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Discussion Starter · #1 · (Edited)
This is quite lengthy. Sorry in advance.

I have a 2008 Shadow Aero 750 that I purchased back in 2011. I use it to commute to work rain or shine and I've raked in 64k miles on it and a problem have developed June of this year. I started the bike one morning, choke on, and while the bike was warming up I heard the RPMs drop and then the engine dies. The bike will crank and crank but will not fire up. So far this has happened 5 times since June and always in the morning.

The first time this happened, I had the bike towed to a Honda service center. They cleaned out the jets and checked the carb for any problems. No problems found. The bike ran fine for 4-5 weeks.

Then the problem happened the 2nd time. Took it back to the same Honda service center. The mechanic discovered that the vacuum hose to the petcock is cracked and is leaking air. Replaced the hose, the bike started up and ran fine for 2 weeks. The battery was also charged but only charged to 20%.

Then the problem happened the 3rd time. I tried to troubleshoot it myself and removed the breather tube from the tank since I read somewhere that sometimes a vacuum can develop in a tank if the breather tube is clogged. I blew into the breather tube leading to the evap canister and plugged it back to the tank. Started the bike and it fired up! Took it back to Honda service and they suspect that the problem could be the Evap canister since I've been overfilling the tank for the past 3 years. They suspect a vacuum is being created preventing the fuel from flowing to the carb. they cut a small hole on the breather tube and the bike ran fine for 5-6 weeks.

Then the problem happened the 4th time. This time I definitely drained the battery trying to crank it over and over out of frustration. I replaced the battery, removed the gas tank and checked the hose that goes to the evap canister to make sure it wasn't blocked. Yes, I blew into it too. Put the bike back together and it ran fine for 3 weeks.

Then the problem happened the 5th time last week on Monday. I decided to disconnect the fuel line from the petcock. I felt air blow out at my thumbs as the fuel line disconnected from the petcock. Pressure in the line? or could it be a vacuum? I'm not sure. I reconnect the fuel line back and the bike fired up right away and I've been riding it for 2 weeks without any problems.

Obviously the fuel is not getting to the tank when this happens and there is pressure in the fuel line. What gets me is what could possibly be causing this? Its so intermittent and only happens in the morning and the bike runs for weeks like nothing happened until it just comes back again!

Has anyone experienced this? Honda service dept is stomped and not even sure what to check for next.

So far I've ruled out dirty carbs/jets, battery, vacuum line to petcock, breather hose is not clogged.

Any ideas?
 

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Next time it does it, check your plugs for spark. It sounds like you've ruled out fuel delivery. Not to say it's not a fuel issue, but at least this way you can narrow it down. If you're taking it to the shop, can we assume you're not mechanically inclined? If they've already taken your money, I'd see if they're going to stand behind their work. Obviously they've not addressed the real problem.
 

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Use your spare key to open the gas tank and see if that starts the bike, sometimes hot weather can cause flow problems.. The fact that the bike runs for weeks at a time and then always fails, added to the fact that you ride in rain could be connected to the fuel..

Try pulling the hose from the tank and draining the gas into a clear glass bottle for examination, you could have filled up at a bad pump and got water in the gas, does the failure to start occur when the tank is running low..If you have an inline fuel filter replace it with a new one, making sure the arrow on the new filter faces away from the tank and towards the carbs.. Cut the old fuel filter in half lengthways and examine the inside to see what (if anything) was blocking it..and fill up at a different gas station.

John.
 

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Discussion Starter · #4 ·
Thanks for the replies. But I may have found the cause of the issue. It was discussed here before. Doh! I should've done a more intensive search before I posted.

http://www.hondashadow.net/forum/72-technical-discussion/116163-09-aero-750-not-starting.html

This member had the exact problems I'm having now and was fixed by cleaning/replacing the petcock diaphragm. I ordered the parts and will install when it comes. Hopefully Honda can do it for free based on a recall for the 2007-08 750s.

I'll post a follow up if this fixes the problem.

BTW, I'm sort of mechanically inclined. I've been doing most of the maintenance on the bike including the valve adjustments. Still a lot to learn though. I have a torque wrench and everything ;)
 

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Discussion Starter · #5 ·
Update....

Its been 3 weeks since I had the diaphragm replaced by the dealership under a Honda recall. Before the fix the bike would stall every 3 to 4 days every morning and I would fix it by pulling the fuel line off the petcock and placing it back on.

Now that the diaphragm's been replaced, the bike has not stalled since, :lol::lol::lol: and its been running like a champ.
 
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