Hi guys !

I recently helped a friend with his 2007 CVO springer who was looking for more Harley music, less hot engine and more response.

As I use a TFI fuel box on my 07 Night Train with K&N a/c and Khrome Werks mufflers which work great, I've also ordered a TFI box for his bike
but he wanted slash down mufflers, so I've ordered Rush slip ons with 2.00 baffles and a K&N air cleaner.

I've installed all the parts this week and I've triyed to set up the TFI box to avoid the pop on decel and on upshifting at around 2000 rpm with no chance.
After having triyed several different set ups on the TFI box without success, I've called the helpdesk of Dobeck. When I told the guy at Dobeck that I use Rush slip ons with 2.00 baffles, he told me immediatelly that the problem comes from the Rush slip ons and that he receive about 25 calls a week about this problem on every models... As I've read a lot of post on this board regarding pop on decel and Rush slip ons recommendations, I was just wondering if other guy had the same problem and if 1.75 would solve the pop Ã* 2000 RPM ?

Thanks in advance for your help and your answer.

Best regards.

Pierre-Yves

 

I have Rush Slashdown Slipons on my 07 FXSTC and first tried 1.75" and later changed to 1.5" baffles. The engine on my bike is otherwise stock with no modifications to the fuel injection or aircleaner. I get a bit of decel popping on a closed throttle with the engine slowing below 2-2500 revs (no tacho so cannot be sure). The 'decel popping' is not severe; it is not a loud backfire - just popping and gurgling when slowing. It bugs me at times, but, I get used to it. Above these revs when slowing I have no decel popping and if I open the throttle slightly when decelerating at any revs no popping. I have no decel popping when the engine is cold and the choke is operating which perhaps indicates the popping is related to a fueling issue at closed throttle. When fitting the pipes I used high temp. silicone on the joints and later water tested for leaks. I have never experienced a pop on the upshift when accelerating or any other problems ( apart from the decel pop).I always fuel the bike with 98 octane ULP and most of my riding is open road;plug colour is good and consistent with industry manual pictures.

I changed from the 1.75" baffles to the 1.5" in an attempt to increase backpressure in the exhaust to help in stopping a portion of the fuel charge from escaping from the exhaust port and igniting in the exhaust; ie to reduce / eliminate the popping without over quietening the great sound. This change had a slightreduction on reducing the popping and, with hindsight,was probablynot worth the expense or effort to do - although, I was personally happy with the quieter exhaust which makes the bikemore pleasant over long distances to ride.

I would check the fittings of the pipes to ensure there is no leaks and believe careful tuning of the fuel management system you already have will certainly reduce and/or eliminate the popping.

Oh, if you get a piece of your boot on the mufflers do not rub too hard or use abrasive (as I did) as you will quickly damage the chrome.[:@]

cheers,

shep.

 

Hey !

Thanks a lot for your answer !

I'm quite sure about the fine fuel box tunning, but I still have a doubt about an air leak around the slip ons.
I think I'll have to change de exhaust clamp first and then I'll think about smaller baffles.

But I' was very surprised by the answer of the tech guy at Dobeck about the Rush parts as I've never read anything like that on this forums ... and a lot of guys are riding withRush mufflers ...

PY

 

I can't reallycomment on what was said by the Dobeck guy.

The air leak at the clamps is a common problem that effects not only Rush slip ons but all brands of slip on mufflers as a result of fitting. It is my understanding Harley recommends the replacement of the clamps after each use - pretty expensive if you follow this to the letter.

At the end of the day slip on mufflers are not exactly rocket science; a metal tube that contains another metal tube that has holes drilled in it surrounded by non-flammable material to muffle sound. The less restriction the less back pressure and more noise. The design trick appears to be in the qualityof the noise andloudness vis a vis the effect upon performance and engine tune as a result of the reduction in back pressure.The greater the reduction in back pressure the greater effect upon performance; not necessarily always an improvement and sometimes accompanied with engine damage as a result of too lean engine tune. However, I feel sure you know all this and I am probably telling you how to suck eggs.

Ride safe and let us know how you got on with the tune and its effect upon the decel popping.

cheers,

shep.

 

Thanks for the infos Shepo !

I'llprceed step by step, but what I'm sure of is that the fuel box is right settled as the plugs got the good right brown ...
I hope not having to change the mufflers as the sound and the look are very good and exactly what my friend was looking for ... maybe new clamp (I hope this going to do the trick), maybe smaller baffles and the last solution will be changing the mufflers for an other brand ...

I'll let you all know about my progress.

Thanks.

PY

 

PY,
I have the 1.75'swith a Stage 1 mod (Cobra Fi2000) and the pop is exactly as Shepo described. I'm realy getting annoyed with the noise, though,and will probably put the stock mufflers back on this weekend.

Steve

 

Hi Bikeknight,

Thanks for your input ! That's what I'm actually afraid of ... that changing the baffles are not going to cure the pops ...
What about your slip ons clamp ? do you use new onesat each mufflerschanging ? I also have a doubt that new clamps are going the make the whole difference, but I'll try.

 

I wonder what the deal is. I just bought the TFI and was in the markt for RUSH slip-ons. Last thing I want is popping in the exhaust !!!!

Jim

 

I've had the Rush 1.5, 1.75 and 2.0 slip ons, and all of them popped on deceleration and sometimes a backfire as well. My system was well sealed with high temp sealant and new HD clamps and gaskets. I have the SE air cleaner and the stage 1 reflash.
My plugs were running a bit white (lean) so I sprung for a PCIII from FuelMoto with a pre-loaded map. I installed the PCIII and that was the end of the decel popping and banging.
Since then I have played with the fuel settings on the PCIII, and now I have great performance, good fuel mileage and my plugs look perfect.
The map that was supplied had plus 15% fuel from 2000 to 3500 rpm in the zero throttle column. This is what cured the decel popping. I've reduced the 15% to 12% and it still does not pop at all.
The map was a bit "fat" overall and I have since reduced some of the fuel additions in the 2000 to 3000 rpm range from 5% to 20% throttle. This raised my fuel milage from 37 to 41 mpg, and the performance is still exceptional.
I am sold on the PCIII...
I

 

I was considering the PCIII, however very limited funds since I bought the '08 and got 4 mouths to feed. So for now I did the TFI/DFO and getting slip-ons. Then by end of the year SE air cleaner. Got the Dobeck box for 175.00. I'm hoping I will be able to adjust out any popping on decel.

Jim