Hitchcocks Forum

since fitting the correct inlet valve to my 500cc Indian bullet much has changed. i have increased power, speed, noise, and i have no figures for mpg as yet. This message is on the noise topic as I fear my new found compression has meant my little Indian has crossed over the obnoxious line.



I'm still working on the carb setup but what to do with the baffle. I once strayed upon a web site that sold pieces of wool fabric for quietening the bike. No idea where that site was. My exhaust from our beloved hosts has one of their baffles fitted which has numerous tabs along with a straight through pathway. If i close the tabs I open the straight through. Think i might put a coin (foreign obviously) in to restrict the straight through.



Has anybody been down this path? If I mess with the exhaust that'll effect carb again but I'm still tuning anyhow. Love to hear thoughts. Old wooley sock?

Hi JFW ----------------- Have a look at this }----http://www.ebay.co.uk/itm/Exhaust-End-C ... Parts_Vehi ----- and this }--------http://www.ebay.co.uk/sch/i.html?_trksi ... &_from=R40 ----------------------- or just put "motorcycle exhaust baffle" into E-Bay search. That should keep you busy for a while ??

Thanks Alan never thought of ebay at all, paypal is always a struggle. Thanks a million for the pointer

Not so "Baffled"??? now----- my pleasure !!!

I've made the exhausts for my bikes and they are basically hollow. The way I've made them moderately couth is by making a piece a of blanked off pipe the fits snugly into the end of the header pipe where it goes into the muffler. It then drilled enough holes in it to equate to the size of the hole in the header so there is no actual restriction but more of a diversion. Works well the bikes is sporty but not rowdy.

Hello SIMON----- as an extension of your idea I wonder if fitting our hosts "Baffle" at the input side of a silencer rather than at the outlet side would have the same type of results ?? Anybody done this at all ???

Probably the biggest problem with getting a quieter exhaust note is the actual internal volume of the silencer. All the Enfield silencers sold are very small and there is just not enough volume to allow a good expansion of gas to buffer the output pulse. Fitting highly restricting baffles simply raises the flow restriction and raises the average pressure which "squashes" the output pulse and quietens the sound however that increased back pressure prevents good scavenging and looses power. Simons method of having a drilled output tube will have some quieting effect as will having absorbent material wrapped round a perforated straight through pipe (Goldie style), but nothing is going to compensate for the lack of volume. Many classic bike exhaust pipes are sold open ended whereas the original design was usually longer and had a sealed end with 6"-8" of the pipe fitting inside the silencer and this section was drilled radially which diffused the exhaust slug. This gives a much softer tone with the correct silencer. However there is still a fairly hefty output slug of gas which is why the fishtail end piece was designed. The Velo fishtail item is drilled at the side of it with about 50 small holes and at the pinched end has 4 flattened output slots. This combination breaks up the output pulse and also causes high frequencies to be cancelled out due to phase differences. Incidentally, the Velo silencer has a very large capacity which can absorb and buffer the pulses and it’s probably twice the volume of an Enfield silencer. Not that long ago, I suggested that twin silencers could be tried for owners who would like good performance but with a well rounded exhaust note to avoid annoyance to neighbours. I was hoping that Mr H might give the idea a go but nothing as yet. So it is a matter of physics which cannor be bypassed, to silencer a 500 4 stroke single efficiently (acoustically wise) without robbing too much power requires a large capacity can in effect to act as a short term gas storage vessel or buffer and then have a set of baffles that can break up the solid pulse without creating too much back pressure.

CORRECTION: "which cannot be bypassed, so muffling a 500 4 stroke single efficiently... etc etc."

Hi Alan, I do put them in the input side. I pinched the idea off the old AMC type muffler. If I pull off the muffler body so to speak the header pipe is sitting there with a baffle poking out the end. The plan was that if the input side wasn't enough I could stick one in the tail pipe side but it wasn't necessary.