starting sequence

KiwiShane said:
Ok so when you adjust the screw when the engine is warm...does the idle change from one turn out to 4 turns?
I'd ring/email a dealer that sells these kits such as Colorado or Holland Norton works for the supplied jet starting point for that instrument especially the settings/jets for the idle circuit...Sweet people...
Click to expand...
the idle does not change from 1 turn to 4 the only time the idle changed is when i reduce the screw to nearly closed ,but from one to 4 it does nothing
 
I'll post up some links here to see if any comments/info helps you or rings any bells for you mate
www.accessnorton.com

Mikuni vm34 "choke" no help starting

SO i kicked and kicked and finally found that with the choke off and a little twist of the grip the 850 would start. So whats wrong with my "choke" circuit ? settings ; needle 6dh3 main 260 air 2.0 slide 2.5 pilot 35 needle jet 159 -P0 air screw out 2.25 turns, once its running i can get a...
www.accessnorton.com www.accessnorton.com
www.accessnorton.com

Dual Mikuni VM34 Jetting

Rebuilt engine on a 1974 Commando Mk2 850 running twin Mikuni VM34 carbs and K&N filters. The engine/head has not been modified and is running a stock cam. I live near sea level in Southern California (Los Angeles). New NGK B7ES plugs are black but do not foul. Valve clearances are within...
www.accessnorton.com www.accessnorton.com
 
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UPDATE FOLKS,

have tried 27.5 i am still having the same result will not start with choke on cold,will try 25 pilot tonight , and when warm or even after running 30 seconds she ticks over perectly , so at present this is my starting sequence from cold full choke 2 kicks,turn off choke and 1/8th throttle she starts but needs choke on and off for 10 to 15 seconds then she runs without it but i do turn up idle for 30 seconds then im off on the road, warm start is one kick no choke starts first time and ticks over perfect, bike pulls like a train

will send results with 25 pilot later, as with 4 turns out on the air screw using the 27.5 pilot i still cant get the bunson blue colour thru my colour tuner
 
It sounds like your carb is blocked somewhere hence why it won't start with choke on..
I wouldn't worry about colour tuner at this point...I know you have cleaned the carb before but it sounds like a passage has a obstruction in the idle circuit .
1/8 throttle is by passing that circuit.
 
Head said:
UPDATE FOLKS,

have tried 27.5 i am still having the same result will not start with choke on cold,will try 25 pilot tonight , and when warm or even after running 30 seconds she ticks over perectly , so at present this is my starting sequence from cold full choke 2 kicks,turn off choke and 1/8th throttle she starts but needs choke on and off for 10 to 15 seconds then she runs without it but i do turn up idle for 30 seconds then im off on the road, warm start is one kick no choke starts first time and ticks over perfect, bike pulls like a train

will send results with 25 pilot later, as with 4 turns out on the air screw using the 27.5 pilot i still cant get the bunson blue colour thru my colour tuner
Click to expand...
That is because TUNING was never the problem.

It ran well BEFORE the cleaning/pilot jet drilling/etc.

Again, going back to find what was changed. Not knowing your skillset, it's hard to help.
If you want problem solving guidance, just raise your hand.
I have fixed some very obscure/wierd/unusual Mikuni problems.

I had a VM32 that would not idle slowly, similar symptoms.
I found a hay seed in the air passage from the intake horn leading to the main well. PARTIALLY blocking it.

starting sequence
 
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update folks,

i bought a new carb a vm34 with 260 mains and 40 pilot from cafe racers in holland for 150 euro

fitted it in still not start with choke 2 kicks then off choke first kick and she started perfectly and idles perfect and rides perfect,

the biggest mystery to me is i ultrasonic cleaned the original went thru everything and every option .the new carb the bike seems to tick over very very smooth,very responsive too,

i still prefer her to start on the choke from cold tho ?

i will put the colour tuner on her tonight and set the air screws,

i recall ye telling me my pilot was too large at 40 this might be the issue with her not starting on the choke ?

again i thank you all so much for your help i think i am nearly there now
 
Head said:
i recall ye telling me my pilot was too large at 40 this might be the issue with her not starting on the choke ?
Click to expand...

That could be as much to do with the VM Mikuni choke/starter jet as it is known to be very rich.
www.accessnorton.com

Hard start

75 Norton Mark 3 - 125PSI compression cold after 3 kicks, carb is Mikuni single 34-rebuilt with .240 main jet as I live at 3500 feet plus. Pazon ignition new, timing is 28 Degrees dead on. This puppy won't start cold without starting fluid, once hot starts so easy I am amazed. Right cylinder...
www.accessnorton.com www.accessnorton.com
starting sequence
starting sequence

The 'rubber' tip of the choke/enrichment plunger can degrade so the choke circuit not completely shutting off could have been the cause of the rich idle on the 'old' Mikuni.
 
L.A.B. said:
That could be as much to do with the VM Mikuni choke/starter jet as it is known to be very rich.
www.accessnorton.com

Hard start

75 Norton Mark 3 - 125PSI compression cold after 3 kicks, carb is Mikuni single 34-rebuilt with .240 main jet as I live at 3500 feet plus. Pazon ignition new, timing is 28 Degrees dead on. This puppy won't start cold without starting fluid, once hot starts so easy I am amazed. Right cylinder...
www.accessnorton.com www.accessnorton.com
starting sequence
starting sequence

The 'rubber' tip of the choke/enrichment plunger can degrade so the choke circuit not completely shutting off could have been the cause of the rich idle on the 'old' Mikuni.
Click to expand...
it is brand new carb
 
Head said:
it is brand new carb
Click to expand...

Yes, that's why I said "old carb" when I referred to the choke plunger possibly being the cause of the rich idle as I understood you'd replaced the old VM with a new one from Holland Norton Works but that doesn't necessarily alter the rich starting problem.
 
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L.A.B. said:
Yes, that's why I said "old carb" when I referred to the choke plunger possibly being the cause of the rich idle as I understood you'd replaced the old VM with a new one from Holland Norton Works but that doesn't necessarily alter the rich starting problem.
Click to expand...
thanks Lab,i am going to do the colour tuner later on this evening and try have the air mixture set correctly, as for choke plunger on new carb is there anything i can do with it ?, when my old carb was running perfect first kick when hot or cold she had 260 mains and 40 pilot, so i will try get the pilot with the choke working tonight
 
Head said:
as for choke plunger on new carb is there anything i can do with it ?,
Click to expand...

There's probably nothing wrong with the choke plunger on the new carb (assuming the plunger is seating correctly?).
My comment regarding the choke plunger was intended for the old carb.
Head said:
when my old carb was running perfect first kick when hot or cold she had 260 mains and 40 pilot, so i will try get the pilot with the choke working tonight
Click to expand...

The pilot and starter (choke) jets are different jets.
The problem is the VM choke jet is pressed into the float bowl so it's not easily changed or adjusted.

The Mikuni VM starting/choke jet (arrowed in my previous post) gives a very rich mixture so it can often be too rich for starting in warmer temperatures (see the link in my previous post) the engine can then flood if the choke continues to be used after only one or two kicks.
 
L.A.B. said:
There's probably nothing wrong with the choke plunger on the new carb (assuming the plunger is seating correctly?).
My comment regarding the choke plunger was intended for the old carb.


The pilot and starter (choke) jets are different jets.
The problem is the VM choke jet is pressed into the float bowl so it's not easily changed or adjusted.

The Mikuni VM starting/choke jet (arrowed in my previous post) gives a very rich mixture so it can often be too rich for starting in warmer temperatures (see the link in my previous post) the engine can then flood if the choke continues to be used after only one or two kicks.
Click to expand...
thanks buddy, i do know when i kick once or twice with choke then one kick without choke and little throttle she fires up i then turn up idle screw for 10 or 15 seconds until she idles on her own at 1k
 
My T160 has VM Mikunis and they are the same. If my T160 doesn't start within two or three button presses/kicks then I have to knock the chokes off and then it normally starts immediately on the next press/kick. If the chokes are left on it floods. Once the engine has started, the chokes can be applied as necessary until the engine has warmed up.
 
L.A.B. said:
My T160 has VM Mikunis and they are the same. If my T160 doesn't start within two or three button presses/kicks then I have to knock the chokes off and then it normally starts immediately on the next press/kick. If the chokes are left on it floods. Once the engine has started, the chokes can be applied as necessary until the engine has warmed up.
Click to expand...
thanks that is exactly the way mine has developed now, identical to what you just said, it nopw has 1200 miles on rebuilt top end i thought that might have had something to do with it, it is a pity as old carb started first kick hot or cold until i went near it lol
 
Head said:
thanks that is exactly the way mine has developed now, identical to what you just said, it nopw has 1200 miles on rebuilt top end i thought that might have had something to do with it, it is a pity as old carb started first kick hot or cold until i went near it lol
Click to expand...
Try kicking it over with choke on (one full kick) Then take choke off and kick bike over to start
With MKII amals put choke on kick till it coughs turn off choke and kick to start...
 
well folks the bike is going very well now, did notice an issue with smoke as sitting on bike out of r/h exhaust does not smell like oil it is a bit white mainly on tick over and stopped in traffic , only started last night, take in to account i have had a complete top end rebuild about 900 miles ago, she is pulling like a train, before i got the top end done it used to be smokey from same exhaust and i was told it was valve stem seal, any ideas folks ?
 

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