Fuel System: Gas (Petrol) tanks, Carburators
I just finished dialing in a rack of CB750 carbs, with a bench sync, and the bike runs perfect. Now here sits my 1965 CL with two little measly carbs that is driving me up the wall. I thought I pretty well had it dialed in but found after a few outings I was still running really rich on the the right side carb only. The bike has a Charlies Place electronic ignition that I have double and triple checked and it is spot on. Valves are adjusted perfectly, and after finding I had a sticking slide, I completely rebuild an extra set of 26 carbs and used a bit heavier springs in the slide barrels, which solved that issue. The motor is fresh, complete rebuild from top to bottom. I went with the following set up........
40 Slow Jet
Mixture Screws 1 1/2 turns out
Needle clip in middle notch
NKG 8 Plugs with a 28 Gap
Bike started with a about 3/4 choke on with first kick and warmed up great. After a good run for about five miles, I let it cool and pulled the plugs. The left side is almost too the point of lean, and right still comes in sooty as hell. I have tried everything I can think of to get both sides running equally with same set up. I am getting to point where I believe I may have to run different jets, needle notch locations, or a hotter plug on one side to get the job done. I guess I need to know if anyone has ever done this to rectify the problem or can offer suggestions on how to get both sides producing nice plug color with the same set up. Thanks all and hope everyone is staying safe.....
If you're sure that the choke slides are synchronised properly and that both chokes are fully open when the choke is OFF then almost certainly the float level needs to be adjusted.
It sounds as if the fuel level is too high on right hand carb. Fuel level in the carbs affects all throttle openings.
Make sure you have the correct float needles in the carbs as the lengths do vary.
You could try swapping float and float needle from one carb to the other to see if the problem changes sides.
Thanks DJM, I should have mentioned I have set and reset the float level at 22.5 numerous times and the choke slides are dead on. You are on the right track, it is just a matter of too damn much fuel on that side. I am going to try again, after ordering in some new plugs, looking at my notes on past set ups, and making a sacrifice to the "Vintage Honda Motorcycle Gods", a couple of cold Coors Lights should do it. Good suggestion on a swapping the floats and needles.....
A couple of other checks.......
Check plug cap resistor values/and or connections.
I had the exact same problem on a single carb Dream, and changing plugs, caps and trimming the wires solved it., so it was one of the three.
I have also found mis-labeled or mis-manufactured jets from aftermarket suppliers.
A quick pour-boy flow test can confirm whether the jets are flowing the same. (hook some tubing to the jet and graduated container and time a given quantity of water flowing thru by gravity.)
Also check needle jets are not oval from wear.
If all else fails, re-install points and see what happens.
66 dream, 78 cb750k, 02fz1, 09 wing
Thank you Gentlemen, gives me some different avenues to explore. I will be in garage for a long period evening, my Wife is hosting her annual Christmas craft making night for her family. Maybe I need to sprinkle some glitter on the damn thing to solve the issue.
If you're sure the floats are set correctly any chance one has a pin hole or two in it?
Still perhaps worth trying to swap floats and float valves left to right to see it changes anything. Just lately I've also heard of a few cases of condenser failure which would have been very unusual only a few years ago, Like the owners the condensers are all getting older and (dare I say it) perhaps approaching the end of their useful working life. Replacing them with N.O.S. items won't necessarily help either as the N.O.S. items will still be fifty plus years old.
Condensers are a thing of the past, I am running a Charlies Place electronic ignition. I have checked compression with my cheapo Horrible Freight gauge, 150 on both barrels. Checked resistance on coils and plug wires, spot on, good clean spark when kicked over so I am pretty sure it is a fuel problem. Will try a new set up tonight and see what happens. I am keeping good notes on changes....