[AndrewGilbert]

Here in Missouri it has been dipping down into the upper 20's the last few weeks, and when it does my VN750 doesn't like to start. lots of cranking with a back-fire or two before it fires off. Once it starts it runs perfectly as usual. Only has this issue on cold mornings when its less than 35-40 degrees out.

Is there a carb adjustment that can allow it to start more easily in colder temps? Re-jet?

Since it's just the start of winter I'm even thinking about a heater for the radiator to keep the engine temp up during the night.

Any thoughts or suggestions are welcome. Thanks.

 

[michiganteddybear]

check that choke (really enricher circuit) is working properly.

the lever on left handle bar causes 2 plungers (one on each carb) to pull out of the carbs partially, allowing both more fuel and air into the system.

 

[thtanner]

I immediately think battery, not fuel.

What kind of battery do you have? I'd suggest an AGM as they handle the cold better than standard batteries. When batteries are weak it likes to backfire.

Check the choke plunger operation anyways, just to be sure. Takes 2 seconds.

 

[OleDirtyDoc]

I immediately think battery, not fuel.

What kind of battery do you have? I'd suggest an AGM as they handle the cold better than standard batteries. When batteries are weak it likes to backfire.

Check the choke plunger operation anyways, just to be sure. Takes 2 seconds.

Yup Yup.you had me at backfire

 

[VN750Rider/Jerry]

If it turns over as usual, the battery is probably ok. IMO, the VN750 has a weak ignition system by design. Mine fires right up at 40 degrees with full choke. It has also started easily at below 32 degrees, which only happens a few times a year here in central AZ. If it runs fine after warm up, I'd say the jetting is ok. I would look into the enrichener system. If the cable is adjusted right, have a look at the diaphrams. I have found both mine melted (not at the same time) I blame ethanol fuel, which has also melted my petcock a couple of times. Depending on where they are currently set, turning the pilot screws out a little more might help.

Upper 20s? I would definitely be taking a car. Riding a bike when it is that cold is no more fun than it is at 115 degrees. I have ridden in both. Not anymore.

 

[OleDirtyDoc]

A non agm battery will crank and crank and backfire.mine did that until I put in an agm then was fine

 

[thtanner]

AGM probably gives enough juice to overcome the weak ignition, for most people's bikes anyways. Otherwise the ignition coil relay mod (or the other various mods in discussion like the two wire mod) may be helpful.

 

[Scubawerx]

I'm having the same issues with my '03. New AGM battery, but I still get the crank and crank with occasional backfiring. Sometimes the bike will start right up, but usually I have to hit it just right. Often it will not start, just crank.
I know the enriching screws are set properly and the choke is working properly as well.
In fact, if I use the choke AT ALL I can forget about it starting.
In 2001 I had a '94 that never gave me issues. Any season, it would start immediately, 1st try. I'd love to have that success with this '03.

 

[Spockster]

I'm having the same issues with my '03. New AGM battery, but I still get the crank and crank with occasional backfiring. Sometimes the bike will start right up, but usually I have to hit it just right. Often it will not start, just crank.
I know the enriching screws are set properly and the choke is working properly as well.
In fact, if I use the choke AT ALL I can forget about it starting.
In 2001 I had a '94 that never gave me issues. Any season, it would start immediately, 1st try. I'd love to have that success with this '03.

That sounds like the carbs are already too rich. But I wouldn't expect to see backfiring in that condition.

On my '03, it's always taken choke and a bit of cranking for stone cold starts. But it always started like an electric motor when warmed up, that is until I started having trouble in the Junction Box.

After doing the Two Wire Mod, it's back to starting like an electric motor again. About 1/4 turn of the starter and it's idling, on warm starts. Cold starts are still the same, but not bad. It sat three months and fired right up last week. hadn't been maintaining the battery at all and the AGM was ready to go.

 

[Scubawerx]

I've dialed my enriching screws in to 1-3/4 turns out. Seems to have improved things greatly. Too cold right now to do a run out, but starts are better, hot or cold.

 

[Scubawerx]

DID NOT have a beneficial effect after all. Reset screws to 2 turns out. Tried the TWO-WIRE mod, NO DIFFERENCE, so I switched it back to original.
It's carb related. Just can't put my finger on it.

 

[Spockster]

DID NOT have a beneficial effect after all. Reset screws to 2 turns out. Tried the TWO-WIRE mod, NO DIFFERENCE, so I switched it back to original.
It's carb related. Just can't put my finger on it.

If the headlight still worked, should've left the mod in place.

Did you check the charge volts with the mod?

For the carbs: dirty pilot jet, enrichers (choke) not working?

 

[Scubawerx]

Pilot jets are sterile. Choke is working.

 

[Spockster]

Check two of the plugs before and after trying to start. Are they wet or dry?

 

[Scubawerx]

No longer an issue. I sold the bike. Best thing I could have done with it.