1 Red Light= Hot and Sputtering

[Conman]

My bike cruises on the highway fine, with the temp gage just below the black dot, but in slow driving it heats up really quickly. If I come from a 55 to a long red light, I’ll go from below the black dot to most of the way to the first red line. My fan kicks on about half way between the dot and the red line, but at that point the bike is already sputtering at the stop and takes about 4k rpm to get away without stalling, though once moving it’s fine even when hot. My last VMAX didn’t heat up like this at all. On an 80 deg day I can’t go through any sort of traffic without heat issues. I’ve never let it get into the red, but it gets close, though I feel like the bike would die first.

Why does this Vmax overheat so quickly? Could my old carbs be the only cause of the sputtering once it’s hot? Do all Vmax run badly above 3/4 temp gage?

Thanks,

Connor

 

[Vinmax]

Here's my opinion on this.............. you could be running rich.
What 'may' be happening is that as the bike gets warmer from slow running, it keeps getting richer. The richer it gets, the more extreme the carbs get in running rich. It's a vicious cycle. Then when hot enough, the bike runs like crap until you get moving and get that temperature back down again.

Good thing to check..........
Start with the bike when fully warmed up, and just when you start to run a bit warmer than normal highway runs and come to a stop, blip the throttle when fully stopped. If the idle dips down a bit right after the throttle blip, you're rich. The idle should come right back to where it was and not hang up higher for a bit (would indicate lean) and not dip down (which indicates rich).

If it dips way down, then you're very rich and would explain the faster rate of heating up and also would be the reason for the very poor running when hot.

I've had my bike in traffic and the temp needle climbs, but the bike runs the same. I used to have the 'throttle blip dip' when I was running too rich at idle. After correcting that issue (many, many, years ago), I've never had traffic idling issues.

One more thing to check............
When you first start the bike from cold, can you immediately run without the choke? If so, you're probably rich. The bike when cold should need just a bit of choke. If it runs too smoothly when still cold, that means that it's running rich. I mean obviously the bike should run perfectly when warmed up fully and not be perfectly carbureted when still cold, or it's the equivalent of running with the choke on.

This is the thing; running too lean can lead to hot running, but also running way rich will lead to heating up also. Usually it's the lean running causing overheating, but running too rich will leave unburned fuel in the exhaust and combustion chambers and can cause hot running.

When the bike is idling, does the exhaust stink of unburned fuel? Are the exhaust tips sooty black? Does the bike smoke when warmed up and idling?
Check all that and let us know before we start diagnosing the cooling system.
Even if you have some cooling issues, the bike should not run too badly when getting a bit warm. You did say it gets hot but not 'needle in the extreme red' kind of hot, and that's why I'm thinking carb/jetting issues are the culprit.

Vinnie

 

[Conman]

The throttle does dip a bit, but I had attributed that to the 23 year old carbs. I don’t have fuel smell, soot, or any other symptoms of running rich. It needs choke to heat up. The bike is a totally stock 95 and the PO did little maintanence other than oil changes. I fully expect the culprit to be the cooling system, but I have no idea what component(s).

Richness may well be a contributing factor, but it seems to me that the possible richness at high temp is spurred by something else driving the temp up so rapidly? Just thinking out loud.