Hyosung GT250R mods on a budget

**NOMIS** · 26th May 2008, 11:32

Originally Posted by Ragingrob

I doubt that 20yr old bikes' ratios are still the same as when they came out of the factory anyway... Who knows what exact difference it's made in terms of performance but if it's done anything at all it is so minimal that it's unnoticable. I know for a fact though that it seems to idle smoother now so there's a pro for ya.

yeh other wise your cbr should have been smoking my hornet. :-)

**BadCompany** · 26th May 2008, 17:38

I'd be more worried about trying to pass a WOF with an exhaust that has wholes in it. Not sure about bikes (or where abouts you put the wholes) but cars fail on it.

**fizbin** · 26th May 2008, 17:55

Back to the thread. is there anyone that can show me how to do some of this stuff. i have a bit of a shoe string budget and the sound of being able to get a few more pony's out of the gt250 sounds great!

As i am a fat bastard as some will testify to.

What would you recommend i start with.
Can you re-jet with out doing the exhaust?
now play nice kiddies this was a sensible question if not a newbie one!

**Ragingrob** · 26th May 2008, 19:06

Originally Posted by BadCompany

I'd be more worried about trying to pass a WOF with an exhaust that has wholes in it. Not sure about bikes (or where abouts you put the wholes) but cars fail on it.

Well as I said, the holes are inside the exhaust between the baffle hole and the outer shell. Unnoticable unless you are looking right into the exhaust. So hopefully should be sweet, WOFs in the past the guys haven't even looked at anything mechanical at all, pretty much check it goes, lights, brakes, forks, tyres, done deal

**Ragingrob** · 26th May 2008, 19:08

Originally Posted by fizbin

Back to the thread. is there anyone that can show me how to do some of this stuff. i have a bit of a shoe string budget and the sound of being able to get a few more pony's out of the gt250 sounds great!

As i am a fat bastard as some will testify to.

What would you recommend i start with.
Can you re-jet with out doing the exhaust?
now play nice kiddies this was a sensible question if not a newbie one!

You CAN re-jet without doing the exhaust. Correct me if I'm wrong though but I think re-jetting is done in order to re-tune the bike's engine for the newly done exhaust. So re-jetting a non-modded bike would only make it run rich or lean, whereas after you've done the exhaust then it would be correcting how it runs. I think...

**CookMySock** · 26th May 2008, 19:09

Originally Posted by BadCompany

I'd be more worried about trying to pass a WOF with an exhaust that has wholes in it. Not sure about bikes (or where abouts you put the wholes) but cars fail on it.

Grab the pop rivet gun and bang some rivets in them. All looks stock now. Total cost = seven cents.

DB

**Ragingrob** · 26th May 2008, 19:16

Originally Posted by DangerousBastard

Grab the pop rivet gun and bang some rivets in them. All looks stock now. Total cost = seven cents.

DB

Will keep that in mind if I have any trouble. Also I'm sure I could use some kinda sealant just to cover them up. It's so dirty inside the exhaust anyway ya can't see them

**CookMySock** · 26th May 2008, 21:32

Originally Posted by Ragingrob

You CAN re-jet without doing the exhaust. Correct me if I'm wrong though but I think re-jetting is done in order to re-tune the bike's engine for the newly done exhaust. So re-jetting a non-modded bike would only make it run rich or lean, whereas after you've done the exhaust then it would be correcting how it runs. I think...

Yes this correct. The free-er flowing exhaust reduces the back pressure on the engine. The result is less exhaust gas retained in the combustion chamber and carried over to the next cycle. This carried over gas is actually a good thing for emissions because it lowers the whatsits name bullshit thingy in the doodad mixture whatsit. Some shit like that anyway, but yeah something to do with introducing inert gas to the combustion process and helping emissions. Opening up the exhaust stops this from happening, and wrecks the nice clean green-ness of your bike whilst introducing more "grunt" in the process.. ie, the whole point to begin with. More fuel-air, less inert gas = more grunt. The trouble IS, the carby was never set to allow this, and now more air = leaner mixture ish, and you need to richen the mixture slightly lest ye burn yer valvies and ringies and stick them to other, or WORSE, burn a hole in yer flamin piston like frosty sed.

The short story is, if you drill a few holes so its a little bit farty you will prolly be fine, but if you open the bugger right up and do lotsa highway driving, you will (what we call it in the trade) "fuck it."

so, yeah.
DB

**woza** · 27th May 2008, 16:00

did you intall the AIS kit it recommends?

**Filter_nz** · 27th May 2008, 19:40

Originally Posted by fizbin

Back to the thread. is there anyone that can show me how to do some of this stuff. i have a bit of a shoe string budget and the sound of being able to get a few more pony's out of the gt250 sounds great!

As i am a fat bastard as some will testify to.

What would you recommend i start with.
Can you re-jet with out doing the exhaust?
now play nice kiddies this was a sensible question if not a newbie one!

If you can't afford a new can take the stock one off and drill holes into the internal baffle at both ends, this will free it up and sound better.
I still disagree with a few posts about the jets. Perhaps on other bikes but the Hyos if anything seem to run a little rich stock. Dropping the needle setting is something you can do yourself and is the least you should do if you've done the filter and exhaust - you'll still lean out on full throttle but like I said, besides lights and corner exit's not full tap that often and I doubt you’ll do any damage.
After doing the filter and exhaust I initially was going to take my bike to TSS motorcycles in Lower Hutt but after talking to the mechanic he said all they usually do is adjust the needle and suggested they run fine without doing anything which I was a bit surprised to hear. They had a black demonstrator model with a cycle-works can with nothing else and they seemed to think it was fine.
The crabs are Japanese on the Hyo's at least mine is on the 07 model. The jets took 3 times as long to do as the needles and almost impossible to get at without stripping the screws and stuffing it altogether.
That said if you can buy the jet sizes I had for $14 and have decent tools go for it.
I might not be able to "ride my 250 properly" as someone said... however I've only just got my restricted, I'll get there.

**2wheelsbetterthen4** · 18th August 2008, 14:04

You mentioned de-baffling the origional pipe using a big drill bit...
Does this just involve drilling straight down the middle of the pipe or what? And how big a drill bit?
Also would this make it sound better? or just make it tinny?
And do you think the bike would need to be re-tuned after drilling baffler and opening up airbox a bit?

Its just i can't see how me in my shed with a drill bit can make the bike better then a whole team of engineers at hyosung designed it to be...
thanks.

......
ok 4get i asked... that last post explains it.

**wanpo** · 5th February 2010, 13:48

Sorry if this is reviving an old thread.

Just a question about sourcing the jets themselves; Where from and are they standard to all motorbikes? (the fit, not the value. I'm on a GT250R also)

I've got a custom tailpipe and am thinking about doing the intake mod to cram in more air.

Reading on the korider forums they seem to say change up to 97.5/100 or 100/100 for a bike with aftermarket/modified tailpipe/intake.

Cheers

**disenfranchised** · 6th February 2010, 07:49

I can propose a slight variation on the exhaust mod.

Seeing as I already fitted a SD pipe to my bike, I have a spare stock one sitting around....and I suspect others out there may do too.
Find one, buy it cheap, and drill that instead, so you can go back to your original one if you have a problem (or to pass warrants)