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Pop crackle bang - is it supposed to do that
Topic Started: Mar 4 2013, 07:09 PM (1,469 Views)
Hoggyf
Baron
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Just Ben out on my 644 tonight ( was bloody cold) and its very noisy on the overrun, banging away all the time, my guess is air ingress into the exhaust?

I know they tend to pop and bang on the over run but this constant - any advice
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RB636
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Potato Farmer
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Exhaust air leak? I don't think it'd make too much difference.
As far as I know, the banging/popping happens when you close the throttle whilst moving thus the piston is trying to suck in air 'against' the carb slide. It cannot fill the cylinder quick enough so is at negative pressure. This smaller amount of air/fuel mix at negative pressure gets compressed as usual but because it was at a negative pressure to start with it isnt under sufficient positive pressure to ignite well. The unburnt or improperly combusted mix gets sent out on the exhaust stroke to meet your nice hot manifold or continue burning if already ignited. Remembering as the compression pressure goes up, the mixture burns faster so in this case the the mix burns too slowly and is sent out the exhaust port before the charge is burnt, it finishes burning in your exhaust and pop bang crack.


Sorry that was a bit of an essay...

It also didn't answer your question. Mine popped and banged a lot today as per!
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Rob 110
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God
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fairly normal
but check your jetting if its an aftermarket pipe

easiest way is do a plugchop properly:

put plug spanner in your pocket
warm bike up for 10mins riding
give it a good blat preferably 4th/5th gear up an incline
if safe, then instantly hit the kill switch and pull the clutch and coast to a halt
remove plug (very hot) and check colour

light grey/brown/tan is fine
white is lean, so bigger jets
black sooty is rich, so go leaner (or you didn't do it right and coasted up with engine running ;) )

hth
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Hoggyf
Baron
[ *  *  * ]
Might have to try a plug chop, std pipe, no idea if there's much baffling inside (if they have it) I expected the odd pop and bang but dropping down a hill in 3rd at say 40mph it bangs every second type of thing,
Got to say I'm new to big singles but never heard this before. Not fussed for excessive noise, would rather be a little more stealthy
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bighit
outta here
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Rob 110
Mar 4 2013, 08:32 PM
fairly normal
but check your jetting if its an aftermarket pipe

easiest way is do a plugchop properly:

put plug spanner in your pocket
warm bike up for 10mins riding
give it a good blat preferably 4th/5th gear up an incline
if safe, then instantly hit the kill switch and pull the clutch and coast to a halt
remove plug (very hot) and check colour

light grey/brown/tan is fine
white is lean, so bigger jets
black sooty is rich, so go leaner (or you didn't do it right and coasted up with engine running ;) )

hth
i bought a colour tune kit but did not get the adaptor for the size of plugs on the 644 lol so its never been used

i do a plug chop the same way as you do rob .
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rossonza
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Supermoto Mad
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mine bangs like crazy too!

http://www.facebook.com/photo.php?v=10151335409376299

if that works
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thumb
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Earl
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think most of our bikes pop and bang on the over run, i "shoot" my mate in the chest quite often when he's behind me on a long downhill streach near mine
DIABOLUS FECIT UT ID FACEREM - The devil made me do it !
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stevenfuture
King
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RB636 has got it right, so pour neat petrol into the down pipe & get sheets of flame like us with Big (running rich) Mikuni's on!!! :worthy:
Testiculos habet ingens et bene sedeant
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rossonza
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Supermoto Mad
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anyone kill switch pop?
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wR1sty
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King
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rossonza
Mar 4 2013, 10:52 PM
anyone kill switch pop?
Noooo I never do that :shy:
If your not on the edge, your taking up too much room
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RB636
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Potato Farmer
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rossonza
Mar 4 2013, 10:52 PM
anyone kill switch pop?
I have done on bikes that don't pop and bang anyway, but never on this as the exhaust takes enough of a beating.


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Hoggyf
Baron
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Just a thought, and I know this will go against most of you's principles but I'll whisper it lol

Can I re-pack the standard can to make it quieter? it looks like the std baffle is in there.

I'll stand back and wait for the screams of disgust!!! :poke:
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Monty
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Charlie Big Banana's
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If its the std baffled can then NO, there is no wadding in it, except a 2 ton tube of mild steel full of plates to deflect the exhaust

If its the std race can with a removable baffle the yes

The popping can be reduced a bit by increasing the size of the pilot jets, tho not by much

Popping is std on any large single, enjoy the noise :twss:
If it aint sharp I can play with it
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Hoggyf
Baron
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Baffle looks removable as there's a torx head screw under the tail pipe and diffusers inside, I'll take a pic tonight of the inside if I don't remove it 1st.

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Monty
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Charlie Big Banana's
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If it has a removable baffle, and it has ccm on the side, its the race/straight threw jobby.

This can be opened up and repacked
If it aint sharp I can play with it
My Utube Channel, lots of bike vids here. Subscribe if you likehttp://www.youtube.com/user/choppermark?feature=watch

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Hoggyf
Baron
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Baffle looks removable as there's a torx head screw under the tail pipe and diffusers inside, I'll take a pic tonight of the inside if I don't remove it 1st.

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Alex_H
Earl
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What you can do to help is increase your tickover a bit, won't pop and bang so much but obviously it'll sound a bit quick at idle. You get used to it though lol.
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thumb
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Earl
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rossonza
Mar 4 2013, 10:52 PM
anyone kill switch pop?
used to do that on suzuki gs 550 nice flames out of the piper exhaust - shot the baffle out many a time, had some fun in the 80s. MAD MAX had a lot to answer for
Edited by thumb, Mar 5 2013, 06:35 PM.
DIABOLUS FECIT UT ID FACEREM - The devil made me do it !
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Hoggyf
Baron
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Spent 2 nights polishing up my spare front pipe all nice and shiny shiny from caked in mud to find that the inner manifold allen bolt is siezed solid, the one where its tight against the frame - arghhhh so the end can's getting re-packed , existing front pipe, cleaned up then its all getting re-fitted until I take the engine out next winter to paint the frame.

Gonna clean the carbs out, spray the oil cooler and give it a clean up for summer aand then see if its any less raucous!
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Will
Will
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Would be worth trying to get bolt out when you have got it good and hot, and give it a tap also tightening it slightly sometimes works :chin:
ccm 644ds 2007 trf
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