Poor starting from cold

[clanger9]

My Dart is a pig to start from cold. It feels like the choke lever isn't having much effect.
The carbs are balanced, the mixture & timing is set and the bike runs perfectly once it's started.

It appears that the choke lever only works on the rear carb. Is this right?

Where do I need to start?
I read something about replacing an o-ring in the carb - presumably take the rear carb off and have a look?

[72degrees]

My Dart is a pig to start from cold. It feels like the choke lever isn't having much effect.
The carbs are balanced, the mixture & timing is set and the bike runs perfectly once it's started.

It appears that the choke lever only works on the rear carb. Is this right?

Where do I need to start?
I read something about replacing an o-ring in the carb - presumably take the rear carb off and have a look?

Does the lever look like this?


No idea if that's OEM, but the seller of that says:
Moto Morini Dellorto Choke lever. This is the choke lever control unit for various Moto Morini bikes, the lever is flipped which pulls 2 cables which can be added to the opposite end. It is meant to operate the choke on dellorto carbs. This unit is black . Made in Italy

The Kokusan ignition is supposed to be much superior than the earlier Ducati Elettrotecnica system, but worth checking the spark too. "It's always ignition."
Possibly the starter jets are actually at least semi-blocked with gunge and as access is not easy even to check the starter jet plunger operation I guess (never had a Dart) it's probably time to have a close look at both carbs while you are at it.

[clanger9]

Quick update: everything seems to be in order with the carbs and choke mechanism.
The o-ring at the top of the choke puller is in good order and everything seems to be clean.

It is slightly easier to start if I manually operate the choke on the front carb, but even with both chokes there's no fast idle from cold: I have to manually catch and hold it on the throttle. It feels like a blockage somewhere.

Next step is probably to strip & clean the carb. Is there a jet or drilling in the choke circuit that is prone to becoming blocked?

IMG_1121.jpg (155.6 KiB) Viewed 14265 times

[EVguru]

No fast idle with the 'enrichener device' open can mean you have the timing retarded. With an unmodified trigger on the rotor, engines with the Kokusan ignition can 'hang' on the advance curve (step!) resulting in too fast an idle when hot. Retarding the base timing was a common trick.

['It must be a .....']

Hello, on the Dart I had there was a flip up choke lever on one carb and the other carbs choke was operated by cable from the left handlebar.
If I had kept the bike I would have used a cable splitter so that both chokes were cable operated from the handlebar.

[MickeyMoto]

The Dart should have a choke lever integrated into the left hand switchgear if I remember, which operates both carbs.

Check plugs and leads, too. If original, get some nice copper core leads and NGK caps.

How clean is the air filter?

[EVguru]

The Dart should have a choke lever integrated into the left hand switchgear if I remember, which operates both carbs.

Rear carb only.

One enrichener is normally enough, but if you really need it you can reach in through the side panel vent and flip up the manual lever on the front carb.

[MickeyMoto]

My brain ain't what it used to be!

The Excalibur operated both carbs...

[72degrees]

My brain ain't what it used to be!

Welcome to my world!

[clanger9]

All fixed now!

I stripped the rear carb and found a perished o-ring at the base of the choke jet:

IMG_1127.jpg (104.92 KiB) Viewed 14113 times

Replaced with a new o-ring and it now starts fine from cold:

IMG_1129.jpg (99.54 KiB) Viewed 14113 times

[EVguru]

The act of removing the starter jet probably dislodged the debris that was blocking it. The O-ring has no effect.

[clanger9]

That makes sense - I couldn't see what the point was of the o-ring!

[EVguru]

That makes sense - I couldn't see what the point was of the o-ring!

To hold the float bowl on whilst you search for the main jet holder!

[72degrees]

The act of removing the starter jet probably dislodged the debris that was blocking it. The O-ring has no effect.

"Possibly the starter jets are actually at least semi-blocked with gunge."

Sh1t in the carbs - always near the top of the list for poor starting on anything

[clanger9]

I agree - though (surprisingly) the carbs were spotless inside. I couldn't see anything in the choke jet, but it could easily have been a bit of unleaded gunge that wasn't visible.

Anyway, it's fixed now...