SuzukiSavage.com - Re-jetting after Harley Muffler install

hawk41 Junior Member Offline SuzukiSavage.com Rocks! Posts: 65 Gilbert, AZ Gender:	Re-jetting after Harley Muffler install 07/06/16 at 10:38:17 Before I try to change the jets after my recent Harley muffler install I would like to know how many turns out on the idle mixture screw is stock. At 1.5 turns to 2.5 turns I really can't tell much difference in the idle, however, when riding there seems to be more backfires at 1.5 than at 2.5. Suggestions would be appreciated.
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Re: Re-jetting after Harley Muffler install
Reply #1 - 07/06/16 at 11:58:56

In order to properly set the idle mixture screw, you may need to turn the idle speed down a little bit....down to around 800 rpm. This is lower than recommended for a healthy cam (low oil pressure at low idle speeds) - but at 1,000 - 1,100 rpm some fuel begins to flow out of the needle jet and makes adjusting the idle fuel mixture impossible. Start at 1.5 turns out and then adjust. If you can turn the screw all the way in without the engine dying - the pilot jet is too big.....and if you have to turn the screw out more than 2.5 turns the idle jet is too small. Don't let the engine lean over on the side stand while you are making the adjustment....hold the bike upright so the cam is oiled properly. Then turn the idle speed back up when you are done. And you can open the mixture screw up a 1/8th turn or so extra to help reduce the backfire - but you really should be jetting for a bike that runs properly when the throttle is open, and ignore what it does when the throttle is closed.

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

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

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hawk41

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Re: Re-jetting after Harley Muffler install
Reply #2 - 07/06/16 at 12:42:31

Thanks for the info! Results are as follows:
1.5 turns - backfires a lot while throttling up
.75 turns - engine dies
2.5 turns - While underway, rolling the throttle off gently to shift, pretty loud backfire almost every shift.

Does this indicate the idle jet is too small? How many sizes up should I go or is that just trail & error.

Is this a typical change when you go to a Harley muffler? Thanks! Huh

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Re: Re-jetting after Harley Muffler install
Reply #3 - 07/06/16 at 13:08:22

hawk41 wrote on 07/06/16 at 12:42:31:

2.5 turns - While underway, rolling the throttle off gently to shift, pretty loud backfire almost every shift.

You need to double check for exhaust leak.

Also, does the HD muff have the straight thru baffle intact?

After you're sure about these Q's, then I'd up size the pilot.

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hawk41 Junior Member Offline SuzukiSavage.com Rocks! Posts: 65 Gilbert, AZ Gender:	Re: Re-jetting after Harley Muffler install Reply #4 - 07/06/16 at 13:14:09 New exhaust gasket and torqued to specs. Bought the HD muffler here on SuzukiSavage.com and it has the straight thru baffle. When sizing up, should I purchase several diff. sizes and experiment? Thanks!
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Kris01 Serious Thumper Offline Eat, sleep, RIDE! Posts: 3767 Tennessee Gender:	Re: Re-jetting after Harley Muffler install Reply #5 - 07/06/16 at 16:57:16 What jets are you currently using?
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hawk41 Junior Member Offline SuzukiSavage.com Rocks! Posts: 65 Gilbert, AZ Gender:	Re: Re-jetting after Harley Muffler install Reply #6 - 07/06/16 at 17:04:00 Don't know yet! Have to study how to remove it! Am I correct in assuming there is only one pilot jet. I am sure there are instructions here on SuzukiSavage.com on the procedure for removal. Just need to find the correct thread. I will post the jet size once I get my hands on it.
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Re: Re-jetting after Harley Muffler install
Reply #7 - 07/06/16 at 17:12:40

Yes, 1 pilot jet, 1 main jet. You'll also want to shim the jet needle. It controls about 1/4-3/4 throttle. That's where you'll spend most of your time.

http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1098869040

http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1157720585

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1309246277

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1221818822/0#0

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1350749896/0

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hawk41

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Re: Re-jetting after Harley Muffler install
Reply #8 - 07/06/16 at 18:45:48

Thanks! Is there a particular size of shim that I need to buy? It does sound from reading the links that you provided that I probably just need to get the next jet size up. It will be interesting to see if the previous owner has changed the factory jet as the plug over the idle screw had already been removed. Just need to find out how to remove the pilot jet and shim the jet needle! Undecided

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Kris01

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Re: Re-jetting after Harley Muffler install
Reply #9 - 07/06/16 at 20:07:11

3 #4 brass washers should do the trick! That's about 2/3 the thickness of the original nylon shim. You can find these washers at larger home improvement stores (Home Depot, Lowes, etc) or you can contact Lancer. He sells a kit that has everything you need. Wink

The original owner of mine had drilled out the pilot screw plug but it still had the stock jets.

Lancer's jet kit:
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1336741909

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zipidachimp Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 1416 surrey, b.c. Gender:	Re: Re-jetting after Harley Muffler install Reply #10 - 07/06/16 at 23:02:32 At sea level, Dyna muff, white spacer 1/2 thickness, pilot 55, main 155, my bike has become a rocket, 95% no backfires! Woohoo!
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hawk41 Junior Member Offline SuzukiSavage.com Rocks! Posts: 65 Gilbert, AZ Gender:	Re: Re-jetting after Harley Muffler install Reply #11 - 07/06/16 at 23:11:10 Nothing about carbs makes sense to me (sh*t, life doesn't make sense to me but what else is new)! So! Are you saying that the shim needs to be "less" in size than the original. "Shims" are supposed to be make something bigger,right? I think it's time for another Gin & tonic!
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Dave YaBB Moderator ModSquad Offline SuzukiSavage.com Rocks! Posts: 18099 Camp Springs, Kentucky Gender:	Re: Re-jetting after Harley Muffler install Reply #12 - 07/07/16 at 03:52:09 hawk41 wrote on 07/06/16 at 13:14:09: Bought the HD muffler here on SuzukiSavage.com and it has the straight thru baffle. Does that mean you can see straight through the muffler....if you look into one end can you see daylight coming from the other end?
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hawk41 Junior Member Offline SuzukiSavage.com Rocks! Posts: 65 Gilbert, AZ Gender:	Re: Re-jetting after Harley Muffler install Reply #13 - 07/07/16 at 06:32:00 Yep! Can see straight thru. How do I get access to the pilot jet, etc.? Do I have to remove the carb or can I do it on the bike?
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Re: Re-jetting after Harley Muffler install
Reply #14 - 07/07/16 at 06:53:56

hawk41 wrote on 07/07/16 at 06:32:00:

Yep! Can see straight thru. How do I get access to the pilot jet, etc.? Do I have to remove the carb or can I do it on the bike? Embarrassed

Well....that is part of your problem. Somebody has knocked the little plate out of the baffle - you should not be able to see straight through the muffler. Halfway down the muffler there is supposed to be a little metal plug - it forces the exhaust to go out the holes into the outer shell, then on the backside of the plug the exhaust comes out of the outer shell and back into the center pipe.....the out the back. Without that plug in the center you don't have a "muffler"....you have a "straight pipe" or "drag pipe". You will never be able to jet your carb to stop the backfiring and noise when the exhaust just goes through a straight pipe.

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