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General Category >> Rubber Side Down! >> What causes and how to fix acceleration flat spot?
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Message started by goofballs on 07/07/14 at 23:15:10

Title: What causes and how to fix acceleration flat spot?
Post by goofballs on 07/07/14 at 23:15:10

I have a 2013 Suzuki Boulevard S40 which has developed a flat spot at about 70 mph. When rising on the freeway the bike stops accelerating but keeps speed and won't go over 70 mph. It has a long delay in some cases taking 1 minute or more in wide open throttle for it to start accelerating again.

Does anybody know the cause and how to fix it?

I have taken it to a repair shop but they say the bike runs lean and that is the reason. They say they are not allowed to richen up the mixture due to CA laws but I have a hard time trusting them.

Title: Re: What causes and how to fix acceleration flat s
Post by verslagen1 on 07/07/14 at 23:46:05

sounds like you have a sticky slide.

add a couple ounces of seafoam to your gas tank.

or remove and clean.

Title: Re: What causes and how to fix acceleration flat s
Post by Dave on 07/08/14 at 04:52:03

If it ran good once, and now doesn't - then it is most likely an issue with dirt or gum in the fuel system.

Since it will eventually respond, I doubt that it is dirt in the jets, and Verslagen is most likely on the right track with the sticky slide.

Sounds like a carb cleaning is needed.....or you can try SeaFoam and see if it does any good.

Dave

Title: Re: What causes and how to fix acceleration flat s
Post by HAPPYDAN on 07/09/14 at 09:24:24

I'd like to toss in a non-expert learned-about-the-quirks-in-this-bike the hard way suggestion. How many miles do you have on the 2013? Have you done an oil change yet? The right oil makes a difference. Are you still running the stock petcock? Have you done the air screw adjustment and the white-spacer mod yet? My 2012 acted funny like that too, until I did some easy mods and got about 1,000 miles on it. Now it runs pretty good. The veterans on this site can guide you thru the -necessary- mods. Many new owners become quickly disillusioned with the newer S40's, that's why many can be found for sale quite reasonably. I know mine almost was. Now I truly love the little bugger!

Title: Re: What causes and how to fix acceleration flat s
Post by goofballs on 07/09/14 at 09:37:13

I have about 6,500 miles on it. I have done the air screw adjustment and the white spacer mod already. I haven't done the petcock mod and will look into that.

As for the oil change, I have done 2. Once at 600 miles and again at 5k. Overall the bike is running awesome. This new issue just came about and I had tried other carb cleaners but not Sea Foam. I put some in this morning and started feeling some improvement toward the end of my 20 mile ride.

I am going to let the SeaFoam do it's magic for another day or so and will let everybody know.

Title: Re: What causes and how to fix acceleration flat s
Post by HAPPYDAN on 07/09/14 at 20:32:28

WOW! 6,500 miles already? You must live on that sled! Disregard everything I said. Here in western Washington, with our greatly reduced riding season (aka crappy weather) it takes 2 or 3 years to get that kind of miles. The Vets are probably on track here. Good Luck! But on a final note myself and others have noticed an improvement in overall performance once changing to the Yamaha Raptor manual petcock, especially with fuel delivery at higher rev rates. Mine had a noticeable "flat spot" until the petcock quit altogether just over 1,000 miles. If you haven't done so already, try running on "PRI" to see if that helps. If so, then you know the culprit.