[djKail]

So my brother just picked up a Honda day Shadow and even though it ran great both times we looked at it, for some reason it has been acting up when he brought it home, rough idle, stalling, backfiring ect.

Bike is a 2003 shadow spirit 750, it has after market pipes, and a bullet style air filter. When I test road it, I did not hear any decel popping so I assume it has been rejetted but can't be sure.

The issue is that when it is cold, the engine idles very rough, stalling out, some backfiring ect. It wants to idle higher when we pull the choke out but usually it makes it stall as well. After running the engine for a few minutes it was doing better with no choke actually.

Now, the bike has sat for awhile, maybe 2 seasons. When we had it running it felt OK, just a little hesitant at times. I filler her up and added about 4 oz of seafoam to the fuel. I ran her for about 15-20km around the city the other day and the bike seemed to be running much better.

However, when attempting the cold start today, the same issue is happening. Any suggestions? Again, when we first looked at the bike, it fired up first try with full choke, warmed up, and idled great. Now, with a tank of fresh fuel she just doesn't want to run right.

 

[smilie]

You have crap in the carbs. If your gonna store a bike for an extended period, do it right. If not, you get what you're now experiencing. Get your service manual out as it sounds like you're going to learn about carburetors now. Also drain and clean the fuel system. If you left it for a couple years, chances are it's full of crap.

 

[LuvinTheV]

I agree with smilie, it probably wasn't stored properly. Was the bike cold when you test rode it or had the owner warmed it up. A lot of people warm the bike so it will start right up and run well when a potential buyer comes to look at it.

 

[djKail]

We verified the engine was cold the second time we looked at it. She fired right up and I didn't notice any issues during the test ride.

The previous owner mentioned it was stored for awhile and I figure he didn't do it correctly. I'm just wondering why, if the issue is the carb, that the issue wasn't present when we test rode it?

Just the other day as well, after a bunch of fuss the engine started running ok, filled her up and put seafoam in the tank. Pushed her pretty hard for a bit and all seemed OK... Until today when we tried cold starting her.

 

[djKail]

Just as an update, we pulled the plugs and they were all toast. Replaced them with new ones and she fired up right away.

Issue now is that even after warming up the bike doesn't want to idle with no choke. We have to have the choke out at least 1/4.

I assume this means a lean condition is present, either by a vacuum leak somewhere or more likely caused by a blockage in the idle circuit?

 

[smilie]

Just as an update, we pulled the plugs and they were all toast. Replaced them with new ones and she fired up right away.

Issue now is that even after warming up the bike doesn't want to idle with no choke. We have to have the choke out at least 1/4.

I assume this means a lean condition is present, either by a vacuum leak somewhere or more likely caused by a blockage in the idle circuit?

More likely your pilot jet/s are still partially plugged. The fresh fuel and seafoam may dissolve and clear the crap, maybe not. You might also try opening up and the a/f screw/s a turn or so and returning to original position while it's idling to open up the passage some. If it doesn't work, it's time to open up and clean the carb/s.

 

[Maxshiau]

sounds 99% like a pilot jet block, you will be running less of that 50 size pilot jet so beware of over heating and toasting the engine.
why 99% because it might also be that your fuel mixture screw is adjusted wrong or they are clogged up too.
You can check all of those things with the carb still connected on the bike, just release the rubber seats and slightly twist the carb so you can get at the bowls and clean all the jets. 4 h job 1st time round... now takes less then 3 for everything.

 

[Furball Zen]

If its cold (below 50º) you should be pulling the choke ALL the way out and THEN starting it. If its not cold, no choke.

 

[jwinker]

Q1: Are the mixture caps still on the A/F screws?

Yes, they are still present - the bike has not been rejetted or adjusted with the new filter & pipes. You need to rejet. That's a good time to clean and tune the carbs.

No, they have been removed - The P.O. had the bike tuned after installing either the pipes and/or the air filter. He may have rejetted. Contact the P.O. to ask if he rejetted, or remove and disassemble the carbs to inspect. This would be a good time to clean & tune the carbs.

 

[djKail]

Just as another update in case anyone else is having similar issues.

The caps on the mixture screws have been removed. Based on that, and how it was running when we initially test rode the bike I am fairly confident that the jets have been replaced.

We adjusted the air fuel mixture screws on the throttle side of the carb. It was set at just under two turns out. We gently seated it and turned it to 2.5 half turns. Seemed to have made things worse, but we noticed a small puff of black smoke come out of the exhaust from the front cylinder.

We then returned the mixture screw back to where it was and idled the bike with the choke 1/2 out for a minute or two. I noticed that the front cylinder exhaust was still relatively cool while the rear cylinder was heating up much faster.

My brother is thinking of just taking it into a mechanic as removing and cleaning carbs is a bit out of our league.

 

[bmholzhauer]

I would look at this discussion http://www.hondashadow.net/forum/72-technical-discussion/94993-how-remove-carbs.html
it helped me when I did my carb work. FYI I had never messed with carbs before either but everyone on here is pretty helpful. I had almost the same issue when the PO had put on cobra slashcuts although not to the extent you are.

 

[djKail]

Went to fire it up to just scoot down the street to the mechanics shop and it won't start up. Pulled the new plugs out just to see and they look identical to the old ones we pulled. Very black, and wet. Hopefully not oil?

So the bike would only idle with new plugs when the choke is out. It fouls the plugs within a couple days. I don't get it, wet black plugs indicate a rich condition, but requiring the choke to idle indicates lean? So what is it!? Waiting on a tow now.