As the weather gets colder here the backfiring on cold starts is getting worse. From what I've read here, it would seem a valve clearance check is in order. However, that is not my question. Some of you may know that my GS has the ignition (pick-ups and CDI) from an old GS450 and for peace of mind, I would like to know if they are in exactly the same position as they should be. I have seen a mod where you slot the backing plate to make the timing adjustable, but would rather avoid that if I can. As I said, the bike runs fine, I would just like to make sure that is something I can cross of the list. Here is mine
http://img694.imageshack.us/img694/811/photo0835s.jpg
Many thanks.

My 02 GS on TDC

Quote from: bryan88 on May 22, 2013, 12:29:37 AM
As the weather gets colder here the backfiring on cold starts is getting worse. From what I've read here, it would seem a valve clearance check is in order. However, that is not my question. Some of you may know that my GS has the ignition (pick-ups and CDI) from an old GS450 and for peace of mind, I would like to know if they are in exactly the same position as they should be. I have seen a mod where you slot the backing plate to make the timing adjustable, but would rather avoid that if I can. As I said, the bike runs fine, I would just like to make sure that is something I can cross of the list. Here is mine
http://img694.imageshack.us/img694/811/photo0835s.jpg
Many thanks.

Interesting that you do not have a GS500 rotor! Looks like your rotor will cause a spark at top and bottom of the stroke.
Maybe try the correct one for a GS500?

If I remember correctly, he has trouble getting GS500 parts for reasonable prices in SA.  Maybe shipping from the Bike Cave is not too crazy?

USPS flat rate international envelopes cost $24. It's not terribly unreasonable.

Quote from: Paulcet on May 24, 2013, 07:39:05 PM
If I remember correctly, he has trouble getting GS500 parts for reasonable prices in SA.  Maybe shipping from the Bike Cave is not too crazy?

I've shipped to Aus, NZ, Israel, Germany, Portugal, UK, CA. Shouldn't be an issue. Just have to call it the right thing so customs doesn't have a cow over it.
My company has shipped software most everywhere, including SA.

The main issue is there are 2 lobes on his rotor when there should be only 1.

Quote from: adidasguy on May 24, 2013, 07:51:07 PMThe main issue is there are 2 lobes on his rotor when there should be only 1.

With some creative cam profiles, he could make it a 2-stroke.

Interesting, that 2 lobe rotor is part of a centrifugal advance unit used on 80-82 GS450.  The later 83-88 GS450 had a single lobe rotor without the mechanical advance like our GS500 has. OP mentioned he replaced the CDI as well as the pickups.  That would eliminate the advance built into our modules.

Time for Rich or one of our other GS450 users to drop in and take over if they have that 80-82 type, too late at night to try and think it thru.   



http://www.shspowersports.com/fiche_image_popup.asp?fveh=2093&section=92181&year=1980&make=SUZUKI&category=Motorcycles&dc=3378&name=SIGNAL+GENERATOR

Thanks so much for the replies everyone. adidasguy, you are right, shipping is not that terrifying, I recently imported parts for my Honda VFR750 and it was a relatively painless experience. I will leave well enough alone for the moment but thanks for the offer. gsjack, do you think the advance system, or lack thereof would affect high revs? I don't ride the bike hard so I have never tried, but I doubt my GS would see 9000rpm. I've never taken it past 7k, but when I'm there it does feel a bit wheezy. I suppose that could also be fueling though.

According to my old 97 GS owner's manual the ignition timing was 12* BTDC @ 1200 rpm and 40* BTDC @ 4000 rpm and the  California models were 5* BTDC @ 1000 rpm and the same 40* BTDC @ 4000 rpm.  I assume my current 02 GS is the same as the 5-40 California models.  Unless this is a typo in my old OM the bikes are both the same 40* advance from 4000 rpm to redline.

If you've replaced the module from your GS500 with the GS450 CDI I believe you are only getting spark advance from the centrifugal advance unit of the GS450.  I have no idea how much advance it provides but if you do you can compare it with module provided advance we have on the GS00s to see if it's adequate.  If I can find the spark advance info for 80-82 GS450 later I'll post again.

Many here have had fuel flow problems with the GS500s at higher rpm like you noted, you might want to try your fuel selector valve in the prime rather than the on position at higher rpm eliminating the vacuum diaphragm shutoff from the picture to see if that is the problem rather than the spark advance.  Hope your not comparing your GS performance to your VFR.   

Like Adidas above, I too am wondering how that 2 coil and 2 lobe rotor setup works, it doesn't produce a spark in each cylinder every 180* does it?  Our single lobe rotor only fires every 360*.

"Hope your not comparing your GS performance to your VFR."
Not at all. My GS is my daily transport bike and I love her for what she is  , thats why I've never really wanted more performance. I mean 7k must be about 140-150km/h which is as fast as I'd ever want to go on it. I mostly change gears and cruise at about 5k. Running costs and simplicity it beats the VFR hands down (A little aside here, I have actually hankered after a GS500 since the early '90's so I was thrilled to pick this one up)
Interesting what you say about the advance though, I suppose you could run the bike with the pick-up cover off and watch for any movement? I must also check if there is only a sensor(?) on one side of the rotor, if that makes any sense.
Thanks again for your help and input.

Ooooh I should've chimed in here a long time ago by the looks!

That is definitely off the 80 - 82 450's... can I assume you have the mechanical advance mechanism under the signal generator plate there?

The timing for the 450's is 10 BTDC below 1650 RPM and 40 BTDC after 3500 RPM.

Also, only one side of the rotor has magnets embedded in it to trigger one signal generator coil at a time, so in that regard it is the same as the later 450 and the 500 setups.

The only real difference aside from the slight timing change is the fact it is mechanical advance rather than electronic advance.

The difference in timing shouldn't make that much difference but maybe isn't quite advanced enough at idle for a nice start?

I'm not a guru on this stuff, just spent a lot of time looking at ignitions when my 450's ignitor died.

The only issue I could think is maybe some pinging below 4000 RPM if it's advanced too quickly?

Quote from: peteGS on May 26, 2013, 03:24:18 AM
Ooooh I should've chimed in here a long time ago by the looks..................The timing for the 450's is 10 BTDC below 1650 RPM and 40 BTDC after 3500 RPM..............................Also, only one side of the rotor has magnets embedded in it to trigger one signal generator coil at a time, so in that regard it is the same as the later 450 and the 500 setups.............................The only issue I could think is maybe some pinging below 4000 RPM if it's advanced too quickly?

Better late than never, could have saved a few days speculation on the rotor info, all makes sense now.   

Seems the GS500s should run well enough with the 80-82 450 timing.  The 10 BTDC falls between the 12 BTDC of my 97 GS and the 5 BTDC of my current 02 GS, closer to the more advanced figure of the older 97.

I agree the 40 BTDC max coming in sooner at 3500 rpm rather than 4k might cause more pinging on the 500s for some.  I had to use mid-range gas in hot weather to eliminate pinging at those speeds on my 97 GS using 15W-50 oil for the 1st 50k miles.  When I changed to 15W-40 at 50k I never heard another ping from it for the next 30k I ran it and also using the same 15W-40 oli in my 02 GS year around I've never heard a ping in 98k miles using regular gas all the way.  Lighter oil provides greater top end cooling and no pinging for me.

Cool... glad I could at least be of a little help

I guess the next question is does the mechanical advance allow the rotor to line up with the timing marks the same as on the 500 rotor?

This is where I get a little confused with timing (F and T marks and so forth) but I have a Clymer, Haynes, and factory manual for my 450 here...

Thanks peteGS. I did check today and you are right, there is only a sensor on 1 side of the rotor. I'm a bit clueless when it comes to ignition timing so I haven't really looked into it too much, but prior to the valve clearance issue it always started perfectly, and I didn't notice any pinging.

So your valve clearances are out at the moment? Did you do anything with your cam chain tensioner? I'm wondering if your cam chain timing is out... sorry don't know the history here?

Busy doing the valves at the moment. Nothing too serious, I never checked them when I bought the bike and have done 15000km on it. Just in time by the looks of it, I've had to go down almost .15mm on the left exhaust valve. Been wondering that the exhaust has always run very black and possibly with the valves being so tight that contributed to it running a bit rich? It doesn't really bother me though, it was only the starting and backfiring that was bugging me. If I can get it running like it was a few months ago, I'll be a happy boy. Interesting you mention the cam tensioner, the 500 is self adjusting compared to the 450 which you could do yourself. Cam chain looks fine and I haven't had any issues there.

Wow that's a big step on the valve! Since rebuilding my 450 I changed a couple of shims... one after the first 15 minute run, then another one after the first 1000km, then she's stayed solid since then. My tensioner is also auto adjusting 

Hopefully once you get your clearances sorted she'll be much happier to start.

Have you done any carb work at all? Could be worth a sync and adjusting the mixture screws as well depending on the state of your intake/exhaust (stock airbox, stock exhaust, etc.).

I've been setting exhaust valves at .003-.005" (.08-.13mm) as many others here have.  An exhaust valve on my 97 GS that was on the tight side of factory specs required repeated shim changes until it was down to a min 215 shim before 80k miles.  When the tighter exhaust valve started the same pattern on my 02 GS at around 30k miles I went to the wider spec and it went another 40-50k miles without a shim change.  At 98k miles now I doubt I'll ever check it again.

http://www.gs500.net/gallery/data/500/GSvalvelogs.jpg