85 Overheating/running lean

[Whaven]

So I’ve been having a progressively worse overheating problem with the bike. Noticed it overheating bad one day sitting in traffic and the bike will run horrible, would barely idle/rev past idle until I got it moving, once it’s moving it cools down some, but still hotter than it normally does but runs well enough. Runs and idles beautifully when I first fire it up and up until it gets warm. Changed the stat, flushed the entire cooling system, new radiator, checked out the water pump with zero luck. Decided to pull the plugs and they’re whiter than white, carb has recently been cleaned/ tuned/synced properly so I’m at a complete lost at the next move here, not sure why else it’s acting up.

 

[Whaven]

So I’ve been having a progressively worse overheating problem with the bike. Noticed it overheating bad one day sitting in traffic and the bike will run horrible, would barely idle/rev past idle until I got it moving, once it’s moving it cools down some, but still hotter than it normally does but runs well enough. Runs and idles beautifully when I first fire it up and up until it gets warm. Changed the stat, flushed the entire cooling system, new radiator, checked out the water pump with zero luck. Decided to pull the plugs and they’re whiter than white, carb has recently been cleaned/ tuned/synced properly so I’m at a complete lost at the next move here, not sure why else it’s acting up.

Also not sure if the two issues are even related

 

[02GF74]

I'm sure you have but did you check if the fan turns on?

 

[Sniffbooger]

Are the idle mixture screws set properly? If they are set too lean on my Vmax, I notice the temp runs hotter... But this may not be what you are describing exactly....also, from my experience the last few times I pulled my carbs off and clean/synched them, it doesn't always mean they are perfectly clean...last time I saw some little tiny metal shavings that had settled in the bowl that were probably from the Phillips screws in the jet block...one little speck plugged up the pilot fuel jet, ran like crap...after cleaning and putting the carbs back together again...

Also, is your fuel filter new? Is your gas tank clean and rust free? Are the float levels set correctly? These things could contribute to carburetor issues and a lean condition....I think you would notice it at idle, after the choke is off and the bike is warmed up...but yours runs fine when cold?? It's odd, but I'm thinking it's carburetor related somehow....

 

[Whaven]

I'm sure you have but did you check if the fan turns on?

Yeah it’s working as it should

 

[Whaven]

Are the idle mixture screws set properly? If they are set too lean on my Vmax, I notice the temp runs hotter... But this may not be what you are describing exactly....also, from my experience the last few times I pulled my carbs off and clean/synched them, it doesn't always mean they are perfectly clean...last time I saw some little tiny metal shavings that had settled in the bowl that were probably from the Phillips screws in the jet block...one little speck plugged up the pilot fuel jet, ran like crap...after cleaning and putting the carbs back together again...

Also, is your fuel filter new? Is your gas tank clean and rust free? Are the float levels set correctly? These things could contribute to carburetor issues and a lean condition....I think you would notice it at idle, after the choke is off and the bike is warmed up...but yours runs fine when cold?? It's odd, but I'm thinking it's carburetor related somehow....

 

[Whaven]

Are the idle mixture screws set properly? If they are set too lean on my Vmax, I notice the temp runs hotter... But this may not be what you are describing exactly....also, from my experience the last few times I pulled my carbs off and clean/synched them, it doesn't always mean they are perfectly clean...last time I saw some little tiny metal shavings that had settled in the bowl that were probably from the Phillips screws in the jet block...one little speck plugged up the pilot fuel jet, ran like crap...after cleaning and putting the carbs back together again...

Also, is your fuel filter new? Is your gas tank clean and rust free? Are the float levels set correctly? These things could contribute to carburetor issues and a lean condition....I think you would notice it at idle, after the choke is off and the bike is warmed up...but yours runs fine when cold?? It's odd, but I'm thinking it's carburetor related somehow....

Yeah it’s a head scratcher for sure. Probably could check the fuel filter but it’s only 3ish years old, same with the tank, it’s brand new. Floats check out to factory spec. Only things I haven’t fooled with is the idle mixture screws, but I thought you couldn’t fool with those on these carbs?

 

[Sniffbooger]

Yeah it’s a head scratcher for sure. Probably could check the fuel filter but it’s only 3ish years old, same with the tank, it’s brand new. Floats check out to factory spec. Only things I haven’t fooled with is the idle mixture screws, but I thought you couldn’t fool with those on these carbs?

Most people drill out the idle screw cover plugs on the side of the carbs, right below the diaphragm cover plates so they can adjust the idle mixture. They are factory set and measured to spec but they go out of adjustment over time as valve clearance, compression and other things change. Is your exhaust all stock? Were any of the jets changed with the carb rebuild? Are the needles stock? Were the needle settings changed? Are you running with the factory air filter and the airbox in place, plus the airbox cover in the bike? The bikes run lean if you run it without the airbox cover and the factory 'Y' piece mounted on top of the airbox. But it still may not run as lean as you are describing....

 

[Whaven]

Most people drill out the idle screw cover plugs on the side of the carbs, right below the diaphragm cover plates so they can adjust the idle mixture. They are factory set and measured to spec but they go out of adjustment over time as valve clearance, compression and other things change. Is your exhaust all stock? Were any of the jets changed with the carb rebuild? Are the needles stock? Were the needle settings changed? Are you running with the factory air filter and the airbox in place, plus the airbox cover in the bike? The bikes run lean if you run it without the airbox cover and the factory 'Y' piece mounted on top of the airbox. But it still may not run as lean as you are describing....

Exhaust is after market but it’s been on the bike since I’ve owned it and long before this problem, new jets were put in but the same size, but again, I was having this problem before this rebuild, needles are stock, needle settings haven’t been changed. Air box and filter are all stock. I haven’t checked my valve clearance, so maybe that’s my next step, maybe my idle mixture is it, but it happened so quickly over a short amount of time I didn’t think it would be something like that

 

[02GF74]

My only suggestion is to check the rubber boots for cracks. They age and develop cracks letting air in that would weaken the mixture and would happen over a short period of time.

Also check the carbs are fully seated in the boots to the vboost manifold and the clamps are tight.

 

[Whaven]

My only suggestion is to check the rubber boots for cracks. They age and develop cracks letting air in that would weaken the mixture and would happen over a short period of time.

Also check the carbs are fully seated in the boots to the vboost manifold and the clamps are tight.

I went over all that once but I’m gonna double check that again just to be sure

 

[02GF74]

They're cheap enough to replace. I have a spare set ad mine have hardened and are showing small cracks at the openings, that I will replace next time I pop the carbs off, I mean the bike is 24 years old fer crying out loud!!!

 

[Jack Hammer]

Thermostat ok?

 

[Sniffbooger]

I went over all that once but I’m gonna double check that again just to be sure

Get a small propane torch and open up the flow (without lighting it) and wave it over the rubber carb boots while the engine is running...if there are vacuum leaks the motor will change RPMs as it sucks in the unburnt propane thru the cracks.

 

[Jack Hammer]

Carb cleaner works well too.

 

[rreed]

Have you checked the thermostat? And at what point on your temp gauge is the fan kicking on! And have you put temp gauge on your header and if so, what is the temp reading? Also have you checked your Water Coolant Pump?