Mikuni TM34 jetting

[voelser]

Small update: I found some angled elbow cable adjusters by Dell Orto (couldnt find the Mikuni equivalent in the UK for love or money) that just seem to miss the fuel taps. So that’s a result. Ordered a second one and once that is on I can get back to the tuning.

 

[voelser]

On a side note: I tried the same jetting on my chopper (rephased, 750cc engine) and the PJ of 25 was too small. Hardly any petrol made it into the engine. Put the 50’s back in and got it to run, but way too rich. So back to the drawing board on that one!

 

[grizld1]

There are very strong interactions between PJ size, slide cutaway, and needle position. The #4 slide should be fine, but the 5FP17 needle with the clip at #2 could be an issue. You might try the known good combination of P-6 NJ and 6F9 JN with clip at #3.

 

[voelser]

Cheers. I have 6f9 needle in, but unfortunately Allens Performance currently out of p6 needle jets, so stock needle jet in for now. Having said that the PJ at 25 did nothing, not even a puff...lol...as soon as the 50 was in it wanted to run. So probably the p6 needle jet in and a pj somewhere between the 50 and 25. But first I need to figure out my sparkplug issue from the other thread.

 

[ulfagren]

So what are you all running at the moment?
I have a 256 engine with standard pipes and free flowing silencers. UNI pod filters.
I currently have following TM34 setup
PJ 22.5, with air screw 1.5 out
Needle Jet P-4
Needle 5F3 at the leanest setting : 1
MJ 190
Air Jet 2.0

It runs really sweet, but I will continue testing small changes. I will try the needle at 2 again and if that works fine maybe increase MJ since I think it is bogging a little at full throttle. Anyways I don't want it to run too lean. Better to be on the rich side while still running good.

 

[toyotatrdt]

i just ordered a jet kit from 6 sigma for a single carb TM34 setup for my xs. willpost about it when i get it

 

[Hamos]

So what are you all running at the moment?
I have a 256 engine with standard pipes and free flowing silencers. UNI pod filters.
I currently have following TM34 setup
PJ 22.5, with air screw 1.5 out
Needle Jet P-4
Needle 5F3 at the leanest setting : 1
MJ 190
Air Jet 2.0

I’ve just ended up at this exact same setting. Had to keep dropping the needle to get it to run clean at half throttle.
Seems to be running fine now, but I suspect a leaner needle is what is needed with the p4 needle jet.
I do have a P6 needle jet and 6f5 needle available, so could try either of those.

750 big bore 256 cam, 1.5 headers with reverse cone megaphones. Currently with baffles in.

pilot jet 22.5
Needle jet P4d
Needle 5F3 in slot 1 leanest setting
Slide 4
Main 180
Air screw 1 3/4 out.

Only just rebuilt the engine, so not checked the mains yet.
I need a longer run on the above setting to check plugs, but a round the block run and this is the only setting that pulls clean through 1/2 throttle.

 

[ulfagren]

So what are you all running at the moment?
I have a 256 engine with standard pipes and free flowing silencers. UNI pod filters.
I currently have following TM34 setup
PJ 22.5, with air screw 1.5 out
Needle Jet P-4
Needle 5F3 at the leanest setting : 1
MJ 190
Air Jet 2.0

It runs really sweet, but I will continue testing small changes. I will try the needle at 2 again and if that works fine maybe increase MJ since I think it is bogging a little at full throttle. Anyways I don't want it to run too lean. Better to be on the rich side while still running good.

Update, I have today changed jet needles to 6DH2 at 3rd from top (middle)
The stutter at 1/4 disappeared and the bike now runs good but I think it bogs a little at 3/4 to full so I will experiment further with main jets.
I am very happy that the bike is now nicely rideable without hesitations.

 

[Trigg choppers]

Thanks. I have seen the original feature. I recognize the alternator cover. Amazing bikes. The bike shed is a great, inspiring place.

hi installed Flat side TM 34 mukuni with the jets it came with that was supposed to be for a XS650
absult runs shit.
supplied with pilot jet 27.5 mainjet 230
so rich black sooted plugs
delivered from Mukuni OZ
crap out of box wish i gone for Vm 34

 

[toglhot]

I'd rethink the pods. Assemble a pod on the TM and look through the bellmouth. The rubber fitting ring on pods partially obcscures the jets at the bottom of the bellmouths. Pods don't fit in with the performance upgrade TMs provide.

 

[grmp]

hi installed Flat side TM 34 mukuni with the jets it came with that was supposed to be for a XS650
absult runs shit.
supplied with pilot jet 27.5 mainjet 230
so rich black sooted plugs
delivered from Mukuni OZ
crap out of box wish i gone for Vm 34

I am no expert but that sounds way over jetted. Mine is bored to 750 and rephased using TM 34's. I started with PJ 25; 170 main; 5f3 needle. I was suffering terrible sooting. All way too rich. I am now down at a PJ 15; main 165 and a 6DH2 needle. When cold it backfires a lot but when warmed up it settles down better.