Bike won't start after warmed up (Part 2)

ThatFiveOhTho wrote: So, kind of unrelated (maybe.) But I seem to have an oil leak from the head gasket, on the left side of the bike. I cleaned the oil off a few days ago and it's back. I'll probably retorque the head nuts to a full 42 ftlbs before the valve clearences are checked next weekend.

Instead of an oil leak from the head gasket, could the leak possibly be ooze from an export port?

If still needing 7 seconds of electric starter action before the engine starts, this could likely be shortened by a good tune-up to almost immediate start-up upon pressing the starter button. Does it make any difference whether the engine is cold or warm?

Good Fortune!

Cold the bike does start up in a half a crank. Takes about 5-10 min to reach idle without choke. The bike warm handles great, from cruise to wot. Idle is satisfactory as well. Also, when I park the bike, I can start it up in a half a crank as well as long as too much time has passed by. Anything after ten - thirty minutes and it's 7 seconds to ignite and clean up the throttle. It idles about 300 rpm lower until you drive it around after this point.

If however, you kill the bike then start it relatively soon, no change in idle can be heard, and the start is near instant.

The leak is directly adjacent to the oil passage, with nothing above or below it, nor in front of the motorcycle.

I initially thought spark, but I have good spark with the coil mod done. At this point I'm probably going to pull the valve cover tomorrow since the gasket is going to arrive early.

ThatFiveOhTho wrote: So, after going through everything, I still have a hard starting problem when warm. The motor turns over freely and I have adequate spark, and compression. but if I wait more then 20 or so minutes after a ride it takes about 7 seconds of cranking with the throttle open to attain ignition. . . .

cranking with the throttle open to attain ignition --- It's usually best to leave the throttle untouched when starting the engine, regardless of whether the engine is cold or hot or anywhere in between. Perhaps partial application of choke might help reduce the 7 seconds scenario.

Good Fortune!

Choke doesn't seem to have an effect on the time to be honest. Although, it adds about 3-6 seconds of start time if I do not touch the throttle. Initially I didn't touch it at all and about 12 to 15 seconds, the motor would fire on one, then two and then four with a low idle. I've been avoiding taking the bike in places where I know it will sit for a while because of this.

It has never failed to start up. It has also never failed to resist starting hot after sitting as well.

ThatFiveOhTho wrote: Choke doesn't seem to have an effect on the time to be honest. Although, it adds about 3-6 seconds of start time if I do not touch the throttle. Initially I didn't touch it at all and about 12 to 15 seconds, the motor would fire on one, then two and then four with a low idle. I've been avoiding taking the bike in places where I know it will sit for a while because of this.

It has never failed to start up. It has also never failed to resist starting hot after sitting as well.

If not already done, would try opening the fuel tank cap and leaving it open for a few moments before engaging the starter motor (hands off the throttle grip) and leaving the cap ajar.

Then repeat the same experiment by turning the petcock to PRI position -- along with opening the cap -- and leaving the petcock in PRI , thereby allowing a few moments for the float bowls to fill, and then engaging the starter motor (hands off the throttle grip).

The idea is to rule out some vacuum issue inside the fuel tank that might be preventing the float bowls from readily filling with gasoline, whereby the starter grinds until the bowls slowly fill.

Given the hot carbs -- near boiling temps -- am wondering if the gasoline in the float bowls evaporates and/or leaks out over the 20-30 minutes while the engine sits without running.

Good Fortune!

I've left the petcock on with no effect, and also have left the cap open to to effect either. On a side note the nuts have been retorqued, and im about to check clearences now.

Well, using the FSM, the valves are in spec. All of them are either .10 or .12mm. nothing abnormal in the upper head. Not really sure what direction to take after this point.

ThatFiveOhTho wrote: I've left the petcock on with no effect, and also have left the cap open to to effect either. On a side note the nuts have been retorqued, and im about to check clearences now.

As I understand the problem scenario, it's attempting to start the warm engine after sitting for 20-30minutes which is taking an unduly long time grinding the starter before the still warm engine starts running..

I've left the petcock on with no effect, --- that could be okay for a manual petcock, but is WRONG for a vacuum operated petcock. For the mentioned test (which is to assure pre-filling the float bowls before any cranking), a vacuum operated petcock should be left in PRI -- not "on" -- along with the tank cap ajar for at least 10-15 seconds before engaging the starter without touching the throttle .

Only the PRI position in a vacuum operated petcock allows pre-filling the carb float bowls during the 10-15 seconds before engaging the starter.

If the float bowls need time to fill, that could be happening during the unwanted extended starter grinding, because the "on" petcock position did nothing toward pre-filling the carb bowls..

Good Fortune!

My apologies, suppose I should have been more clear. I've tried leaving the petcock on prime as well as on, either one makes no difference. Ive switched it to prime and waited a few minutes, as well as left it on prime throughout the entirety of the shut down. I have a can of starting fluid that I may try later this week to see if it is indeed a lean start.

My question for the day is, if say I had a rich condition where heat caused the bowls to fill the intake with fuel vapor, would the plugs fowl because of this? I also have the crankcase venting downward to atmosphere. Should I connect this back to the air box?

I'd look for the carbs overfilling after that time.
Steve

ThatFiveOhTho wrote: . . .
My question for the day is, if say I had a rich condition where heat caused the bowls to fill the intake with fuel vapor, would the plugs fowl because of this? I also have the crankcase venting downward to atmosphere. Should I connect this back to the air box?

Wouldn't suspect either as influencing the hard warm start scenario.

Could perform clear tube tests on the "warm bike" carbs to ascertain the fuel level when the engine has not been running for 20-30 minutes.

If easily starts hot or cold but not warm, there's something about warm that's different from hot or cold, and the difference has to be related to ignition or fuel or compression. I could be wrong, but it seems to me that fuel is the most likely variant in this particular situation.

Perhaps time for a truly thorough cleaning of the carb pilot circuits.

Good Fortune!

Thanks for the input. I'll be going through the carbs again to make sure all is well. In the mean time I've thought of a test for fuel. I'm going to use starting fluid to see if it is indeed a lean start condition where fuel in the bowls isn't high enough. If that doesn't work, ill give the bike another ride and before parking it I'll drain the fuel out of the bowls to see if it prevents a rich start 20 to 30 minutes later. If it does, I'll know that excess fuel is making its way into the cylinders while parked.