Mikuni VM36 help

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Apparently the only way to do a proper plug chop these days is to take a pair of new plugs inserted into an already warm engine, pin it in third or fourth and as mentioned & cut the engine, remove those plugs and put them in boxes marked right and left. Put back in the originals ride home and then carefully saw (or mount them in a lathe) and cut all the way around the thread about 8 - 10 mm below the end of the threaded section. Once that piece is removed there will be a mixture indicative coloured ring visible near the base of the centre electrode.

Cheers,

cliffa.
 
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Apparently the only way to do a proper plug chop these days is to take a pair of new plugs inserted into an already warm engine, pin it in third or fourth and as mentioned & cut the engine, remove those plugs and put them in boxes marked right and left. Put back in the originals ride home and then carefully saw (or mount them in a lathe) and cut all the way around the thread about 8 - 10 mm below the end of the threaded section. once that piece is removed there will be a mixture indicative coloured ring visible near the base of the centre electrode.

Cheers,

cliffa.
I was talking to someone recently that works in the endoscope industry ,he has a camera that he uses to look inside an Amal concentric pilot jet bush
So maybe a camera to look inside a spark plug if you are that intent?
 
I've said it before and I'll say it again. The only accurate way of getting mixture correct is by fitting an O2 sensor and an air/fuel ratio gauge. This will tell you everything you need to know over the whole range of fuelling and not just the top end running. If your plugs are black, it's more than likely that it's too rich in the low end or the mid range. The gas analysers that the dyno guys run are not necessarily correct. My gauge told me the exact opposite of what the dyno sheet said. Fit one. It's very educational.
 
Tried to post this yesterday. It is from a Mikuni manual and shows the influence of the various jets and settings. Note in particular the Air Jet which is a key difference to Amal set up. Air Jet covers pretty much the same range as the main jet. And contrary to other references suggests that the needle jet has influence up to Full Open!
 

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I've said it before and I'll say it again. The only accurate way of getting mixture correct is by fitting an O2 sensor and an air/fuel ratio gauge. This will tell you everything you need to know over the whole range of fuelling and not just the top end running. If your plugs are black, it's more than likely that it's too rich in the low end or the mid range. The gas analysers that the dyno guys run are not necessarily correct. My gauge told me the exact opposite of what the dyno sheet said. Fit one. It's very educational.
G’day...which mikuni are you running and how is it set up? I think I have read one of your previous posts regarding your selections but reading this article now I just thought to see what you recommend at this point in time...Tnx in advance
 
G’day...which mikuni are you running and how is it set up? I think I have read one of your previous posts regarding your selections but reading this article now I just thought to see what you recommend at this point in time...Tnx in advance

I run a VM34 so the jetting will be different. My jetting has also been considerably altered by a local crook when my engine was rebuilt. I said that when I got it back, one plug was black and the other one was white. His solution was to put three sizes bigger pilot jet in, making them both black. Also, when I pulled the carb down to check the jet sizes, the main jet was hanging on by a partial thread and dropped out. My isolastics had been adjusted up so that vibration was bad. Because of my experiences with this bloke, I am reluctant to run the bike over any distance because I don't know what he's done to make it tough for me. My love for my Commando has diminished somewhat so I am not riding it as much as I was. He owes me a lot of money from unpaid invoices for heads, amongst other things and I am now preparing a legal case to get the money and parts back from him.

Unfortunately I am not participating to the same extent as I did because of this situation and the way I feel about it. My O2 sensor has stopped working and I have to buy a replacement before I can get my bike running as before.
 
Tried to post this yesterday. It is from a Mikuni manual and shows the influence of the various jets and settings. Note in particular the Air Jet which is a key difference to Amal set up. Air Jet covers pretty much the same range as the main jet. And contrary to other references suggests that the needle jet has influence up to Full Open!
The air jet has a much bigger influence on carbs with bleed type needle jets (the type that has a bunch of little holes along the length of the jet). VM36 carb uses the primary type needle jet, so changes to the air jet can be used for fine tuning.
 
The air jet has a much bigger influence on carbs with bleed type needle jets (the type that has a bunch of little holes along the length of the jet). VM36 carb uses the primary type needle jet, so changes to the air jet can be used for fine tuning.

Understood. But you need to be in the ball park before you do your fine tuning. And as far as I can tell a 2.0 air jet isn't! It is moot if road riding will readily reveal this with 3/4 throttle being used far more than Full Open!
 
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