3CL won't maintain idle until fully warmed up

Chuck3CL

Chuck3CL

Senior member
Location
OZ
Is it just this 3CL or is this characteristic of this model.....

I have a 1976 3CL with Ignitech ignition, Nology coils, Dellorto PHFs.

Starting:

I use full choke and it starts immediately, then I take the choke off to get smoother running.

When the engine is up to running temperature ( after 3-4 min) the bike can't be faulted, runs great, idles all day at 800-1000 RPM. Like new.

Carb idle jets are set to about 1 1/2 turns out, and adjusted when the engine was up to temp. Carbs are balanced.

But.....until it warms up it will not idle and I have to hold the throttle at 1500 RPM to keep it going, otherwise it stalls.

Once up to temp, no problems.

Question: Is this cold-start-no-idle characteristic or typical of this model, or is there something I've got set incorrectly.

I would appreciate any suggestions or experience from other 3CL or Jota owners.





 
Richen up your idle mixture some more, wind the air mixture screw out another half a turn and see what it does, just because the book says 1/1/2 turns doesnt mean it will work.
What size pilot jets have you got??
 
That is what a choke is for.
Cold starting and running until the engine has warmed up.
If you want it to idle immediately after a cold start then keep the choke cracked open a smidge.
As soon as you set off, switch off the choke.
 
I'll try both those suggestions tomorrow.
Info: PHF 32
slide 60/2, needle K1 mid-ring
Needle atomizer AB265
Main Jet 125
Idle Jet 55
Choke jet 70
Float needle valve 250
Float body gr10
New accelerator pump diaphragms and all new o-rings, seals
Carbs cleaned in ultrasonic
Running 98 octane

 
All looks ok, just try turning out the mixture screws quarter to half a turn.
Any more than that and you will need bigger pilot jets, likely 60s.
I still think the symptoms you describe are standard cold running effects.
 
What kind of ambient temperature are we talking - big diff in warmup to idle time between Melbourne summer at 40C+ degrees and winter in Glasgow.

BTW, Maurizio, they're fuel screws not air screws - many Japanese carbs use air screws - easy to tell them apart: they're on different sides of the slide (ie air side, engine side). Turn a fuel screw out = richer, turn an air screw out = leaner. Being pedantic, I know, sorry!
 
Aussie ambient--cold start I'm talking about can be over 30C. Basically whenever the engine has been off for more than  an hour.
 
30?C ambient is nowhere near the operational temperature of an engine. Switched off for an hour the engine will be well outside it's optimal running temp.
Use the choke to help start it, ride off, switch the choke off.
 
"BTW, Maurizio, they're fuel screws not air screws - many Japanese carbs use air screws - easy to tell them apart: they're on different sides of the slide (ie air side, engine side). Turn a fuel screw out = richer, turn an air screw out = leaner. Being pedantic, I know, sorry"
And the exception to the rule is.......... Amal (Mk2), they managed it!!
Plenty of "old fashioned" bikes won?t idle dead cold, no fast idle attached to the choke, other than opening the choke fully to let more air through.
 
Thanks for the replies guys, in particular to Maurice who got it in one....
I wound out the idle mixture screws to 1 3/4 and got a marked improvement.
Originally I set them up as per Parker, ie, with an engine up to temp.
But as Maurice said, they need more for the cold engine condition.
This was more effective than trying to use the choke to keep the idle.

Appreciate the help.
 
Chuck, one thing more to check, please: You said the carbs are balanced - have you balanced the choke sliders, too? I had several bikes going through some setup by me that came with totally different settings for the choke sliders, which causes one cylinder to go richer than the other and caused some bikes even to stall after some seconds of running.

Since 30 years, that is one of the first things I always check (Richard K. from lovely Pacific Grove might remember...  :-*). Easy to check if you have the rubber hoses off that connect the carbs with the airfilter box. stand right of the bike, look into the rear of the carbs and pull the choke lever until the first slider hides at the top. now adjust the other 2 accordingly (slide the rubber up that seals the choke-cable against the carb body, there is a counter screw that you need to unfasten and then adjust the hight by screwing in or out the distance piece. re-tighten the counterscrew and put the rubber back in place - job done).

Next point is: are the float hights correctly set? To low might cause the bike also to run leaner...

The issues with the Dell'Ortos are mostly basic ones, but in the case of our bikes, they are not running in the best conditions: lots of heat, lots of vibrations etc. makes them change settings almost right after you set them right. Also check the screws under the top covers that hold the slider actuation levers on the rod. They tend to unfasten themselves over time... a bit of loctide helps to prevent this for the future.

if carbs are not blocked and valve-clearance is right, the bike should run smooth with basic settings. everything away from basic settings should cause you to think what is out of adjustment or not mounted correctly.

I had a set of carbs where the sliders (not the choke, the main sliders) went up and down unequally.  :o syncing them in idle position made them off sync in WOT. After disassembling (for ultrasonic cleaning and further examination), I found the rear connecting plate and the front connecting plate massively bent. I straightened the plates, cleaned the carbs and re-assembled them with new gaskets and jets, set all the different points to standard settings et voil? - the bike ran as smooth as it ever could!

 
Thanks L.L.,  good points.

All those you mentioned ok, but I did go back again and tweak the choke sliders a bit to bring them in sync, will test tomorrow.


 
Results depend a bit on how much they were out of sync. Had one where one slider was still almost closed while the others were completely open.

On Richards bike, the sliders were all in different positions. Funny enough, he had also the idle mixture screw in different positions to compensate that. Still the bike did stall after 4-5 seconds of somewhat OK running. Adjusted the sliders, screwed in the idle screws completely and 1,5 turns out and all of a sudden, the bike kept running...  :D
 
Glad it was of help!  ;) Easy to forget, as mostly it still starts. I bet that on 8 out of 10 self maintaned bikes, they are not correctly adjusted... not sure if all dealers ever check when adjusting the carbs...?

I can see now a lot of Laverda-Owners worldwide going into the garage, checking the choke-slider settings...  :LOL:
 
Laverdalothar said:
Glad it was of help!  ;) Easy to forget, as mostly it still starts. I bet that on 8 out of 10 self maintaned bikes, they are not correctly adjusted... not sure if all dealers ever check when adjusting the carbs...?

I can see now a lot of Laverda-Owners worldwide going into the garage, checking the choke-slider settings...  :LOL:
Click to expand...

Dealers don't know what a carb is.
They don't do anything anyway.

Been keeping away from them for a long, long time.
( apart from new bikes to validate the warranty. )

Paul
 
Hey Lothar, 

I did indeed check the choke settings on my Jota as you described.
They were closing fully, but were slightly out when opened, so I equalised them.
Previously, the bike had started OK and had settled into an easy idle. 
But there used to be some clutch rattle until it warmed up, the sort of thing that can happen when the carb balancing is out.  However, the carb slides and idle screws had been in sync.
After the choke setting the clutch noise was gone. 
So, a very useful exercise and many thanks for the tip.

Tom

 
 
@Tom: very glad it helped you , too. Isn't it interesting what such a little setting can do?

@Paul: some dealers (or better: workshops!) are really brilliant. Lucky me, living just 80 Km from one of the best of them (OCT with Piet). If only they would not take always that long to do an engine... ;-)
 
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