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Discussion Starter #1
So, rear jug has been slowly getting lazy over the last couple years. Was headed home last month from work and it basically **** the bed on me. I putted at about 30 tops rest of the way home. I pulled plug and couldn't really tell anything at first and just decided to change out wires and plugs. Fired it up and same thing, rear jug is jacked. Pulled plug, had fuel... hooked gage up and did a couple bumps on each cylinder and have the same compression. Put plug up against the block and I have spark???? I know, I know right??!! At this point I pulled the carbs. I found one of the slide diaphragms had four rips.. bingo right?? Went nuts and got on TJBrutals site and ordered velocity stacks, carb rebuild kit with performance jets, and two new pistons with pins and diaphragms. Rebuilt carbs, installed. Same issue?! Swapped coils and the gripe didn't follow?!? I have a buddy that is parting out a 2000 1100 aero and was wondering if anyone has tried an ECU swap of this nature? I havnt had the top off in about 7 years, but the valves were good then. I do run a short pipe on that jug...possible valve damage, but I would think I would still get a thump here and there if the quick compression check I did was the same as the front???!
If anyone can follow my rambling and has any input I would gladly take it.
Yours truly,
Prime-8
290730
 

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1983 Honda vt750 Shadow
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Check the manual to see if both ICMs have the same amount of wires. That is a place to start.
Some engines have 2 pulse generators and some have one.
 
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What were the compression readings? It should be done with open throttle and be up around 180 pounds.
 
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1999 Shadow 750 ACE VT750CD3 Modified
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That's a 750 ACE (I think?) so only one pulse generator for both cylinders and if one cylinder is firing that is good and the ICM with a single plug, serves both cylinders although things are then separated internally and out to the coils, so it is possible for it to go bad internally. Check where it plugs in to the harness under the seat for corrosion.
The ICM box is pretty much specific to the bike model although any year 750 ACE (1997/8 to 2003) should work, units from other models are likely a no go.
 

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Discussion Starter #6
What were the compression readings? It should be done with open throttle and be up around 180 pounds.
I didnt do a full blown check, just a couple quick bumps on each cylinder, so my pressures were low, around 60, but the same on both. Again front cylinder firing, fine. The check was just to check for anything major. It just doesn't seem right, cause I'm getting nothing, I would get some kind of fire out the pipe even if the valve seat is burnt up? For some reason, im thinking im shorting out somewhere.... ive checked for spark on several types of engines using the screwdriver method or the plug against the block. Each time I have checked for spark, I seem to get bit. Is it a correct statement that there are resistors in the plug boots? I was hoping to tinker last night.. i have two coils and a set of stock wires and boots off the 1100. I was going to try the wires, thinking maybe a boot is bad. I reused my old boots when I made the new wires.. i may be on a wild goose chase here?
 

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Discussion Starter #7
That's a 750 ACE (I think?) so only one pulse generator for both cylinders and if one cylinder is firing that is good and the ICM with a single plug, serves both cylinders although things are then separated internally and out to the coils, so it is possible for it to go bad internally. Check where it plugs in to the harness under the seat for corrosion.
The ICM box is pretty much specific to the bike model although any year 750 ACE (1997/8 to 2003) should work, units from other models are likely a no go.
I
 

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The wire is copper no resistance if still a factory wire, The end caps have 5000 ohm resistors in them and they can burn out.
 
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Discussion Starter #9
The wire is copper no resistance if still a factory wire, The end caps have 5000 ohm resistors in them and they can burn out.
This may be the issue then. I was going to swap the wires again with the boots this time and see what I get.
 

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1999 Shadow 750 ACE VT750CD3 Modified
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Make sure you use the copper core wires, just like Honda intended.
No resistor carbon core wires or fancy helical wound wires with the fibre core.
 

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I'll add the wire can burn up and go bad at the ends if it's been loose and arcing inside. If there's enough slack, might be able to trim a half inch off and reconnect. Measure the resistance through the wire/end combo and just the ends, should be practically the same. Most any Ace hardware should have the solid core plug wire by the foot.

I've also had ends go bad and start arcing to the head instead of firing the plug. look for any signs of that.
 
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