Mikuni Carb Settings

[blethermaskite]

To quote Robert M. Persig.........from, 'zen and the art of motorcycle maintenance' .......no experiment result is ever really conclusive because the number of hypothesis available are infinite .........28 degrees here in N.Ireland.....too hot to ride the baby desmo!
Cheers,
George

[Duccout]

By 'Eck it is hot George! I rode on my big Desmo yesterday to Bedfordshire to visit the Shuttleworth Collection, hoping that it would a, be cooler than the day before, and b, be cooler in the hangars, which was wrong on both counts. I was so hot riding home that I felt really rough, and found it hard to concentrate. I was totally knackered by the time I got home and struggled to get my leathers off, which had stuck to me, and was only partially restored by a cold Budweiser. I suppose that a Heineken would have done the trick.

Keep cool, Colin.

[themoudie]

Aye George and Colin,

Too hot! Never! Well, maybe, 28°C in the shade at 17:00 here! I've been going for a canter on the 450 or the SRX600 at the back of 20:00hrs and finding most of the roads up here deserted. Some places the tar ripples have become very dangerous and in others the tar spraying and chipping lashing season has started, so good practise for riding on the ripio.

Pleased to read that the carb experiments are moving in a positive direction Colin, keep at the bu**er!

As for a thirst quencher, that dosen't blow your brains out, try a bitter, with either a non-alcoholic ginger beer, or a Crabbies from the fridge, slid down the side. Should slake the thirst and then have a cooled Guinness for sustenance!

Just back from a circuit session at Knockhill race circuit for my wife on 4 wheels! Very hot, when the sun came out at the back of 12:00 midday, with a lot of stored heat in all that tarmac. But, a very chuffed wife!

Slainte, Bill

[Duccout]

I just gave the bike a run, with the 30 pilot jet in and the needle at the centre notch. The bike started first kick and ran ok, until I pulled away, then it showed low-down weakness for a short time, before settling down to run perfectly, with no problems. I could try a no 35 pilot jet, or a 1-1/2 slide, but I think I will leave it for a while and see how things go, as the weakness is only apparent with a cold engine.


Colin

[Scottish888]

I have a new VM30 for my 250 mk3, it came with the wrong jetting all round.
If anyone has successfully tuned the vm30 for a 250 I would appreciate to know the settings.
Using the original Dellorto as it is better than the mikuni.

Regards

[Blaine.Hale]

So after bumping up to a 35 pilot jet on my 250 Monza, it no longer bogs on the initial throttle and comes back down to idle right away, but I have my idle mixture screw turned all the way in. Been running great but I noticed it smelled very rich. If I back it out the idle mixture screw until the flame is blue, the idle races and I get the bog/hesitation in throttle again.
I pulled out my colortune and it's very orange (rich) at idle and all the way through 1/4 throttle, maybe even 1/2 throttle. Seems blue and fine beyond that.

Question: Could this be because of bad ignition timing on my part? New points + condensor and I set the timing to 5-8 degrees BTDC. I'm using an NGK B7HS that's just the factory NGK gap, at the moment. Zero issues starting the bike. Should I run a hotter plug, perhaps?

[Duccout]

Hi Blaine,

It never does any harm to re-check the ignition timing. I wonder if a worn A/R unit could be causing your idle problems? The spark plug will depend on how you are riding, but generally for a Monza I think that you should be running with a B6HS.

Keep us informed.

Colin

[Blaine.Hale]

Hi Blaine,

It never does any harm to re-check the ignition timing. I wonder if a worn A/R unit could be causing your idle problems? The spark plug will depend on how you are riding, but generally for a Monza I think that you should be running with a B6HS.

Keep us informed.

Colin

Checked and rechecked ignition timing. Kind of hard when the cam lobes make it slide right past that 10-0 degree area before TDC but I usually hold the back wheel right around 5-7 degrees BTDC then move my points plate to the point where my light goes on/off then set it.
So, assuming that's good and B7HS wouldn't make too much of a difference...you'd think I would be good on the ignition side. I ordered some B6HS, just in case. I still don't feel 100% on the ignition but it starts first kick, every time, on choke and doesn't do the "I'm too advanced so I'm going to kick back on you."

Here's how it runs with the air mixture screw all the way in and a 35 pilot jet. Great idle, smooth throttle, comes back down to idle fine. Waaay too rich.
https://youtu.be/Tyqri38ADlg

And here's when I back the air mixture all the way out in order to get a blue flame, where the mixture should be. Notice the racing idle and complete loss of power with any bit of throttle.
https://youtu.be/7262KvHAsVE

Edit: This is why I'm not convinced the ignition isn't the issue. It's almost on a full retarded position with all new components.

[Jordan]

That's a nice clear photo of your installed points.
What points gap are you using?
Did you set it at the max open position?

[Blaine.Hale]

That's a nice clear photo of your installed points.
What points gap are you using?
Did you set it at the max open position?

Yep. They're set to 0.014. I reset them again while doing today's ignition timing.