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RipGroove99

Excessive popping on deceleration? (Video)

27 posts in this topic

New to dirt bikes/supermoto so need some pretty basic instructions! I have a wrf450 (2003) that pops alot on deceleration. Exhaust is repacked (Akra) so am looking for info on setting the mixture and idle as i think this might help? As it is it pops and bangs really loud

http://www.youtube.com/watch?v=rqLBuOUEVMA&feature=youtube_gdata_player

Edited by RipGroove99

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Decel popping is normal when you have a open exhaust. Your bike also has a ACV (Automatic Coast Valve) that you should check (follow the manuals procedures). Also confirm you have not exhaust leaks.

If your bike idles properly, it is not the fuel mix. But this is the procedure:

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

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Thanks! Have just put gasket sealant on the exhaust , can't find the check instructions for the acv valve so took the cover off and it looked ok? Will wait for the sealant too set and try it out. I noticed there was no gaskets on the exhaust anywhere? Bike runs just fine other than the extremely loud popping, im pretty confidant that the amount of popping i have is not normal!

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There should be one in the head. It may be there and not apparent due to carbon build up. If the header has been removed mutiple times, it can be simply a bit crushed and shot. Easy test is to fire the bike up, hold a towel over the end of the muffler and listen for hissing. There should be none.

Go Here and D/L the service manual, it will tell you about the ACV.

But decel popping is normal with a open pipe. Loud fast and slow.

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Thanks again for the info. Just uploading a video of the bike decelerating, will link it shortly when its up.

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Here's a video of the bike decelerating through 4th 3rd and 2nd. The video really doesn't capture the sound at all (mobile phone)but gives you an idea of the frequency of the popping.

http://www.youtube.com/watch?v=rqLBuOUEVMA&feature=youtube_gdata_player

The video may not be available to view yet as i've only just uploaded it from my phone, also it may take a little while longer to be available in HD.

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Another .02 to spend. how long has the gas been sitting in the tank?

My 560smr has an Akro exhaust and popped alot on deceleration with old gas. I drained the tank and put fresh 91 and the popping stoped.

Also I believe Akro has a grease sealant they recomend using where the head pipe connects to the header and the muffler. your susposed to reapply when you reinstall the exhaust. Hope this helps a little

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Another .02 to spend. how long has the gas been sitting in the tank?

My 560smr has an Akro exhaust and popped alot on deceleration with old gas. I drained the tank and put fresh 91 and the popping stoped.

Also I believe Akro has a grease sealant they recomend using where the head pipe connects to the header and the muffler. your susposed to reapply when you reinstall the exhaust. Hope this helps a little

It had fresh fuel yesterday, bike has been uses regularly for the last 7 months. Will look into the grease, but i did apply sealant to the whole exhaust yesterday which made.no difference at all.

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Still have excessive popping with stock exhaust. Although nowhere near as loud but that's down to my really really loud Akrapovic amplifiying the popping. Strangly didn't notice any power loss at all between stock and a full titanium Akrapovic?

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That sounds pretty normal to me. As long as you don't hear ones that sound like a shotgun being fired you'll be ok.

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Still have excessive popping with stock exhaust. Although nowhere near as loud but that's down to my really really loud Akrapovic amplifiying the popping. Strangly didn't notice any power loss at all between stock and a full titanium Akrapovic?

How is your header crush washer?

Have you done a 'spray' test using brake cleaner, to all intake and exhaust junctions?

What happens, while running, if you turn the fuel screw out one turn?

May have to do this while moving, to prevent stalling.

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Cool, maybe it just seems worse because the exhaust is REALLY loud. I can't seem to pack it properly. Last time i used Simmi racing blanket packing and followed advice on packing but its still far too loud. There's no way its under 94db. The video really dosent pick up un the sound of this thing.

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How is your header crush washer?

Have you done a 'spray' test using brake cleaner, to all intake and exhaust junctions?

What happens, while running, if you turn the fuel screw out one turn?

May have to do this while moving, to prevent stalling.

Hiya, couldn't see any washers or gaskets on the header, don't know how to do a spray test. Will try the screw when out next, do you mean the big black one that adjusts idle?

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Do not set the fuel screw for anything but a perfec idle. Usng the pilot circuit to deal with decel popping is the wrong way to do things. Set it for a perfect hot idle and leave it alone.

See post #4 regarding the gasket.

Check your hot start too for proper setting.

If you have a vacuum leak, it will make setting the fuel screw difficult if not impossibe. To do a spray test, you spray the intake manifild (between the carb and the head) with a non-flammable chemical (like wd40). If the engine speed changes, you have a leak.

I am positive your excessive popping is muffler related. Is the packing fresh? It only lasts about 10 hours in an aftermarket can. The more open the can, the louder the popping.

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Ok thanks, some good info there, Will work with that lot and post back. Thanks! The packing is probably due but it was exactly the same when it was fresh.

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My 09 yz450f has always done this and i have messed with everything,live with it brudah no big deal.

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Would a high idle setting cause excessive popping? Just been out real quick and warmed it up and set the idle very low and it reduced the popping quite a bit. Will get the exhaust packed again and see what its like then.

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A open exhaust will do it. You have a race bike. You have an open pipe. decel popping is fact of life. If you ride like it was designed to ridden, the decel popps will be minimal. If you putt about and coast, expect them.

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A open exhaust will do it. You h
ave a race bike. You have an open pipe. decel popping is fact of life. If you ride like it was designed to ridden, the decel popps will be minimal. If you putt about and coast, expect them.

lol i definitely ride it like its supposed to be ridden! My exhaust has always been louder than any others I've seen so i think its just amplifiying the sound. Am going to re pack it a bit tighter than last time and see what its like Its also always had a harsher sound, others seem to have a softer sound where mine barks and cracks for some reason.

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