SuzukiSavage.com - Bogging down at stop after dyna + carb rejet

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Bogging down at stop after dyna + carb rejet (Read 15 times)

motobutch

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Bogging down at stop after dyna + carb rejet
Yesterday at 06:26:43

Hi All,

I ride a 1998 savage and recently did the harley dyna muffler swap and rejetted the carb to 52.5 pilot and 152.5 main. I replaced the white spacer with 3 washers and have the mixture screw out about 1.5 turns (I ride at sea level). For the most part it's been riding well, but sometimes when I slow down quickly and stop, the engine RPM drops really low (and has died twice). If I give it a tiny bit of gas when it's bogging down at a stop it will recover after a few seconds and idle better without needing any throttle.

I have also noticed that it idles best when starting from cold, but as it warms up the RPMs drop. This makes me think it might be running rich and the pilot jet is too big (I don't wanna go under 1 turn on the mix). However, when I start opening up the throttle and going from the pilot circuit to the main in second gear, the bike feels really lean in the 1/8-1/4 throttle zone (where it sometimes backfires), making me think the main is too small? This is my first time tuning/rejetting a carb and am looking for pointers on where to start troubleshooting Huh

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Serowbot YaBB Moderator ModSquad Offline OK.... so what's the speed of dark? Posts: 29792 Tucson Az Gender:	Re: Bogging down at stop after dyna + carb rejet Reply #1 - Yesterday at 09:23:55 My tips Serowbot's carb tuning tips for beginners http://suzukisavage.com/cgi-bin/YaBB.pl?num=1309246277
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DragBikeMike

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Re: Bogging down at stop after dyna + carb rejet
Reply #2 - Yesterday at 13:25:55

Motobutch, my experience with the engine dying under hard braking is that it can be related to float level. Too high or too low can both cause the engine to die under rapid deceleration. Same goes for hitting a big pothole or other abrupt obstacle.

I have seen some Mikuni VM carbs that have a special brass baffle that surrounds the main jet in the bottom of the carb. That baffle is meant to mitigate fuel slosh during abrupt maneuvers. The Keihin PWK carbs come with the special baffle built into the metering block. Try and check your float level.

Hey Serowbot, pretty cool tutorial. You put a lot of work into that. Nice job.

Knowledge is power.

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Re: Bogging down at stop after dyna + carb rejet
Reply #3 - Today at 04:01:12

The bog just off idle is not likely related to your main jet - it is most likely the needle. The needle has more affect on the mixture at very low throttle opening.

For my riding area of 500-800' msl a #52 or #52.5 pilot and #150 main works best with the Dyna muffler. The white spacer is replaced with 3 machine screw washers or the spacers made specifically for the needle that you can get from folks that sell Mikuni parts.

My bike didn't like 3 washers and it had a uneven surge at very low throttle settings.....(like when you are riding through a School Zone and the Police are watching you). I removed one washer from the needle and tried 2 - and it ran great.

To adjust the fuel mixture screw you need to drop the idle speed down to around 800 rpm before you will be able to hear any noticeable affect while you turn the screw in/out. (When the idle speed is up at the normal 1,100 rpm the slide is going to be lifted slightly and you will have some fuel coming out of the needle jet, and this makes it impossible to get an accurate adjustment on the idle mixture screw). With the bike fully warmed up and the bike held upright between your legs - drop the idle down and then adjust the fuel mixture screw until the bike runs the smoothest. IF your screw can be turned all the way in and the bike does not begin to run rough - the pilot jet is likely too big - if you can turn the screw out more than 3.5 turns and the bike is not idling too rich - the mixture screw is too big. (NOTE: The #50 or #52.5 pilot jets are going to be very close to what the bike wants and really won't show any extreme lean/rich issues). With the stock airbox and Dyna muffler you should never need a #55 pilot jet. Once the smoothers idle is obtained by adjusting the mixture screw - turn your idle speed back up to 1,100 rpm minimum. (NOTE: Turning the idle fuel mixture screw out more than 3.5 turns does nothing to increase the fuel flow....after 3.5 turns the screw is out of the hole so far that the flow is maximum and additional turns have no affect).

Someday I will be old......But not today!

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