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Message started by cygnet on 09/17/17 at 16:40:27

Title: Another carb question
Post by cygnet on 09/17/17 at 16:40:27

I'm having a little trouble setting up my carb. The bike is a 2017 with 3600km I'm at 3500 ft altitude. As all S40 are real lean from the the factory so was mine, it was doing a lot of popping and such. I drilled out the plug and set the idle which helped a lot, but in 2nd and 3rd at say 3000rpm the bike would surge like it was running out of fuel. So I did the white spacer mod I took the spacer out and put in two washers now the bike runs like a top, no popping smooth as all get out only one problem it wants to load up at idle to the point it will stall at a stop light. I tried setting the low speed idle again but now I can turn the screw all the way in with little affect. One other thing I was getting 67mpg and now I'm getting less than 50. What should I do now?

Title: Re: Another carb question
Post by Dave on 09/17/17 at 16:49:41

It sounds like your idle fuel mixture is set too rich, and you might have the idle speed set too low.

What jets are you using?

Title: Re: Another carb question
Post by cygnet on 09/17/17 at 17:04:55

Well I can turn the idle screw all the in and it still runs, the jets are stock but I can't tell what they are as I never looked, I turned the idle down to 800 rpm to set the idle screw but then I set it at 1300 I have a tach installed so it's easy to see the RPM.

Title: Re: Another carb question
Post by batman on 09/17/17 at 17:07:37

You may have gone to far with the needle lift ,I'd try 3 washers at 3500ft,(usually 2 washers is used for 1000ft to sea level)then a retune of your mix screw.

Title: Re: Another carb question
Post by cygnet on 09/17/17 at 17:17:13

That's kinda what I was thinking My gas mileage might also go back up a little. But it sure runs nice off idle smooth as glass and no popping or afterfire. also when I let it idle for say a minute and hit the gas it bleches black smoke.

Title: Re: Another carb question
Post by batman on 09/17/17 at 19:15:31

Black smoke and black soot at the muffler tip(inside) is a pretty good sign you running rich,and yes you probably will regain a couple of mpg with another washer.If the mix screw still doesn't effect the idle speed you may have to go to the next smaller pilot jet (50)

Title: Re: Another carb question
Post by stewmills on 09/17/17 at 19:57:24

I had a similar issue that ended up being a result of raising the needle too much. I was consistently having the bike stall at idle. The longer it idled the lower the RPM got until it choked, and on restart I had the same poof of smoke. Aside from this, my bike ran perfect as well.

I'd agree, start with adding a washer to push the needle back down and see if that makes it better.

Title: Re: Another carb question
Post by ohiomoto on 09/18/17 at 05:32:01

342E30393223570 wrote:

---------------------------

Your at 3500ft so the "lean factory" settings might not be so lean. You have to understand that the people who use the "white spacer" mod are mostly around sea level. I would go back to the white spacer and try to lean out the pilot or possibly the main. See what affect that has before assuming you need to go richer.

Backfires can be caused by rich conditions too. I recently put stock jetting in my bike and it backfires less than it did with a bigger main and the white spacer mod. You need to figure out what works for your bike in your area. Overly rich setting will sound good and run smooth, but that doesn't mean it's really running better.

Title: Re: Another carb question
Post by cygnet on 09/18/17 at 09:40:42

I wasn't to worried about the backfires it was the surging in the 3000 rpm range that was most worrisome. Making it richer solved that problem, I'm going to add one more washer and see if that clears up my idle problem. I will report back when it gets done.

Title: Re: Another carb question
Post by ohiomoto on 09/18/17 at 10:09:55

If the washer helps, you may want to drop the pilot jet as suggested. But make sure your slide opens smoothly. If it sticks while the vacuum is trying to pull it open, you'll get a momentary lean condition.

You might be trying to jet for another problems. Especial if the problem didn't exist before. A super rich condition will smooth over or mask such a condition due the the excess fuel being present.

My slide has been sticking this summer. The black coating is wearing off and being deposited inside the body of the carb. Once it wouldn't open past halfway for a few seconds on my way home from work. Most of the time is sticks just on either side of the mid-range when I crack the throttle wide open. I can feel the sticky spots when the carb is off. Cleaning has helped, but only for a short period of time (a week or two).

I bet if I handed my bike off to most anyone on here, they would richen it up right away to solve the lean condition. And if they go rich enough, it will "solve" the problem. The PO had a 155/55 main/pilot in there and it was smooth. Could hardly get 40 mpg and struggled to go 75 mph, but it was smooth. Problem solved, right?

Point is, make sure you cover all your bases. Maybe the jetting is lean, but at 3500 feet, I have to wonder if something else is at play.

Title: Re: Another carb question
Post by cygnet on 09/18/17 at 10:22:16

The bike is new and the slide is smooth,it just surged a lot in the mid range. Even running as rich as it is I still have lots of power but the gas mileage is way off. I will add one more washer and see how that goes, if it still loads up I guess I will put the white spacer back in and live with it. I have a five year warranty, but when I talk to the dealer he says that's just the way they are, so much for warranty doing anything.

Title: Re: Another carb question
Post by cygnet on 09/18/17 at 21:10:13

Well I added one more washer and no change. Great mid range but loads up at idle. I can turn the idle screw needle all the way in and it does nothing. So it's back to stock, good mileage, good idle, crappy mid range.

Title: Re: Another carb question
Post by Dave on 09/19/17 at 04:16:22

544E50595243370 wrote:

If your idle speed is high when you attempt to adjust the idle fuel mixture, you won't get a response as the needle will be supplying fuel. You need to drop the idle speed down to 800 - 1,000 rpm to get in the range....don't leave it in this range after the adjustment is made, and don't spend a lot of time with the bike leaned over on the side stand while making the adjustment (but a board under the kickstand to level the bike up a bit).

The ideal place for the idle screw to be is between 1.5 - 2 turns out. A pilot jet that allows the screw to be in that position is the correct size. If you have to go out more than 2.5 turns to get the smoothest idle - the pilot jet is too small. If you turn the screw out less than 1.5 turns to get the best idle.....or you can turn it all the way in...then the pilot jet is too big. (There is a bypass hole that flows fuel around the fuel screw, and even if the adjustment screw is turned all the way in, fuel is still flowing...too big of a pilot jet and too much fuel flows).

Don't forget to turn your idle speed back up once you have completed the adjustment of the idle fuel screw (pilot screw).

At your elevation - the #47.5 pilot jet is probably going to be a good place to start.

In the diagram below, at #2, you can see the bypass holes prior to the pilot screw. This is where the fuel is flowing when you have the adjustment screw turned all the way in.

http://i67.tinypic.com/o5uckl.jpg

The surging you were having at light throttle settings is related to the needle being too low - so you need to raise the needle to correct that. The 2 or 3 washers that works for us at lower elevations may need to be 4 screws at your elevation - to correct the surge you need to raise the needle a bit to provide a slightly richer mixture.

Title: Re: Another carb question
Post by LANCER on 09/19/17 at 06:47:35

5349575E5544300 wrote:

The bike is new and the slide is smooth,it just surged a lot in the mid range. Even running as rich as it is I still have lots of power but the gas mileage is way off. I will add one more washer and see how that goes, if it still loads up I guess I will put the white spacer back in and live with it. I have a five year warranty, but when I talk to the dealer he says that's just the way they are, so much for warranty doing anything.

I'll bet the dealer doesn't say that to his crotch rocket or big twin cruiser customers.

As Dave suggested, go back to the 47.5 pilot, and since adding a washer to the needle did nothing for you, go back to just 2 washers, or if needed you can go to 1.