Carburetor Boots

[ClayNation]

Hello -

I have heard quite a bit about checking carb boots to make sure they don’t allow air in which could lean out a motor and burn it down. I have a 1999 VMAX 700 and 2003 VMAX 600. The boots on both sides are in good shape, however I am certain they are original.

1. Is it accurate that cracked or damaged boots will result in a motor burning down..?
2. If accurate, which side is more important, the air intake side, or the manifold side?
3. Is it recommended to change the rubber boots on a 20+ year old sled even if they look to be in good shape?

Thank you.

 

[ironman_gq]

If the boot between the carburetor and the engine is leaking your engine will run lean which will cause a melted piston. The airbox side isn't as important but it can cause a lean condition (less restriction than pulling through the airbox) and it'll let whatever is floating around down there get sucked into the carbs.

As for proactively changing them, I've run sleds that are over 40yrs old with original rubber. It's not a bad idea to have a set on hand in the event one starts to crack but I wouldn't say it's a priority part to have in stock.

 

[74Nitro]

The Yamaha boots stand up well. If they appear to be in good condition, carry on.

 

[mod-it]

It is super easy to check if they are leaking. With the sled running, mist some carb cleaner around the boots. If the idle changes or picks up, you have a leak.

 

[fourbarrel]

It is indeed accurate that a cracked carb boot will cause an engine failure from a lean condition.What happens is raw air is sucked into the combustion chamber through the cracks and causes the air/fuel ratio to be too lean on fuel which results in a higher combustion temperature and the dreaded melting of the piston and breaking of rings and scoring of the cylinders.
As far as which one is most important, definitely the carb to cylinder boot is most critical because the fuel and air has already been mixed into the calibrated ratio and is being delivered to the combustion chamber.If one of the boots on the airbox becomes deteriorated and cracked or just doesn't have a good seal then what little extra air that gets drawn into the carb won't have as detrimental affect.You obviously want the airbox sealed up as it's supposed to be because it metres air into the carbs,but it is not uncommon for guys to mod the one in their sled for extra air.Of course when you add more air you need to add more fuel too so jetting up in a must when more air is added.
If the original ones still look solid then run them.Of all the brands to have problems with dry rotting rubber carb boots,Yamaha probably is the least one to worry about.Or maybe I just haven't heard of very many going bad.If you r concerned about them,get yourself something that will soak into the rubber to keep it pliable.

 

[Maim]

Only Yamaha carb boots I have had fail are on the old air cooled atv/motorcycle when they are over 15 years old. Heck the one was running awesome and only the air box was holding it in the boot it was split that bad.

 

[MURDER YAMAHA]

Yea, on these sleds, the boots hold up very well, mine are all 25 years old and still like new.

 

[ClayNation]

It is indeed accurate that a cracked carb boot will cause an engine failure from a lean condition.What happens is raw air is sucked into the combustion chamber through the cracks and causes the air/fuel ratio to be too lean on fuel which results in a higher combustion temperature and the dreaded melting of the piston and breaking of rings and scoring of the cylinders.
As far as which one is most important, definitely the carb to cylinder boot is most critical because the fuel and air has already been mixed into the calibrated ratio and is being delivered to the combustion chamber.If one of the boots on the airbox becomes deteriorated and cracked or just doesn't have a good seal then what little extra air that gets drawn into the carb won't have as detrimental affect.You obviously want the airbox sealed up as it's supposed to be because it metres air into the carbs,but it is not uncommon for guys to mod the one in their sled for extra air.Of course when you add more air you need to add more fuel too so jetting up in a must when more air is added.
If the original ones still look solid then run them.Of all the brands to have problems with dry rotting rubber carb boots,Yamaha probably is the least one to worry about.Or maybe I just haven't heard of very many going bad.If you r concerned about them,get yourself something that will soak into the rubber to keep it pliable.

Thank you!