1983 Honda Shadow VT750 Build Thread
#3
Re: 1983 Honda Shadow VT750 Build Thread
You picked the right bike, these make some GREAT bobbers, not to mention, really reliable. I believe there are forums dedicated to this bike and all it's possibilities. Google it.
#4
Originally Posted by TATTRAT:8154778
You picked the right bike, these make some GREAT bobbers, not to mention, really reliable. I believe there are forums dedicated to this bike and all it's possibilities. Google it.
#5
Re: 1983 Honda Shadow VT750 Build Thread
Shot some starting fluid into the carburetors and cranked the bike. It turned over, but wouldn’t run. I changed the spark plugs, still would not run. Held the throttle open and cranked and would get an occasional single backfire either through the carburetor or the exhaust, and that’s the closest it has been to running.
I arc’d the plug wires to the cooling fins on the block and I’m getting good spark. I’m not sure that it’s at the correct time though.
So to try and figure out what the deal is, I downloaded the factory service manual and went through the ignition system troubleshooting process.
Factory Specs:
Coil Primary Resistance - 2.0
Coil Secondary w/ Plug wires attached - 29 to 40k ohms
Coil Secondary w/out Plug wires - 20.6 to 27.4k ohms
Pulse Generators - 480 ohms ( plus or minus 10%)
My readings:
Coil 1 Primary - 2.8
Coil 2 Primary - 2.5
Coil 1 Secondary w/ Plug wires attached - 33
Coil 2 Secondary w/ Plug wires attached - 34
Coil 1 Secondary w/out Plug wires - 23
Coil 2 Secondary w/out Plug wires - 24
Pulse Generator Cylinder 1 - 425
Pulse Generator Cylinder 2 - 438
The pulse generators are where I believe the problem may be. They relate to the timing, like a cam or crank sensor does in a car. Cylinder 1 doesn’t meet specification and Cylinder 2 barely does. I’m just wondering how conclusive that necessarily is.
It does have compression, spark, and fuel...so in my mind it has to be timing issue. The only other thing on the bike that is left is the 3 CDI igntion boxes, but I'm thinking that if they were bad then I wouldn't have ANY spark...
I arc’d the plug wires to the cooling fins on the block and I’m getting good spark. I’m not sure that it’s at the correct time though.
So to try and figure out what the deal is, I downloaded the factory service manual and went through the ignition system troubleshooting process.
Factory Specs:
Coil Primary Resistance - 2.0
Coil Secondary w/ Plug wires attached - 29 to 40k ohms
Coil Secondary w/out Plug wires - 20.6 to 27.4k ohms
Pulse Generators - 480 ohms ( plus or minus 10%)
My readings:
Coil 1 Primary - 2.8
Coil 2 Primary - 2.5
Coil 1 Secondary w/ Plug wires attached - 33
Coil 2 Secondary w/ Plug wires attached - 34
Coil 1 Secondary w/out Plug wires - 23
Coil 2 Secondary w/out Plug wires - 24
Pulse Generator Cylinder 1 - 425
Pulse Generator Cylinder 2 - 438
The pulse generators are where I believe the problem may be. They relate to the timing, like a cam or crank sensor does in a car. Cylinder 1 doesn’t meet specification and Cylinder 2 barely does. I’m just wondering how conclusive that necessarily is.
It does have compression, spark, and fuel...so in my mind it has to be timing issue. The only other thing on the bike that is left is the 3 CDI igntion boxes, but I'm thinking that if they were bad then I wouldn't have ANY spark...
#9
Yeah, pulse generators are difficult to locate for those bikes. Installing isn't bad really, even though they are inside the crankcase on the right side of the bike.
After tinkering more, I am fairly sure that the fuel pump is the issue as well. Because as long as gas stays up there, it will start, idle, and rev with no problems. after it runs for a second I can't see anymore fuel coming up through the clear hose until i put my hand over the carb and the suction from the cylinder pulls more through because it cant suck air.
Hoping for another easy fix...
After tinkering more, I am fairly sure that the fuel pump is the issue as well. Because as long as gas stays up there, it will start, idle, and rev with no problems. after it runs for a second I can't see anymore fuel coming up through the clear hose until i put my hand over the carb and the suction from the cylinder pulls more through because it cant suck air.
Hoping for another easy fix...