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Homemade rev limiter

Started by wladziu, November 08, 2008, 07:56:40 AM

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wladziu

I haven't done it yet.  I want you to do it, cause I'm busy.   :flipoff:

Doesn't seem like a bad idea to find the throttle spring position at 10K, and then mount a bracket like a bumpstop to keep it from going further.  At the carbs, of course, and it'd have to be a fairly strong bracket.  Any bending, and it'd fail exactly when you were depending on it. 
Or, some epoxy built up where the throttle cable housing meets the handgrip.  Sort of like the steering lockout thing.  I like the previous idea better, though. 

ohgood

do that, and you'll be pulling the carbs UP and putting stress on the intake pipes. just something to think about. :)


tt_four: "and believe me, BMW motorcycles are 50% metal, rubber and plastic, and 50% useless

Kasumi

Why bother? The point with the GS is it doesn't require a rev limiter, because the engine stops producing power far before you reach the limits of the engine and its componants. Not like a superbike where the revs shoot up so fast that you risk overspeeding the engine in the lower gears. Change gear when you reach the point where the power stops, then you don't need a rev limiter.
Custom Kawasaki ZXR 400

wladziu

I bother, because I'm new and don't want to screw my bike up in some sort of mistake. 

And, the carbs don't need to be pulled up, depending on where and how the bracket is mounted.  Besides, it doesn't have to be a bracket.  A limiting strap like the suspension on my jeep could work just as well.  I'm not sure what is held by those two bolts above the throttle spring (on the engine itself), maybe a strap could be placed there and the other end could wrap somewhere around the screw that ties the two carbs together.  Or, maybe a strap put on the tranny housing below the carbs, and wrapped the other way around (from the rear).  I don't have time to argue this right now, but it could work fine. 
Right now, I've gotta put this thing back together. 
Talk amongst yourselves. 

Kasumi

You arn't going to screw it up. The bikes are like 20 years old and have had almost nothing changed on the engine in that time, theyve done 100s of thousands of miles some of them and still run sweet as a nut. If Suzuki thought you were going to screw it up they would have fitted one themselves, think of it like that. They didn't put one on and you don't need to. Noobs ride them all day long and do all sorts of stupid things on them and don't break em. Stop worrying about it and get out and ride the damn thing.
Custom Kawasaki ZXR 400

Jackstand Johnny

Quote from: Kasumi on November 08, 2008, 09:17:10 AM
You arn't going to screw it up. The bikes are like 20 years old and have had almost nothing changed on the engine in that time, theyve done 100s of thousands of miles some of them and still run sweet as a nut. If Suzuki thought you were going to screw it up they would have fitted one themselves, think of it like that. They didn't put one on and you don't need to. Noobs ride them all day long and do all sorts of stupid things on them and don't break em. Stop worrying about it and get out and ride the damn thing.

+1

wladziu

Until the steering head bearings come in, I'm limited to just sitting on the frame and going "Vroom".  

If what you say is true, then I'm tired of hearing people say "Hit 11 1/2 K, and you'll be soowwwwy".
Pretty condescending, when an alternative isn't offered besides simply not revving it very high.  I've ridden a grand total of 25 minutes, how am I not supposed to be nervous about that?  

Kasumi

Ignore them. They are wrong.

Trust me you arn't going to rev it too high. The only time you could ever rev the GS higher than you would normally go is when you arnt in gear, your sat with the bike in neutral (or clutch disengaged) and your blipping the throttle, throttles are resonably sensative but from ticking over a 1000rpm your not going to get anywhere near 11.5k unless you hold the throttle wide open, and why would you? And so long as the bike is warm even if you did rev it right round as high as it would go your only going to do it briefly. TO kill the engine or damage it, 1. is very hard, they would have installed a limiter from the factory if they knew the componants couldnt take it, 2. you would have to pin the throttle open as high as it would go for a significant length of time to cause damage. You have half a brain right? This isn't something you can do by accident you have to activly go out and try and over rev the engine, trust me you arn't going to do it by accident.

Now when it comes to riding in forward motion, there is no need for a rev limiter either, the revs will only build as fast as the bike can allow (its theorteical best rate of acceleration) Even if you pin the throttle wide open the revs cant build higher than the engine turns over and the engine can't turn over faster than your moving. So with the throttle wide open you will get the maxiumum accelerative force, the revs will build accordingly, but the engine runs out of puff way before you could over rev it, there won't be anymore power after a certain number of rpm. No more power means no more pulling force which means no more acceleration and no moving faster which in this huge cycle means that the revs can't go any higher. Thus no over revving. Plus your not going to get even close to the limit of the bike for many hundreds if not thousands of hours in the saddle. Trust me you will be babying that thing down the road because your 99.9% more likely to outride your own limits than the bikes limits.

Don't worry about it. Its a nigh on indestructable engine. Start it up, let it warm up. (oil needs to be warm for the engine to lubricate properly) this can take 5 minutes. So start the bike then put your gear on. Then ride it. You won't do any damage until you fall off and even then the bike stands up well to it.

Being scared of your machine is making a difficult task (learning to ride a motorcycle) twice as difficult as your worrying about something that you don't need to worry about.
Custom Kawasaki ZXR 400

ecpreston

#8
FWIW, a throttle stop wouldn't keep you from overreving the bike. With the driveline disengaged, it only takes a little throttle (I would guess less than half) to rev it as high as you want. And again, depending on the gear you're in, it would take different amounts. That same half throttle in 1st gear would probably still let you overrev it. So you put the stop at less than half throttle? That'd be a fun GS once you go on the highway!  *puke*

And yes, don't worry. It really does run out of steam up there. And around ~10, 10.5, you hear audible valve float and power REALLY drops off. You'd have to really REALLY not be paying attention to just stay in it. You'll be shifting before 10 (maybe 10 tops) even if you're trying to drive the hell out of it. It's not wrong to say "Hit 11 1/2 K, and you'll be soowwwwy", that might be true. But you'd have to be trying to destroy it to do that.

wladziu

That's all what I was hoping.  The way some of these folks talk, though....
I figured maybe it was something about these tiny little valves (or their springs, rather) or something that caused it to Jihad immediately at 11.5K. 

Heh, can't blame me for wanting to keep my bike in shape, though.  This thing's so gorgeous now with the new powdercoat, I want it to have my baby. 



ohgood

Quote from: wladziu on November 08, 2008, 10:59:42 AM
That's all what I was hoping.  The way some of these folks talk, though....
I figured maybe it was something about these tiny little valves (or their springs, rather) or something that caused it to Jihad immediately at 11.5K. 

Heh, can't blame me for wanting to keep my bike in shape, though.  This thing's so gorgeous now with the new powdercoat, I want it to have my baby. 





didn't realize we were talking about a non-ridable bike. sorry, would have told you to get a sanding project like a chest of drawers or something to tide you over.

:) when you get her back together, just enjoy the fun, and be careful :)


tt_four: "and believe me, BMW motorcycles are 50% metal, rubber and plastic, and 50% useless

wladziu

What is that in your avatar, Kasumi?  A cassette tape? 

Is that the little cassette tape Transformer, and you've held him hostage in order to give you more precise throttle control?  Is that what we have to do to get fuel injection around here? 

sledge

Quote from: wladziu on November 08, 2008, 07:56:40 AM
I haven't done it yet.  I want you to do it, cause I'm busy.   :flipoff:

Doesn't seem like a bad idea to find the throttle spring position at 10K, and then mount a bracket like a bumpstop to keep it from going further.  At the carbs, of course, and it'd have to be a fairly strong bracket.  Any bending, and it'd fail exactly when you were depending on it. 
Or, some epoxy built up where the throttle cable housing meets the handgrip.  Sort of like the steering lockout thing.  I like the previous idea better, though. 

Rev limiters work by cutting the spark or fuel at a predetermined figure. Limiting slide travel wont limit revs, just performance.....for instance what would happen on a uphill slope when the bike is labouring and you need the throttle wide open to keep momentum?? Limiting slide travel is one of the ways of restricting bike to comply with learner laws.

Do what everyone else does and keep an eye on the redline.

Kasumi

Its a home made fuel injection kit, with a power commander fitted to get 100hp out of the GS motor without boring it out!

It works in theory...
Custom Kawasaki ZXR 400

wladziu

What's it have in it?  Unicorn piss?

Kasumi

Remove carbs, fit fuel injection system from a ninja650 twin, fit powercommander and bobs your uncle :)
Custom Kawasaki ZXR 400

cafeboy

IF I COULD FRAME MY MIND---WHERE WOULD IT HANG ?
I've Seen The Future, and It's Cafeboy-Shaped.

wladziu

An inside joke or something?  Are you gonna try to sell me one now?  $399 and a subscription to Bullshit Weekly?

Kasumi

Bobs your uncle is an english phrase for jobs done, or the like.

It is sort of an inside joke. Me and another forum member were discussing it and he came up with an avatar of our idea. CndnMax. Then people stumbled across the thread and actually thought we had created FI for the GS. Its being going on for like 6 months now and i still get PM's asking me how we did it lol.
Custom Kawasaki ZXR 400

wladziu

Figured as much.  Did the FI work, at least? 

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