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Just a teaser - I'll take some pics shortly and bung them up.
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---- Dave
79 GS850N - Might be a trike soon.
80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
92 XJ900F - Fairly Stock, for now.
Only a dog knows why a motorcyclist sticks his head out of a car window -
Have you gotten distracted by a few Gunniness's?Originally posted by Grimly View Post1981 gs650L
"We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin -
Sorry, but I have to ask, ... who or what is "big SU"?
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mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
#1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
#2 son: 1980 GS1000G
Family Portrait
Siblings and Spouses
Mom's first ride
Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
(Click on my username in the upper-left corner for e-mail info.)Comment
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One big SU carburetor?
Life is too short to ride an L.Comment
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SU is a carburetor on British cars. I had a 1 3/4" SU on one of my hot rod Minis."Thought he, it is a wicked world in all meridians; I'll die a pagan."
~Herman Melville
2016 1200 Superlow
1982 CB900fComment
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Oh ok I thought SU was text for suck upOriginally posted by tkent02 View Post1984 GS1100GK newest addition to the heard
80 GS 1000gt- most favorite ride love this bike
1978 GS1000E- Known as "RoadKill" , Finished
83 gs750ed- first new purchase
85 EX500- vintage track weapon
1958Ducati 98 Tourismo
“Remember When in doubt use full throttle, It may not improve the situation ,but it will end the suspense ,
If it isn't going to make it faster or safer it isn't worth doingComment
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Could be Super Ugly too.
Life is too short to ride an L.Comment
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Had them on my 67 Rover 2000TC. I think they were a common upgrade for 240Z owners......
Old age and treachery will beat youth and skill every time1983 GS 750Originally Posted by Schweisshund I mean, sure, guns were used in some of these mass shootings, but not all of them
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Originally posted by Steve View PostSorry, but I have to ask, ... who or what is "big SU"? Originally posted by tkent02 View PostOriginally posted by GS1150Pilot View PostOriginally posted by hjfisk View PostSee? That is the whole point.Originally posted by tkent02 View Post
Not everybody texts, and even those who do, don't exactly know what's going on.
Please say what you mean.
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mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
#1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
#2 son: 1980 GS1000G
Family Portrait
Siblings and Spouses
Mom's first ride
Want a copy of my valve adjust spreadsheet for your 2-valve per cylinder engine? Send me an e-mail request (not a PM)
(Click on my username in the upper-left corner for e-mail info.)Comment
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SU's where great carbs. New a guy who had a set of twin units with remote fuel bowls on a CB750. Nice and simply butterfly valves controlling air flow, so fuel / air mix was controlled purely by the pressure difference lifting the piston/needle (if memory serves correct). MOD seemed quite easy. Units came of a mini, rejetted, he made up a manifold out of copper pipe.
Same bloke had a Z9 supercharged methanol burning drag bike being feed through a single SU.
Lots of filter choice to boot.Last edited by Guest; 01-11-2014, 08:56 PM.Comment
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You could change the mixture by changing the weight and volume of the oil in the vacuum chamber, complicated stuff to figure out on your own.
MAybe the Big SU is really Big Sue.
Life is too short to ride an L.Comment
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No need to **** around with the dashpot dampner. Just play with the needles. The carb did the rest. No vacuum chamber, pressure dif, was transmitted to top of piston, bottom was at atmosphere, so piston rises and falls depending on the demands of the engine. No direct throttle link. Throttle open/closed butterfly which controlled air flow through venturi.Originally posted by tkent02 View Post
"Since the position of the piston controls the position of the needle in the jet and thus the open area of the jet, while the depression in the venturi sucking fuel out of the jet remains constant, the rate of fuel delivery is always a definite function of the rate of air delivery. The precise nature of the function is determined by the profile of the needle. With appropriate selection of the needle, the fuel delivery can be matched much more closely to the demands of the engine than is possible with the more common fixed-venturi carburettor, an inherently inaccurate device whose design must incorporate many complex fudges to obtain usable accuracy of fuelling. ,The well-controlled conditions under which the jet is operating also make it possible to obtain good and consistent atomisation of the fuel under all operating conditions."Last edited by Guest; 01-11-2014, 09:40 PM.Comment
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Had a pair on a 63 Volvo- ok, but it took Keihin (and old man honda) to improve the CV scheme.1981 gs650L
"We are all born ignorant, but you have to work hard to stay stupid" Ben FranklinComment
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As promised, here are some pics...
Technical details...
S.U. Carburettor, c. 1980
Model HIF 38 (38mm throat).
Yellow spring
AAZ needle at the moment.
The first one I fitted was an HIF44 (44mm throat) and while it was ok, it never idled properly. The better gas speed over the jet on the smaller carb leads to a better idle and pickup, and for local running around the loss of top end isn't an issue. The 44 ran up to 115mph, this one tops out at 95mph or so.
Fast enough for around here, at any rate.
When I did this conversion I was looking at the thick end of £600 (would have been around $1000 at the time) to rebuild the original carbs, so stupidly expensive were genuine Suzuki carb parts at the time, and since I had a deal of experience with S.U. carbs I decided to go with this. I did this on the other GS too. So, as you can see, I saved a thousand pounds by doing this. Both bikes at the time were just used as work hacks, spending their days running up and down the motorways at steady speeds, so a bank of multiple carbs was definitely over-kill anyway.
It works, and for my needs, works fine.
DSC_0001pancake.jpgLast edited by Grimly; 01-27-2023, 03:14 PM.---- Dave
79 GS850N - Might be a trike soon.
80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
92 XJ900F - Fairly Stock, for now.
Only a dog knows why a motorcyclist sticks his head out of a car windowComment
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Last edited by Grimly; 01-27-2023, 03:15 PM.---- Dave
79 GS850N - Might be a trike soon.
80 GS850T Single HIF38 S.U. SH775, Tow bar, Pantera II. Gnarly workhorse & daily driver.
79 XS650SE - Pragmatic Ratter - goes better than a manky old twin should.
92 XJ900F - Fairly Stock, for now.
Only a dog knows why a motorcyclist sticks his head out of a car windowComment
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