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Discussion Starter #1
I have a 2003 Honda 750 Shadow ACE.

If the bike sits for a week, when started it ideals rough but I can travel a short distance before the bike dies. It will not restart immediately but if I wait a little, it starts and runs fine.

I have had problems with the battery over the last couple of years with a new battery last fall. I say this because it is almost acting like it did when I had the battery problems.

When the shop looks at it, they do not find a problem as the bike runs for them and their diagnostics do not say there is a problem (new plugs last fall).

Any suggestions for what to look at?

Thanks
djj
 

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Discussion Starter #3
Thank you for the reply.

Could be. However if that was the case why could I then start the bike later and ride for several miles?
 

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Discussion Starter #5
Never thought of that.

How do I check this? (Note that I am at work and repair manual is at home).
 

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Simply ride until the engine quits, then open the gas cap to release the vacuum built up in the tank and attempt to restart.

If the vent is clogged, air does not replace the fuel leaving the tank, stopping fuel flow.

It only takes a second to check and will confirm if that's the problem or not.
 

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Thank you for the reply.

Could be. However if that was the case why could I then start the bike later and ride for several miles?
Don't know. It was just the first thing that popped into my head. Dodsfall has a good suggestion. I didn't think about that.
 

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It could be a number of fuel flow related problems or possibly a coil that overheats. Might as well start with the easy and cheap stuff first when tracking down the problem.
 

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So, sits for a week, rough idle at start, dies, wait a bit, starts and runs fine without issue until the next cold start after sitting a week?

Sounds like moisture in the gas.

If you live in a high humidity area, don't use ethanol fuel in a low use engine...corn alcohol absorbs moisture...normally, that's actually good and helps keep the system dry and rust free...BUT...if the engine does a lot of sitting, you end up with a lot of water in the gas...and since water sinks, it's the first thing the engine sucks in when you start it.

As a test, I would let it sit for a week with the fuel valve off..pull the hose off the valve and drain out a cup of gas, put the hose back on and start it up...that cup will be the gas with the most water mixed in..
 

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Discussion Starter #10
Turned out to be the carburetor. Needed to get the cooling system flushed and the brake line flushed so had them look at the problem.

Bike runs a lot better now.

However, now the bike seems to backfire (just small ones) when I let off the throttle.
 

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Probably after-fire from running a bit lean; factory settings for most bikes made since the '80s make them lean out when the throttle is released, which causes the popping. Many have 'coast valves', or 'transient enrichment systems', to try to stop it, but most still have some after-fire.
 

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Discussion Starter #12
Probably after-fire from running a bit lean; factory settings for most bikes made since the '80s make them lean out when the throttle is released, which causes the popping. Many have 'coast valves', or 'transient enrichment systems', to try to stop it, but most still have some after-fire.
Thanks! I guess I will not worry too much then.
 

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Check all the main electrical connections, on all the main devices. one of them might be loose and rattling until it make a good contact.

(another true story?)
 

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I can travel a short distance before the bike dies. It will not restart immediately but if I wait a little, it starts and runs fine.
If the vent line to the fuel tank is plugged (common, spider nests...) exactly what you describe will happen. Air can't get IN to replace the fuel flowing OUT.

Try riding with your gas cap open; if that solves it, unplug the tank vent line.

I've also seen debris moving back and forth in a fuel line cause this and/or debris in the fuel tank. A piece of cardboard, ping-pong ball, or other debris in the tank, which nominally FLOATS, but gets sucked down over the pickup, is another cause. After the suction goes away, it floats back up, bike restarts....repeat,
 

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Valve adjustment, valves too tight will sometimes allow an engine to start, then when it warms up, the valve won't close and you lose compression. Cool down, starts right up.
 
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