"Warm starts" harder than "cold starts"?

[datter]

I got my bike back from the shop last week after having a few things done, one of which was unsticking my number 3 carb, which was causing grief with the related cylinder. Within two days of getting it home number 4 started sticking causing fuel to dump out the airbox etc. I used the old screwdriver/mallet trick by banging on it a bit and it seems to be ok now. Number 4 pipe gets hot where it wasn't before due to the cylinder flooding out from the stuck carb.

My issue now is the following two things...

1) A lack of power at low RPM... I have to rev it up a fair bit to get going from a stop, and slide the clutch off. That said, highway speed... or any speed above 3k on the tach and the bike seems to whistle along beautifully.

2) The title of this thread... "warm starts" harder than "cold starts". I went out this morning and it fired up instantly with no choke or anything. This evening was the same, when I rode down to the store. On coming out of the store 10min later I found the bike would crank and crank until finally starting up. I've never heard of a bike being easier to start cold, than warm but this one is all of a sudden.

Any idea if these two problems are related to each other, and also if one or both is related to my screwdriver/mallet "fix" for the number 4 carb?

Thanks in advance.
datter

[oldnortonrider]

Your No.4 carb probably hasn't sorted itself out just yet; I have often used a wooden dowel piece and light tap with a hammer to get float needle to seat in right. Harder to do this the more the machine is leaning on side stand. It probably won't clean up, until you've done it a few times. And yes, as a rule, these XS11s are easier to start when cold , and sometimes quite cantankerous to start when warm. I've seen other guys on here, talk about it often~~"nature of the beast".
One thing that you might try when it's stubborn to start when warm~~if it tried to "cough", and didn't catch, and you're grinding on it again~~the headlight has come on. Turn the switch off and back on again before hitting the starter, so headlight will be off. For this reason, I put an on/off switch on my headlight long ago. They'll start easier with the headlight off.

[Ken Talbot]

Re: "Warm starts" harder than "cold starts"?

Originally posted by datter
1) A lack of power at low RPM... I have to rev it up a fair bit to get going from a stop, and slide the clutch off.

This is not right.

I would guess your carbs are still dirty and out-of-sync. If you were having trouble with sicking floats and have done nothing more than tap the float bowls to jiggle them back into operation, you still have work to do.

With that poor of a low end, I would also suspect a broken pick-up coil wire causing you to be running on only two cylinders. This is easy to check by spritzing a bit of water on the pipes to see if they all sizzle the same.

[yadada]

+1 on hard warm starts, but mines not real bad.

[bbaldwin84]

My carbs were rebuilt b4 I got it, along with new carb boots. I have the same problem taking off from a stop, but after about 3K rpms it pulls right along no problem. I also have a charging issue along with the headlight and tach working when they want to. Any ideas?

[ag9123]

You may want to check your crankcase for gasoline contamination. Fuel in the airbox can easily make it into the engine via the crankcase vent hose. This makes for hard warm starting due to the amount of gasoline evaporation into the airbox. If your crankcase was fuel of gasoline, it may take a few oil changes to flush it all out. One thing you can try is to disconnect the crank vent hose from the airbox for a while and then try to srart it. If it fires right up, oil contamination was your problem!

[LoHo]

My XS will often crank slowly after some hard riding, and once, on a 103 degree day and a long freeway stint, stalled out, then cranked a couple of times slowly, then not at all. After stomping around wondering what to do for a half-hour or so, I tried it again and it fired right up.

Researching a similar problem for my '68 Malibu has led me to believe that engine heat is cooking the wires and electrics (which are all attached to the engine but away from cooling airflow) that raises their resistance and drops the starting voltage down.

Letting everything cool off solves the problem. If anyone has a real reason why this can't be so, I'd like to hear it. The solution would be to isolate and insulate the wires and starter, but I haven't tried that yet. For the Malibu, I'm going to install a remote solenoid to get the solenoid and wires away from the headers and engine heat.

[The Lorax]

Someone correct me if I am mistaken, but if it starts well with the enrichening circuit off when cold, and needs excessive rmp to go from a start, and if it runs good above 3000 rpm, would that not suggest that the idle circuit is running rich? It appears that way to me, but I am no carb. guru. someone with infinitely more knowledge than I will very likely throw in their two cents and all will make sense. I believe, that you have more carburetion work to do. just my stinkin' two cents. have a nice day and ride safe.

[DiverRay]

"You are correct, sir"
to mimic Ed Macman.
If you have those symptoms, you are running rich at low RPM, and probably have a large pilot jet or idle mixture out of wack.

[Dennyz]

Or float levels set wrong.

[Crazcnuk]

Mine is doing the same thing. I've had the carbs off a few times, now, but after I synched them the last time, it is really hard starting warm.

Before that it was easy starting at any temp.

Just recently it has also become gutless below 3000rpm. I have to feather the clutch and rev it to get it moving. Never had to do that before either.

I fixed one broken p/u coil wire, set the gaps, put new plug boots on and replaced all my fuel/vacuum lines.

Mine burns a fair amount of oil, but always ran and started fine, just lays down at the top end a bit, but mine is 310kg with the Venture package.

[planedick]

Sounds like

your synch job was (is) flawed. Bad synch tool or bad job of doing it. Also problems starting hot could be caused by being too lean at idle.

[81xsproject]

If it fires right off cold, with no enricher, your idle circuit must be rich.

[Crazcnuk]

I don't have a sync 'tool' I use two high quality vacuum guages, and I set them the same off the same cylinder to start with.

The synch was not that far out to start with, it was more of a check because I've changed quite a few other things in the system.

I suspect I may have caused a vacuum leak somewhere because, if I set the idle speed so it will idle cold, after a few blocks it wants to idle at 2000-2500rpm. Whereas if I set the idle warm, it won't idle cold.

If it was the enrichener circuit, to which no changes have been made, why did it choke and start proprly last week?

I am ging to drop the floats to 25mm then check the idle mixture settings, and resynch to see if that makes any difference.

[Del Tysdal]

Found a similar problem

Rode my XS 1100 to town for gas. Could not get it started after many tries. Left it on the berm about 1 1/2 miles away over night. Next morning it started right away and I drove it home, Then decided to try to figure out what was wrong. I started by replacing the carb hoses. Found one on the left side vac line that was severely cracked at the input to the carb. I cut 1/4 inch off and replaced it to the carb. Works fine now. I also tied the hoses to their connects with new 'Z' connects rather than the old spring ties.