im going to put a couple of ba washers under the needle and see what happens but need some reasonable weather to give it a run.

Gwilly,

your info regarding your jetting, not quite sure how cc passed equates to jet sizes do you mean the flow sizes = the jet sizes ie 125,130,135 and so on, I found a chart on google that suggests 1.524mm drill = approx. 133.1 in mikuni equivalent size and a 150 main jet comes out at approx. 1.77mm.

Hi guys---------- try this for jets >>>> http://www.allensperformance.co.uk/jetsizeconv.html ---------- I used the same needle-lifting idea on my Honda GL1000 when fitting the later 1100 carbs to it...The choke bore is slightly smaller giving rise to hunting in mid-range.....a thin washer ( 0.015") under all 4 needles did the trick !!

-------forgot to say that for the 535 engine I'd consider a 30mm or 32mm carb...