OzVMX Forum
Clubroom => VMX Sidecars => Topic started by: SAABCOMBI on May 19, 2011, 06:06:07 pm
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At HBB weekend l was on a corner for the total weekend and could not help noticing the sounds that sidecar race bike made, why do these bikes sound out of tune, popping and spluttering, their was only one sidecar that had a crisp in tune sound, Are the owners of these bikes tune the engine by the lenght of the exhaust pipe and carbie, years ago l remember Bert Nevall from geelong raced his sidecar and it was so crisp and quite it sounded great and alway a front runner. The speedway sidecars sounded very crisp and running in tune.
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Walter, am I write in saying tuning a 4 stroke engine, should be tuned by taking making the exhaust pipe longer and slowly shorting it unit sounds right.
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Sounds like they dont know how to tune and balance a set of carbs to me. It can happen on multi cylinder solos too, its not uncommon in solos and more common in sidecars, its just that the carbs are not synched. Get you carbies balanced and jetted right and the sound will be a lot better. There is nothing mysterious about it.
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I am sure that carbie play an important roll, l also believe that the pipes need to be tune as well to the engine.
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Dave , LW has given you the key ;) Pipes now cannot be straight out...Noise output is the powers that be big scene, so surpression of said noise means tuned length unrestricted pipes are basically dead.. OK . Speedway Vintage sidecars seem (luckily for us ;)) to sneak beautiful unrestricted sound in . Also speedway, flatracks and tar are I have over the years noticed a hell of a lot smoother than motocross tracks saving fuel being sloshed about maybe affecting tuning.... Cheers
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You idiots, just to get one to run is hard enough, then to be actually able to get one around a circuit is another thing altogether.
If you ever get one to run right-they frighten the living christ out of you.!!!!!
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Yours should run perfect Vaughn, u have the same exhaust setup as Walter! ???
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Everyone wants to know why my Wasp 650 revs so hard too. Now you know.
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Back in the early '80's I mechaniced for a couple of speedway sidecar crews. With the outfits running on methanol, we would initially jet the carbies so that the they were way too rich at full revs and would burrble, pop and missfire. Then we would go down in jet sizes until the engine ran clean, then go back up one jet size just to be on the safe side. Then end result was that if you held a gear too long the engine would start to pop and misfire at peak revs.
CJ
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We are not idiots, i have been listing to sidecar race bikesengines and watching them since 1990 when the vintage started, most sidecars sound like they need to be tuned properly, this thread is not about pointing the figure at anyone person, I feel that the currant tracks are not long enough and their is no main straights to open these machines up. The motocross tracks on today standard compared to the 60`s and 70`s are crap. European tracks are long fast and flowing.
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Sorry 33M I didn't mean to insult anyone, I just meant that sidecars never seem to be tuned right for all occasions/circuits, and we're usually having too much fun to care.(usually-there are exceptions that could bring a man to tears-mostly to do with money :D)
And you are dead right-there are only one or two tracks that do the sidecars justice-and we are losing them quickly.
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Bring 'em to Nepean occasionally, that will blow the cob-webs out...And your eyes will be as big as saucers before you get to the end of the straight!
cheers pancho.
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We'll be running them at the Dirt track nats at Nudgee with trials tyres and geared to 100 so that will be fun.
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You don't have brakes at the dirt track-they must be disconnected or they'll slow you down-that;s what popeye said anyway????
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FEELER GAUGES with FEELING:
Not just a spectacular sidehack driver; I am just as proficient at tuning them.
I am available for $7.70/hour @ CD8