What should happen with power after 9k rpm?

[Kito]

Hey Guys,

Once I already chatted with you quickly about this.. but now I feel itchy about this thing...

My bikes runs well.. however I can not go further than 9K rpm ( I know there is nothing that justifies going further than this)

However, I am suspicious that maybe I have an electrical problem (ignitor)... because the loss of power is sharp, like a revving limiter.

My main jet (2004 GS) was 1.20mm, I drilled to 1.35, hoping that maybe she was starving.. but.. no... did not make any difference.

Your GSs does the same?

Ideas?

Thanks

[J_Walker]

Check the sparkplugs.

Check the coils directly above the sparkplugs. [multimeter]

when the GS tops out at rev limiter, it "pops" Because basically its not firing spark letting fuel enter the exhaust.

[Kito]

1) Check the coils  [multimeter]
Ok .. I will check them!

2) when the GS tops out at rev limiter, it "pops" Because basically its not firing spark letting fuel enter the exhaust.

This is maybe my primary question... the GSs "electronics" have this function?.. in the service manual I did not found it metioned clearly... so... there is a limiter after all?

[mr72]

According to the wiki, there is no stock rev limiter.

[Kilted1]

http://gstwins.com/gsboard/index.php?topic=45924.0

[Kito]

Thanks guys.. I think these dyno charts say it all!

Or my tacho is miscalibrated or my ignitor is going dead.

At the weekend I will check the coils... just in case!

[Kiwingenuity]

It would be interesting to measure the voltage across the battery when you hit the 9k - a weak battery or failing coil may be resulting in a "wall". 

Each coil when it charges has a time constant after which you cannot get enough energy back into it between firing pulses.  You may also see the misfire / not enough energy triggering the spark plug - and unburnt fuel getting out into the exhaust - popping at this stage.  So I would suspect the coils are not getting enough energy into them between ignitiion pulses.

Having had a partially failed battery I ran into issues about 6k or higher - the coils would rob too much energy from the system and the bike would bog down / cut out. It behaved EXACTLY like a rev limiter. I chucked a scope + analog current clamp onto either side of the coil and found it was the culprit (It could be useful to post some scope shots of a good system - will add that to my list). 

Am sure someone else here probably has the nominal resistance values for the coils - but equally check the grounding points to the frame etc. It could just be a high resistance connection on one of them.

Hope you sort it.   

[mr72]

It would be interesting to measure the voltage across the battery when you hit the 9k - a weak battery or failing coil may be resulting in a "wall". 

That's a really good suggestion.

There's plenty of opportunity to drop voltage between the battery and the coils. And by putting resistance in series with the coil through corroded connectors, corroded wiring, excess length of small gauge wire, bad ground, etc., it increases that time constant.

Good call on the check the wiring stuff. Measuring just the coil is maybe not quite enough, look into the rest of the wiring path, everything from the battery to the coils to ground.

On my GS a ton of wiring was corroded. I've replaced a whole lot of it. Wouldn't surprise me.

[Kito]

It would be interesting to measure the voltage across the battery when you hit the 9k - a weak battery or failing coil may be resulting in a "wall". 

Each coil when it charges has a time constant after which you cannot get enough energy back into it between firing pulses.  You may also see the misfire / not enough energy triggering the spark plug - and unburnt fuel getting out into the exhaust - popping at this stage.  So I would suspect the coils are not getting enough energy into them between ignitiion pulses.

Having had a partially failed battery I ran into issues about 6k or higher - the coils would rob too much energy from the system and the bike would bog down / cut out. It behaved EXACTLY like a rev limiter. I chucked a scope + analog current clamp onto either side of the coil and found it was the culprit (It could be useful to post some scope shots of a good system - will add that to my list). 

Am sure someone else here probably has the nominal resistance values for the coils - but equally check the grounding points to the frame etc. It could just be a high resistance connection on one of them.

Hope you sort it.   

Hi, very interesting your comment, (applaud)

Indeed I have some electrical spookiness happening... however in general the bike works fine (really)

My stators do not reach more than 65V, however... my battery works fine ... mistery...

One time I measured the voltage on the battery.. and indeed, I remembered that the voltage falls when revs go up...

But in this opportunity, I substituted ONE coil only.. but did not repeat the test.

In this occasion, I taped the multimeter on the tank and plug the wires on the battery directly and went for a ride.

[mr72]

65VAC is enough to get the job done from the stator. But you may wind up with corroded or melted connectors between the stator and the reg/rect which will not only create a fire hazard but also seriously affect charging capability. This is a double whammy, limiting current so it slows charging but also limiting voltage by dropping voltage across high resistance joints. So I'd inspect that and if possible rewire to eliminate the extra wiring and connections that are in there.

Also on my bike the main ground wire from the reg/rect literally melted. That reg/rect is really a poor design. I replaced mine with a ZX6 unit and never looked back. Any FET reg/rect will be far better than the shunt one that's on there that dumps a ton of heat, literally right into the wires.

Anyway, this is all worth inspecting.

[Kito]

Hey Mr72,

Thanks.. you guys are really kind to spend some time sharing your experiences.. As I already said .. perhaps the best thing about the GS's.... is this forum! priceless, indeed.