I finally got to do some high speed testing of my 2005 GS500F to see the effect of fairings, exhausts and jetting.


I have the advantage of this nice 2km long straight stretch of private road being close to my house.

I have tested on the road before in stock form but I wanted to do all my testing on the same day after different mods to see the effect they have.

I drew two lines on the road. The 1st I wanted the bike to hit at 130km/h in 6th gear. Then full throttle to another line 1.5km down the road to see what speed I could get to.


STOCK + FAIRING

So I first did a stock run (bike was well warmed up) with the fairing (my head tucked well under the air bubble of the fairing).

185km/h indicated

Repeated the test to verify. Yep 185. Speedo was pretty stable and not too willing to climb any further.


STOCK NAKED
Now I went home and took off the front and side fairing.
(The bike was well warmed up again, with my helmet to tank)

180km/h indicated.

Repeated to verify. I could only get the GS to 180 over the same distance. The speedo was slowly ever so slowly climbing at the 1.5km distance mark so given more distance it may have gone higher. But this does seem to indicate the fairing does reduce drag allowing the bike to accelerate to top speed quicker.



EXHAUST - NAKED

I fitted a full system, straight through Jardine Exhaust. The systems weight was almost half of the stock system, sound improved greatly as did mid/low response to full throttle openings. Now to see if it improved top end.

180km/h indicated.

Verified by 3 repeat tests just to make sure. Nope, just bolting on the exhaust did nothing to improve the top end speed. My theory is the back pressure reductions is not being utilised by lean jetting.


Note: Having tested a stock jetted bike with a lunchbox airfilter [Ru-2970] I can tell you the bike will not go over 6000rpm due to it running super lean.


EXHAUST + JETTING 145 MAIN + AIR FITLER - NAKED

The same exhaust as the previous test was used.
Fitted 65 mid main jets and 145 main jets (left the pilots stock)
Removed the airbox and fitted a K&N RU-2970 lunch box airfilter.

A whisker over 185 km/h . Aprox 187

but the sound was now awesome!!! Did 5 runs to soak it all in.



EXHAUST + JETTING 150 MAIN + AIR FITLER - NAKED

I was concerned that maybe, just maybe the main jet could still be increased. I went home and fitted some 150 mains. Back to the strip.

Again approx 187km/h. Repeat tests did nothing to gain more speed. Though it did appear the bike got to top speed a fraction earlier than the 145's. Just the bike runs out of puff and can't get through the brick wall of resistance.



EXHAUST + JETTING 150 MAIN + AIR FITLER + FAIRING

Well for my final tests I bolted the fairing on and headed out for my last few blasts for the day.

1st run netted me a whisker under 190. In repeat tests I got the bike to nudge the 190 indicator, but that was it I'm afraid. The bike was at its limit and you could tell it had nothing left in reserve. Repeat tests proved that 190 was it.

I took a gamble and kept on the throttle a little longer than my end marker to see if I could get any more speed out of the GS to no avail.

The interesting thing with this last test was the perceived speed difference with and without the fairing. You feel that without the fairing your doing twice the speed of what you do with the fairing. The feeling of air blasting into you at over 180 clicks is amazing. The fairing makes the ride so much more mundane, well as mundane as going 190 on a GS can be 



CONCLUSION

These tests make me think the heads can't flow any more air. So major head work or increasing the engine capacity would be needed to give the bike more torque to improve the top end.

So I guess in conclusion I have to say, bolt on mods do very little in increasing the GS's top speed.


As for around town. The mods have improved seat of the pants performance. Acceleration in particular is much more linear with the bike willing to rev more willingly. The noise is louder and can be slightly irritating.

These tests actually make me appreciate the stock GS's setup. For how quiet it is, and with its great fuel economy, it really does go really well. Well done Suzuki 

not that I would go back to stock   

Very interesting read. The fastest I've ever taken a vehicle is about 105MPH (~160kph). I'm not sure I have the guts to do that on a bike...

However, I have been surprised a couple of times to look down and see I was going about 90MPH (~145kph).

I find the GS rockets its way to 160 easily then just sought of winds its way up to its top speed with no real urgency.

Still not bad for an air cooled 500cc twin 

Very cool little experiment.  Sometimes I wish I had only changed the pilot jet to get rid of the cold starts and left the rest stock.  The pipe, jets, and K&N filter killed my mpg, especially in the city.  \

Jake

I actually left my stock pilot jet in to help maintain fuel economy. Being in Australia I don't have to many issues with cold starts.

I am currently doing fuel economy tests to see how these mods have effected my bike.

for the record I returned to using 145 mains as the benefits of the 150 didn't seem worth it for the extra fuel it used.

"I like your style, dude."  (Drunk Turd says name that movie!)

Honestly, awesome post!  And yeah, no way could my naked 05' aftermarket pipe'd and jetted GS could get to 190 kph!  Good work!

-Turd.

Found exactly the same with the same mods but I'm unfaired except for my little monster faring.

Interesting read. Great to see some data. 

Horsepower is for top speed.
Torque is for accelleration.

I seriously believe however it is as much a lack of torque preventing the top speed as much as a lack of power.

I could not get the bike to redline in 6th making me think it needs more pulling power to force it through the resistance created by the wind and other things.


But yeah, power is usually what translates into top speeds.

mmm tourque is so much more thrilling than HP.....

Quote from: galahs on December 01, 2006, 08:18:26 AM
I seriously believe however it is as much a lack of torque preventing the top speed as much as a lack of power.

Well, thats torque up top that's missing. Which directly translates into power.

Quote from: galahs on December 01, 2006, 08:18:26 AM

I could not get the bike to redline in 6th making me think it needs more pulling power to force it through the resistance created by the wind and other things.

Switching up your sprockets (read: geared lower) will utilize your entire rpm range, and might net you a MPH or two at the top end. I'd try adding a tooth or two to the back sprocket. Just a thought.

i'v had mine upto 125mph put slowed down cuz i thought i seen a cop  was on the the highway and mines pure stock

How long did it take you to get that high? Cuz I know with 3 miles of open road, I could barely get my stock GS to edge over 115... granted, mine's naked... but still...

My 99 is completey stock and I've gotten it to 120 pretty easiely...too bad I have problem with the bike now. 

when it was running, my naked stock 91e would hit 100 quick and take an hour to get to 110, where it would putter out and give no more. dramatic drop off in power just after redline for me, but a decently broad powerband, for what the bike is.

Just keep in mind that these numbers are indicated. I compared my bike's speedo reading with a GPS and it's off by about 10% So those of you who get your bikes up to 120mph are actually probally going about 108.

Bikes all seem to read fast, especially the really fast ones. 

it was a pretty long strech i live in texas so ... most our highways are pretty freaking stright ........ so finding a long road is normaly not a poblem

I clocked my GS beside my cousins 04' CRB600RR and i got 180 km/h out of my GS. That was stock. I have since added Vance and Hines SS , K&N filter and DJ needles. I dont find any differences in top speed, just more torque. Bottom to mid pulls harder.

Oh yeh mines naked too....

Hyabusa's typically hit 180mph and are indicating well well over making their owners believe their nudging the 200's Despite alot of claims that they are a 200mph bike it is very rare to find one that does it stock out of the box (granted it takes little modificating to make them hit 200) The last one i saw that did 2 tonne out of the box was at santa pod a couple o weeks back. Indicated 201 on the top speed run.