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2008 GS500F + full exhaust + K&N + rejetting

Discussion in 'Modifications and Projects' started by DrewBytes, Feb 8, 2009.

  1. This weekend I've modded my 2008 GS500F. After reading as much as I could from the GS500 forum and GS500 Wiki I decided to do exhaust, K&N filters and re-jet to suit the mods. Other dyno results point to approx 7-10 hp gain at the wheels from these mods which isn't bad considering they dyno at 35-40 hp standard.

    First off was an exhaust from Formula 1. For $720 delivered I got a complete exhaust, chromed headers + mid pipe + polished allow muffer. Initially I wanted a Jardine or Vance & Hines exhaust which is what the guys in the USA use, but I couldn't find one for the 2008 model so I decided to buy local.

    Removing the standard exhaust was very easy and quick. However I struck a hurdle putting on the new headers. The flange on the original exhaust is very thick and on the new headers very thin, meaning the stock header bolts were too long to be screwed in all the way. A trip to Bunnings to and I bought 4 x 8mm nuts which spaced the bolt out enough to screw in properly.

    Started up with the exhaust and I grinned, certainly loud. Took it for a short ride to make sure ok and it's certainly loud - maybe too loud.

    Next, remove the fuel tank to get at the carbs. I followed instructions from the "Poor mans rejetting pictorial". Spent a few hours removing all the necessary stuff to get the carbs removed from the bike. It was pretty quick apart from it took me a little while to work out how to get the choke and throttle cables removed. I labelled everything as I went with electrical tape and a small note with a numerical order to make sure I wouldn't forget anything or do out of order.

    Next problem was getting the cover off the carbs to get at the jets. For the life of me I couldn't remove the 8 x Philips head screws. I ended up stripping most of them badly. To fix I hacksawed across each bolt head, and used a flat head to remove quite easily.

    Replacing the jets was quite easy, just screw out and replace with new jet, except for the main in which the jet is part of a bigger jet and has to be removed from that first.

    After putting the carbs back in, I put the twin K&N filters on which means you no longer need the stock airbox and single filter which is apaprently quite restricive.

    Going back together was easier than pulling apart. Took 1 hour to put it back together. Went to start the bike and it cranked over but wouldn't start. Bugger, I was thinking I'd have to strip and check everything. After a moments thought I realised I hadn't turned the pet-cock screw back on under the tank. Fixed that and started first time.

    Took it for a decent ride and gave it some stick to test out. Stock the jets from 2004 onwards are 17.5 pilot, 60 mid mains and 130 mains. All the advice on the net said 22.5, 65, 147.5 was the go with good exhaust and K&N's so that's what I did. Today is another scorcher here so it's hard to tell how much effect the mods had, and whether it's jetted correctly.

    I have a feeling it may be a little rich, possibly need a 145 or maybe even a 142.5 main jet. I'll ride for a few days and see how it goes, then rejet it if necessary. I think I could rejet quite quickly next time, possibly without even removing the carbs from the bike. I'll update the thread with the results after more testing.

    If any GS500 owners have any questions about the process I'd be happy to help. I am in no way a mechanic, so if I can perform this myself, then anyone should be able to give it a go.








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  2. Good work. Excellent.

    I wouldn't mind doing similar to mine. Not sure I want the noise but a bit of extra power would be fun.
  3. What did this all cost in total?

    I have a 2008 GS500F, and woul dliek to do something like this, but not sure if it is worth it. I will be keeping the bike for a hwile yet, but not sure if I want to invest a lot of money into it if I am going to sell in a year or two. Mine also has the full fairing, so it might be a bit more work to fit the exhaust?
  4. Looks good mate.
  5. Exhaust: $720 delivered
    K&N filters: $160
    Jets: $70 delivered
    Fitting: free if you can do yourself. If not, probably $300 or so.

    Exhaust is very easy to fit. Remove fairings (5-10 mins), undo 4 bolts on exhaust headers, bolt for muffler and it just falls off in 1 piece.

    Whilst the bike is certainly quicker now, I'm undecided on the exhaust. It's maybe a bit loud for my liking, and also seems to be hitting somewhere as over bumps there is a noise that sounds like the exhaust hitting somewhere. Got to try and work out where and fix it.
  6. Yeah, I've been through exhausts on cars, but the GS still makes me wonder how an exhaust would make it sound anything like anyother bike...

    If you managed to squeeze 25% more power out then grats... But I'd rather put those funds toward a seriously faster bike when i'm off my p's!!!


    The GS is economical, but sounds average! I can handle that for12 months.
  7. How much louder is it? Hard to gauge, I know, but does it just add some more rumble, or is it just outright loud? I don't really want to go louder, but maybe just give it a bit more of a rumble.

    Is the increase in power easily noticeable?

    Have you noticed how much it affects your fuel economy yet?
  8. It's LOTS louder under throttle.

    It is certainly more powerful. For example, there is a tight 25kph corner on my way to work that I normally take at 60kph in 4th gear (4000 rpm) which leads up a small steep hill. When the bike was stock I'd hit 80 odd at the top of the hill and it's running out of puff. Now I can hit 110 and it's pulling hard. It's hard to notice any difference at regular riding but under hard acceleration it's certainly faster.

    Fuel economy I will know at end of week when I fill up. However it's running rich and I'm going to order some smaller main jets today which will help with economy and make it run better.

    BTW the clunk I thought was my exhaust hitting was actually the centre stand hitting the chain. Doh! I didn't realise the stock exhaust has a stopper for the stand. All fixed now.
  9. Sounds good except for it being lots louder.... I wouldn't mind a bit more noise, but I don't want it to be lots louder. Wonder if there are any othe pipes that might give a similar result power-wise without the excess noise.
  10. did the nex exhaust come with a bump stop for the center stand?

    when i swapped mine over on my old 05, a had to mak up and fit a new bump stop and attach it to the bottom of the shock mount other wise the center stand comes up to far, and bounces round on the exhaust
  11. It did, but I didn't realise what it was for. It's been put on now!
  12. I filled yesterday and returned 4.75L/100 when I used to get 4.5L/100. I was actually expecting it to go up more than that.

    I've got 20/62.5/142.5 jets going in tomorrow, it's just a little too rich everywhere. I think with those jets the economy will only be slightly worse than stock.
  13. Put the new jets in just now, and the good news (for me) is that it only took 1 hour from go to whoa. You don't even need to take the carbs off the bike. I only removed the tank and undid the 3 fuel lines, unclipped the carbs and rotated them upwards so I had access to the bottom where the jets are. So no removing various lines etc. Very easy.

    I'll report back over next few days how it feels with the 20/ jets.
  14. Any updates on the new jets? Has it improved the performance?
  15. The 20/62.5/142.5 jets appear to be runing nicely. I've only done one full tank and it got better economy than stock. Normally I always get 4.5L/100 on my weekly trek to/from work, but 1st tank after the smaller rejet I got 4.22. I'll see what it is at the end of this week, need to do it a few more times to make sure that wasn't just a one off.

    I'm not sure why that is as most people doing the rejet report increased fuel usage - but I have gone slightly smaller jets than the norm. It may be because it doesn't need to be ridden as hard in the mid range to do the same amount of work?

    It seems to be performing well.
  16. Sounds good. Do you know if the people who made your pipes make any others to suit the bike? I like the sound of the performance upgrade, but I don't want my bike to be a whole lot louder. A bit more rumble would be ok, but I don't want it to be very loud as the neighbours might not like it when I get up to go to work of a morning, and besides, I don't want headaches from all of the noise.
  17. Trekka, I asked and they said it was the only one for this bike. It's maybe not as loud as I originally thought (maybe I'm used to it?) and you can vary the noise level with your right wrist. Under load yes it can be noisy at certain rpm's, but it's no problem to keep quiet whilst leaving home if you want.

    It doesn't annoy me when riding with helmet on. I might see if I can do a sound file sometime this weekend.
  18. I've done another 2 full tanks since the last rejet and recorded 4.65 and 4.43 L/100 so it's pretty much as stock economy. I had the bike serviced a few days ago and got them to check the plug condition, roadtest etc and they said it's running spot on as far as they can tell - not lean or rich.

    I've also put on mirror extenders so I can see much better now, cheap upgrade at around $60.

    I've also put on a light smoked Zero Gravity touring screen for better protection - see pic (excuse all the crap in the background).

  19. I really like the look of that screen, very nice.

    Does it stick up much higher then the stock screen?

    Glad to hear it is all running well with the new jets, pipes, etc. I am thinking of keeping my bike for longer then originally planned (probably 5 years minimum) as I want to buy a new boat and can't afford new bikes and boats, so I will be looking further into pipes, etc in the future.
  20. Trekka, it's 10cm higher than the stock screen.

    I'm intending at this stage to keep the GS500 as well when off restrictions as my daily commuter, and possibly get a 2nd bigger bike (GSX1400) for weekend jaunts etc.