those jets... woah.

Sorry about your power issue, I've got no idea  valve check, just for kicks? 

Hm, valve clearance i checked less then a year ago, i did change some shimms out, don't remember why exactly.

I guess ill see if i can have it compression tested somewhere. maybe my valves or seats or gaskets are just worn.

is there a top RPM limit while driving in your gears? might be that there is a tiny tear in a carb diaphragm. I dunno though, by now this is well past the point at which I can provide any helpful advice.

paging Buddha....Buddha to the tread, please...

Are you sure you're not dragging the rear brake, or maybe have a missaligned rear wheel (to the same effect)?
Is the engine achieving redline rpms in your top speed measurements?

Sent from my toilet seat using HTC FartPhone

A good point in last 2 posts, will your engine reach redline in 1st, 2nd, and 3rd gears?

Oh main, i wish i could tell you which RPM's my engine makes, but the tachometer in my dash sucks massive donkey.... ears. I can't seem to install it in a way were it will tell me accurately what RPM's im making :S

I do feel though i can get it in to very high rev's in 1, 2, 3, 4 etc. way more RPM's than in 6th.

Oh, and im sure im not dragging brakes manually. Maybe its poorly installed, that may cause drag maybe, but im not dragging my rearbrakes with my foot.

Your speedometer works and you have standard gearing and rear tire size.  Will it go close to 48, 67, and 86 in 1st, 2nd, and 3rd respectively?



My 97 was same as yout 99 stock, parts fiches are same for all 97-00 GSs and my 97 completely stock would break the redline in 1st, 2nd, and 3rd.  I soon learned though that with 8500 rpm and 7000 rpm hp and torque peaks there was nothing to gain going past 9k rpm and would run for hours keeping it between 7-9k rpm in the mountains.

Check your ignition timing. Carbs arent everything, if your timing is off or not advancing correctly, you will lose power big time, especially at high rpms.
A harbor freight timing light is cheap and does the job fine.

Mph right?! Doing 47 mph in first, and 67 in 2nd seems crazy to me. I will see how fast it will go though today.

My ignition. Haven checked that one out yet. Ill have a look at that aswell.

Quote from: Krav on May 09, 2015, 09:41:43 AM.............I do feel though i can get it in to very high rev's in 1, 2, 3, 4 etc. way more RPM's than in 6th.............

Just saying like others have suggested is it possible your bike has breathing difficulties due to restricted intake or exhaust?  You have altered both the intake and exhausts of that bike.  Reving it up in a lower gear can check that without the wind resistance of higher speeds.

You will never reach the highest rpm's in 6th gear, your GS is geared to reach it's normal top speed at about the HP peak, around 8500 rpm and won't go any faster with wind resistance although it might go a bit higher with a good job of modifying intake, exhaust, and carb jetting.  Your present jets seem very large to me, I reached an indicated speed of 110 mph probably an honest speed of about 100 mph with my 97 engine and did it with stock carbs.  My 97 bought new had about 50k miles on it at that time.

Sooo, i did some testing yesterday. About the max i would do in a specific gear:

1st: about 60 km/h , which is 80% of the theoretical topspeed: 74 km/h (48mph)
2nd: about 90 km/h, which is 83% of the theoretical topspeed: 108 km/h (67mph)
3rd: about 113 km/h, which is 82% of the theoretical topspeed: 138 km/h (86mph)

it seems to underperform about 80% of the theoretically possible speed everytime in low gears. Im quite sure it reached redline, as the RPM were much MUCH higher then normal. I did find out something though.

Yesterday, when most of this was tested, it was quite nice, around 20 degrees Celsius. After a nice long drive with a friend, we entered the highway to go home. Here i tested how far it would go in second. After having established the speed, i'd shift up and proceed to get up to highway speed. Then, sudddenly my TEMP light on the dash went on. (i have a ring under a bougie for the temps). I would link this to the 2nd gear test, i did before, but it was a couple of kilometers later (going around 130km/h). When i inspected the max. temp at my destination it said my cilinder head got to 193C degrees. (light comes on at 175C) I have never seen it surpass even 175.

Could this indicate a lean jet? the excessive heat?


EDIT: This is my current to-checklist.
- Compression test
- Check ignition timing. Stock timing should work right? or should advance timing 5 degrees?
- Check camshaft timing (the shimms should be in spec.)

What happened to your stock tach? can you hook it back up for testing? Do you know anyone with a GS who will let you borrow their tach for a bit? Where do you live? Maybe a near by member has a tach you can borrow.

If you think you are running lean at high rpms, bring some choke on while testing. If the temperature falls, or you notice more power, you may be lean. Remember the choke on our bikes isnt really a choke, but an enrichment circuit. I believe this works by adding pressure to the bottom of the diaphragms. Please correct me if Im wrong on that, but for sure there is no mechanical choke plate to limit air intake.

And if you are courageous enough, if you can find a safe spot to do so, run the bike up high in second gear until the temp rises. Then kill the motor and coast with the clutch in to a stop. Pull both plugs out and see how they look. People have tuned two strokes like that for years, and short of an air-fuel analyzer, its the best way to find out what kind of mixture you have at various throttle openings and engine speeds.

Quote from: Slack on May 11, 2015, 09:03:06 AM
What happened to your stock tach? can you hook it back up for testing? Do you know anyone with a GS who will let you borrow their tach for a bit? Where do you live? Maybe a near by member has a tach you can borrow.

My original tach got slashed up a bit in a crash i had about half a year ago. i ditched it and threw it out. Im the first one of my friends, and the only one i really know of my friends and family to get a motorcycle (what a rebel xD) I don't know anyone with a motorcycle, let alone a Gs500. But in about 2 weeks i'm able to get my hands on a set of original clocks.

I DID do some adjustments to my vapor dash setup yesterday, and it seems to be VERY stable at the moment. Response is still slower than it could be though. but its not all over the place anymore. Who knows...

Quote from: W201028 on May 11, 2015, 03:09:45 PM
If you think you are running lean at high rpms, bring some choke on while testing. If the temperature falls, or you notice more power, you may be lean. Remember the choke on our bikes isnt really a choke, but an enrichment circuit. I believe this works by adding pressure to the bottom of the diaphragms. Please correct me if Im wrong on that, but for sure there is no mechanical choke plate to limit air intake.

And if you are courageous enough, if you can find a safe spot to do so, run the bike up high in second gear until the temp rises. Then kill the motor and coast with the clutch in to a stop. Pull both plugs out and see how they look. People have tuned two strokes like that for years, and short of an air-fuel analyzer, its the best way to find out what kind of mixture you have at various throttle openings and engine speeds.

Ill play around with the choke a bit this afternoon. The temperature is more of a side-effect in my eyes. I've been f#$king around a lot with jets lately, all dell orto's. The first mikuni jet i put in makes it get to hot, and since its the lowest on beergarage and the wiki for this setup, i guess ill just have to assume to raise my jets a bit. Or i get it to a dyno first. then ill know for sure. But that isn't in my budget range righ not.

Im not good at plug reading. I've done a lot of tinkering on 2 strokes, but somehow the plug always looks a healthy light brown-ish color to me, 2 stroke, 4 stroke, 50 70 or 500cc. nah, im not great at that :p

Just another small thingy.



The side vacuum ports on both carbs, I've got them both capped off with a bit of tube and a screw in the end. I don't see a lot of carbs, but are those ports supposed to be capped off?

I have no frame petcock btw. Its a burden.

oh, and the vent (not marked in this picture), between the carbs, i've got that one hosed up just hanging with my coils, to the front. could this cause a problem?

Hey guys, I came across this when exploring the possibilities on the interwebz:

https://groups.google.com/forum/#!topic/ni.motorcycles/MKswPKe1RQU

Specifically this post:

Quote
Hawker wrote:

> On Sat, 29 Apr 2000 23:42:54 +0100, "Rebecca Walton"
> <les...@poohey.freeserve.co.uk> wrote:
> >Oooh yes.  I had one of them.  Performance isn't it's forte - in a
> >waterproof oversuit on a windy day, it'd struggle past 80ish in top.
>
> Either that was one hell of a head wind, or there was something
> quite wrong with your bike....


No, in a way she's right.  In 6th gear a GS500 won't go over 90mph.  In
5th, however it will very happily wind up to 100mph+.  I've gone a few
miles at 90-100 and it didn't seem to mind.  The wind was a Buddha Loves You,
however.

Never measured the times on anything.  However, I can say that things
are much more interesting if you keep the RPM around 8k.

(Brief digression: I think that people get used to not revving the
engine much in their cars, so they come to believe winding up their
motorcycle is a bad thing too.  It ain't.  Keep it under the red-line,
go easy on the clutch, and change your oil, and you won't hurt anything
running at high RPM.)

The suspension is a bigger limiter than the engine.  Supposedly
replacing the front springs will help a lot but I have yet to try it,
myself.

In new bikes, get a SV650 over a GS500.  In used, GS500 is your only
option, but it's a good one.

MJF
'98 GS500E
'82 GL500I

Quote from: Krav on May 12, 2015, 02:01:07 AM
Just another small thingy.

oh, and the vent (not marked in this picture), between the carbs, i've got that one hosed up just hanging with my coils, to the front. could this cause a problem?

I think that hose is supposed to go back, over the battery, and down. Having it pointing forward could pressurize it in the wind and cause problems. I'm not positive about that though. . .

Did a test drive yesterday. I took it to 135-140 Km/h in 5th, then shifted to 6th, and it would pull! It took me up to 152.8 Km/h! Fastest till this day!

Anyway, when i circled around, and wanted to give it another try, it would drop my performance a bit, and six'th felt more like a burden then a blessing. I also found the choke to be hard to operate going 140km/h+

Monday next week ill do a compressiontest, to be sure that power SHOULD be available. And when i get new funds available, ill have a dyno test.

So i took it for another drive today, and took it to 140 km/h in 5th. Then when i shifted to 6th it would pull. Just at the end of my free runway i took it up to 158,9 km/h

I'd say the problem is clear to me now! When i don't go to 140 in 5th, it won't go faster in 6th, if i do it will. So i guess its a performance issue of somekind. I hope the compressiontest will be positive monday, if so, i should probably proceed to finetune my carb and advance my ignition.

I'd say, close this thread! If i need ill open another one. This one has changed too much.

Thanks everyone so far for your help!

Quote from: gsJack on May 09, 2015, 12:10:32 PM.............................I soon learned though that with 8500 rpm and 7000 rpm hp and torque peaks there was nothing to gain going past 9k rpm and would run for hours keeping it between 7-9k rpm in the mountains.

Quote from: Krav on May 13, 2015, 11:16:37 AM............................I'd say the problem is clear to me now! When i don't go to 140 in 5th, it won't go faster in 6th, if i do it will. So i guess its a performance issue of somekind.......................

Like I said above I found 7-9k rpm to be the range of best performance of my stock 97 GS and 9k rpm in 5th gear is about 100 mph (160 km/h) although wind resistance becomes a greater factor at those speeds.  Shifting at 9k rpm drops you down to about the peak of the torque curve.  It is a performance issue, shifting to 6th too soon you don't have enough power (revs) yet to pull top speeed in 6th.  Sixth gear is your interstate overdrive cruising gear.