750 wont start

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750 wont start

Chuck Bachus


I had the bike running very well and sounding great. I went clean it up and used the hose to lightly rinse the lower areas of the bike and now i am not able to start it. I can smell the fuel but will check spark later today. It acts as if there is no spark but will confirm. Any thoughts on what may have happened. It has been a full week anything that may have gotten wet should have dried by now.
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Re: 750 wont start

LukeM
Administrator
I'd check the spark plug wires, where they connect to the plugs.  Older rubber doesn't seal as well, and it's possible either the boot is still wet, or the connection between the boot and the wire got compromised.

Easy enough to check: pull a spark plug, connect the spark plug wire, press the plug to the engine case with an insulated object, and crank the engine.  If you see a spark, check with another plug that's connected to the other coil.  If both spark, then your ignition is good. If not, then you'll need that in order to make the 4 Horsemen (suck, squeeze, bang, blow) work.

I don't think there's a whole lot else on the bottom part of the engine that has to do with ignition...unless somehow you got some water inside the side cover where the points are.

If you're smelling fuel, it's possible the plugs may be fouled.  Pull one, and give it a good visual inspection.  It doesn't take a lot of fuel to mess these plugs up.

Hope this helps.  Keep us informed.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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Re: 750 wont start

TOOLS1
Administrator
In reply to this post by Chuck Bachus
Ditto what Luke said. When I first got the Toolmatic if I just thought of giving it a bath it would not run Turned out the coil wires were bad.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
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It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Re: 750 wont start

Chuck Bachus
In reply to this post by LukeM

Thanks guys for the input. Will keep you posted

Chuck
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Re: 750 wont start

Lucky 1
In reply to this post by Chuck Bachus
Sometimes when the engine has been running and it is warmed up
If you put cold water on it ,it gets condensation inside the sheet metal points cover.
Or it can even leak and get water in the points cover.
Does it have points or electronic ignition.
On a Roadstar Adventure.
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Re: 750 wont start

Chuck
In reply to this post by LukeM

I wanted to follow up with you from the great info from last week. I checked and it looks like there is no spark. Any suggestion where to start the trace of  lost power.

Chuck
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Re: 750 wont start

TOOLS1
Administrator
Start with the fuses. Then the black/white wire to the coils, for power. then check, for power to the points.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."

1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Re: 750 wont start

Chuck B
In reply to this post by LukeM


I have checked the plugs and have no spark. I have checked all the fuses and all check out good. Any suugestion on where to look next or what points to trace the voltage from.

Chuck
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Re: 750 wont start

shinyribs
Administrator
I lost connection one morning on just one coil.It would run,but not very good.I had lost connection one the harness running from the points(mine's electronic,but same difference)to the coils.Wiggled it and it took off.Remade the connections and it has been fine so far.You may have accidentally just bumped something loose.Not real hard to do.The harness comes out of the bottom of the points cover by your right toe,runs kinda under the motor,loops behind the right side foot peg,up by the rear brake light switch,makes a connection here(where I lost connection was here)then continues along the frame from here to the coils.
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Re: 750 wont start

Burro
I would also try the kill switch, make sure it's not grounding itself out on the handlebars. Mine likes to do that from time to time. Turns a easy bike to start into a lump of useless.
I'll believe that corporations are people when Texas executes one!