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Exhausted B175
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Bee175
Felixstowe, Suffolk
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July 10, 2019 - 12:12 am
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After a long fight (a few years) trying to get my friends B175 to run well, and after spending too much money on things that didn't fix it, today, we fitted my silencer (from my B175) to his bike. Job done, goes like a rocket now and sounds lovely and crisp too. 

Both my silencer and his are new within the last 4 years. They are both different internally though. At the front of mine there is a raised honeycomb section that goes for about 6 inches. Further down I can see the first baffle plate has 2 holes of around 10mm. My friends does not have the honeycomb section and his 2 holes are probably about 7mm. Our baffles are welded into place so I can't describe them beyond that, but the differences in our 2 silencers is the difference between a great running Bantam and one that runs poorly.

The reason for my post is to point out how important it is to have the correct silencer giving the correct back pressure and allowing gases to escape at the correct rate. It might be worth people keeping this in mind when all else fails to get their Bantam running well.

I have no idea why these 2 new pipes would be manufactured in different ways, but I have to say that buying our Bantam spares has been a lottery over the years. For us it's been a less than 50% chance that the bought item fits and/or works properly.

If only there was one wonderful shop that we could all rely on for proper good quality spares, and if I ever find it, I expect I will wake up to find it was all a dream🤣

So be warned, don't get exhausted when fixing those Bantams!

BSA Bantam B175 1971 and BSA C15 1966

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Bee175
Felixstowe, Suffolk
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July 10, 2019 - 9:22 am
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Perhaps honeycomb was the wrong word. 20190709_174452.jpg

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BSA Bantam B175 1971 and BSA C15 1966

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SpacedMarine
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July 10, 2019 - 10:35 am
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I reckon you could add 50% extrapower with a well designed expansion chamber never mind a cigar shaped exhaust 

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I'm tempted to try one of these just for that reason 😁

What's 7/16 in mm again?

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mike p5xbx
E-Sussex
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July 10, 2019 - 5:13 pm
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you could always fit a Suzuki X7 silencer supposed to give another 10mph
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personalty I would rather fit a genuine old BSA silencer no matter what the condition in preference to any new Pattern one

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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not henpecked
Near J 11 of M42
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July 10, 2019 - 6:10 pm
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Hi Bee175

So the question is if both of the silencers are relatively new where did you get them from? I have just recently got my B175 on the road after a rebuild and fitted an complete Armours exhaust system but don't know how it will perform since I'm running in. So far I've done 130 miles and the engine seems to run and perform very well.

I need at least 500 miles on the clock before I dare open it up to see how it goes....! More later

B175, being updated & now much closer to completion. Honda XBR 500, and ....... Suzuki Burgman 200 scoot! Nicknamed "The hair dryer" - by me I hasted to add; & great storage under the seat when you get to your destination.

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Bee175
Felixstowe, Suffolk
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July 11, 2019 - 12:12 am
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Hi not henpecked.

Once run in, if you find that the bike is not overly keen on revving at the high end, then it might be worth having a look at your silencer to check it out. My friends bike could be made to work "better" by weakening the carb in all areas, although it still wasn't running great like that.

My friend is currently talking to Armours and Burton Bike Bits. It seems that BBB has the same exhaust as mine exactly, but we are still comparing notes with him to make absolutely certain it is the correct one before shedding pound notes.

Armours is a different set up altogether and has 4 baffle plates, each with a 1/4 section bent over at various angles to control back pressure. These are removable and adjustable baffles, so offer a good degree of tuning. 

However, I suspect my friend would choose the BBB pipe if it turns out to be exactly the same as mine. 

My friends old pipe came from Classic British Bike Spares. I personally think it is for a different model of Bantam.

Mine came with the bike but was brand new. I bought the bike from NSA Motorcycles Ltd, and he was a Bantam spares retailer, so may well have fitted the pipe from his own stock. On Google he is listed as permanently closed, but I wrote to him using his old contact details asking for help, but as yet I've had no reply.

I am still in shock at the vast difference between the two silencers, but very pleased we've finally sussed out the problem😃

It really is worth people bearing this in mind when fettling and tuning their Bantams. 

Gary. 

BSA Bantam B175 1971 and BSA C15 1966

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nickjaxe
Runcorn Cheshire UK
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July 11, 2019 - 7:49 am
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Gary you say.

"Armours is a different set up altogether and has 4 baffle plates, each with a 1/4 section bent over at various angles to control back pressure. These are removable and adjustable baffles, so offer a good degree of tuning"

This design sound more or less the std B175 BSA design Gary.

My Bantam video              https://www.you.....jpOFmzRZRI

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not henpecked
Near J 11 of M42
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July 11, 2019 - 9:11 am
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Hi All

I went out with my local motorcycle club last night for a fish & chip run and on the odd occasion missed a gear change and the engine revved very well. However, this is a no load condition and I'm sure any engine will rev with no load.

Running in (170 miles so far), I'm keeping my right hand under control and using between up to 3/8 throttle for pulling away and increasing speed and about a 1/4 for crusing so difficult to say how my B175 will run at higher openings. Crusing speed is around 40 MPH on the level, up to about 45 MPH down hill, but on any incline slows and I change down so as not to load the engine too much.

Don

B175, being updated & now much closer to completion. Honda XBR 500, and ....... Suzuki Burgman 200 scoot! Nicknamed "The hair dryer" - by me I hasted to add; & great storage under the seat when you get to your destination.

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Bee175
Felixstowe, Suffolk
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July 11, 2019 - 9:30 am
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Hi Don.

I agree entirely about high rpm under no load. A totally different scenario when the engine is loaded up.

You're running in procedure sounds very sensible. Personally I might be going a tad faster on the flat so that the extra wind resistance forces me to keep the throttle open a little wider giving a little more cooling fuel and lube. Like you, I would change down early for inclines, in fact that's how I ride when I'm not running in. Much kinder to the engine.

I don't think Nickjaxe will mind me divulging his secrets, but I know that on declines he will occasionally open the throttle wider than necessary to put some fuel in for cooling. He used to run with an EGT sensor attached and said the difference it made to the temp was significant.

BSA Bantam B175 1971 and BSA C15 1966

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