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Conical hub rear sprocket sizes. #479963 03/05/13 2:33 pm
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looks like the smallest sprocket is 47 tooth.Be nice if a 45 tooth was available...Yes,the chain will come close to the sprocket bolts but a little reworking with flathead Allens can deal with it....
So...is the only option is machining a 45 tooth sprocket from another brand bike to fit?


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
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Re: Conical hub rear sprocket sizes. [Re: ] #480022 03/05/13 8:22 pm
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Alan, Yes,LSR,I'll check your sprocket guys.... The bike has 4.47 overall gearing. I have a 21 tooth gearbox sprocket and the 47 tooth conical hub.With a 120/90-18 26.5 inch tall rear tire that's about 124 MPH at 7000 rpm.Will this bike pull 124 mph or perhaps more RPM at the Ohio mile this summer? I don't know but we have to be options for tuning purposes..
The engine should pull to 7500 rpm in the gears but maybe not on top end.The engine may have enough power to pull top speed at 6800 rpm.
I believe the 650MPG ECTA record at Ohio is 119 MPH.
The rear wheel and tire is something we have and the tire is brand new. So I don't want to lose it and have the expense of a 19 inch rear wheel and new tire for a small gain.The 21 tooth sprocket just clears the case after some grinding.Will have to see what happens as high speed forces get the chain to wiggling like a snake in a hot oven.


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: ] #480038 03/05/13 10:30 pm
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If the wheel was 18 inch and 100 bucks I would go for it.All I do is tell my partner we need it grin
I think I'll cruise eBay and look for one............


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480051 03/05/13 11:51 pm
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Pete R - R.I.P. Offline
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124 mph at 7000 sounds OK.I wouldn't gear it any taller.
Max power will be at around 7000.It would be better for max revs to be a lttle over that,rather than a little under (you'll be making more power,more of the time).

With 4.4:1,I've managed 7,800 rpm in top gear on a quiet back road.The engine wasn't much different on the inside to what you have (650 high-comp,hotter cam).
On the outside,it had 650 Thruxton exhaust system,14" intake length and 932 carbs.

Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480062 03/06/13 1:04 am
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Rebel gears here in the U.S. offer a 46 tooth sprocket:

http://www.rebelgears.com/catalog2012.html

And pre OIF Triumph hubs can be equipped with 43 tooth sprockets.

Btw, I shipped your brake shoes today.


Eric


1971 T120RV (R.I.P.)
1973 T140V/TR7
1993 Ducati 900 SS
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480063 03/06/13 1:07 am
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Bet it wasn't very quiet when you did that

Re: Conical hub rear sprocket sizes. [Re: Mike Baker] #480069 03/06/13 1:28 am
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It was full noise for a minute or so.I might have woken up a few cows and kangaroos that Sunday morning.

Re: Conical hub rear sprocket sizes. [Re: BikeVice] #480108 03/06/13 11:38 am
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BikeVice,thanks....One tooth less is about 3 mph more at 7000 rpm.
I'll stay with the conical rear wheel for now because it's ready to go.
Just have to see how the bike runs. Dyno is good but the real test is on the road.


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480110 03/06/13 12:03 pm
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Hillbilly bike,
The current record for M/PG 650/4 at the ohio mile is 115.454 mph which was set by myself last july when the air temps where around 110 degrees. I run a 19/42t sprocket setup on the A10 and was going thru the traps at around 6400rpms and shifting thru the gears at 7200rpms. Unfourtunatly I will not be able to make the april meet but am definitly planning on june hopefully with the GP carb figured out.

Good luck with the build,

Chris

Last edited by Blown Income; 03/06/13 12:05 pm.

1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
Re: Conical hub rear sprocket sizes. [Re: Blown Income] #480240 03/07/13 11:38 am
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And if it was 70 degrees the record would be higher.....Hopefully we will see you there and both have a run at a new record.
Me talking about 126 MPH is just that ,talk for now.A lot of tuning has to be done.
And 650MPG/4......what does the /4 mean?


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480270 03/07/13 2:41 pm
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The /4 means 4 stroke engine. If it was 70 degrees it would have helped some but at the same time I was having issues with the Boyer cutting out at about the 3/4 mile mark. Have fix that since then(key switch was at fault, have replaced to a waterproof toggle on the bars)
It will be good to have some more Brit iron at the track.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
Re: Conical hub rear sprocket sizes. [Re: Blown Income] #480300 03/07/13 6:01 pm
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One more question....Fuel shut off as in petcock.I know the fuel shut off needs to be within reach of the rider.Is that a "two hand" rule? As in a traditional Brit fuel tank with two petcocks is legal?

Maybe we can draft each other like NASCAR grin


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480310 03/07/13 6:39 pm
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Not sure if thats a "2 hand" rule or not. I have the standard style petcocks that triumph and bsa came with in my Lyta tank and have not had an issue with tech(even at bonneville). I think the best thing to do would be to call Keith Turk(his number should be in the back of the rule book or on the ECTA website)


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
Re: Conical hub rear sprocket sizes. [Re: Blown Income] #480342 03/07/13 9:51 pm
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hillbilly, Im thinking your going to be cutting it close on that back wheel. always have used a disc brake rear wheel even when the class had to use a drum. a bsa quick change hub with little work bolts right to the disk side.guess you have to start some place and can always up grade.


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Re: Conical hub rear sprocket sizes. [Re: phantom309] #480355 03/07/13 10:59 pm
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If the record is only 115 mph,21/47 is already too high.

21/50 would be 116.5 mph @ 7000 rpm,125 mph @ 7500 rpm.

Re: Conical hub rear sprocket sizes. [Re: Pete R - R.I.P.] #480360 03/07/13 11:38 pm
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Originally Posted by Pete R
If the record is only 115 mph,21/47 is already too high.

21/50 would be 116.5 mph @ 7000 rpm,125 mph @ 7500 rpm.


OK,you have experience,I have little with other than stock gearing.If I was drag racing running up to 7500 would be expected....I hear too many broken crank stories if the engine actually will make some power for more than 12 seconds...My rider partner is " Fornicate the torpedoes,full speed ahead till she blows"....50 teeth sprocket it is... :bigt

Phantom; so you think a rear drum only is marginal for stopping at Ohio?




79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480436 03/08/13 11:53 am
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HB, I beleive your rear brake will be fine with stopping at Ohio. Actually, once you go thru the speed trap, when you sit up out of your tuck position the wind drag slows you down very quickly.
I only use the rear brake on my A10 plus you get about 3/4 mile shut down.



1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1970 Triumph TR6C
1972 BSA Lightning LSR Bike
1974 Triumph T150V
Re: Conical hub rear sprocket sizes. [Re: Blown Income] #480449 03/08/13 1:28 pm
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just seems I can punch numbers till hell freezes over and things dont go as planned, I would rather have gearing for anything. if that chain hit on the case you could drop a tooth and go smaller on the back, easy fix, not if you have the conical hub.I dont know what you have for run off to say if thats enough brake. Road racing you could take the rear brake off and I wouldnt know it other then in the pits :-) with I could post pictures that wheel makes a sweet one for disc or drum. you have to start someplace so what you have will get you out there.


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Re: Conical hub rear sprocket sizes. [Re: phantom309] #480454 03/08/13 2:15 pm
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phantom309, I hear you on things that might not go as planned.I'm thinking the 4.70 ish overall gear is good for a start.The valve train is supposedly good for north of 7500 rpm....
# 260 jets in 32MM Concentric carbs,total timing at about 36 degrees,100 octane fuel. The Hillbilly dyno.....let it rip down deserted rural roads and see what happens.


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480494 03/08/13 10:08 pm
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Originally Posted by Hillbilly bike
The valve train is supposedly good for north of 7500 rpm....
# 260 jets in 32MM Concentric carbs,total timing at about 36 degrees,100 octane fuel.

Standard valve springs will see 8000 rpm easily enough,if the pre-load is anywhere near right.You may find it happens too easily.

260 mains sounds like a safe place to start.Find the smallest jets that cause 8-stroking at full throttle,then go down 2 sizes.That'll quickly get you close to right,but still safe.

Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480516 03/09/13 12:11 am
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Pete
You mentioning your long inlet lengths some posts earlier reminded me of an experiment I did on a pals TR65 in the early 80's.
At the time I'd read something about tuned length resonance,and how it was possible to get 10% more power tuning the inlet, and another 5% exhaust.
All I had done previously, on my own pre-unit 8-stud T120, was to make up some manifold spacers 2.5" long the ID of which went smoothly from the 30mm Concentrics to the smaller dia inlet tubes of the head, something like ~27mm.
It made an enormous difference to the performance, a quick engine all the way to the top, still with good grunt. Just luck, don't understand why.
With the TR65, stuck on a twin carb head (with the tubes&flanges),10" tube extensions with flanges & through studs & stubby bells to get round about the 14" for 7000rpm.
It was a crude test, tuned length is an inexact science at best.
The thing, a bit awkward but not unmanageable at lower revs, was incredible when thrashed. It blew up on the owner when he was doing rather well against a big ducati, examination seeming to indicate the timing side oil seal had failed.
I don't think 14" inlets would be for everyone, it certainly looked amazing with the bells stuck out behind legs, that's what they'd have tried in classic racing days.
At the other side of the coin, length of exhaust, in my head I've got 67", or is it 73", whatever its somewhere in that region, for something like 6500rpm, and thats what makes TT type pipes, with short meggas, ideal. It works, standard & sweptbacks are too short, and I suspect that's why thruxtons go way back beyond the wheel?
Dave

Re: Conical hub rear sprocket sizes. [Re: koan58] #480549 03/09/13 6:32 am
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Originally Posted by koan58

With the TR65, stuck on a twin carb head (with the tubes&flanges),10" tube extensions with flanges & through studs & stubby bells to get round about the 14" for 7000rpm.
It was a crude test, tuned length is an inexact science at best.

I've got 67", or is it 73", whatever its somewhere in that region, for something like 6500rpm, and thats what makes TT type pipes, with short meggas, ideal. It works, standard & sweptbacks are too short, and I suspect that's why thruxtons go way back beyond the wheel?


Prof.Gordon Blair seemed to think intake length could be determined accurately if you knew the rpm where you want the torque boost.Ambient air temperature has some effect,but a difference of 10 degrees C. only changes the length about 1.8%.

There are short alternatives you can use,but the longer ones work better and also work as a short alternative at lower rpm.Use the longest harmonic length you can,and it will generally out-perform any shorter length at lower rpm.
15" is close to right at 6000 rpm;a short alternative is 11.7" or 9.43".

You might find this interesting : LENGTH CHANGE .Note that they overcame the peaky effect of a hot cam by using a long intake,and got good low-rpm torque.
Correct length won't work so well with a small standard air filter,but it will work with a bell-mouth inside a large air box.

The business end of the Thruxton exhaust was fairly short.Header pipe about 30.5" long from the valve,reducing from 1-1/2" O.D. to 1-1/4" O.D. about 15" from the valve.Big 1-1/2" balance pipe near the head.
The mega inside the "muffler" was about 17" long with a 60 degree included angle reverse cone.The extra length after that included another reverse cone,and was probably more for noise reduction (something it didn't achieve very well).

There are long and short alternatives for exhaust length too.The biggest common mistake would be to use a pipe size that's too big.Compare the later 650/750 pipes to pre-unit pipes and see the difference in cross-section area.Velocity in the pre-unit pipes was less than 60%,so it wouldn't work well until about 9000 rpm.

Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480742 03/10/13 6:49 pm
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Thanks Pete, that length change blog was very interesting, pure trial and error research, as was my little attempt with the TR65 30 years ago.
I wish I could remember what the info was that originally inspired me to try it, must have been in some publication of the time, as this wonderful overdose of information on the internet wasn't available then!
I know I must have based it on a simple rpm vs length judgement, aiming for a higher rpm benefit on the short stroke revvy TR65 than I would have on my own pre-unit T120.
I can imagine to do this scientifically would involve complex mathematical/physics computer modelling, much more than just rpm involved, valve characteristics, intake diameters etc.
I haven't seen Prof Blair's stuff, is it derived form experiments on various engines, or modelling?
At the end of the day, I suspect a "reality factor" would have to be applied to any specific application, based on good old bench tests.
Going back to the blog, it focussed purely on extending the trumpets before the carb, so most of the reflected pressure wave is pushing air through the carbs, which I don't think does any favours for the venturi effect and carburation (but it was the easiest way to experiment). I (simplistically) consider that the intake extension should be between the valve and carb, so that most of the pressure wave, and the following low pressure wave are on the valve side of the carb, allowing the carb to function normally.
Where all this originally started in my case was in 1980, changing my knackered old Monoblocs for 930 Concentrics, on an 8-stud T120, and how blandly it performed. Noticing the inlet step between the 30mm carbs and the manifolds, a pal turned up 2" long adapters that smoothly taper between, and it made a step change in performance, and I wondered if it was due just to the tapering, or if maybe the extension may have been involved, then I saw an article (whatever it was) and had the chance to try it on the TR65.
Ta for all the interesting stuff Dave


Re: Conical hub rear sprocket sizes. [Re: Pete R - R.I.P.] #480760 03/10/13 9:07 pm
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So what exactly are we talking about here,increasing the length of the intake between the carb and head or the length between the atmosphere and carb? or both?
Has anyone messed with using a plenum intake manifold on a Brit bike? two carbs on a "log " style intake or a large balance tube between the intake stubs?


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Conical hub rear sprocket sizes. [Re: Hillbilly bike] #480764 03/10/13 9:43 pm
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last time my 500 ran I had the head backward so the carb inlets were facing forward. ran very well right up till the crank broke,:-) nourish too. just used a uni filter over the bells. radar gun at daytona was something like 117 mph.


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