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Advice for idling noise, smoke, stalling

894 Views 4 Replies 3 Participants Last post by  Porky
This seems like a newbie-novice-ignorant kind of question, so I thought this might be the right forum. I would love your thoughts, opinions, advice, and instruction, as much as I can get.

I have only been riding since March, daily rider on an '07 Kawasaki Eliminator 125. On Nov. 12th I went to Albuquerque and purchased an '07 Honda Shadow Spirit VT750 C2 with only 8,700 miles. It was starting up and running just fine, engine sounded nice and smooth. It was sold by a repair and consignment shop. The owner of the shop said it had just been serviced and had no mechaical issues whatsoever. He said it was ready to ride.

There were issues with the transportation, so it did not finally get delivered to my home in the Phoenix area until Saturday Dec. 8. I took it out for 5 short rides on Saturday, and it ran great. Started up great every time. I always let it warm up a few minutes before I ride.

Sunday morning, again running great. I got gas on my way to church - premium 91. After church, when I started the bike and let it warm up, it wasn't idling quite the same. Instead of a smooth humming purr, it was making a subtle rhythmic, whump, whump, whump sound.

Sunday evening I started it up, and in addition to the whumping sound, there was a more noticeable exhaust smell. My husband said it was coming in to the house from the far corner of the garage, and would I please start up the new motorcycle outside from now on.

Monday morning I drove it to show a friend who rides. He said it was just idling low and was nothing to worry about. So I kept riding it. Several short trips.

Thursday morning I ran a couple of errands; it stalled on me 3 times (tipping over twice,) and had trouble starting once. The final time I started it in preparation to return home, it seemed all smoky coming from the exhaust and had an even stronger exhaust odor.

A friend gave me the number of a mechanic they use; I called him today and if I understand him correctly, he suggests that the bike sat too long and the gas destabilized. He thinks the carburetor just needs to be cleaned.

Does that sound correct? If that was the problem, why would it run fine until I put new gas in it? Does it make sense that the shop I bought it from says it was just serviced and there were no problems with it, is that trustworthy? If I just need the carburetor cleaned, how much would I expect that to cost? Any advice?
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Hi There! From what you described it might be running on one cylinder at times. There can be many reasons for this and certainly if the bike sat for a while a dirty carb or fuel system might be one. When you put gas in it it may have stirred up some nastiness in the tank and washed it into the carbs. This is just speculation I guess, but it is consistent with what your local mechanic said.

Cost? Depends on the shop and it depends on the bike. Some bikes are easy and take less than an hour. I've never worked on your model so it's hard to say. Some can be quite a lot of work.

That said if you want to do some basic troubleshooting here are some things you can try:

From cold, start the bike. Monitor each exhaust header temperature - either with your hand or a good thermometer. Do they both heat up relatively the same?

Do you have access to a spark tester or timing light? Clip one on each plug wire (or try one and them move it to another..) Start the bike and see if it lights up. Is it similar on each cylinder, or is one darker?

The bad smell in your garage might be unburnt fuel or rich mixture, second only to the smell of hot rubber and fresh air!
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Thank you for your insights,cmonSTART

From cold, start the bike.
Is this safe, or is there any chance I might do damage by starting it? I've been afraid to do anything.
No - granted I wouldn't run the bike hard down the road like that, but starting and testing it won't hurt it. Your mechanic likely will, too - it's necessary for troubleshooting.

If you can post a video to Youtube that might be helpful.
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Your 34mm CV carb has some minute passages plugged up from setting so long and possibly from water in the new 91 octane fuel:surprise:

This is no big deal for your mechanic or Honda dealer as they see it all the time. Even I can fix it with my eyes closed and 1/2 my brain tied behind my back:smile_big:

Try this first though as it as worked for me 90% of the time:

Consider draining all of the old fuel out and putting new 87 octane in.

Buy a can of Chevron Techron (my favorite) or Lucas/ Seafoam fuel system cleaner and pour at least a half can or more into the gas tank.

Get on some secondary roads and ride the 'snot' out of it, exploring the upper RPM's often as when going through the gears. Even downshift from high rpm's with a closed throttle, that effectively creates a Vacuum in the intake system and helps 'suck' the debris out of the small passages.:smile:

It has taken me up to 50 miles of hard riding to entirely clean a plugged up carb but it's better than having to take it all apart:grin:

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