Hard starting when Warmed-up

[phat56]

Howdy - I have a '80 XS11 SP. A friend that I have also has one, but his is an '81. Both bikes are hard to start when they are hot. There's no way the gas is boiling out of the bowls, so what's up?? Does anyone else have this problem ?? BTY it's not usually too hot in Alberta. Bill

[TopCatGr58]

Re: Hard starting when Warmed-up

Originally posted by phat56
Howdy - I have a '80 XS11 SP. A friend that I have also has one, but his is an '81. Both bikes are hard to start when they are hot. There's no way the gas is boiling out of the bowls, so what's up?? Does anyone else have this problem ?? BTY it's not usually too hot in Alberta. Bill

Well, Bill, a little more detailed information would be helpful here! You say hard to start, do you mean the engine turns over more slowly when it's warmed up, or that it takes many cranks before it finally catches, do you smell gas vapors?

From what I've read these bikes run leaner once they get warmed up, and if your bikes are set lean to begin with, then you could not be getting enough gas.....have you tried the first position of the choke, or turning the petcocks to PRIME position?
The heat of the engine may not be boiling the gas, but it possibly could speed up the vaporization so the bowls might not have that much in them, and the fuel won't flow until the engine is running to activate the OCTOPUS vacuum valve, hence the idea for PRIME! Then again, your Octopus may not be functioning at ful capacity, and so after using the PRIME to fill the bowls, and the choke to start it cold, then running the bike the bowls are drained due to poor supply so that when you stop, there isn't much in them to provide a good start?!

Then, again, they could be getting flooded if you smell gas, try turning the throttle open a bit instead of just starting at idle setting.

And, just what do you mean by "HOT", like sitting in stop and crawl traffic for 10+ minutes, or just warmed up and were riding along, stopped for gas/pit stop and it won't start back up? Just running through some thoughts, I'm sure others will chime in and correct anything I've stated wrong!

[skids]

Yes, I have one like that. If I take a lunch break while it is hot, I sometimes need the "choke" to restart it. If the duration of down time is just a few minutes, no problem. If the duration is 1/2 hour, it is harder to start without the choke.

[phat56]

Let me clarify - Hot in this case means after reaching operating temp. and sitting for say about 1/2 hr. The engine cranks just as fast as any other time, just takes quite a while to fire, and when it does, you have to keep the starter engaged to keep it goes till it will run by itself. The carbs were leaking via the needle valves, which I have since replaced, but haven't reinstalled yet. I don't think that was the problem because it starts right away when it is cold. ie- park it after a good ride, leave gas tank valve on, leave it for say 2 hrs., it will start right away without touching anything except the throttle. ?? BTY - my buddy who has the same bike has the same prob. Thanks for showing interest-- Bill

[TopCatGr58]

Originally posted by phat56
Let me clarify - Hot in this case means after reaching operating temp. and sitting for say about 1/2 hr. The engine cranks just as fast as any other time, just takes quite a while to fire, and when it does, you have to keep the starter engaged to keep it goes till it will run by itself. The carbs were leaking via the needle valves, which I have since replaced, but haven't reinstalled yet. I don't think that was the problem because it starts right away when it is cold. ie- park it after a good ride, leave gas tank valve on, leave it for say 2 hrs., it will start right away without touching anything except the throttle. ?? BTY - my buddy who has the same bike has the same prob. Thanks for showing interest-- Bill

Thanks for the clarification, I'm not trying to be a Smartass, just trying to think of things to check. You state that you leave the petcocks to ON, however, as previously mentioned, they don't flow until the engine is running and enough vacuum is supplied to the Octopus which then lets the fuel flow to the carbs. I would really suggest trying to switch it to PRIME which bypasses the OCTY, wait 15-30 seconds, then try to start it, and if it starts quickly, then you'll know that you have a fuel starvation problem, that's all!! You may have slightly leaky petcocks that allow enough fuel to flow thru the PRIME tube when it sits for 2+ hours, but not a fast enough leak to refill them when only 1/2 hour?!

[phat56]

10/4 - After my collarbone heals, I'll try the easy fix. I assumed it was flooding but I've wrong many times before. That's why we need people like you!! Thanks again Bill