Mikuni VM36 help

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Luke Turner

Luke Turner

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Hi, it's me, again..

Current settings are:
Needle jet 159-P2
Jet needle 6DH3
Main jet 280
Pilot jet 35
2.5 slide cut around
Clip is in 2nd position of 5
Mixture screw is 1 turn out

EDIT: See video a few posts down.

I've included a video so you can hear for yourselves how she's running.

What do you think?

I also have a 260 & 290 main jet along with a 30 & 40 pilot jet to play with if needs be.
 
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& I'm still dripping fuel at a similar rate! Despite Steve sending me out a whole new float valve assembly! Float height is at 19mm.
 
Yes it doesn't sound good. I would be more concerned with the isolastics, they look worn out .

ELLIS
 


EDIT: View the video in YouTube itself. This forum seems to compress the quality & causes some wild tank & engine movements!

I've just kicked her over again & she seems to have settled down a bit?

Idles around ~1,100.

She kicks very easily!

I guess the proof will be in the pudding if the rain holds off tomorrow.
 
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I've never seen a Norton Commando motor move like that unless the cradle was broken.
The tank was bobbimg up and down, too. What's up with that?
 
YouTube seems to have tried to smooth out my video. It vibrates but it's very exaggerated in that video because of the auto-stabilisation.
 
I really appreciate you all helping me on those things but I'm really just trying to concentrate on getting her running right as I've got a local town show on Sunday.

What do you think of how she's running?
 
I see a fuel filter on the drive side fuel pipe, can’t see if you have one on t’other? Also, obviously, I don’t know how good they are.

But I do know that Japanese carbs are extremely sensitive to dirt. Your fuel dripping could be down to very fine particles preventing seating.

I can’t recall where you’re at with ignition, what system are you using, are plugs and leads NEW and correct? Have you got the correct coils for your set up?

Other than the dodgy sounding tick over the bike sounds good. It IS actually ticking over reliably and it sounds great when you blip it. If you can stop the fuel dripping and the ign is all good I’d put some miles on it and see if it settles down, get some new clean fuel through it, check those fuel filters, and see how it goes.
 
Tomorrow may be ride out weather ISH, so clear her out on a run. There is a lot of movement going on, but not a commando boy so the seers on here have more knowledge. I will keep a eye out for you in Warwick if it's not peeing down. Looking sweet though ! Spoke to a old friend out Banbury way today about your issues, but again he has a Mk 2 A running concentrics , so again not much help. Chin up.
 
I have a VM36 on my 74/850, this is the jetting I have, my plugs look perfect.

2,150 feet above sea level.
260 Main Jet
30 Pilot Jet
6DH4 Needle, e-clip on number 3
159 P0 Needle Jet
2.5 Throttle valve slide
2.0 Air Jet (BS30/97)
Air screw: 1-1/2 turns out

Personally, I think a VM36 is too big of a carb, a VM34 is better suited for a Norton in my opinion.

We all know there is more to a nice running ride and good-looking plugs than just carb settings.
Your carb should not be flushing fuel out of the overflow tube, somethings not right there.
Measurement is from top of the rib to top of the float arm. Lift it another mm?

-correct valve adjustment
-finding true TDC with a degree wheel (only have to do this once) and setting correct timing.
Nortons will start and run with the timing way out of whack, make sure its set correctly and retard it just a tiny bit if its giving you kickback.
-good coils and correct plug leads and plugs.

Electrics count big time.
I use a RM23 single-phase Lucas stator with a Podtronics single-phase regulator/rectifier with my 2MC capacitor still in circuit.
Boyer MK4 analog electronic ignition with 5 ohm Dyna coil, solid copper core plug wires, non-resistor plug caps and non-resistor NGK BP7ES plugs at .025-.026” gap.

All that movement I see with the engine is just weirdness with the video on youtube I hope :)

(edited post Aug10 from 6DH3 to 6DH4)
 
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Fast Eddie said:
I see a fuel filter on the drive side fuel pipe, can’t see if you have one on t’other? Also, obviously, I don’t know how good they are.

But I do know that Japanese carbs are extremely sensitive to dirt. Your fuel dripping could be down to very fine particles preventing seating.

I can’t recall where you’re at with ignition, what system are you using, are plugs and leads NEW and correct? Have you got the correct coils for your set up?

Other than the dodgy sounding tick over the bike sounds good. It IS actually ticking over reliably and it sounds great when you blip it. If you can stop the fuel dripping and the ign is all good I’d put some miles on it and see if it settles down, get some new clean fuel through it, check those fuel filters, and see how it goes.
Click to expand...

Hi Eddie,

I ditched the filters inside the tank in favour of inline fuel filters. I have a pair of these fitted. I did also pick up some of these, they aren't as pretty but the filter material itself looks to be much much finer than the mesh of the first ones I linked.

Boyer Bransden electronic ignition with a Boyer power box. Plugs are NGK BP7ES, the leads are new from Andover (wirewound conductor) & I don't know what the coils are, they're a pair of 6V coils made in West Germany so they've got some age to them.
 
Pushed it n rode it said:
Tomorrow may be ride out weather ISH, so clear her out on a run. There is a lot of movement going on, but not a commando boy so the seers on here have more knowledge. I will keep a eye out for you in Warwick if it's not peeing down. Looking sweet though ! Spoke to a old friend out Banbury way today about your issues, but again he has a Mk 2 A running concentrics , so again not much help. Chin up.
Click to expand...

Cheers Ade, I appreciate that!
 
If you click the video & go through to the YouTube page you don't get the weird movements! Must be how it's compressed for this forum.
 
Chuck_Wagon said:
Your carb should not be flushing fuel out of the overflow tube, somethings not right there.
Measurement is from top of the rib to top of the float arm. Lift it another mm?
Click to expand...
If you are overflowing fuel, then yes. I'd do as Chucky says. Floats are called floats for a reason otherwise they would be called sinks.
 
If your carb is flooding, you will never fix the problem by changing jets. However, if it is not flooding - when you fit an air-cleaner, you might need to go down a size in needle jet. If you lower the needle, you should be able to force the motor to cough when you ride the bike, then raise the needle at least one notch and get good performance.
The first things to do when tuning a bike, is to get the float levels right and replace the needle jets. With old bikes, the needle jets wear. With petrol as fuel that is bad.
 
Mikuni VM36 help
 
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