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GS500 build thread... cf tanks, internal supercharger, etc

That's awesome. I'll have to remember that.

Good luck with the rest of the build.
 
That's awesome. I'll have to remember that.

Good luck with the rest of the build.

It's an awesome place. I've learned all my machining skills there. You'd think they'd covered that in a mechanical engineering program, but nope.
 
I would have had two internships already if SJSU had provided the same as well...damn state schools.

Honestly, it's fairly typical of most engineering curriculum, state school or otherwise. You'd be amazed how many people in the industry I talk to that are shocked that I have machining experience as an engineering student.
 
If you feel like your education is lacking something, go out and find what you're missing. I'd never be able to tackle a lot of my engineering projects without the machining background I have from working at techshop and the rapid prototyping background from the academy of art; at least not in a way I'd be satisfied with.
 
And you could mess with your air pump output by changing that piston's compression. And potentially vary boost and/or parasitic drag by controlling the old intake or exhaust valves to reduce pressure.

there's so much hacking potential here!

And you could potentially fund your whole experiment by selling a few custom CF tanks. :)

(wonders about making the boost cylinder switchable-from running fueled and sparked for low end torque, becoming an air pump for higher end performance?)

subscribed!
 
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And you could mess with your air pump output by changing that piston's compression. And potentially vary boost and/or parasitic drag by controlling the old intake or exhaust valves to reduce pressure.

there's so much hacking potential here!

And you could potentially fund your whole experiment by selling a few custom CF tanks. :)

(wonders about making the boost cylinder switchable-from running fueled and sparked for low end torque, becoming an air pump for higher end performance?)

subscribed!

The idea is to eventually place a bypass valve in the compressor cylinder so it can be "deactivated" when the air tank is full. Basically, fill the air tank to some psi higher than I'll ever run, then shut off the compressor, so that there's very little drag from it. When I want power, I have energy stored up in the form of compressed air. I could then refill this tank using engine braking, etc, so there isn't drag on the motor when I really want power. If the tank runs too low, turn the compressor back "on".
 
Exactly. Speaking of which, I need to update my much more boring build thread. :laughing
 
mllcb42:

A couple of comments about the rear suspension, from a guy who races his GS500:

The shock that was installed appears to be from a Katana 750, which is a pretty popular upgrade for this bike. It sticks well, and is sprung appropriately for my 180lb ass on the track. For a street rider, it would be ideal for someone who's about 200lbs.

The R6 shock you dropped in is a nice piece, but inappropriate for this bike in stock form. The spring is about as soft as the stock GS unit, and wouldn't be ideal unless you are in the 120lb range. Also, the rebound damping circuit is a little too soft. This is a great upgrade if you're willing to respiring / re-valve.

I was contemplating a bike like this, and I think if I were you I would have gone a different approach -- start with a SV-650. Replace the front cylinder cam sprocket with one that matches the tooth count on the crankshaft - now you could actually use the valves themselves. The change in sprocket size would run the engine through a straight 2 stroke intake/compresion cycle. Time it so that the exhaust valve becomes the intake, and connect the intakes of the 2 cylinders together so that the front cylinder feeds the rear.

Curious why you chose your approach. Cost?

Anyway, very cool project. Looking forward to seeing the results!
 
you could electronically pop open the existing valves for your bypass.

Don't know if you'd want to store more air than you need to even out the pulses. The Yamaha 650 Turbo had what was called a "surge tank" (basically a secondary non-filtered airbox) between the turbo and the carbs. It used a one way reed type valve to allow the motor to create some vacuum and bypass the turbo, which closed under boost. The surge tank also had a calibrated pop valve that would allow excessive pressure to vent.

Didn't store more than a few cycle's worth. So you didn't get too much loss with heated air cooling and losing pressure.

I can't wait for engine run updates. Been looking to the smaller megasquirt for a "someday" project of a DI two cycle for my Gyro :)

The idea is to eventually place a bypass valve in the compressor cylinder so it can be "deactivated" when the air tank is full. Basically, fill the air tank to some psi higher than I'll ever run, then shut off the compressor, so that there's very little drag from it. When I want power, I have energy stored up in the form of compressed air. I could then refill this tank using engine braking, etc, so there isn't drag on the motor when I really want power. If the tank runs too low, turn the compressor back "on".
 
mllcb42:

A couple of comments about the rear suspension, from a guy who races his GS500:

The shock that was installed appears to be from a Katana 750, which is a pretty popular upgrade for this bike. It sticks well, and is sprung appropriately for my 180lb ass on the track. For a street rider, it would be ideal for someone who's about 200lbs.

The R6 shock you dropped in is a nice piece, but inappropriate for this bike in stock form. The spring is about as soft as the stock GS unit, and wouldn't be ideal unless you are in the 120lb range. Also, the rebound damping circuit is a little too soft. This is a great upgrade if you're willing to respiring / re-valve.

I was contemplating a bike like this, and I think if I were you I would have gone a different approach -- start with a SV-650. Replace the front cylinder cam sprocket with one that matches the tooth count on the crankshaft - now you could actually use the valves themselves. The change in sprocket size would run the engine through a straight 2 stroke intake/compresion cycle. Time it so that the exhaust valve becomes the intake, and connect the intakes of the 2 cylinders together so that the front cylinder feeds the rear.

Curious why you chose your approach. Cost?

Anyway, very cool project. Looking forward to seeing the results!


I honestly hadn't even looked at the rear shock before I replaced it. Just assumed it was a stock unit. I picked up the R6 unit for <$20, so figured why not. Honestly, the bike isn't likely to be ridden all that much. It's more of a resume piece than anything. I'll certainly look into revalving/spring it, as I much prefer the aesthetics of it.


I would have much prefered to do this project with a v-twin motor. Life would have been WAY easier. Alas, finding a running sv650 for anywhere even remotely near the $400 I paid for this bike would be next to impossible. Add on to that the fact that I already had a GS in the garage, along with a plethora of extra parts laying around, and the GS was an obvious choice.


The only issue with the idea of changing the cam sprocket to run in the way that you're talking is finding/making a cam with the appropriate duration for an application like this. Using the reed valves as a passive set up, they basically act like having a cam with 180 degrees of duration for each lobe and no overlap. I looked extensively into making new cams for the GS head that had two lobes instead of one so that it acted basically in this manner. Unfortunately, it was prohibitively expensive.

I also considered running a v-twin motor and basically milling out a new head for the cylinder acting as a compressor. More work than I wanted to tackle though.



I appreciate the thought process though. It's been others' ideas that they've added to build threads elsewhere that have helped lead me down the path I've chosen and brought up alternatives I never considered.
 
you could electronically pop open the existing valves for your bypass.

Don't know if you'd want to store more air than you need to even out the pulses. The Yamaha 650 Turbo had what was called a "surge tank" (basically a secondary non-filtered airbox) between the turbo and the carbs. It used a one way reed type valve to allow the motor to create some vacuum and bypass the turbo, which closed under boost. The surge tank also had a calibrated pop valve that would allow excessive pressure to vent.

Didn't store more than a few cycle's worth. So you didn't get too much loss with heated air cooling and losing pressure.

I can't wait for engine run updates. Been looking to the smaller megasquirt for a "someday" project of a DI two cycle for my Gyro :)

What I was considering doing was placing an electronically actuated valve in the spark plug port on the compressor side of the motor. When the valve is opened, it essentially would prevent any vacuum from forming, so the reed valve would never open. No air filling the cylinder means no air to compress. Would lower the resistance of the cylinder dramatically.

The best power gains would be had with air being fed from a storage tank while the cylinder was deactivated. Basically a supercharger without any parasitic drag.

The benefit of doing the tank is that you can refill it while you don't need power. Engine braking is the perfect opportunity. Instead of using the brakes to slow, if I can use the engine to brake with the compressor "on", I can store that kinetic energy without using much gas to run the compressor. Then I can use that stored compressed air to make power with the compressor "off". This would be the most efficient cycle, and what would make this an air/gas hybrid system.

That's basically the ultimate goal for the motor.
 
Awesome! Thanks for letting me in on your thought process. I've got to say that the GS500 is really a nice bike to wrench on. Access to the valves is a little bit of a PITA due to the cross-brace behind the steering head and the airbox sucks, but parts are readily available and most jobs are dead simple.

BTW: One piece of advice is to run the exhaust valves .05mm wider than specified by the manufacturer. Stock clearances are very very tight, and indicators show that the extra clearance is enough to reduce valve adjustment intervals from every 4000 miles to every 12K or so (obviously, build a history with inspections before trying this.)
 
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