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Message started by DavidOfMA on 05/06/13 at 10:59:28

Title: New air filter enough to make bike run lean?
Post by DavidOfMA on 05/06/13 at 10:59:28

Installed a new air filter a couple weeks ago in preparation for a 5-day trip. Since then, bike runs rough, especially when going 25-35mph on level ground. Old filter was pretty dirty, couldn't see sunlight thru it. Running stock carb, jets, muffler, air box. Runs much smoother at midrange with the choke out a notch even when warmed up. Could the new air filter have leaned out the mix enough to cause stumbling and occasional misfires at 30mph, or do I have another problem lurking? Checked hoses and exhaust bolts, no obvious vacuum leaks, and the air filter foam gasket is not pinched.

Title: Re: New air filter enough to make bike run lean?
Post by apache snow on 05/06/13 at 11:14:46

Try turning your fuel mixture screw out counter clockwise 1/4 turn at a time and see if it helps. Do not exceed three turns out from fully seated.

Title: Re: New air filter enough to make bike run lean?
Post by justin_o_guy2 on 05/06/13 at 11:26:56

Still have the old one? If so, slap it in & see if it runs better,,
or, maybe youve had one of those Co-Incidental events?

Title: Re: New air filter enough to make bike run lean?
Post by DavidOfMA on 05/06/13 at 11:31:26

Trashed the old filter. Tried turning the screw out, and found slight improvement, but as the problem is in the midrange not much, and the idle seemed too rich. Just trying to find out if others have noticed this. I guess I could try blocking part of the filter with duct tape to fee if that 'fixes' the problem an, if it does, do the white spacer mod.

Title: Re: New air filter enough to make bike run lean?
Post by apache snow on 05/06/13 at 11:37:25

Running 25 to 30 just loafing on level ground you are still on the pilot circuit. You do not fully get into the midrange (neddle) till 1/4 throttle although there is some slight overlap starting at 1/8 throttle.

Title: Re: New air filter enough to make bike run lean?
Post by justin_o_guy2 on 05/06/13 at 11:41:03

A kleenex across it mite make it feel like a dirty filter.maybe too good, IDK, just tossin that out,

Title: Re: New air filter enough to make bike run lean?
Post by DavidOfMA on 05/06/13 at 11:45:29

554455575C51475A5B43340 wrote:

Ah. Okay, I'll try a more dramatic mix screw adjustment and see if I notice an improvement. If not, I'll try blocking part if the filter. If that fails, I'be got some other problem and will try the petcock test. Any other places to look for a suddenly too-lean mix?

Title: Re: New air filter enough to make bike run lean?
Post by justin_o_guy2 on 05/06/13 at 12:05:26

JUst how Co incidental with the air filter change was it? YOu changed the filter, went for a ride & its not okay?
Are you sure it wasnt acting up before the change & you just didnt notice it till you worked on it & then you were paying attention to saee if the new air filter made a difference?

Title: Re: New air filter enough to make bike run lean?
Post by DavidOfMA on 05/06/13 at 12:15:55

Can't be sure if I noticed it right away. The weather go cold and wet, and I didn't ride it for a while. I do think the occasional misfire is new. I don't recall that happening since I had the bike. Rough running at 30mph is not new but seems to be worse.

Title: Re: New air filter enough to make bike run lean?
Post by Dave on 05/06/13 at 12:21:08

Enquiring MODs want to know.

What jets do you have in the carb, and what (if any) exhaust changes have been made? If I remember right....your bike is basically stock.

Title: Re: New air filter enough to make bike run lean?
Post by DavidOfMA on 05/06/13 at 12:42:26

Bike is completely stock. 52.5 pilot, whatever the stock main is (150? Never remove it to check). Stock spacer, too. Except for backfiring, which reduced dramatically once I backed the idle mix out to 2 turns and ran Techron through the bike for about 6 tankfuls, it ran fairly well until I replaced the air filter. Spark plug change and valve clearance check are overdue, haven't had time to tackle that yet.

Title: Re: New air filter enough to make bike run lean?
Post by Dave on 05/06/13 at 12:56:56

Well....you really should do the spacer mod to the needle...the speed that you are describing as the problem area is more needle related than the Pilot Jet.....I think your throttle setting at that speed has moved beyond the range of the Pilot Jet and into the range of the needle. On my bike I had the best results with the 50 Pilor, 150 Main, and only 2 washers in place of the white spacer. I tried a 52.5 and 3 washers at first - but I had a hesitation right off idle as you rolled on the throttle to about 1/4 throttle...which is a place I spend a lot of my riding time. I first took one of the 3 washers out and it ran better...but had actually become too rich and when I changed to the 50 pilot it all came together for me....and the bike ran excellent.

I still got a bit of backfiring - but I honestly believe the big single and CV carb are prone to that. I just put a Mikuni round slide carb on.....I am interested to see if that is less prone to backfiring.

Title: Re: New air filter enough to make bike run lean?
Post by DavidOfMA on 05/06/13 at 13:23:44

Dave,

Thanks. Was your bike stock with those jets and 2-washer replacement for spacer? And what's your elevation? I'll do the mod when I work on the valves but I'd like to do the best guesstimate, as I have no garage to work in. I had been thinking I'd try 3 washers and the 52.5 pilot. I'm at sea level (literally).

Title: Re: New air filter enough to make bike run lean?
Post by Dave on 05/06/13 at 13:32:16

We are at 825 msl on the top of the hills, and around 513 msl at the Ohio River floodplain. My bike was stock with the exception of the Dyna Muffler. I have ridden a couple of stock bikes.....and they both had that lean stumble right off idle.

I bought my bike slightly used, and the previous ownder had already installed larger jets when I got it - but they had not done the spacer mod.

Title: Re: New air filter enough to make bike run lean?
Post by DavidOfMA on 05/06/13 at 13:38:48

I think I'll start with 3 washers and the 52.5 pilot. I've got the mix screw out 2 turns, so I have some leeway if I have to lean out the idle after the spacer mod. I'm now thinking the clogged air filter eliminated the lean stumble. Probably not the best way to richen up the mix!