Collector boxes - Really good news

Sean Kelly said:
It's seems to me that many big twins from other manufacturers use a 2 into 2 or 2 into 1 into 2 system. I know the requirements of a 916 or SP1 are different to a gs but a 916 ain't short of low down grunt. I've always liked the look of the Gaston Rahier PD setup too. I wonder if someone like Arkwrights chap could come up with something well designed to work with a boxer rather than a v or parallel twin.
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There can be a bit of a problem with the 2 into 2 system even with a balance pipe in that they lack back pressure and therefore tend to be less economical.

I've had that trouble with the Caff Racer so I've now got restrictors in the end of the back end of the headers which seems a bit better!

We shall see.
 
There is nothing that difficult about exhaust design - Phil Irvine's book Tuning for speed has the formula and a worked example for a 500 cc cylinder - and the book is online so you dont even need to buy it.

Dave Visard's book- how to build horsepower has useful information too, but a revised edition is still in print so you might have to buy it.
The self styled instant internet experts like the loudmouths over on ADV are probably the least useful - one guy who claimed to be a qualified design engineer didnt even know that the speed of sound in air was different the speed in exhaust gas , and they all seem fixated with long equal length headers which , on a road system, probably dont work that well in the rev band you will be in 95% of the time.
And none seem to understand what a balance pipe actually does.

Almost every system will have its sweet spot, where it works best, and the most unlikely looking system can work very well in the range you use most on a road bike.
Those with long memories might recall the high level "Siamesed" systems fitted to Brit twins like the Triumph Trophy, etc in the early1950's.
They were small diameter, just about as uneven length as you could get, ran into a small restrictive muffler and made a swag of power right where you wanted it, in the 2500/5500 rev band.

If you can find Dunstall replicas with original pattern internals they work very well, and a 38 mm system the correct length with a balance pipe and a pair of Dunstalls should work very well if everything else like the air box, carb size and jetting matches too.
Just dont expect it to work as well as it can if you change one thing like a Y piece and leave everything else the same - it just isn't going to happen!
 
Rob Farmer said:
It ran well until you loaded it up at which point it just ran out of steam but then every 80 I've owned has been like that.
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True. Hence why I Seibenrocked it up to 1000cc, so it does have a bit of stomp and can hold a higher speed better. Its good and torquey and a right hoot, but rolling on the throttle just where you need it for faster overtakes shows up some shortcpoming somewhere in the system.....I suspect the increase in cubes may have compounded the midrange black hole issue despite Seibenrocks claims that rejetting (im on leaner US jets I think) is not required. Hmmmmm.............
 
Migsel and myself swapped bikes a few years ago on Salisbury plain, both mono g/s but his had a siebenrock kit, we did a side by side acceleration test. There was nothing in it speed wise but his had noticeably more torque in the mid range on the road. I suspect youd get more umph by increasing the inlet valve size and jetting as a us 1000gs but you'd be better off talking to Richard Moore about that.
 
I tried the lean US jetting on my 1000 cc G/S which was converted with new factory parts, but found that the richer 150/2.68 jetting worked better with the way my bike is set up.
Runs cooler too, which is important in a country where you are regularly riding if temps well over the old ton, and I actually use it as a G/S and get of the bitumen as much as possible and slow speed low gear work gets the temps up a bit too on lean jetting.
Fuel consumption is a little better too, so there doesnt seem to be any downside, but I dont know what sort of pretty patterns it prints on the dyno/AFR meter so I may be missing out on something there, but I can live with that as long as it goes better on the road.
SS 100, roll on performance is mostly affected by needle and jet type and needle position, slide spring strength , and simply that you are opening the throttle too quickly.
Remembering that there is no direct connection between the carb slide and the twistgrip and you have to manipulate the slide position and the mixture strength another way is a help when it comes to tuning a CV carb.
 
Beemerboff said:
I tried the lean US jetting on my 1000 cc G/S which was converted with new factory parts, but found that the richer 150/2.68 jetting worked better with the way my bike is set up.
Runs cooler too, which is important in a country where you are regularly riding if temps well over the old ton, and I actually use it as a G/S and get of the bitumen as much as possible and slow speed low gear work gets the temps up a bit too on lean jetting.
Fuel consumption is a little better too, so there doesnt seem to be any downside, but I dont know what sort of pretty patterns it prints on the dyno/AFR meter so I may be missing out on something there, but I can live with that as long as it goes better on the road.
SS 100, roll on performance is mostly affected by needle and jet type and needle position, slide spring strength , and simply that you are opening the throttle too quickly.
Remembering that there is no direct connection between the carb slide and the twistgrip and you have to manipulate the slide position and the mixture strength another way is a help when it comes to tuning a CV carb.
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Thanks BB, I am thinking along the same lines. Good point about richer runs cooler - I too green lane/trail ride the G/S and certainly in the occasional slightly more tepid months that we have here that pass for a "summer" it runs a fair touch too hot for my liking (even with an oil cooler). At the next oil service I think I will at least pull the Bings and give them a decent refresh, certainly jet up to Euro sizes and see how we go.

Then at some point there is the front part/collector box of the exhaust to sort, then the cam chain, the cam front bearing, then while im in here I might as well pull the cam/lifters, then have a look at the bottom end, and not forgetting the gearbox which is abut to ingest itself.......etc etc:rolleyes:
 
Ooh ooh my collector boxes have arrived!
Bet I'll need seals ?
I'll be picking them up in a day or two :aidan
 
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There are much better solutions than plated mild steel collector boxes and cheaper!
 
Arkwright said:
There are much better solutions than plated mild steel collector boxes and cheaper!
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I read your earlier postings....but I have a Keihan 'Y' piece and although it does what it say's on the tin, from reading on here the collector box (hey, Captain Black has even offered this scouser a 1 day permit to visit Manchester BMW to buy one :friday ) should make a nice difference.....plus the OE collector boxes last at least 15 years and I'll be well past my sell-by date by then ( so if anyone want's to buy a Y piece, let me know ! ).
 
Arkwright said:
There are much better solutions than plated mild steel collector boxes and cheaper!
Click to expand...

Dyno figures or I call bullshit!

Chrome plated collector boxes are never going to be ideal. In an ideal world they would have been stainless. My last one that I bought new and rode all year round on lasted 9 years but at least the bikes run well on them, don't need any jetting etc
 
I wasn't referring to Keihan 'T' pieces, they're even worse.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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