hard starting when warm

My bike has a similar problem. I started it up and let is warm up for a few minutes rode it around the block and then came back to the house to put on some better riding shoes. I left it running in the meantime. Came outside and rode it around for another 5 minutes. I was about a half mile from home when I pulled out of a stop sign and it killed on me. I couldn't start it after that. So here are my two questions:

1) Why would a bike choke out when warm?
2) Why would it be harder to start when it is warm?

Here is what I know. Compression is good; I checked it according to the manual. Electric is good. I have checked just about every resistance and voltage there is to check. All hoses are clean and free of obstruction. Any ideas?

Did you check the fuel tank vent (normally in the cap)?

What do you mean, 'fuel tank vent'? The cap makes a solid seal around the mouth and there are no other holes in or around the cap. Is that what you mean?

As gas flows out of the tank, air needs to flow back in, otherwise gas will stop flowing out and you won't be going anywhere

Usually (I'm not familiar with your model) there is a little hole on the inside of the cap that allows air to get around the seal and into the tank without allowing gas to slosh out.

Well when the bike cuts out and dies on me I open the gas tank, which should let the fuel start to flow once again. It does nothing in my case. No change at all.

Anyway, so, I just rode it around the block again. It did the same thing. After a few minutes of riding it around it cuts out pretty bad. I have to hold the throttle open to keep it running. However, I did discover something this time.
I jerked the handlebars back and forth rapidly and the bike returned to normal until I stopped. I then tipped the bike from side to side quickly while still seated just to see if that made a difference. No dice. Tipping it back and forth did nothing, BUT jerking the hanglebars back and forth does the trick. Strange I tell you.

Post edited by: dannyh, at: 2006/06/15 22:27

Ok, I'll go with strange

Cutting out like it's running out of fuel, or cutting out like you are turning the ignition off and on?

Cutting out like it is not getting fuel, or the mixture is a little off.
I did another experiment. I jerked the handlebars back and forth and then tried to start it. When I did that it turned over really slowly for a second or two and then went back to normal. Could something be wrong with my wiring somewhere? I am baffled.

www.wgcarbs.com/269767.html

When a bike warms, metal expands. If a bike has very minimal valve clearances, the heat from expansion makes the lack of clearance more pronounced when the bike warms... this may be causing a compression loss. Read the article in the link above. Your bike uses a different technique to adjust valve clearances but the basics are the same.

I'm new here but may I add some simple hints? getting them to run while cold is a step in the right direction. When the failure happens while hot rises other issues. my suggestion for any one that has the hot start problem is to start at the begining and check the simple details.
First! new ngk spark plugs-and get extras!
if you think just sanding them off is good enough I am here to disagree. the plugs condition will show where the carburator is rich or lean or if rings are shot.
next is a list and if you check it all and still have a problem ????
ELECTRIC:batt,charging,ignition,connections.
FUEL: tank vent,fuel tap,float valve, fuel level
ENGINE:valve clearance,compression,cam chain tensioner. Post edited by: trippivot, at: 2006/06/16 10:18

Post edited by: trippivot, at: 2006/06/16 10:20

WG,
About 3 weeks ago I did a compression test according to the manual, (while the bike is warm). All cylinders are getting 150 psi, plus or minus 1 or 2 psi. Since i did the test when the bike was warm I don't think it is a compression issue. I'll look at and adjust my valves anyway, as your advice is always on point.

Trippivot,
I will replace my plugs again just to see if that is the problem. Thanks for the rest of the advice. I have done most of the things on your list but you made me think about a few things I still need to do. Thanks

Post edited by: dannyh, at: 2006/06/16 12:33