Cheapest DIY Servo Bypass

EXUP is supposed to increase back pressure. So, there is more air pressure in the exhaust when the exup is not fully open. Seems that would leave more pressure in the cylinder after the exhaust valves closed and that resulting higher pressure in the cylinder could have an affect on the intake pressure on the following intake stroke. I may have overstepped my pay grade on that one. I was simply attempting to play EXUP advocate as I'm in the pro resistor camp.

I wasn't able to use that R1 link that I put in my last post. One has to go here: http://biketransplant.tripod.com/exup_replacement.htm and then click the "circuit diagram" link from that webpage.

Just a bump to say thank you to the OP. Just stuck my Radio Shack $1.25 1/4w 10k resistor in and success.

Great work on resistor tip. Installed yesterday and works perfectly.

SheWolf wrote:

All you need is a 7.5k resistor (I have two 3.75's because I couldn't find the smaller 1/4w ones, so I went with the 1/2w).

Erm.. You appear to have connected the resistors in parallel, not series. This means the resistance is HALVED not doubled.

Boring science bit: http://physics.bu.edu/py106/notes/Circuits.html

cjard wrote:

Erm.. You appear to have connected the resistors in parallel, not series. This means the resistance is HALVED not doubled.

Boring science bit: http://physics.bu.edu/py106/notes/Circuits.html

I read through this whole thread waiting for someone to point that out. Took the last post for it to happen, LOL.

I bought a WRR yesterday. The previous owner removed the servo and the CEL was on. Today I built a servosub from Steve's diagram and I also tried the single resistor (with both a 6.8K and then a 10K as I don't have any 7.5K's and I was curious). All three "devices" took the CEL light away. I will probably go with the single 10k resistor because it's smaller and less parts to corrode, break, etc. As an adult EET student it was fun experimenting though.

cjard wrote:

Erm.. You appear to have connected the resistors in parallel, not series. This means the resistance is HALVED not doubled.

Boring science bit: http://physics.bu.edu/py106/notes/Circuits.html

That is an old first attempt version. i am using a single resistor now, so that is defunct.

I'm just going to assume that SheWolf's parallel connection was a Freudian slip.

Strange, but 7.5k not works for my bike :(
Pluged in but CEL is still there.

UPD I found the solution. There are two 7.5k.

I'm not a bike mechanic but I am an industrial control systems specialist for 20 years. I have plenty of motion control design and programming experience. I've never personally seen a servo motor that provides position feedback without an external or internal encoder or resolver - there would be a minimum of six wires for this. Power, ground (reference), channel a, channel a not, b, and b not.

So....in my opinion, no position feedback. If the valve only operates in a discrete manner (open or closed) then there would be no reason for feedback. If its variable position.....well that's a different story. Still much cheaper to program the position loop time based rather than event based.

Anyway, I'm rambling. Looking forward to jamming resistor in my bike......

LordEndo wrote:

If the valve only operates in a discrete manner (open or closed)

Seems like its not just discrete (seen many times on youtube)..

But still believe its just programmed.

LordEndo wrote:

I'm not a bike mechanic but I am an industrial control systems specialist for 20 years. I have plenty of motion control design and programming experience. I've never personally seen a servo motor that provides position feedback without an external or internal encoder or resolver - there would be a minimum of six wires for this. Power, ground (reference), channel a, channel a not, b, and b not.

So....in my opinion, no position feedback. If the valve only operates in a discrete manner (open or closed) then there would be no reason for feedback. If its variable position.....well that's a different story. Still much cheaper to program the position loop time based rather than event based.

Anyway, I'm rambling. Looking forward to jamming resistor in my bike......

You may want to do some more research. Yes industrial systems tend to have encoders or resolvers. This is not the best method as it's complicated and isn't absolute in its positioning. For what we have (<360 degrees rotation of a motor) a potentiometer (3 wires) works great. This is an extremely common method as well, look at all the servos used in RC vehicles.

Fair enough. Fuzzy feedback but as you said it works right!

So now I'm about to do the removal - has anybody noticed any long term effect of the resistor vs. Steveakus's circuit? Any more opinions on power difference?

Power difference regarding what?

Different methods of cancelling the error message regarding servo removal?

Power difference between a $60 graves thingy, a 5 cent resistor, and a custom circuit board?


Or between having the EXUP operating on a stock exhaust, and not having it operate on a stock exhaust?

HighFive installed a bypass that a guy named Steveakus designed - http://www.wrrdualsport.com/tech-guide/electrical/84-exupremoval
Steveakus details his circuit and reasoning here - http://www.thumpertalk.com/topic/597178-new-free-servo-sub-diagram/

Some of the posters who are using the Steveakus circuit feel that they're experiencing power improvements on the bottom and top end.

In my case, I've just installed an FMF powerbomb and Q4. With the powercommander that's going in next I doubt there's going to be much need to tweak the mixture through another circuit. Opinions?

I'm curious on how the resistor users are finding their bypass now that it's three years later.

Color me a skeptic - but I refuse to believe any of the "servo eliminators" will have any effect on horsepower, throttle response, or torque.

If that was the case I'd certainly hope and expect the $60 versions would not only achieve the same results, but that a company like Graves would have published, dyno proof of any performance advantage.


But I am a skeptic.

I did the resistor mod and I didn't receive the error code, but I ended up using smaller screws for the battery retention strap bracket to compensate for the servo no longer being there. I read somewhere that you can remove the spacers from the servo and still use the stock screws. I'm sure the answer is obvious, but I can't figure out how to remove the rubber spacers from the motor. I got the plastic caps from the back of them removed, but that's as far as I got with it. Could anyone tell me how to remove the rubber spacers without damaging them? They seem like they could tear pretty easily.

Did you try to push the metal collar out of the rubber spacer, thats the only part you need and they should come out easily.

Oh! I was thinking that I had to get the rubber out as well. Okay. I should be able to figure it out now. Thanks!

LordEndo wrote:

Fair enough. Fuzzy feedback but as you said it works right!

So now I'm about to do the removal - has anybody noticed any long term effect of the resistor vs. Steveakus's circuit? Any more opinions on power difference?

LordEndo wrote:

HighFive installed a bypass that a guy named Steveakus designed - http://www.wrrdualsport.com/tech-guide/electrical/84-exupremoval
Steveakus details his circuit and reasoning here - http://www.thumpertalk.com/topic/597178-new-free-servo-sub-diagram/

Some of the posters who are using the Steveakus circuit feel that they're experiencing power improvements on the bottom and top end.

In my case, I've just installed an FMF powerbomb and Q4. With the powercommander that's going in next I doubt there's going to be much need to tweak the mixture through another circuit. Opinions?

I'm curious on how the resistor users are finding their bypass now that it's three years later.

3 years, 20k miles later, same old resistor, with no problems. All it does is prevent the cel from throwing. It has no other function. I've squeezed all the power i can from this motor, & it is enough. I can cruise on the pavement at 70, or rumble along gnarly trails. I still get mpg in the 60's & it runs fine with minimal maintenance. I've got a valve check coming up, but other than oil & filter changes, & broken turn signals, i've not had any issues with this bike. It is as reliable as my old drz, which is a well known low maintenance ride.

It seems the amount of resistance is not critical.. as you see in this thread, many different levels of resistance have worked. It is important to have the exup hooked up so the cel is off, before you do the mod. Evidently, the resistor will keep the cel from coming on, but it will not turn it off, once it is on.

I did mine today, 2012 WRR. used a 10K resistor from radio shack. good so far.

Thanks for all your inputs guys/gals! Going to Circuit City today (Canada's version of Radio Shack) to pick up a 1/4W - 10ohm Resister. Going to take out the entire EXUP system and install my full FMF exhaust (Q4 and Power bomb).

I have not yet purchased a Fuel Programmer (will be buying the Dynojet PC 5 in the spring). Would I run the bike to lean with the full exhaust and no fuel programmer? thanks in advance!

SheWolf wrote:

The light want away with ONE little resistor, not a bunch and diodes.

Is this resistor a 1/4W in a 7.5ohm or is this one a 10ohm? reason I'm asking is I purchased a bundle (bundle of 75 and there is NO listing to show exactly which one is the proper Ohm). so I will try and find the same color coding as I'm assuming they are all the same.

thanks.

1.1M ohm unless I'm reading it wrong.  Looks like 1/4 watt in pic. Brown brown green purple?

LordEndo wrote:

1.1M ohm unless I'm reading it wrong.  Looks like 1/4 watt in pic.  Brown brown green purple?

thanks for the help. The online Color coding for Resistors doesn't give a Purple (or violet) as the last color options. Thus it's Violet, Green, Gold, Gold which is 7.5K ohm. got it!

Well....I think there is a violet tolerance band now.  From electronics class 20 years ago (ahem....) I only remember gold and silver, but....apparently there's others.  

http://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-band

The problem I'm having with the pic is that I can't tell left or right on the resistor.  Normally (if memory serves) there is a larger space between the three bands and the tolerance band.  Also, I'm not so sure those are gold and not brown bands.  Anyway.....it's all kind of a moot point.  Verify the resistor with a multi meter and then you know what you've got.  I put in an 8.2k ohm (from a multi resistor kit like yours) which was gray, red, red I think.

Gold is a 0.1 multiplier (according to digikey) so you have a 7.5 ohm (not 7500) with violet green gold if violet is on the left.

With all this action some electronics whiz is bound to chime in......