Hello from Perth, GT250R Rider

[Julien]

Hi all,

New to the forum and wanted to check in as I’ve been using the advise and information provided on here. I have a 2005 GT250R, which I bought off a friend for literally peanuts (it had only done 2,500kms). I’ve had it for about a year and a half now and it’s only up to 7,000km. I use it as a daily rider to work and back. Overall I feel that it’s a good bike for what I need it for but have had trouble in the earlier days with carbs needing maintenance (pretty typical when it had been sitting in the garage for years).

Anyway I’ve decided to take it on as a new little project to modify it for track purposes whilst still making it legal enough to ride on the street. Looking for any advice people may have on what modifications I should do to it to start off with, I have a number of ideas myself which is based on people’s comments and my own personal experience. First modification I want to do is to get an aftermarket exhaust, slip-on or full exhaust. But can’t seem to find anything out there, I’m after more of a short exhaust that finishes relatively close to the rear sets. Not necessarily set on that configuration so happy to consider people’s opinions, what I am set on is getting rid of the heavy stock muffler at the least and ensure that there isn’t any baffles or restrictions in the remaining pipework. From the posts on here, I’ve seen that I’ll need to tune the carbs by upjetting them, getting a K&N filter as well as the coils and regulator changes. Also looking to change sprocket sizing to get more acceleration, hence a reduction in teeth.

Overall I want to be able to take it to the track in a 250cc class and give it a red hot go.

Just as a side note before everyone tells me not to do all of these mods and just to get a bigger bike, the intention behind all of this work is that I’ll be doing it myself and learning along the way. I’m keen to strip the bike and rebuild it as part of my education. I should also mention that I won’t be going out to spend heaps of $$$ on the exhaust etc, but do want to do something to try and reduce weight and push a little bit more horsepower.

Lastly, I know that some people may also comment suggesting that before I do any work to my bike I should get track riding lessons, I am doing that too so this won’t be just a rider modifying a bike for the sake of it.

With that all said, keen to hear from people and either what they have done, what could be a possibility, what not to do and anything in between. Cheers.

[♠️ MARCEL]

Welcome!  – Hope you will take a picture journal thread in the forum so we can follow you exploits all the way to the track 😉 Be nice to see that!

Let’s start with the exhaust…..
– Do you have a budget ?  There is a UK company that makes stainless exhausts for us here in UK but it is possible they will ship to AU as they do have an ebay shop themselves by the name of BLACK WIDOW EXHAUSTS

Or

– Do you know someone locally who is able to “cut” the middle cat box of your stock pipes ===> then replace the middle with a straight pipe , then go grazy with VHT paint , nature forbid it rains and the oem pipes start rusting due to unpainted surface on it.

For muffler , }
– Have you learned any regulations in your State about how loud the bike should be ? any meters they use to test bike noise levels. ?
There may be a chance that they want a “full size” muffler  (similar to the OEM version) but aftermarket ones will be loads lighter.

If you keep the stock exhaust pipes ====> Cut the 4 bolt flange off ==> The find any “51mm slip-on” exhaust can/muffler that will comply with your local track noise levels ?

// Meditation doesn't mean you have to sit still....

[Julien]

Hi Marcel,

Thank you for the welcome and suggestions. I’ll definitely be taking a lot of photos/videos along the way, until I hit that penultimate track day.

Overall I don’t want the modification of the bike to cost be a lot. Mainly because of a) it is only a 250cc and b) I’m doing the work myself and I’m learning. It’s a project to get me into modifying and improving bikes. For the exhaust itself I’d say it would be no more than AU$200-$300 at this stage. Mainly as it would be my first modification and I’d use it as a starting point to continue modification on my bike. Essentially coming back to the exhaust once I’ve upgraded everything else. My thought is that if I start with an upgraded exhaust to get rid of my heavy existing muffler set up then it gets me off on the right track. After I can then start to tweak the carb jets, the air filter and other parts of the bike. I think it would be better use of money and time to do it that way than spend $1000 on a single exhaust system to then restrict myself on other mods. In your opinion do you think that this is the way, or should i just start with the K&N filter and upjet option thats in the shop? Then work on the coils and regulator and finish with the exhaust.

I’ll take a look at the Black Widow systems and see if they tickle my fancy.

I don;t know anyone personally but I have seen custom exhaust shops around the place and have enquired about a full new system which would be in the ballpark figure of $1000. Out of curiosity, would you have a schematic of the exhaust system on a GT250R? Only because I’d be interested to see what restrictions are in place within the pipe system. Then I can gauge on whether its worth doing mass mods to the existing or scrapping it and starting from scratch. Interested also in your comment regarding cutting the cat box, do you have an image you could send through for me to look at?

Not too sure about noise levels in my state, but I almost want to just run the gauntlet and see what happens if i just put an optimised unrestricted (or at least as unrestricted as possible) set up on. Will need to check on track noise levels though.

I would love to install some form of motogp style exhaust system, one pipe per cylinder but not sure how realistic that is. Seems like it would be too technical to start designing something that may reduce my power rather than improve it.

My GT250R

Bike without stock muffler which I like the look of as the short exhaust seems more aesthetically pleasing.

[♠️ MARCEL]

Hey,

For the exhaust since you want it short, i find that personally this one  (is short but fat) is loud but not too loud with the DB Killer fitted inside and it will not restrict the bike, in fact , it might “too free flowing” ,   if you get a DB Killer, you want to crush the “inner pipe” of the DB killer itself so that the hole is about  2cm diameter.   If the hole is too big  (generally with these aftermarket mufflers aimed at 600cc bikes) , the 250cc will lose some torque.
This one
https://www.lextekproducts.com/part/YP4
I believe they ship to AU , but worth asking them ?  It is also stainless 51mm slip on.    Lextek is a common exhaust brand in the UK, that’s why it was at the top of my head but there is loads of other mufflers out there in similar dimensions as the  Lextek YP4

The actual rear pipe for the rear cylinder has no restrictor inside  , neither does the front portion.        See the black box that is on the exhaust system under your fairings,  that kills most of the noise  (silencing) and there may be something else in there that restricts the flow of the bike a little bit to comply with some countries that require the bike to be less loud & restricted in some form.    Cut the box in the middle there, and find some  “Y” shape pipe to join “rear + front + exiting pipe” , now you have a free flow system, even welding is OK.  Just make sure the rear engine cylinder pipe is detachable incase you want to remove the engine!

K&N is discontinued forever for carb models , however fear not, we actually send  BMC Italy & D/A EU filters as a replacement and are more superior than K&N ever was for carb models.     K&N still has filters for EFI 650 bikes but ofcourse they do not fit the 250cc .  The jets are important yes , that’s why it was mandated to include them with the sale , we wouldn’t sell the filters without jets as more air  = more fuel or the bike gets too lean.

As for coils ,  send me an email for a custom quote in the future as i may be able to get you Mitsubishi Japan ones or Hitachi Japan coils , if the bike is going to be subject to the track runs.    NGK caps = trusted brand, you will be OK and recommended. I would not use OEM HT caps on the tracks, we don’t even sell the new ones.

Regulator = Very very important,  send us an email and we may find you a monster shingden regulator , like this one below  (but i will create the harness to plug & play on the 250cc)   (ignore the 650 stator, just look at the galley that shows the regulator)

Upgrade Regulator Rectifier & Stator Generator – GV650 GT650 Hyosung {Carby & EFi up to 2013}

Chinese regulators always pop and sometimes they set the hyos on fire. We did have 1 picture of a bike on fire due to a bad regulator.

Stator = Should be fine if its within spec.

// Meditation doesn't mean you have to sit still....

[Julien]

Thanks again Marcel,

That Lextek exhaust isn’t too bad, definitely a short exhaust but relatively fat. Certainly within my budget. I was looking at a SC Project or Racefit muffler, if I can pick up one for cheap second hand. I have also found this Akrapovic exhaust for an R6, Yamaha R6 Akrapovic Megaphone Slip-On for cheap. Just trying to find out if the pipe size is 51mm. That way i can just cut off the additional pipe that extend past the rearsets and just install this slip-on whilst I look to do what you mentioned regarding removing the muffler and installing a Y-pipe. Wondering your thoughts on the Y-pipe, I’m aware of the importance that the negative pressure from one pipe to assist removing the exhaust air from the other is critical to the performance improvements. With the one pipe coming from the rear cylinder to the front of the bike a Y-pipe straight onto that pipe section will be a little restrictive for flow as it needs to move forwards then backwards. Unsure if I’km over thinking it. Either way keen to get ride of that muffler box.

Will keep in mind the other modifications and getting in touch beforehand. Keen to remove that power lag in the 5k -7k rev range.

Just to confirm from your view, is starting with the exhaust the best way to start or should i start with other components.

Not sure if I mentioned this before but I did want to strip the bike completely down and look into the engine and gearbox, think this is worthwhile? Anything to gain here? I’m also wanting to strip it so I can respray my frame from the current grey to a neon green. Going for a neon green, black style, so fairings will get repainted in mainly black with some green too. Will also repaint wheels.

Also noticed your comment re stator being in spec, is the OEM in spec? Or do I need to check.

On a side note, watching Circuit of Americas grand prix FP1 and getting more and more excited about doing this project.

[LaserBeam]

Julien wrote:

Bike without stock muffler which I like the look of as the short exhaust seems more aesthetically pleasing.

Quote

Your bike looks nice; i’m a bit jealous. One of the many memorable things i did on my Fireblade was to take it for a ride with the muffler removed. It sounded like a rally car, no joke. It’s not great for the bike but it’s a hugely memorable experience. 😀

-----LaserBeam---->

[Julien]

Thanks Laser,

I was lucky to get a fairly clean bike from a friend that had barely ridden it. Funny you mention Fireblade I used to have one too, never took off the muffler was always chasing a TaylorMade exhaust for it but then crashed and was a write-off. The Hyosung sounds very much like a rally car too, fairly low growl.

What are you doing with your 250? I saw that you just got one. Any upgrades planned?

[Charger1284]

Hi Julien welcome to the forum Nice bike I love that color

[Julien]

Thanks Charger,

Glad to be here. It is a nice colour, certainly stands out. I’m actually of thinking of changing to black fairings but with some graphics on it as I’m looking to respray my whole frame to neon green. Then looking at the wheels, I think similar to you going to that gold colour but instead i was think of a going a two tone, neon green and black.

[LaserBeam]

Julien wrote:

Thanks Laser, Funny you mention Fireblade I used to have one too, What are you doing with your 250? I saw that you just got one. Any upgrades planned?

Quote

The GT250R i bought was not treated so well, although low kms. I’ve been giving it a lot of extra attention but slowly. It’s about to get a few minor enhancements. It has a good pipe on it but don’t know what size jets are on the carbs. They’ll need work later; im not looking forward to it. To date i’ve made it cleaner, safer & smoother. It’s got some new parts; it’s about to get more. Will post some pics of the work on the forum.

-----LaserBeam---->

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