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Message started by Thurston on 06/08/16 at 04:25:29

Title: Seems to be running lean lately
Post by Thurston on 06/08/16 at 04:25:29

Hi everyone. My 2013 S40 very recently started exhibiting symptoms similar to a lean condition at about the 35-45 mph range. Not a lot of hesitation, but enough to be a bit bothersome when riding around town. The following modifications have been done over the past 2 years:

White plastic spacer replaced with ½ size
Low speed mixture screw backed out 2 ½ turns
Pilot jet replaced with # 55
Carburetor thoroughly cleaned
Raptor petcock installed
Air filter cleaned
Spark plug checked

The elevation where I live is about 175 feet above sea level. Would replacing the main jet with perhaps a # 150 smooth it out any further? I’m puzzled as to why it seems to be running lean out of the blue like this. Maybe what's going on has nothing to do with carburation at all? Most of the mods above were done about 2 years ago and seemed to solve the original ridiculously lean problems I had when I bought the bike new. Thanks all.

Title: Re: Seems to be running lean lately
Post by justin_o_guy2 on 06/08/16 at 05:09:09

Hominy miles?

Title: Re: Seems to be running lean lately
Post by Dave on 06/08/16 at 05:09:09

A #55 pilot is pretty big....you really shouldn't need that big of a pilot with a stock airbox and stock exhaust.

If the bike runs good at 1/2 throttle and above....the main jet is not the issue.

If the hesitation occurs as you open the throttle a small amount, but goes away when you add more throttle - you likely need to raise the slide needle.

And, the way the bike runs can change a bit with weather - but if the bike suddenly made a change - the jetting changes may just be compensating for some other problem that has started, like a loose or cracked rubber clamp at the cylinder head, a rubber cap on the old vacuum port that has cracked or fallen off, or a clogged pilot jet or dirty carb.

A #150 main, #50 or 52.5 pilot, and 2 or 3 washers (#4 machine screw size), and remove the air mixture plug and properly adjust (by ear) the idle mixture....and you should get you a good running bike.

The setting on the mixture screw is not done by "counting turns" that worked for somebody else....it needs to be set for your bike when the engine is fully warmed up, and it is set by adjusting the screw and listening.....you need to find the point where the bike idles the smoothest. If the setting ends up being less than 1.5 turns out - your pilot jet is too big. If your best setting is more than 2.5 turns out....you need a bigger pilot jet. To make this adjustment you need to drop the idle speed down a bit lower than is recommended - but with a high idle speed the slide is starting to open and will allow fuel to flow out the needle jet....and this will prevent you from getting a proper adjustment of the idle fuel screw. When the adjustment is done you can set the idle speed back up.....and do the adjustment while you are sitting on the bike and holding it off the sidestand.....long idle times on the sidestand can starve the exhaust cam lobe and rocker to wear.

https://www.youtube.com/watch?v=YxpQjDQzX7g

https://www.youtube.com/watch?v=zm5mB3R8Ucw

Title: Re: Seems to be running lean lately
Post by Thurston on 06/08/16 at 06:23:37

Dave, thanks so much for your sage and timely advice. This will be very helpful as I undertake the next steps. Justin, my bike has 18,000 miles on it. Thanks again gentlemen.

Title: Re: Seems to be running lean lately
Post by Serowbot on 06/08/16 at 07:34:17

35 to 45 in what gear?...
In 5th,... that is lugging, and lugging will make for a jerky ride.
I'm usually in 3rd at around those speeds...

#55 pilot is large... too large a pilot just hurts mpg's...
Judge your pilot size by which size gives you a good idle with 1 1/2 to 2 1/2 out on the idle mix screw...

Title: Re: Seems to be running lean lately
Post by Thurston on 06/08/16 at 11:12:01

Serowbot, thanks for your feedback. I'm usually in 4th gear when it occurs, so pretty sure it's not lugging. Both you and Dave feel 55 is pretty big for the pilot, so I think I'll look at changing that in the very near future. Thanks again.

Title: Re: Seems to be running lean lately
Post by Dave on 06/08/16 at 13:33:35

2D3323202D2D410 wrote:

Serowbot......Both you and Dave feel 55 is pretty big for the pilot, so I think I'll look at changing that in the very near future. Thanks again.

We are on the same team!

Title: Re: Seems to be running lean lately
Post by Kris01 on 06/08/16 at 19:35:42

Thurston, what is your altitude? Higher elevations have thinner air causing the engine to require less fuel (and smaller jets). Regardless, a #55 is probably still too big.

Title: Re: Seems to be running lean lately
Post by Serowbot on 06/08/16 at 19:45:36

655C475D1E1F2E0 wrote:

Thurston, what is your altitude? Higher elevations have thinner air causing the engine to require less fuel (and smaller jets). Regardless, a #55 is probably still too big.

0D1303000D0D610 wrote:

The elevation where I live is about 175 feet above sea level.

I miss stuff all the time, too... 8-)

...but, Dave tells me the right thing to say anyway... ;D ;D ;D

Title: Re: Seems to be running lean lately
Post by batman on 06/10/16 at 07:06:06

between the 55 pilot and half spacer on the needle it sounds like you're running to rich all the way around. I'd change to the stock 52.5 pilot as suggested, lower the jet needle (3 num.4 washers) and check /change your air filter.All these will make your motor bog down at low throttle settings.If you're in 4th gear at 35-45 you are lugging ,Try wot in from 35 in both gears an note the difference.

Title: Re: Seems to be running lean lately
Post by Kris01 on 06/10/16 at 19:09:39

Oops! Thanks 'bot!