Jerky ride on new Dynas

[dickey]

I bought a new FXDI35 anniv. in '06. From new, the bike had a jerky ride when you tried to cruise at a steady speed. It was barely noticeable, but it was there. Sometimes worse than others,sometimes hardly there at all,but always there. No dealer could tell me what it was, let alone fix it. Some techs couldn't even feel it. Finally sold the bike in disgust. 2 years later, I buy an '08 FXDC, same problem--jerky ride when cruising at a steady speed below 40mph--highway speeds no problem. Went the race tuner route,tried different belt adjustments,nothing could get rid of it. Finally sold THAT bike in disgust, went back to a carbed Softail ('04 Fatboy) That bike rides smooth as silk. I was wondering if maybe the jerkiness was caused by the Dyna's rubber mounted motor flexing in the frame, since the Softails doesn't do it,or is it the EFI. My carbed Dynas never did it,neither did my Softails; just the injected Dynas. Anybody know?

[BVBOB]

Originally Posted by dickey

I bought a new FXDI35 anniv. in '06. From new, the bike had a jerky ride when you tried to cruise at a steady speed. It was barely noticeable, but it was there. Sometimes worse than others,sometimes hardly there at all,but always there. No dealer could tell me what it was, let alone fix it. Some techs couldn't even feel it. Finally sold the bike in disgust. 2 years later, I buy an '08 FXDC, same problem--jerky ride when cruising at a steady speed below 40mph--highway speeds no problem. Went the race tuner route,tried different belt adjustments,nothing could get rid of it. Finally sold THAT bike in disgust, went back to a carbed Softail ('04 Fatboy) That bike rides smooth as silk. I was wondering if maybe the jerkiness was caused by the Dyna's rubber mounted motor flexing in the frame, since the Softails doesn't do it,or is it the EFI. My carbed Dynas never did it,neither did my Softails; just the injected Dynas. Anybody know?

My 06 Dyna was the same story, on the ride home from the dealer I finally used the throttle lock to test it because I thought I was pulsating the throttle, I believe the reason for this mainly is the lean mixture coupled with the higher gearing of the 6 speed, after installing the SERT and tuning with a map that eliminated the 02 sensors I had no problems at all, eventually I built the bike into a 98 and have no surging issues at all.

[dickey]

Yea, I went the SERT route;gave me fantastic acceleration,power,and torque,but did absolutely nothing for the surge. I think what I was feeling was either the motor flexing in the frame being transferred to the drive, or possibly something to do with the automatic primary chain tensioner. My 3 carbed Dynas,however,did not do this. I rode several HD's at the demo rides in Daytona this year, and it seemed like only the Dynas did this;the Softails were smooth without a hint of surge. Of course, it's possible that the counterweights in the motor helped to balance out the surge. It's a mystery to me, and although I don't have a Dyna anymore,and I love my Fatboy too much to ever sell it, I might someday like to own another Dyna, but I am hesitant because this problem makes the bike very unpleasant to ride. I did notice,however,that using the throttle lock DID help somewhat with the surge;maybe it's due to an overly-sensitive throttle with the EFI

[84FXRP]

Originally Posted by dickey

I bought a new FXDI35 anniv. in '06. From new, the bike had a jerky ride when you tried to cruise at a steady speed. ... ....,or is it the EFI. My carbed Dynas never did it,neither did my Softails; just the injected Dynas. Anybody know?

My 05 FXDI does NOT have a surge and I know about SURGE from a BMW R1100RT that I once owned. My opinion is that the surge on the HD is the result of the CLOSED LOOP fuel injection (Oxygen sensors in the exhaust pipe) on the 06 and later bikes.

My R1100RT also had a closed loop fuel injection system. When the O2 sensors read a LEAN condition they richen the mix and when they read a RICH condition they lean the mix. The problem was that the computer didn't react so as to give a smooth fuel delivery. The transition from LEAN to RICH to LEAN to RICH was too abrupt and you got a "surge" most notable at a steady throttle position.

The 05 FXDI has an OPEN LOOP fuel injection (no O2 sensors) and fuel delivery is calculated from a "map" within the engine management computer. This "map" results in a consistent fuel delivery given sensor inputs of temperature/load/atmospheric pressure/etc and that consistent fuel flow means NO SURGE.

[murphdog]

My '07 surged at steady throttle after changing mufflers, air cleaner and Race Tuner download. I bumped the closed loop bias up until the surging went away. You have the option of running closed loop or not as well as making closed loop richer or leaner.

[dickey]

Well, I had the SERT installed;oxygen sensors turned off,SEII slip-ons,and K&N, and it made absolutely no difference in the surge. The bike accelerated strong & smooth, but the minute you tried to ride at any steady speed under,say,around 40mph,you got a jerky ride. I almost think it might be the rubber mount,'cause like I said before,I've never felt the jerkiness in a Softail,but have felt it in Dynas and my friends wife's Nightster.

[claydbal]

we are not lugging are we? of all the injected motors i have built and tuned, never had this problem.

what gear are you running at steady speed---40 mph? 2nd? 3rd?

[gizz46]

Had a frind had this and it was the rear belt to tight!!

[dickey]

No,definitely not lugging (it was my 17th Harley,so I have experience) It would do it no matter what speed or gear I was in. Tried loosening the belt--made no difference. I'm thinking it was the motor-flex being transferred to the final drive, And like I said,had it to 5 different HD dealerships. Most of the techs AND NONE of my friends who rode it could feel it. Sometimes it was worse than others;sometimes barely perceptable,but it WAS there. Softails DO NOT do this!

[towboattrash34]

mmmmmm haven't noticed that on my 06 dyna lowrider

[Orange1200R]

No surging but mine is far from stock.

[C-Cat]

no surging when i was stock, stage 1, or 103 upgrade ever. my neighbor let me try his 103 dyno and no surging there either. both bikes are 07's and i went from stock, to t-max on stage 1 and 103, then went to tts mastertune on 103, never experienced it. haven't tried any newer soft tails, or baggers.

[splatter]

I've read that veteran Harley riders have this problem with the new bikes because they're used to running lower RPMs. The 96" six-speed bikes have higher gearing than the bikes that came before. I've heard riders talking about "winding out" their bikes at 3,000 RPM -- it's hard not to laugh. 3K is a low shift-point on the newer bikes.

[Huck Finn]

I don't notice any surging issues with my '09 RK — not a dyna but essentially the same motor.

[rastas]

The surging was due to the injectors they used in the 06 model dynas(it was a running change later in the year).I had the surging on my 06 street bob and had the dealer change them to the 25 degree injectors as per the service bulletin.It fixed the problem.