Starved for fuel?

Status
Not open for further replies.
K

kevbo82

quick recap, trying to wake up my dad's 73' 750. So all i did so far was remove old fuel from the tank, change all the fluids, replace the spark plugs and the battery. so today i tried starting it, put about a gallon of gas in the tank, tickled the carbs and after a bunch of cursing and kicking it started, but quickly died. So where i'm at, it seems if i tickle the carbs A LOT and get the bowls good and full of gas, i can start the bike and it will idle for 20 seconds or so pretty nicely then die. also will die the second i touch the throttle. so it seems to me it's starved for fuel. Is there a common place to start looking for the restriction with these? They are amal carb's, the bike has sat in a garage since about 1990, the fuel lines and carb's were dry, very little gas left in the tank, and the tank had a cream sealer in it. the one thing that totally slipped my mind was checking the fuel petcocks to see if maybe that cream gunk clogged anything up, but i do get fuel in the lines, and at the carb when i use the ticklers... also is there any chance it's not fuel starvation? it sounds GREAT for the little bit it idles, so i was thinking points/timing/spark were okay?
 
Inspect the floats for distortion. The tags that grip the float valve should be parallel with the top of the float. It's been known for them to distort and droop if a bike has stood for a long time so that the valve shuts before the fuel comes up far enough. There was even a batch that emerged distorted from the moulds about 15 years ago. If the level is very low the bike will idle after you have flooded it until the fuel level drops down again and then it's likely to cut out. With a very low fuel level it's also possible for the bike to cut out as you open the throttle.
 
great info there dave, i was just on the amal site and they have a rebuild kit that includes jets and float for $36.00, i think i might grab two of those and take them off since i have no idea if anything was ever done to them or what kinda shape they're in after all these years. the carbs are 932's and a manual i have is telling me the jets should be... pilot-25cc, main-220, needle 106. can anyone confirm those with me before i order!? Thanks so much guys i'm blown away by the knowledge and helpfulness here
 
On the 'Norton Commando Motorcycle' page, up at the top is a link 'Norton Commando Technical', I think you will find the factory jetting in there if you don't have the Riders Handbook.

Dave
69S
 
You have to get that idle circuit cleaned out.
Do you play the guitar? Guitar string works great for poking in the air fuel screw holes to clean out the oxidation which is what I suspect to be clogging the carb and not letting it idle.
Once you open the float bowl you'll see what I mean.
 
haha i do play guitar and i've been reading around and watching youtube videos and the strings seem to be the mostly commonly used tool for the job. guess i'm in luck!
 
In addition to the suggestions above, the carbs can be boiled in soapy water to remove internal gunk and hardened on varnish deposits.
Take the carbs apart as much as possible, remove jets, throw the carb body and float bowl into a pot of boiling soapy water for a few minutes.
Use a pair of tongs to remove the parts from the still boiling water. Immediately apply some compressed air to dry off the water.
Because the metal is hot, the parts dry very quickly and completely with the application of compressed air.

This method works well to clean up the outside of the carbs as well.

Glen
 
Before you take the carbs apart, run the engine with the gas tank cap open just to eliminate breather hole plugged possibility.
 
A friend of mine was having trouble with one of his ATV's not running properly. He'd had the carb off and apart on numerous occasions, but still no luck when he'd put it back together. Someone else told him about Boiling it in water and lemon juice. His wife had a fit because it stunk up the whole house, however it cleaned all the little circuits out completely and the engine ran perfectly afterwards. Just a thought in case it doesn't tune well with the "E" string. :) Cj
 
Status
Not open for further replies.
Back
Top