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Author Topic: 1981 Suzuki GS450L - Cruiser to Scrambler  (Read 14389 times)

Offline trek97

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #135 on: Mar 19, 2017, 07:35:30 »
Also, I had the single sensor setup and just grew tired of swapping it from side to side, to check performance of each carb.  Thats why I went a picked up the duel sensor unit.

Now considering installing the old single sensor unit on my bmw triple w 3x1 exhaust.

OH am most importantly, its a bunch of fun to watch the gauge as you ride...keep your eyes on the road!!!

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #136 on: Mar 23, 2017, 12:14:23 »
Also, I had the single sensor setup and just grew tired of swapping it from side to side, to check performance of each carb. 

Hey trek97 - Thanks for passing on your experiences with AF measurements.  After reading your exhaust leak comment I went back and re-tightened the headers to make sure they were well seated.

Would you mind telling me how much of a difference you found between your two carbs?  I'm trying to gauge how much of a risk I'm taking by not reading both carbs individually.  My thoughts were that the carbs have been rebuilt with new o-rings and all jets and settings to be identical, and then they were synchronized at idle and high throttle.  And I should be able to tell with plug readings if there are any major problems between the two carbs.

Currently, my AF system is just about fully installed.  The O2 sensor is installed and the unit has been wired into the bike's loom.  Now I need to rebuild the carbs again to clean out last year's gas that seems to have plugged something up as I'm getting pretty bad rev hang at part throttle.  A bummer, and probably should have just drained everything before parking it, but I tried going with fuel stabilizer.  Still learning...

Offline trek97

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #137 on: Mar 23, 2017, 20:00:21 »
I have no idea about Suzuki carbs.  Only the bastards that come stock on 360s.

The only reason for checking both carbs individually is setting up A/F mix at idle.  (for fastest idle speed)  So you know both carbs are performing at their peak.  Basically making the most power along w best fuel economy.  Without going too lean.  Air cooled engines require a bit richer mix, the richness helps to keep the engine from overheating during extended idling periods.  Stuck at railroad crossings etc...

I found on my bike 12.8 to 1 gives me the best performance at idle.

So, I shoot for 12.8 as the minimum throughout the rpm range while cruising.  I would like to see mid 13's to 1 on WOT.  But cant hit that due to limitations of needle size availability.  And I dont have the proper equipment to make my own needles.  Otherwise I would try.

If I do jet her to accelerate leaner.  I find she occasionally wants to die during deceleration from higher rpm to a complete stop.
 
You will find, when rolling off throttle this closes the butterflies and she cant get any fuel through high rpm jets, making it crazy lean.  Mine gets upwards of a 21 to 1 mix.

thus if I could make a leaner needle for WOT I could install richer low rpm jetting and she would be able to recover quicker.

This is what causes the exhaust "popping" during decel.  Its a lean condition.

AND, you would be a very lucky dude if your carbs were able to simply match A/F mix adjustment and have them both running the same mix at idle.  They are crazy touchy adjustments on my bike.  As little as a 16th of a turn can be enough to make a big difference between set up properly or not.  I have a sickness, a lot of guys dont need that type of accuracy to be perfectly happy w a decent running machine.   ;D  As a lot of guys know its hard to keep a 360 running period.

You may find your A/F idle mix adjusters land in different spots.  (number of turns in or out) as long as both are giving the max idle speed.  It dont matter if they match turns.  Its performance your looking for.  And a difference may be that the PO had tuned one in too hard, messing up the seat a bit.  Therefore it would allow for more or less air or fuel at the same # of turns as the other carb.

At this time I have no idea the number of turns my A/F mix adj needles are set.  I just know they are both operating at perfect 12.8 to 1 mix.

I hope this helps a bit and keep me posted on your results. 

 

 

« Last Edit: Mar 23, 2017, 20:08:06 by trek97 »

Offline trek97

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #138 on: Mar 23, 2017, 20:15:36 »
Also dont make any adjustment unless your machine is at full operating temp.  If you cant ride it, it will need like 10-15 full minutes idling.  Atleast. 

The head and carb manifolds must be hot for fuel to atomize properly.  Otherwise, atomized fuel will re-condense to back liquid state between carbs and cylinders.  Screwing up your readings and adjustments.

I also park it on the center stand and shove a 2x4 under front tire to level the thing.

AND make sure your float levels are matching dead nuts perfect.

LOL is my sickness showing yet?    ::)

Offline trek97

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #139 on: Mar 23, 2017, 20:31:07 »
And one more thing.

You will find that even the air temp/weather and altitude will affect the A/F mix adjustments.

This is the reason the engineers made the A/F mix adj external for quick and easy tuning on the go.

If you leave home at 5am and temp is 65f.  Mix can change that same afternoon when its 90f.  So, you can adj for that.

I dont mess w all that.  I made my system easily removable and just check it a couple times a season to make sure everything is healthy.

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #140 on: Mar 24, 2017, 09:25:50 »
LOL is my sickness showing yet?    ::)

You sound about particular as I am so I appreciate the insight and experiences.  My bike ran fine enough once I had rebuilt, re-jetted, re-leveled, and synchronized everything but the engineer in me knows that it can probably tuned a little better yet. 

All the tuning I did last fall was qualitative  (plug color, sound, butt dyno) so it'll be good I think to have some quantitative info (A/F #'s) to tune a bit further with.

It's supposed to get up to 51°F here tomorrow so maybe I can take a break from my house project to make sure my A/F unit is working properly.

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #141 on: Mar 29, 2017, 09:17:25 »
Finally got some time to tear down the carbs fully after finding that the bike wasn't running quite right after winter storage.

Found that one of the mixture o-rings had been smooshed and split into 3 pieces, probably my fault when I had replaced it last year.  So, more o-rings ordered from cycleorings.com.  I'm hoping that's the reason for it rev-hanging like crazy.

I had picked up an ultrasonic cleaner this winter, so at least I got a chance to use it again.  All the carb pieces got a bath in ChemDip and then 15 minutes in the ultrasonic spa.  The bath got pretty murky so it seemed to do a pretty good job.

Offline trek97

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #142 on: Mar 30, 2017, 05:37:22 »
Wow, very nice.

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #143 on: May 02, 2017, 09:37:56 »
Was able to get out for the first decent ride of the year and really test the state of the carb tuning with the A/F meter.  Two big observations from a couple hours of riding - The carbs are a bit lean in the mid-range and a bit rich on full-throttle.  At cruising speed (~3.5k rpm) I'd see an A/F around 16.1 and temps would start to climb.  The lowest the Koso gauge will read is 12.2 and at full throttle the A/F was dipping below the minimum reading of the meter.

Regarding my worries about the O2 sensor placement being too far away from the exhaust ports was somewhat valid.  The sensor won't get hot enough to give a decent A/F reading until you're up and moving.  It doesn't look like it'll give me an idle measurement but I think I'll live.

So, I've got a little more tuning to do.  I'll have to see if I can slide another washer under the Jet Needle to richen out the mid range and then I may drop the Main Jet from 137.5 to 135.

Overall still really happy with the bike.  The fork rebuild with Progressive springs is really nice.  It wasn't bottoming out on big bumps like it had been prior.  Wasn't able to get out on the gravel back roads on this ride as was with a good friend on a CBR600rr and they said absolutely not!

Offline trek97

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #144 on: May 02, 2017, 21:30:02 »