Gs500 only goes +- 130 KM/h (Problem "solved")

[Krav]

Hello!

I've got a GS500 with a 1999 engine. with front spocket 16t and read sprocket 39t. Wich is normal. My rear tire is 130/70-17 michelin tire.

nothing out of the ordinary. However, i recently tuned my trailtech vapor speedo with a GPS. Everything is pointing to it being tuned correctly. (you've got those signs by the road, wich will display your speed to make you aware of the speed you're driving.) and its always dead on correct with my display.

Now, when i go WOT on the freeway, i only get up to 130 Km/h. This while i oftenly read that the Gs500 should be able to reach about 160km/h
Even if im a bit off with my tuning (wich i think is unlikely), this is a huge gap! When i drive 130km/h the revs are very high. (can't check what rev's im on, cause its hard to dead on install the tach of a vapor on the Gs500.)

I don't really need to go much faster then 130, but even then, the rev's feel unsafely high.

Ideas anyone?

[Krav]

Oh, This is my setup:

These filters:


I offcourse had to rejet my carburettor, adjust my fuel/airscrews and rebalance my carbs.
im now running:
- main 148
- Pilot 40 (3,5 turns out i believe)

The pilot screws i did one carb at a time. Disconnecting the other sparkplug, then i balanced by connecting and disconnecting the plugs after the carbs performed their best on their own.

I also have this exhaust. Takkoni Slip on (no db killer)

[Iarn]

What are "high" revs? Can you provide a number for us?

You should be able to do 130Km/h reliably and easily. 160km/h is a bit tough to get to but def not impossible.

[Krav]

Its hard for me to establish the rev's im running at. this particular dash has issue's with interpreting the tachometer I should read up on that. Right now the lead is twisted around a bougie cable, and it does produce output, but its jumpy, and im not sure im using the right setting now :p

I'll look into getting that fixed, and provide the number im be running at, at top speed.

What i can say though is that i feel the engine vibrations fairly heavily. Im just sitting there, wishing that i could shift up another gear, but im allready in top gear.

[Iarn]

Well, these bikes are pretty heavy on the vibration. That's normal behavior as far as I am aware.

As far as unsafe Rev levels. It's tough to call that by ear. You'd be able to better establish that if you could get your tach working.

That's my suggestion.

98km/h is 5k rpms. Or should be. So that's a start.

[Krav]

True dat.

I did some modding just with an electrician, who helped me get a 560 K resistor in the circuit, but it still jumps occasionally. So that still needs some work.



On the other matter, how did you get the 5K = 98km/h number?

Please correct me if im wrong!

This applies to the top gear:
9500 RPM is where the top HP lies of a Gs500. So I assume that 9500 rpm should be what maxes out when going at 160Km/h

So: 9500 RPM = 160KM/h
therefore: 5000RPM = 84 KM/h

___________________________________

IF: 5000 RPM = 98KM/h
then: 9500 RPM = 186KM/h
and: 8260 RPM = 160KM/h

Stating that the bike tops out before it reaches its maximum HP, which seems rather strange to me.

Can someone explain if im doing something wrong here?

[gsJack]

The GS500 with stock gearing and tire sizes would have to go over 100 mph before hitting redline in 4th gear so I doubt your even close to over revving.  A stock GS should easily hit 100 mph if nothing is wrong.  I had my stock 97 up to 110 mph indicated which should be at least an honest 100 mph considering the GSs speedo error with 240# me and a big Plexi 2 shield on it .  I thought it was smooth all the way. 

Data from all published roat tests I've found:

http://img.photobucket.com/albums/v443/jcp8832/GS500tests_zpsd738ea8a.jpg

http://img.photobucket.com/albums/v443/jcp8832/GS500gearing-rpms_zps86c965d4.jpg

[Iarn]

I don't use km/h in my every day life, so my conversion could be off a bit.

All I know is that 60mph is roughly 98km/h and 60mph sits at 5k rpms for me at 6th gear. It's just a base for comparison. I don't think it has to be extremely precise, at any rate.

Also, I agree with Gsjack. 160km/h isn't top speed. About 180km/h indicated is... if you're going down hill with the wind blowing at your back. :p

[Krav]

fairly helpfull scheme's. Gs500 1999 has 6 gears right? :S im actually not sure now :p
Anyway, that i reach about (according to google) 80mph in my presumed: 6th gear with stock gearing, and a normal tiresize. that can't be even remotely right :p

I deduce from your second picture that at stock gearing if you were to have 11K RPM you should go 140mph in 6th.
So the target 100mph (which should be achievable.) should be reached in 6th at (about)  7800 RPM. Which sits just above the max torque, which seems fine.

IF i were to have all my gears, and everything works as it should, then i should be doing 130KM/h or 80mph at 6240 RPM :S

Or my tuning is WAAAAY off and i feel things that aren't there (unproven though), or my gearing is wrong (sprockets are confirmed 16t front  and 39 back)

[Krav]

Ill be back, im going to check if i even have 6 gears :S

[gsJack]

Both my stock GSs turned about 4800 rpm at 60 mph in 6th with stock size tires, the Cycle mag gearing link above shows 4730 rpm, close enough.  So:

60 x 5000/4800 = 62.5 mph x 1.6 = 100 km/hr @ 5k rpm, again close enough I think.  Don't split hairs it's all approximate.

All GS500/E/F have 6 gears.

[Krav]

Offcourse, its all a bit of approximation. Maths don't always scale to the reality.

I just did a testrun, and im glad to say that i indeed have 6 gears.
I did a flatout on the highway though, and my GPS is telling me that (with wind from the front) im going almost exactly 130KM/h 

At high rev's / speeds my tach isn't to much of a help either, but it seems stable enough at 100kmh / 60mph
It tells me im doing about 6-7K rpm at 60mph. I would take it with a grain of salt though. i can't really rely on it working very properly atm.

I think, next step is to take it to a testbench, and see what they can tell me. It's a bit pricey at 50 Euros for 1 run, but if it helps me clear up this issue, it'll be 50 euro's well spent.

[J_Walker]

Did you try to restart it? turn it off then wait 5 seconds and turn it back on. 

[Shepa]

Hm... this may be a stupid question, but is it possible that your bike was restricted to lower HP?
Have you noticed some washers on the intake side while mounting those air filters?

Sent from my toilet seat using HTC FartPhone

[Krav]

Did you try to restart it? turn it off then wait 5 seconds and turn it back on. 

As an IT worker i approve of this joke 

Hm... this may be a stupid question, but is it possible that your bike was restricted to lower HP?
Have you noticed some washers on the intake side while mounting those air filters?

Sent from my toilet seat using HTC FartPhone

I did look for that specifically at the time, and thought i didnt have restrictors in them anymore.
I also have had the carbs apart a couple of times allready, I didnt find any washers that were out of place.

Can you post me a photo of the restricter you're talking about?

[Shepa]

No pictures, but the (intake) restrictors should be metal washers or discs with smaller diameter hole than the intake rubber flange, so if you hadn't notice 'em while disassembling the carbs, they're probably not there.


Sent from my toilet seat using HTC FartPhone

[Krav]

Yeah, i remember now, and they are definately not there. So no restriction there.

[MeeLee]

Mine does the same in 6th gear.
I have a 17/35 or 17/36t installed, I believe.
It reaches to 80-85MPH (130-140kmh) at around 5k RPM.

When I shift to 5th, and duck forward, it accelerates to 100MPH indicated pretty ok, and creeps up to top speed, which I got to 112MPH indicated once; but ran out of road to test more.
It revs around 9.5k RPM at that speed, I'm just saying from the top of my head...
In 4th gear it does 100RPM per MPH (10k RPM at 100MPH).

All I did was install a new air filter online, and it breathed a lot better; but my throttle works best a little less than fully opened!
Like, open it, release it a bit, and find the sweet spot where the engine pulls the hardest.
The higher the RPM, the higher that optimal point is on the throttle (eg: in 4th gear, I have no problems opening the throttle all the way. In 6th, I can open it 75% at 85MPH, and slowly open it more as I gain speed).

Top I've ran it in 6th with a 17/35 or 17/36t (forgot which one it was), was 95MPH, with a 10 to 20MPH tail wind, ducked forward.

[Slack]

All I did was install a new air filter online, and it breathed a lot better; but my throttle works best a little less than fully opened!

You need to rejet. If your running lean you can do horrid things to your motor.

[ragecage23]

After reading this thread I decided to give my bike a go and I topped out at 90mph, so consider yourself lucky lol

EDIT: just realized 90mph is more than 130kmh