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

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. Ive also checked valve clearances, which leads me to my series of questions before I tear open the valve cover gasket again:

1. If valve clearances were tight, would I still get compression on the cylinder. The bike runs perfect other then this issue which has plauged me.

2. Would an overheated pickup produce delayed enough trigger to fail to fire until it cooled off?

3. What is the proper procedure for checking valve clearences? Is it at exactly tdc or the lowest clearences attained between points where the valve is closed? I used the tdc timing mark method and am beginning to think that I'm still tight enough to cause a failure to fire.

4. I can hear the carbs boiling with my ears near them. They are hot to the touch from the transmission baking them when parked. Is this normal?

I'm sure I forgot something but I'll be sure to post it if I remember. Thanks ahead to anyone who responds. You've made this bike damn near perfect.

I'd adjust the valves according to the FSM.
Steve

At engine temperatures less than normal operating temperature (such as when performing a compression test), a valve with insufficient clearance may seal completely when in its closed position and allow for a satisfactory compression reading. But when the engine attains normal operating temperature, the heat expansion results in failure of a valve with insufficient clearance to seal completely when in its closed position.

This is why a cool engine with insufficient clearance may start and run okay until it warms up, and then begins losing compression when the too tight valve begins failing to seal completely when in its closed position.

A typical symptom is failure to idle after the engine warms up.

Good Fortune!

ThatFiveOhTho wrote: . . . Would an overheated pickup produce delayed enough trigger to fail to fire until it cooled off? , , , What is the proper procedure for checking valve clearences? Is it at exactly tdc or the lowest clearences attained between points where the valve is closed? I used the tdc timing mark method and am beginning to think that I'm still tight enough to cause a failure to fire. . . can hear the carbs boiling with my ears near them. They are hot to the touch from the transmission baking them when parked. Is this normal? . . . .

Would an overheated pickup produce delayed enough trigger to fail to fire until it cooled off? --- imo, most probably not.

What is the proper procedure for checking valve clearences? Is it at exactly tdc or the lowest clearences attained between points where the valve is closed? I used the tdc timing mark method and am beginning to think that I'm still tight enough to cause a failure to fire ---


can hear the carbs boiling with my ears near them. They are hot to the touch from the transmission baking them when parked. Is this normal? --- Imo, no, not normal for fuel in float bowl to ever reach boiling temperature.

Good Fortune!

I've checked compression both cold and when the problem occurred, and obtained the same exact reading of 130psi. Does this mean I can rule out clearances?

I will most likely have to pop the valve cover off anyways. I believe I used the FSM to check and have proper clearances but with this issue it's making me second guess myself. Just didn't make sense that the bike runs great at idle, take off and wot unless it sits for a bit.

I also have drained the fuel bowl to verify flow. I don't have any starvation issues when riding and it doesn't matter if the petcock is on prime or run. Choke has no effect and fuel levels in the bowl are at spec when the problem is there.

Well, I can rule out the bike needing more fuel. I sprayed fuel in a bottle into the intake and still, 7 second delay then fires up and clears out. I can kill the bike after this point and as long as I start it up within a few min it will kick right over. It's just when it's been sitting hot. I took off the spark plug before adding fuel manually and saw what I believe to be fuel condense around the spark plug, not a lot since the plug was dry but a ring was present none the less.

ThatFiveOhTho wrote: I've checked compression both cold and when the problem occurred, and obtained the same exact reading of 130psi. Does this mean I can rule out clearances?

I will most likely have to pop the valve cover off anyways. I believe I used the FSM to check and have proper clearances but with this issue it's making me second guess myself. Just didn't make sense that the bike runs great at idle, take off and wot unless it sits for a bit.

checked compression both cold and when the problem occurred --- not unless somehow performed a compression test while cruising down the highway. :lol: Satisfactory compression test result does NOT rule out a valve clearance issue, and is NOT evidence of sufficient valve clearance, regardless of when the compression test is performed. Because the compression test is performed when the engine is not running.

If not already done, would also use a timing light to assure proper functioning of the automatic advancer, especially to see that it's not stuck or hanging.

Are the factory specified spark plugs fitted?

Good Fortune!

Cool. I suppose the only thing to do is to pull the valve cover off and check again, which will have to wait until next weekend.

Timing has been verified with a timing light, and the advancer has been polished and lubed.

Yes, factory spec. B8ES if I remember correctly.

The new valve cover gasket has been ordered. Just to clarify, I looked in the manual and came up with a different photo then you.

The carbs "boiling" is what bothers me. Could be compression leaking back through the intake valves being too tight or out of time. I wouldn't ride it until the issue is found.
Steve

To be honest I don't think they were boiling. Hot maybe but I realized the battery makes the same noise that the carbs did that night.. probably not a coincidence since fuel didn't boil when I added it manually. Also I've edited my previous message in what I found in the FSM.