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DohPee (Computer) (OP)
20 Jul 06 6:47
Hi Guys,

Im looking to build my own exhaust muffler for my bike. Its a Hyosung GT650R (similar to Suzuki SV650). It is a V-Twin Engine and currently has a stock muffler on.

Ok I know that I will have to rejet etc to ensure the engine runs properly with the new exhaust.

I took the Muffler off the other day and started her up, There was a massive response increase from the engine, It really revved up quick and dropped nice and fast.. I am leaning towards a straight through design but am a bit worried that I might hurt the motor.The dB of the pipe is not to much of a worry as well as the emmissions control as I am in a country where they dont do tests after the bike has been for inital test.

My Quesstions:

Does the V-Twin 4-Stroke need back pressure from the exhaust?

I have been told to watch out for "Piston Detonation", What causes this and how can I prevent it?

I want to build a straight through but have been told to use  "deflector plates"? what are these and how can they be usefull?

Im open to Ideas here so if you have a good any ideas on how I can get the machine to go like a bomb..gimme a shout.

Thnx
Martin
mburgess (Mechanical)
21 Jul 06 0:53
Most aftermarket exhausts will be straight through. don't know what deflector plates are??? If you want to controll noise a small amount have a reverse tapered baffle. i.e. start at the tail pipe spigot at 2" and taper down to 1 1/2" at muffler exit. Use stainless perf for the core, wrap the core in a thin layer of stainless steel wool & pack the muffler with muffler packing. Unless you have access to reasonable workshop facilities it will prob be cheaper to buy an aftermarket one.
Regards,
MB
tripleZ (Industrial)
21 Jul 06 13:40
Hyosung owner?  How's it ride, and how is the build quality?  Not trying to threadjack here, but not too many people up here in WI have them or have ridden them.  I hear they're not bad for the price, but that the build quality (i.e. fit & finish, plastic fitting and paint, etc.) needs some improvement.  For a racebike they look reasonable, as long as the spare part network exists out there.  But as each one of these negative comments comes from someone who doesn't own a Hyosung, I prefer to go straight to an experienced source.
DohPee (Computer) (OP)
24 Jul 06 1:49
Hi TripleZ,

The Bike Rides Well. It has the most comfortable seat out of all the 600's I Tried. EN-6f,Zx-6R,CBR600RR,GSXR600.

The Build quality is Good on the Frame and Engine components but the Paint work is really Shoddy. One Coat of Colour and Clear, No Hardner so it scratches real easy. The Fairing also leave a bit to be desired as the fit is not spot on due to its segemented panels. And has a terible Resonant Vibration at 4500rpm.

I have set my Front shocks pretty soft so the bike flings into corners and holds them damn well, even without a dampner but I would suggest a Dampner as it gets a bit of head shake when decelerating in a straight line. (down from 200 to about 140).

The Top end is not as High as the straight four bikes but it gives huge Torque from the V-Twin and gives them a good run for the money especially in the corners. I have only taken my bike to 227 and it still had a little more to go so I would think topend would be near 235-240. Raced a Fireblade along a 60k stretch last weekend and held my own, He did pull away on the straights but in the corners he was no match and I caught up everytime.

Im pretty impressed with Engine reliability as I sat at 220 (9500rpm, bike limited at 10500rpm) for about 15mins yesterday and it didnt even blip or skip. The only thing I do worry about is the AIS or second air system, So if you dont have to strict emission laws in your state I would suggest getting it disabled.

But all in all the bike is well worth the money! as the money that you save on the purchase if you fork out a little more for a new spray job, new fairing mounts, dampner and aftermarket Can you still havent paid anywhere near the nearest equivelant price for a popular Brand bike and got one that is just as good and maybe even better.

My Biggest Grip at the moment is that Aftermarket parts are almost non existant or incredibly expensive. As for standard spares Hyosung normally insure that their dealers have a decent stock of spares and if need be when spares are ordered they get shipped very fast. Some dealers have been known to try the whole "Stuck in Customs" bit so I would suggest that you research your dealer first and ensure that they have spares in stock.

Here is a financial Egsample of the savings: in ZAR

GT650R = 47000
Dampner = 2000
Paint = 4000
Can = 3000
Mounts and bolts = 200

Total = 56200

New SV650 (Standard) = 82000

Its a no brainer!

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