carb sync and fuel mixture

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Hansmanbo

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Finally got the old girl running. Took a couple of weeks, but wrapping it up. Adjusted valves, new timing belts, new tires, and rebuild carb. Took me all day to sync the carbs cause of chasing vacuum leaks. Intake tubes need to be tight.... Carb sync seems to be even across the board @ 5lbs.. should I have more? Maybe just an old motor having 88k.
Fuel mixture has me puzzled though. with all 4 at 2 and a half turns out, there is no difference in rpm if changed to 1 and a half. Getting some backfire at rpm above 7000. Pulling out in first gear it seems to be sluggish. I have read ALL of the forums concerning this, but is not specific enough. Backfire indicates lean meaning I should turn screws in to richen mixture.. is this right?
 

dan filipi

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Out to richen but that only affects lower rpms and idle.

You might be running lean in the primary jets.
Have you done the needle shims? That will richen the higher rpm's.

How do your plugs look and what is the compression?
 

slabghost

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2 1/2 turns on the airmix screws is baseline. This is just a starting point to get the motor to run. Warm the bike to operating temperature and set idle to 1000 rpm. Adjust air/fuel mix screw to highest rpm on the first carb. Then reset idle to 1000 rpm. Adjust second carb air mix as the first. Go through and adjust all carbs twice as each carb affects the others. If you still have issues at higher rpm check your air filter is clean. If it is you may need to increase jet size. Have you modified the exhaust or has a PO removed baffles?
 

Hansmanbo

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Brand new air filter and exhaust is stock. Does not like to idle under 1200. Turning mixture screws dosn't affect rpm no matter which way I turn them. Slow throttle response, and slow returning to idle. Backfire occurs when throttled over 7000. As stated earlier, sync is only 5lbs on all 4, but even across the board.
 

slabghost

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This is on the 78 1000? It sounds very much like you have ignition issues. No vacuum advance on the 1000s but the mechanical advance needs to move free. Are you running points or dyna? Have you checked spark? Is it fat blue spark or weak white spark. Are the plugs sooty black?
 

mcgovern61

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Hansmanbo":2j58dp12 said:
Brand new air filter and exhaust is stock. Does not like to idle under 1200. Turning mixture screws dosn't affect rpm no matter which way I turn them. Slow throttle response, and slow returning to idle. Backfire occurs when throttled over 7000. As stated earlier, sync is only 5lbs on all 4, but even across the board.
Be careful on the carb sync.....you can get them to read the same and not be correct left to right. (2&4 vs 1&3) Other than clogged idle passages, you should be able to get the engine to idle down to 950 without stalling or stumbling. Recheck the sync (with the engine hot) by setting #1 to match #3, #2 to #4 and then left to right. You will need to adjust the idle down after each side is adjusted.
 

dan filipi

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Something not right with only 5 lbs vacuum.
It makes sense if throttle plates are open too much as is the case at a 1200 rpm idle.
That alone will lower vacuum.
I find at 950-1000 rpm idle you should get 9-10 vacuum.
I'd go after the idle jets most likely.

Compression check will help diagnose.
Low compression will affect the readings and many other things.

Have you adjusted valves?
 

Hansmanbo

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Took my first look at the ignition. PO said it was electronic, so I assumed it was a Dyna, but instead is something called Martek. contact plate and rotor are extremely worn, which could be causing my problems. Now, with a Dyna S ignition in hand, for the life of me, I cannot find where to plug them into the coils a described. Who the hell thought that would be a good place to mount the coils.....Bah engineers. :head bang:
From one problem to another.
 

slabghost

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Pickup wires from dyna will go to one coil each. Power to most GW coils is black with white stripe. Power to dyna can be tapped from that wire. Isn't it fun fixing old wiring :head bang: :head bang:

Oh BTW. I almost forgot. If the martek didn't already eliminate the ballist resistor you'll want to do that and use Dyna coils or at least verify the coils you are using are 3ohm.
 

Hansmanbo

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Dyna instructions say to plug yellow and blue wires to where old contacts were plugged in. Cant find these because of the old Martek ignition. I can see the y/b coil wires go into the harness but cannot figure where they go from there. Thinking to just slice them in, but not sure. Keeping the ballast supplyed by Dyna. Red wire goes to switched hot lead. Was thinking the old harness from where the old points plugged into would still be there, but colors arn't matching.
 

joedrum

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the dyna wires off the dyna ignition hook in the side cover that holds the battery there you will see the yellow and blue wires ...im thinking that these wires are realy yellow and green ....and blue and white not sure tho....i am sure that the wires are doulble hook ups and the other wires that hook up there are the condenser wires they uplug you dont need them with the dyna ignition .....the stator wires are there also and are yellow three wire connectors dont confuse them with the ignition wires ......the black and yellow wires are keyed hot wires and are not wires that hook up to the dyna wires ....

question what kind of coil is in the bike ....is it the stock old one with a ballist resister .....the 78 stock coils had a pig tail on it that plugs in that wiring in that mess of wires in the side false tank cover ....

if you can takes pics post what you can but dont start splicing yet :mrgreen:
 

Hansmanbo

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That helped.... did find the double plug wires. Condenser is allready gone, but confused that the wires have continuity between each other. Same with the yellow and blue that come directly from stock coils. Tried to time it with a test light. On the blue wire @T2, the light comes on as it should. On the yellow wire, it should light @T1, but the light comes on dim throughout revolutions. :beg:
 

joedrum

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if your getting continuety thur the blue and wellow wires from the dyna then take the power off this aint right now
 

joedrum

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the best thing would be to have the dyna coils too and wires to take full advantaged to the set set up the 3 ohm dynas use no ballist and give 12 volt fire all the time...i guy could use irridium plugs to make even better spark
 

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