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Discussion Starter · #1 ·
I have a 1982 Honda Sabre VF750. I finished bring the bike back to life recently. I went to take it out today and killed the battery trying to start it. The bike starts just fine but I have to put a heater next to it for 30 minutes prior to trying to start. It will then start right away with no hesitation. I just wanted to see it there is something wrong with the bike or is it just because it is still a little cool and it is hard to start an older bike in cooler temperatures (50-55 degrees F). The battery is brand new as well.
 

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Choke or starting enrichment on?
 

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Move to Florida maybe?

Just kiddin guy.
No, there is something not quite right. Choking that thing should start when it's cold.
Maybe try twisting the throttle 3 or 4 times before hitting the button. Some bikes have a small, I think they call them accelerator pump, my 750s do, in the carb. It squirts a bit of fuel right into the throttle body.

But really, you should not need to do even that. The choke should increase vacuum in the carbs, thereby sucking more fuel into the airstream. Or restrict airflow thru the carbs, thereby enriching what fuel is coming into the mix.

Id pull the airbox, watch the butterflies in the carbs as you pull the choke out. There might be a cable adjustment to get them to close tighter.

If it's done electronically, me can offer no help. Good luck guy.
 

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Certainly seems to be an issue with the choke/enrichment. Ensure everything is working. Cable, butterflies, etc.
 

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I have a 1982 Honda Sabre VF750. I finished bring the bike back to life recently. I went to take it out today and killed the battery trying to start it. The bike starts just fine but I have to put a heater next to it for 30 minutes prior to trying to start. It will then start right away with no hesitation. I just wanted to see it there is something wrong with the bike or is it just because it is still a little cool and it is hard to start an older bike in cooler temperatures (50-55 degrees F). The battery is brand new as well.
You need 3 things to get an engine running....FUEL, AIR AND SPARK. You're missing one of them. It could be timing, dirty carbs of not enough air.

You've got some research to do.

The temperature has nothing to do with it.
 

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Discussion Starter · #8 ·
I was out riding around on it today and the same thing. I almost killed the battery trying to start it. After giving up, I put the heater next to it and came back 30 minutes later and it started right up. I don't know if it is just a weird coincidence but this has worked many more than one time. In the summer I do not have this issue at all.

The fuel lines are all new and good. I pulled the spart plugs and I went fancy with the iridium ones. They have no residue or anything. Air would be the last thing, but the bike doesn't run lean or rich so the air seems to be fine.
 

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I was out riding around on it today and the same thing. I almost killed the battery trying to start it. After giving up, I put the heater next to it and came back 30 minutes later and it started right up. I don't know if it is just a weird coincidence but this has worked many more than one time. In the summer I do not have this issue at all.

The fuel lines are all new and good. I pulled the spart plugs and I went fancy with the iridium ones. They have no residue or anything. Air would be the last thing, but the bike doesn't run lean or rich so the air seems to be fine.

Have you tested the voltage regulator, stator, etc.? You can buy a cheap multi-meter at Harbor Freight for about $6.00 if you don't have one. Instructions included, and then there is YouTube for instructions.
 

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Discussion Starter · #10 ·
Have you tested the voltage regulator, stator, etc.? You can buy a cheap multi-meter at Harbor Freight for about $6.00 if you don't have one. Instructions included, and then there is YouTube for instructions.
I have not. I have a multimeter. I will look up the video.
 

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You need 3 things to get an engine running....FUEL, AIR AND SPARK. You're missing one of them. It could be timing, dirty carbs of not enough air.

You've got some research to do.

The temperature has nothing to do with it.

My guess is that you have some heavy resistance somewhere in your system. Check all electricals for resistance, not just the stator and voltage regulator as I suggested earlier. Plus wires as well.
 

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Discussion Starter · #12 ·
So (it's been a while) I checked everything. The voltage regular was out of spec so I replaced it, I replaced the ignition coils just because they were a good price. I tested the spark plug wires and one showed as open. I replaced all the spark plug wires and caps. The issue was that one cylinder was not firing. It was originally firing and stopped which was causing the hard to start issue. Unfortunately after replacing the spark plug wire and spark plugs just to be sure. I re-tested everything again and the cylinder is still not firing. I'm guessing that something is clogging a passage in the carb (worst case scenario). Those carbs are a major pain to put back on with the outrageously tight fit.

Before I take the carb off (again) next weekend. Any ideas what else could be causing the one cylinder not to fire?

Thank you.
 

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You're going to get good at servicing carburetors right up until you own a fuel injected motorcycle.
Compression test? If that cylinder is low on pressure it's not the carburetor.
 

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Discussion Starter · #14 ·
Yeah, I haven't checked compression. I'll put the compression tester on it and hope that is not it. That would be depressing. I've replaced a piston and had a cylinder rebored before but that was on a single cylinder ATV. I'd bet this is a much bigger pain.
 

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Maybe it's something small like a clearance adjustment or a stuck ring.

... thinking positive here for you.
Plus you can't make carbs work if the cylinder doesn't have good vacuum and you can't have good vacuum on a cylinder if you have poor compression.
 

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If the compression is okay, I am still thinking it is a lack of fuel when cold.
I am also assuming you have diaphragm type carbs, and they have a mystical enrichener system.
My 79 XS1100 has them, and is the best at staring after sitting, in colder weather.
My 83 XS400 has them, and is giving me grieve on jetting. It does start okay tho. UK
 

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I had a Sabre 700 (1985) that ran well but no great amounts of power.
Turns out that one of the ignition boxes was not firing a cylinder.
Finally replaced it and it ran great.
 

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Discussion Starter · #19 ·
It has been a while but I wanted to give an update. I'll start with the compression was good on all cylinder (thank you sweet baby jesus). It turns out some debris got sucked up the pilot jet. I went ahead and just got a new set of jets for all carbs and runs perfect! Starts right up from cold! This bike had a lot of power in my opinion. My other bike is a 78 yamaha XS750 so I don't have much comparison.

The enricher is pretty awesome on this model I do have to agree.
 

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Thanks for the update. It's amazing what new jets will do for a bike or any carbureted machine for that matter. (y)
 
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