Only Runs On Choke

Francois 180/120

Francois 180/120

New member
Location
USA
I rebuilt the carbs twice, ultrasonic cleaned, 2nd time with all new jets. Only runs on choke (same as before rebuild but slightly better) , measured different temperatures between cylinders and if i hold the throttle at least at 3000 rpm without the choke it runs but seems to run fat, and won't idle . I'm beginning to think there is a weak spark. Not a motorcycle mechanic, not sure what to do next. Any help would be much appreciated
 
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The idle circuit(s) are likely blocked despite the ultra sonic bath.
What jets have you got in there, what setting on the mixture screws, what float height?
Paul
 
Where are your mixture screws set ? If say 1.5 turns out ? what happens if you move them to 3 turns out ?....and what bike is it ?
 
Are you sure the tickover screw is not wound right out ?
Has the bike just started doing this ? ie did it run ok before some other change ?
 
I recently bought the bike as a "running" bike, sat in a collection prior. When i first got it it ran, not great but i managed to ride it around the lot for a bit but that's it. Sputterred and backfired a little after that. Then ran it on the choke after cleaning, seemed to run rich or not burning all the fuel then i noticed the difference in temperature between cylinders. Cleaned the carbs again put new jets and so on, then ran the same but only slightly better. Exhaust is little smokey, not blue or black. After second cleaning all passages seemed clear, ran carb spray through everything, nothing appeared clogged
 
I think you were right in your earlier post where you mentioned a weak spark.
I had this on my Jota, rebuilt the carbs 3 times and i do it for a living and still thought it was carbs. Eventually i ran a live wire from the battery to the live feed to the coils and its was 100% better. that bypasses the switches and half a dozen bullet connections. Then i fitted a Sasche ignition and it ran like a dream.
the problem is people ( like me ) initially check they have 12v at the coils but that doesnt tell you the connections can carry 4-5 amps
My advice would be to be 100% happy with the ignition before you do anything else to the carbs TBH.
 
They dont include coils in the kit so you still need to be sure you have a good feed to the ones you have. If they are white ND coils check their resistance across the low voltage side, it should be exactly 4 ohms
 
Everything you’re describing is exactly what my Jarama did after I cleaned the carbs and replaced the float needle valve. Need to adjust the float level. Fuel level in bowl is too low. I sent you a PM with my phone number. Call if you have questions.

Dave
 
If it's a series 1 your best bet ignition wise is the kit Redax on here sells. He has an Ignition that's better than most others plus an uprated Alternator that has the ability to charge the battery at a way more useful rate plus coils and a billet coil mount that are much smaller and neater. Then you can reduce the battery size to one that weighs about half of the original 32amp hour ones. Add a digital dash-mounted Volt Mitre off eBay for $20 and then your Laverda will have it all. I love spending other people's money.
 
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