Mikuni Carb Settings

[Duccout]

THAT is exactly what I was thinking off! Thank you Jordan, looks like I'm going to be doing some modding.

[Duccout]

Much exercising of the grey matter, trying to find an answer to the impossible-to-get-to pilot air screw. Eventually I turned up a short brass tube which I soldered over the end of the screw, and then glued a plastic thumbwheel over that. I've no idea how it will work in practice, or if I will be able to turn it when the tank is on. At the moment the weather is below freezing and I have no desire to try!

[Duccout]

At last the weather is slightly warmer and I risked starting the engine. It started with the choke lever on, but was difficult to keep running with it off - kept spitting back and cutting out, but I managed to get the engine warmed up and adjusted the pilot air screw until I had a nice tick-over, and then the engine ran beautifully, certainly better than I've seen a Ducati Single run before, and much smoother when opening and closing the twistgrip. So, although the carb seems a bit weak when the engine is cold, I don't think that there is much point changing anything until I've road tested it, and that may be a way off yet, looking at the forecasted weather and lockdown. Very frustrating!

[ranton_rambler]

You’ve done better than me! I’ve also been messing with trying to get my carb (Dellorto) right but am no further forward. Tempted to put the old camshaft back in....

[Duccout]

Did it run properly with the old camshaft? I think that tuned engines are harder to set up. My old Sebring ( which, in spite of the styling, and the fact that at the time you couldn't give them away, was a fantastic bike) took changes in the carb in its stride. I went from the original small Dell'Orto, to a monobloc that I had laying about, then on to another bigger concentric, and it just seemed to run OK on them.

This cold, damp weather does not help, my 750 Sport used to hate cold weather, spitting back all the time.

[ranton_rambler]

Did it run properly with the old camshaft? I think that tuned engines are harder to set up. My old Sebring ( which, in spite of the styling, and the fact that at the time you couldn't give them away, was a fantastic bike) took changes in the carb in its stride. I went from the original small Dell'Orto, to a monobloc that I had laying about, then on to another bigger concentric, and it just seemed to run OK on them.

This cold, damp weather does not help, my 750 Sport used to hate cold weather, spitting back all the time.

It was fine before, easy starting, steady idle when warmed up and rideable across the rev range. It just seemed to lack a bit of go at the top end.
The new camshaft is not too radical - hardly any difference on exhaust valve and a bit more lift and duration on the inlet.
I'll shove it in the corner and do some work on my Guzzi 1000 until the weather warms up.

[George]

It was fine before, easy starting, steady idle when warmed up and rideable across the rev range. It just seemed to lack a bit of go at the top end.
The new camshaft is not too radical - hardly any difference on exhaust valve and a bit more lift and duration on the inlet.
I'll shove it in the corner and do some work on my Guzzi 1000 until the weather warms up.

Ian perhaps you should have tried the change of engine sprocket first that you was thinking about to give you that extra few MPH top end.

[ranton_rambler]

Ian perhaps you should have tried the change of engine sprocket first that you was thinking about to give you that extra few MPH top end.

Possibly....not ready to give up yet . I’ve still got more things to try.

[Duccout]

At long last I managed to brave the weather and lockdown ( purely for exercise) and try the bike out. First problem is that it won't start with the choke on, far too rich, but starts first kick with it off, but is then too weak......let it warm up a bit and gradually got it to rev up a bit, but it is still obviously too weak right up the rev range, spitting back all the time. Sigh... Out with the spanners and raised the needle to the highest groove, and it was good enough to go for a run.

As the engine got hotter the spitting back decreased and stopped, and the engine ran perfectly, much smoother than before......Work that one out.... And really runs beautifully. So, this afternoon I will ring Steve at Moto Carb and ask if he recommends a different needle or different needle jet.

[Duccout]

Right, I've spoken to Steve at Moto Carb and he is going to send out a 169 0-6 needle jet to replace the 169 0-2, so we'll see how that goes.