hi all,

bob seems to be the resident expert on this, so hopefully he or others can help me understand.

so i have read much about advancing the ignition and so on, my bike is an '02, so has the 5-35 rotor.  i did not know that the dwell was different as well! the 12-28 rotor has 28 degress dwell instead of 35.....was wondering what that number was!

so I did the DIY advance, and when you go to advance by 12 degrees to bring it to 17 deg from 5, the slot no longer needs to be a slot as the holes are now 7mm center to center away, simply mark out and drill 2 new holes, and you will have a bit of metal between the now 2 holes.  much easier that making slots that long, although i guess you could connect the two holes after and have a fully adjustable timing advance.   harder to get the electrical clip to now cover the new hole however a bit of dremel work there and all is good.  just made round holes off to the side of the slots where the bracket wants to rotate into.  bike runs WAY better, warms up faster and takes off with more power and almost no stumbling!!  some people had said that you cannot advance the 5 deg all the way to 17, wondering why???

bob, for your modification of the 5-35 rotor, do you advance all the way to 17?

so, why does the dwell need to change? why did it change at all when the rotor changed to 5 deg btdc?  did something else change in the electrical system? do we know that the icu (black box) is the same between the older models (-'99) and the newer (00-'02).  i could understand if at low btdc, say between 5 deg and the 12 deg, the system needs more dwell, but does the additional dwell hurt things after the timing advances past 12 deg?

the description of where to shorten the rotor tab i am not fully understanding. which side of the tab should i remove material from? if the tab is pointed straight up, and i remove material from the right side of the tab, am I not advancing the timing even more? (as this is the part of the tab that first rotates by the sensors) so i guess i would remove it from the left side? or is it only after the tab passes the sensor that the spark fires, and the dwell is what happens just prior to the firing? (this would seem to make more sense and would compare more to the points in a car)

it seems like no matter what, the total timing advance would want to be limited. i think i read 40 degress somewhere on here. so wouldnt the black box be different between the models with different rotors???

12 deg stock rotor.  black box adds 28 deg to get to 40
5 deg stock rotor. black box adds 35 deg to get to 40

so if i advance a 5 deg rotor to 17 deg, would not the black box now add 35 deg and bring it all the way up to 52!!! this is a little scary. 

how would the black box limit the actual timing to 40 deg? how would it know the actual spark firing time compared to the pistion position? confused here....

thanks for any info!

haha 7 veiws 0 replies.  I bet they all did what i did. opened it, saw how long it was and hit back. aha

I read it, I understand it, but I just don't see any need for it.  My 02 GS runs perfect the way  Suzuki built it.  If it ain't broke don't fix it!   

yes, perhaps I am a bit long winded... and you might not think its broken, but it made a HUGE noticable difference for me. and does that mean that all the bikes prior to the 5 deg rotor are "broken" and should have their ignition retarded back to 5 deg? suzuki was pushed to go to 5 deg for reasons of emmisions control, and at the expense of performance is my understanding.  Been thinking about the issue a lot and unsuccessfullly looking for information and wanted to get it all down in one go.  hopefully someone who has some good answers will take the time to read it

So I just read this thread, went and bought a chainsaw file and spent a half hour doing the mod. Lengthened the holes by 4mm, which I figure is about 6 degrees.

After a half hour test ride I noticed a distinct increase in acceleration, improved fuel economy, and the bike started sounding like a Ducati. When I got off I saw that the original black paint had turned red and the bike had twin Termignonis.  

Seriously?........
I didn't notice any obvious difference. (other than that, the bike is stock).

the box advances the timing based on RPMs on an internal curve. with stock timing the advance on a 5-35 rotor goes from 5* at idle to 37*(I think) at redline, if you advance the timing 5* (like I did) you will have 10* at idle and 42*(I think) at redline.

The box on the 12-28 rotor also advances the timing based on RPM but with a different curve. with stock timing with a 12-28 rotor will have 12* at idle and 37* at redline (yes, both have the same advance at redline) So increasing the advance 5* would yield 17* and 42*.

I don't know what timing will start to give knock but I would assume that much over 45-50* would be seriously unsafe without higher octane fuel. with your 5-35 rotor advancing the timing 12* would be 49* I think. so your theory sounds correct, but the black box does not know what the actual timing is if you advance it, the only inputs are rotor position and rpm so it can't limit the timing. If I was you I would slot the holes and decrease the timing a few degrees and put in colder plugs, then see how she likes high rpm. If you hear knock try reducing the timing or putting higher octane in.

P.S. the 04+ F models with 3 circuit carbs also adjust timing with the Throttle Position Sensor.

the mole, no difference? interesting. i guess you were going from 12 deg to 17? what year bike? mine was from 5 deg to 17, so maybe that is why i noticed the difference, i can back it off to 12 and see if its any different, i suspect that the difference between 12 and 17 is fairly minimal, and most of the gains are from 5 to 12. i bet if you turned yours the other way to reduce to 5 deg, you would notice the drop in low end performance immediately. very interesting, i went through a lot of time getting the timing right in my car, which is a 1966 volvo 122s, and it made a huge difference in power, economy etc getting it right.

5 deg btdc is VERY conservative. it was changed to that so that the bikes would pass idle emission requirements, and the california models went to 5 deg first, followed by all models in 00 to 02. not sure on the 04+ models. the only problem being that once you get on the gas, you are firing too late to get full burn on the fuel.  and for bikes in Australia, i dont know what is stock..

black and silver twin, i think you might be correct that the black box is additive, as i THINK i have lost a bit at the top end, which might be due to too much advance at the top. no knocking though... i do think i will back off the rotor a bit.  i think with a timing light i would be able to get a rotor position at say, 6000 rpm and compare the position of it between having the timing at 5 deg initial and 17 deg initial, that would answer the question, if the position of it is off by 12 deg, then the black box is purely adding timing as you suspect, and would not know what total timing it is going to.

although with the throttle position sensor with the 3 stage carbs, is that present on the 00-02 as well as they have 3 stage carbs too? i will have to dig into the service manual. 

thanks, this answers some questions, good stuff! still wondering why the dwell would be different, however. different coil or other components in there that want more dwell time?

hmm, just checked on parts lists for the 1990 vs the 02, and the 90 california model has the same parts as the 02 model. BUT NOTICE THAT BETWEEN THE CALIFORNIA MODELS AND THE OTHERS, THE BLACK BOX IS DIFFERENT AS WELL, NOT JUST THE ROTOR.  this is true for say, the 1998 model as well, not only is the rotor different, but the black box too.

check out the screen capture, the left is the 1990 showing all the various models available then, the right is the 02 model. red splotches show the rotor and the black box (ignitor) being the same between california and 02 model. 

so, the 12-28 rotor uses a different black box than the 5-35 rotor. i would guess that the 12-28 black box adds LESS total timing than the 5-35 black box.

conclusion: I am going to back off my advance, I will repost when I find something that balances low end and top end.  i think my total advance is probably too aggressive, having added 12 degrees to the whole range, might be dangerously high at higher RPM. 

the dwell difference would match some other difference in the black box, i would think. changing the dwell might be a BAD idea, not knowing what the black box wants. reduced dwell may reduce your spark intensity or cause other bad things.

(posting my first pic, lets see if it works)

My bike is a naked '06.
I'm not saying there was no difference, just that my backside didn't notice it. Its not as sensitive as a dyno. (but much cheaper!)

yeah, no dyno runs for me, i dont have the cash! seat of pants difference is all i need. this made a big difference at the low end, but after driving for a bit, i have found that the top end has definately taken a hit, and this is a bit scary as it means full burn is happening too soon = heat = loss of power = bad.

so i will be backing this off, i will try 5 deg advance. (to be 10 degrees BTDC on my '02) like "black and silver twin" did.

i know the '04 + models are completely different. i dont know that you can or should modifiy in the same way at all.

byron bay, nice place! my wife is from brisbane.

If you come back here to visit her relatives, pm me and come down to Byron, there's a GS here you could take for a ride in the hills!

thanks! i should have contacted you a month ago! we spent xmas new years in bribane. very very nice. took me 2 weeks of depression here in the grey rain before it cleared up enough to go for a nice ride and regain the hope of sun.

Riding in the rain is the "perk" of living in Seattle 

Ghost, what you doin with that tank?!

when I dyno tuned my bike for the V&H exhaust and lunch box filter I also played with the timing afterward. with +2* my bike gained 1 horse power at peak and 2whp above 10000rpm. with the full 6* She gained a total of 1.9whp at peak and 3whp above 10000rpm. I didnt even look at the torque but it idles smoother and shudders/bogs much less at low-rpm/high-throttle.

Quote from: O.C.D. on January 29, 2010, 05:20:14 PM
Ghost, what you doin with that tank?!

Hey OCD, I just gave it a quick and dirty rattle can job and slapped it on my commutefighter 
I plan on filling the dings and giving it a proper paint job when I have less motorized vehicles to fix.

I also picked up some '89 clip ons 

black and silver twin, that is very good info!

i played with the timing on mine as well this weekend, and ended at +5 deg. really feels better, seat of the pants, than before, and also better than when i had it cranked all the way to +12!! that was a mistake, i think it would have caused serious engine trouble after too long, and the top end power was gone. my mistake for assuming that the only difference between the older models and the 00 to 02 was the rotor timing.

good stuff! loving it went for a 120 mile on the weekend and it was grand!

yeah, 5* advance is perfect for high rpm, but I wish there was a way to give more like 10* in the low end without upping more than 5* in the top. basically change the curve not just advance the static base timing. I dont know if more in the low end would help though, its just a guess because the old gs' had 12* in the bottom whereas the new ones have only 5*.

My bike had the pin on the end of the crank which indexes the rotor sheared off.   So my rotor is just held on with the end bolt.  Totally adjustable I guess?  Set it and it's never moved, don't know what it is set at I just kept clocking it around till the bike idled smoothly?

commuterdude, oh boy, that sounds bad! personally i would drill and put a little dowel in where the old pin was, if you can see where it broke off from, center punch then drill. if you get the timing off by too much you can do serious damage to the engine, and best case you are running innefficiently. unless you guessed right and its spot on. then shift the plate a few degrees to do the couple of degree advance. at least then you will know where your at.

black and silver, i am with you there! when i advanced mine all the way to 17 initial from 5, the low end was totally and completely changed for the better! but of course the top suffered, so yeah, having the initial set to somewhere around 15 and then ramping up to the top being around 40 seems like it would be ideal. putting an ignitor from one of the pre '01 bikes in there would get us a lot closer! they are not cheap however. wish there was a DIY way of messing with the timing "map".

d