Forum

[Creaky45]

Scotty, I'm in Brisbane. Not too far eh!

[vince]

Hi, had exactly the same problem with an ex Indian army 350 bullet, transpired the slide cutaway was far to big. Vince

[Creaky45]

TimNZ Well I have done all the right things. Bought a new needle from Hitchcocks. There is only one type to buy from them, the standard needle which is exactly 50mm long. I put it in with the same standard slide (3), 120 main (richer than the 117.5 recommended) P0 needle jet and 27.5 pilot. Started and idled perfect. Would not run from 1/4 throttle and no way could it be ridden unless the "choke" was fully on. So then I changed the pilot to a 30 and still it was no better. Then leaving the 30 in I changed the needle jet to the P2 and away it went. Still not the best though. To get it to run anywhere near perfect I had to raise the needle even richer with a washer under the clip. I thought it was ok till I rode my mate's bike which is exactly the same. (120 main, slide 3, P2, 30 and richest slot) but with his strange needle which is only 46mm long not 50. His bike ran like a dream with even acceleration all the way. So I put his carby complete on my bike which made my bike run perfectly. (Trouble is he wants his carby back)I have checked everything I can on my carby and blown it out etc.so it seems I need a 46mm needle. That's the only difference. As far as I can see Mikuni needles are similar but they don't have one 46mm long. I would happily buy a new Mikcarb if I thought it would work but I may as well get a Mikuni. At least I can get all the parts for them locally.

[papasmurf]

I would have though there was enough adjustment on the needle to compensate for the difference in lengths.

[neddy]

How close are those grooves ?

[ric]

Only when matched to the correct needle jet
From the descripion given, a P4 is required.

[Tim NZ]

Your mate possibly has 4L13 needle fitted, similar mixture metering as the 4DH7 at early open stages and then becomes very rich for transition from Needle to main jet.


If you contact Mikuni (Sudco USA) they can supply over 14 different taper needles to suit your Mikcarb; single or double taper.


It would also be advised to do some study on carb tuning sequencing, as switching the pilot jet (Idle/off idle metering) in an attempt to correct 1/4 throttle (Cutaway/needle jet transition )issues is not the way to go.

[Creaky45]

Neddy, The grooves are about 1mm apart but that's not the problem. Thanks for the reply.Ric, not sure what you mean. I thought Mr. H only has a P0 and P2 suitable for my requirements. Tim, I found a 4L13 in the Mikuni catalogue but its taper is nothing like the one on my mates bike. But, long story short, I may have cracked it. I had another 54mm needle (see my first post)so I cut 2 more grooves below the five (call them 6 and 7) so I can get it richer and put the clip in 7 and she goes like a rocket but the plug showed a bit rich so I moved to my leaner slot 6. Now it goes great and the plug is the right colour. I just have to test it out now at full throttle but I think it will be ok. I will do a couple of plug chops at different speeds. The set-up now is, standard 3 slide, 120 main, P2 needle-jet and 30 pilot and slot 6. Thanks to you all for your interest.

[ric]

Sorry, reply was to Papasmurfs comment.
This may be helpful... http://www.mikunipower.com/Manuals/VM_Manual.pdf.

[neddy]

Ah, now another 2 grooves 1mm apart !