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Author Topic: 1981 Suzuki GS450L - Cruiser to Scrambler  (Read 39304 times)

Offline AimlessMoto

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #90 on: Aug 30, 2016, 21:25:41 »
I absolutely love how this is coming out! Great work!

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #91 on: Aug 31, 2016, 09:11:01 »
Worst case scenario, doubt it would come to this with all your meticulous work, you have a killer looking piece of art to put up in the house.
Haha!  You hit the nail on the head danejurrous... I've been telling people essentially that; that I'm just making very expensive garage art.  I suppose I could try to get it in the house somewhere though...  :o

I absolutely love how this is coming out! Great work!
Thank you, DannyMotor  :)  That means a lot.  I see you've had to mess with 4 carbs on your GS.  I can't even imagine... The two on mine are intimidating enough.   :P

Offline 5ivemoto

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #92 on: Aug 31, 2016, 10:36:15 »
Very cool project. Really dig it. The rattle can paint job looks stellar nice tape lines. Just all around good stuff. Kudos

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #93 on: Aug 31, 2016, 10:51:24 »
Very cool project. Really dig it. The rattle can paint job looks stellar nice tape lines. Just all around good stuff. Kudos
:) Thx 5ivemoto - I appreciate the kind words. 

The cosmetics of the bike are pretty much done, so at some point I hope to get some nicer shots outside of the garage.  I'm forcing myself to hold off on final pictures because to me it still needs to run correctly before I can post "done" pictures.  Tonight I'll be starting her up and seeing just how much of a mess I've got on my hands to tune up.  I've never tuned a carb before other than adjusting the idle on a weed-whacker, so again, expecting the worst and may be posting lots of frantic "What does this sound mean?!?!" posts.

For starters, where does one plug their laptop into the carbs at to tune them?!?!   ;)

Offline AimlessMoto

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #94 on: Aug 31, 2016, 18:24:46 »
Thank you, DannyMotor  :)  That means a lot.  I see you've had to mess with 4 carbs on your GS.  I can't even imagine... The two on mine are intimidating enough.   :P

Yup! That's why I'm only working on parallel twins from now on! :)

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #95 on: Aug 31, 2016, 23:06:45 »
This update has its ups and downs... or rather downs and then ups :)

I was able to get some gas in the bike and start it for the first time since January 2016.  It was a little sluggish to get going at first and had to put it on full choke to get it to kick over.  It did fire up though... well, at least half of it did.  It sounded pretty rough and I quickly found out that the left cylinder wasn't firing at all. 

I had a sneaking suspicion that it had to do with the way the RPM pick-up wire from the Koso digital gauge was wired into the signal wire going to the left cylinder coil.  The pick-up wire for the gauge is actually 2 wires, one black that was supposed to grounded and the other connected to the signal wire coming from the ignitor.  The Koso directions were tough to decipher and I was a bit suspicious about grounding the signal wire.  Sure enough as soon a I disconnected the ground the cylinder started working and the gauge started to display RPM info.  Got lucky there figuring that out right away; boy was I nervous it was something else.

It was still running pretty rough after that.  I wasn't really able to take it off choke even once it warmed up.  I did a lot of messing with the mixture screws and was able to get it off the choke by turning them out a fair amount.  But, then I was no longer able to give it any throttle whatsoever.  It would just instantly die.  I could put the choke on and then quickly twist the throttle and it would get up and out of the low end, but I couldn't slowly roll out of the low end.  It was very frustrating.  Very very frustrating.

Settings at this point:
Mixture screw - 3.25 turns out
Pilot jet - 17.5 (stock)
Float height - 23.5 mm
Jet needle - plastic spacer removed, one 0.5 mm washer in its place
Main jet - 145.2

Parts:
Mac 2-1 exhaust, shorty muffler, K&N pods with Outerwears prefilters

I decided to just pull the carbs back out and tear them apart since I wasn't getting anywhere with the adjustments I could make.  They were acting like the pilot circuit was plugged or something very wrong.  I've seen a lot of discrepancy in float heights reported for these GS450.  Clymer says 22.4 mm, others say 26.6 mm.  I ultimately set the float heights to 26.3 mm and upped the pilot jets to 20 just to see where that would put things.  I was pretty much grasping at straws at this point.

Settings after changes:
Mixture screw - 2 turns out
Pilot jet - 20
Float height - 26.3 mm
Jet needle - plastic spacer removed, one 0.5 mm washer in its place
Main jet - 145.2

I got dead lucky.  I'm pleased to say the bike started up much much more easily :)  It required a little choke to get warmed up, but once warmed I was able to take it off and it fell into an idle at about 900 rpm.  I did a few throttle blips, which were impossible before, and it indicated a little rev hang which I read to be too lean.  Working on the mixture screws ultimately brought the idle speed up to 1,200 which is where it should be factory.  When blipped, it responded very well.  I ultimately found that 3.75 turns out on the mix screws was best.  Getting close to going up another pilot jet size.  I wouldn't normally confound things by changing more than one variable but I was frustrated.  Feeling much happier as I can work from this base.

Final settings tonight:
Mixture screw - 3.75 turns out
Pilot jet - 20
Float height - 26.3 mm
Jet needle - plastic spacer removed, one 0.5 mm washer in its place
Main jet - 145.2

Ultimately, I intend to follow the standard tuning steps of find main jet first at full throttle, then move to jet needle shimming in mid range and finally pilot and mix screws.  At the moment though, I need to get insurance and registration set up.  Helmet is being delivered tomorrow as well as a license plate bracket and mirrors :)  Hoping I can get out and ride yet before the frost comes!

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #96 on: Sep 01, 2016, 10:11:47 »
Everyone likes pics and videos over text, so here's where things stand after the carb work last night:

Offline Maritime

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #97 on: Sep 01, 2016, 10:27:17 »
Nice, a ride will tell you a lot more for your jetting but sounds like you have a good start.
The GL Rebirth: http://www.dotheton.com/forum/index.php?topic=68337.0
CX500 Low budget Bobber : http://www.dotheton.com/forum/index.php?topic=43617.0
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Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #98 on: Sep 05, 2016, 16:12:56 »
I've spent some time balancing the carbs.  They weren't too far off but there was a slight difference.  Attached are before and after pictures of the gauge readings.

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #99 on: Sep 09, 2016, 09:52:37 »
So, I've been having some trouble getting the bike to run right at partial throttle openings.  It would sound like it was going very rich and would start running really rough/stumble and lose power.  Not a very reassuring thing to have every time you are pulling away from a stop light.

I went looking for some advice on gsresources.com and a couple knowledgeable folks there recommended looking at the slides/needle area and not the pilot circuit.  Here are the results and what I found to be the issue:

I've broken down the carbs again tonight after work and gone through everything again. I focused on the slide/jet needle/diaphragm parts. The diaphragms showed no holes when backlit. The slides were buttery smooth upon lifting and dropping and lifted when presented with air. The jet needles were genuine Mikuni non-adjustable 4C2's (somewhat unfortunately) and showing no wear.

The issue was completely my fault and ended up being the C clips in the slides not being seated correctly. I thought I had gotten them below the ridges but they were slightly above. This caused the jet needles to be too high up which was flooding the carbs with gas at partial throttle when the transition off the idle circuit was occurring.

I'm happy to report that the low throttle stumble is gone and I took the bike on the longest ride I've ever had with it (which was about 1 mile.) It seemed to be a hair lean, with a little rev hang when blipped, but I am happy to have a base I can work with.

And a picture of me smiling behind the helmet  :D