Carb/fuel/heat question

[WuzzaCBXRider]

Can this be true? Given in response to questions from a new CBX owner having issues upon cold starting.

“When you shut down the bike, fuel remaining in the bowls is subject to the heat of the cooling bike, which cooks off the lighter components, the part of the fuel that's easier to light.”

This he says is probably why the bike is hard to start. (He nor the new owner know it’s history). He also advises to drain the carbs after each ride by running them dry with the petcock closed to eliminate this (issue).

I’ve never done this but unlike the vast vast majority of CBX owners, I actually rode mine, at least once a month or more. It’s in a three bike rotation now, like the others, always parked with a full tank and plugged into a tender.

 

[Bumblebee]

Can this be true? Given in response to questions from a new CBX owner having issues upon cold starting.

“When you shut down the bike, fuel remaining in the bowls is subject to the heat of the cooling bike, which cooks off the lighter components, the part of the fuel that's easier to light.”

This he says is probably why the bike is hard to start. (He nor the new owner know it’s history). He also advises to drain the carbs after each ride by running them dry with the petcock closed to eliminate this (issue).

I’ve never done this but unlike the vast vast majority of CBX owners, I actually rode mine, at least once a month or more. It’s in a three bike rotation now, like the others, always parked with a full tank and plugged into a tender.

Never heard of this with a carbureted bike.....

It's probably hard to start because the carbs are in need of a good thorough cleaning...especially the starting circuit...

I always drained my carbs if the bike was going to sit for any length of time but if it was ridden daily, I never had any issues and I'd run fuel stabilizer....

 

[sixpack577]

That bike just needs the carburetors cleaned, adjusted correctly individually, then synced.
There will always be fuel left in the float bowl of any carburetted motorcycle when you shut it off (unless you turn off the fuel valve at the tank first and let the engine run itself out of gas) and as most well tuned carburetted bikes start up easily, that whole gas not burning as well is simply not true.
If there are still hard start problems after, then there is an ignition or timing problem.

 

[WuzzaCBXRider]

That bike just needs the carburetors cleaned, adjusted correctly individually, then synced.
There will always be fuel left in the float bowl of any carburetted motorcycle when you shut it off (unless you turn off the fuel valve at the tank first and let the engine run itself out of gas) and as most well tuned carburetted bikes start up easily, that whole gas not burning as well is simply not true.
If there are still hard start problems after, then there is an ignition or timing problem.

You left out the final ingredient. They have to be ridden and when not ridden, they have to be stored properly. If they’re not ridden for 9 months, empty the tank and carbs or store it with a full tank with conditioner. And don’t fire it up for a few minutes in the garage from time to time either. Ride it already!

 

[Bumblebee]

That bike just needs the carburetors cleaned, adjusted correctly individually, then synced.
There will always be fuel left in the float bowl of any carburetted motorcycle when you shut it off (unless you turn off the fuel valve at the tank first and let the engine run itself out of gas) and as most well tuned carburetted bikes start up easily, that whole gas not burning as well is simply not true.
If there are still hard start problems after, then there is an ignition or timing problem.

Most carbs are CV and there is no shut off on the fuel valve....just prime, on and reserve....

 

[jellyrug]

Most carbs are CV and there is no shut off on the fuel valve....just prime, on and reserve....

It’s been a while, but if I remember right, all mine had a shut off. My last was a Suzuki 750GT. Looking at that image though, seems my memory is failing me.

1973-77 Suzuki GT750 Restored Original Fuel Petcock | eBay

Correct for 1973-77 Suzuki GT750 Fuel Petcock. Note picture of the parts that have been installed. It is missing the bowl fuel screen. This can be used on the 1972 GT750, but not original.

www.ebay.com

 

[sixpack577]

Most carbs are CV and there is no shut off on the fuel valve....just prime, on and reserve....

I'm not sure, but I thought that there was an 'Off' position, as well as On, and Reserve(lower pickup tube on top of the valve) on most carburetted motorcycles, especially during the '70's and early '80's.

 

[sixpack577]

I see that I forgot to add above that hard starts can also be caused by tight valves, even though this bike's problems sounds more carburetor related, but there may be several issues going on as well.

 

[jellyrug]

I see that I forgot to add above that hard starts can also be caused by tight valves, even though this bike's problems sounds more carburetor related, but there may be several issues going on as well.

If I recall, me and Wuzza were haggling about what I thought was really bad gas consumption, 24mpg cruising at 80mph.

Think those carbs need some TLC, all six of them, sixpack.

 

[Bumblebee]

It’s been a while, but if I remember right, all mine had a shut off. My last was a Suzuki 750GT. Looking at that image though, seems my memory is failing me.

1973-77 Suzuki GT750 Restored Original Fuel Petcock | eBay

Correct for 1973-77 Suzuki GT750 Fuel Petcock. Note picture of the parts that have been installed. It is missing the bowl fuel screen. This can be used on the 1972 GT750, but not original.

www.ebay.com

Non CV carbs had a shut off....all CV carbs run on vacuum so there's no way to shut off the fuel

My two strokes all had an off position but they were non-CV....