Cleanliness is next to Go... Oh, wait. CARB PROBLEMS!

[Jack Nicholls]

Hi!

Recently I decided it would be a good idea to get my carbs cleaned out by ultrasound. How wrong was I...

So, carbs are back on bike, nice and clean, but it’s been a nightmare trying to get it running again. It starts and ticks over with choke off rather nicely, as soon as I pull the throttle back even slightly, it cuts out.

I thought that it was maybe getting too much air, covered the air filters, pulled the throttle back and surprise surprise, sweet F’ all …

Not going to lie, I’m no expert, so any suggestions or advice would be great. I’m a bit confused by it all!
Just need a “simple” explanation on how to sync and tune the carbs. It’s a 1974 model.

Cheers!

 

[littlebill31]

Did the bike run before you cleaned the carbs?
Did you change anything on the bike after the cleaning?

The problem with having carbs cleaned is people fail to blow out all the tiny little orifices, ports, ect. Then, little pieces of crud get stuck in there. Just the small port in the float bowl (so many fail to clean this) has caused serious headaches.

Read this: http://www.amckayltd.com/carbguide.pdf
It is the carb guide

 

[MaxPete]

...and it is an excellent resource.

 

[retiredgentleman]

The first place to look is the pilot jets. They are located in the float bowls. They need to be removed and visually confirmed to be clear. They have a very small orifice and are easily plugged. Caution....................you need to use a screwdriver that is an exact fit into the slot of the pilot jet. If it's not an exact fit, you risk damaging the soft brass jet.
While the jets are out, you can read the jet size and compare that to the stock size that is listed in the carb guide table.

 

[Jack Nicholls]

Did the bike run before you cleaned the carbs?
Did you change anything on the bike after the cleaning?

The problem with having carbs cleaned is people fail to blow out all the tiny little orifices, ports, ect. Then, little pieces of crud get stuck in there. Just the small port in the float bowl (so many fail to clean this) has caused serious headaches.

Read this: http://www.amckayltd.com/carbguide.pdf
It is the carb guide

Yeah, the bike was running ok'ish' before I took them for cleaning... That's really the reason why I took them, wasn't running great. Didn't change anything, no.
I guess I'll have to take it apart and give it a check over.
Thanks for the advice and the kickass carb manual!

 

[littlebill31]

Those little ports can clog quick. I had a friend recently ultrasound a pair himself and forgot about the little o-ring in the mix screw. That shit the bed.

 

[650Skull]

Electrical problems can be mistaken for carb issues. Is your battery holding a full charge and is the charging system putting out a proper charge.

 

[Jack Nicholls]

Electrical problems can be mistaken for carb issues. Is your battery holding a full charge and is the charging system putting out a proper charge.

Could be onto something there… When I got the bike (working and ok) the electrics were worn so I stripped it all down to the bare minimum and was going to fit a PMA with a nice new loom, etc. It’s on South African plates at the moment and in order to put it onto Spanish plates, I need to have the bike as standard as possible (stupid Spanish bureaucracy), so installing the PMA was out of the question. The battery is dead; I’ve been connecting a car battery to the bike battery to get it started. Is this where you tell me I’m crazy and that’s more than likely the reason for my headache?


What should I check first? Electrics or Carb…?

 

[5twins]

Without a good battery, these bikes won't run right. The ignition system won't function properly. It relies on the battery for juice at lower RPMs when the charging system output is low.

 

[retiredgentleman]

Could be onto something there… When I got the bike (working and ok) the electrics were worn so I stripped it all down to the bare minimum and was going to fit a PMA with a nice new loom, etc. It’s on South African plates at the moment and in order to put it onto Spanish plates, I need to have the bike as standard as possible (stupid Spanish bureaucracy), so installing the PMA was out of the question. The battery is dead; I’ve been connecting a car battery to the bike battery to get it started. Is this where you tell me I’m crazy and that’s more than likely the reason for my headache?


What should I check first? Electrics or Carb…?

You are going to have to check into both. I recommend you remove the carbs to the bench, remove the float bowls, and take out the pilot jets, as I said in post #4. Note the stamped number on the pilot jets. Also remove and note the size of the main jets. This is the time to check and adjust the float levels.
If the pilot jets are clear, you can re-install them.
If you want to make life easy, replace the float bowl screws with allen head bolts. Later on when the carbs are installed on the engine, and you have jetting problems, you can use an allen wrench to remove the float bowls, without removing the carbs from the engine.

Buy yourself a new battery. Some come precharged and others need about 10 hours of charging.Now that you know the pilot jets are clear, you can start the engine and see if the engine will respond to increasing the throttle.
If the engine will rev up normally, put a volt meter on the battery and rev up to 3000+ rpm. Volt meter should read 14.1 to 14.4 volts if the charging system is working correctly.

 

[Jack Nicholls]

Great advice! Busy day ahead.
Thanks for all the help!