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Author Topic: Back fires and surges at low rpm  (Read 12699 times)

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crunch29

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Back fires and surges at low rpm
« on: May 02, 2010, 09:05:56 AM »

Over the winter I had my modifications done. Basically I copied Steve's stage 2 mod with the exception I had D&D fat cats installed. My bike runs good above 1800-2000 rpm.
The dealer I purchased my 2010 seuc from has in the shop again (3rd time).  This time as I explained what it was doing, which is if you accelerate while in 2nd gear at about 1500 rpm it will surge and backfire. The service guy said I need to shift down and not lug the motor. He went on to say that the idle spec is 900rpm to 1200 rpm and it won't likely run well until I get up in the 2000rpm range.  By now I was pissed, I explained to him my other bikes didn't do this and this bike didn't do it until I had my modification done.  So when I left I got the feeling that they won't have it fixed and am going to have to find someone else to fix it. At this point if I need to change out or add some parts so be it. I just want a good running bike.

I've even been second guessing this and wonder if the service tech was right about not lugging the motor? Has any experienced this? I'm sure some of you have completed nearly the same modifications, does your bike fine if you accelerate while in second gear at low rpm?

Guys any advice on this matter would be appreciated.

Crunch
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Mr. Wizard

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Re: Back fires and surges at low rpm
« Reply #1 on: May 02, 2010, 09:55:37 AM »

Over the winter I had my modifications done. Basically I copied Steve's stage 2 mod with the exception I had D&D fat cats installed. My bike runs good above 1800-2000 rpm.
The dealer I purchased my 2010 seuc from has in the shop again (3rd time).  This time as I explained what it was doing, which is if you accelerate while in 2nd gear at about 1500 rpm it will surge and backfire. The service guy said I need to shift down and not lug the motor. He went on to say that the idle spec is 900rpm to 1200 rpm and it won't likely run well until I get up in the 2000rpm range.  By now I was pissed, I explained to him my other bikes didn't do this and this bike didn't do it until I had my modification done.  So when I left I got the feeling that they won't have it fixed and am going to have to find someone else to fix it. At this point if I need to change out or add some parts so be it. I just want a good running bike.

I've even been second guessing this and wonder if the service tech was right about not lugging the motor? Has any experienced this? I'm sure some of you have completed nearly the same modifications, does your bike fine if you accelerate while in second gear at low rpm?

Guys any advice on this matter would be appreciated.

Crunch

This is the correct answer...  Unless I have 2000 RPM's or better my clutch is not engaged. Below 2K is lugging and very hard on your motor. You don't have to ride it like you stole it but do keep the RPM's up. Keep your cruising range RPM's from 2500 to 3000 and enjoy that ride.

 :2vrolijk_21:
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grc

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Re: Back fires and surges at low rpm
« Reply #2 on: May 02, 2010, 10:54:39 AM »


I beg to differ, but 1500-2000 rpm in 2nd gear is not lugging the engine.  Lugging isn't a number on a tach, it's a combination of factors including load, rpm, gear ratio, throttle opening, etc.  My question for those who say anything below xxxx rpm is lugging; how do you get from idle up to your magic number of rpm? :nixweiss:

The area from idle to 2000 or even 2500 is one that a lot of so-called "tuners" (I call them something else) ignore.  Find someone who actually knows what they're doing , and not just someone who can hook up the cables to the bike and download canned maps or make wide open throttle runs on a dyno.  Best bet is to find someone with a load cell attachment on his dyno so he can actually do light throttle, light load adjustments without having to use the seat of the pants method, but an experienced tuner can get real close just with seat of the pants. 

BTW, while it isn't necessarily "lugging" to accelerate normally in low gears from relatively low rpm, it isn't very wise to make a habit of nailing the throttle at those speeds, as it's a good way to scissor the crank and beat the snot out of the roller bearings.  Liberal doses of common sense should be applied, but it isn't necessary to ride around using only the top half of the rpm range to protect your engine. 

Jerry
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crunch29

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Re: Back fires and surges at low rpm
« Reply #3 on: May 02, 2010, 11:24:07 AM »

The reason I posted here was for a gut check and realize this could stir a debate.   If the dealer doesn't get it right or what I think is right this time. I'm going to go to another shop or dealer. In Southdakota you are limited. Jerry I had someone recommend the Harley shop in Southbend IN.  Like I said if I'm not satisfied then I'm going to make a road trip. Sort of a second opinion?

Thanks again guys for the advice or comments.
Any shop recommendations would be appreciated.

Crunch
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Re: Back fires and surges at low rpm
« Reply #4 on: May 02, 2010, 11:30:57 AM »

Running at 1500 rpm in second gear is definately lugging the motor.  Just gear down and be done with it if it runs good above that.
I can't run my bike at 1500 in second and it has a perfect tune.

Cheers, Moe
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Chains

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Re: Back fires and surges at low rpm
« Reply #5 on: May 02, 2010, 11:38:09 AM »

I would never run my bike in 2nd gear at 1500 rpm and it runs great, I would consider that a first gear rpm
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Steve Cole

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Re: Back fires and surges at low rpm
« Reply #6 on: May 02, 2010, 12:23:58 PM »

Not to keep the pissing match going about the RPM but the motor should run just fine there when tuned properly. It should not buck and backfire, period. If your lugging it or not doesn't matter, it's about how it runs at 1500 RPM and there is a problem there on this one.
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Re: Back fires and surges at low rpm
« Reply #7 on: May 02, 2010, 12:52:46 PM »

  As stated previously, your bike needs a proper tune.  The presence of backfiring and, or surging confirms there is an issue.  And, it is possible, something other than the tune could be the culprit.  Whatever the cause, backfiring is not an acceptable condition. 
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HOGMIKE

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Re: Back fires and surges at low rpm
« Reply #8 on: May 02, 2010, 02:00:32 PM »

 :2vrolijk_21: :2vrolijk_21:
I can run both the new bikes at 1500RPM, little or no load, flat road.
No bucking, surging, backfiring, etc.etc. Also, no power!
My carb bike will also run at low RPM with no issues, but, all the bikes WILL GET A DOWNSHIFT if I increase the throttle or load!

Usual RPM on the newer bikes: 2000-3000
Carb bike: 2500-3500 (bigger cams, etc) and power/torque band to the "right".

JMHO
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crunch29

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Re: Back fires and surges at low rpm
« Reply #9 on: May 02, 2010, 02:28:30 PM »

When I notice my problemmost is when I'm decelerating and turning a corner, I'm in second gear and role into the throttle.  It will fall off and then surge slightly and pop multiple times unless I throttle back or downshift. I never noticed anything like this on my past bikes. It's not like I run this way often but because my exhaust is on the load side I tend to take it easy within city limits. I should also add my milage is poor, I get around 33mpg. I'm not too concerned with poor milage but I think it's running very rich.

It's a little frustrating as I think it should run with out backfiring.

Like I said if they can't get it I'm going to find a shop that is willing to work on it for a second opinion. If I have to I'd consider some hardware change.

Everyone will have their own opinion and thats OK. If someone has a similar package I'd be interested in hear how there bike runs in the low rpm.


Keith
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Doc 1

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Re: Back fires and surges at low rpm
« Reply #10 on: May 02, 2010, 05:33:14 PM »

Over the winter I had my modifications done. Basically I copied Steve's stage 2 mod with the exception I had D&D fat cats installed. My bike runs good above 1800-2000 rpm.
The dealer I purchased my 2010 seuc from has in the shop again (3rd time).  This time as I explained what it was doing, which is if you accelerate while in 2nd gear at about 1500 rpm it will surge and backfire. The service guy said I need to shift down and not lug the motor. He went on to say that the idle spec is 900rpm to 1200 rpm and it won't likely run well until I get up in the 2000rpm range.  By now I was pissed, I explained to him my other bikes didn't do this and this bike didn't do it until I had my modification done.  So when I left I got the feeling that they won't have it fixed and am going to have to find someone else to fix it. At this point if I need to change out or add some parts so be it. I just want a good running bike.

I've even been second guessing this and wonder if the service tech was right about not lugging the motor? Has any experienced this? I'm sure some of you have completed nearly the same modifications, does your bike fine if you accelerate while in second gear at low rpm?

Guys any advice on this matter would be appreciated.

Crunch

First off your trying to use a map made for Fullsac pipe for you FatCat.....won't work..... try a map in the MT7 Calibration file for a 2 into 1 pipe.
Mr Cole is correct .... the bike won't lunge or surge when the tune is done right. 1500 rpms in 2nd gear is NOT lugging the motor.....1500 in 6th might be another story.....lol
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Mr. Wizard

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Re: Back fires and surges at low rpm
« Reply #11 on: May 02, 2010, 06:27:45 PM »

Although I respect your opinions I would still never try to run my bike at 1500 RPM's with my clutch fully engaged and give it any kind of throttle. Some of you say it's not lugging, some of us say it is. Like Steve, I don't want to encourage a pissing match but this can't be good practice. As far as the popping, agreed, tune issue.

Cheers





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Doc 1

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Re: Back fires and surges at low rpm
« Reply #12 on: May 02, 2010, 06:48:32 PM »

Although I respect your opinions I would still never try to run my bike at 1500 RPMs with my clutch fully engaged and give it any kind of throttle. Some of you say it's not lugging, some of us say it is. Like Steve, I don't want to encourage a pissing match but this can't be good practice. As far as the popping, agreed, tune issue.

Cheers
Mr Wizard....I'm here in Atlanta right now, if you want to I could show you how to ride in 2nd gear at 1500 rpm through a parking lot with the clutch fully engaged....lol....only kidding, however I am here to train the techs at Harley-Davidson of Atlanta this week.
Doc





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hdctss

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Re: Back fires and surges at low rpm
« Reply #13 on: May 02, 2010, 07:18:31 PM »

I try to keep my rpm above 2000 when cruising.  If it is lower than that then I will usually downshift.  My bike, however does not surge or buck even when I am below 2000, but of course if I try to lug the engine to 1200 or so then it will buck if I try to accelerate until I downshift to get it to the proper rpm.
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Mr. Wizard

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Re: Back fires and surges at low rpm
« Reply #14 on: May 02, 2010, 07:20:44 PM »

Thanks for the offer Doc... Ya can't change this old dog's habits so easily. HDA is about 1.5 hours away from me or I'd come say Hey.

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