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1980 GS550 from the dead

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wheelzz
L Plate Warrior



Joined: 19 Sep 2015
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PostPosted: 03:11 - 19 Sep 2015    Post subject: 1980 GS550 from the dead Reply with quote

Hello, I am new to this forum and wanted to post a couple of questions to see if I could get some knowledge about my recent purchase. I bought a 1980 Suzuki GS550 and a 1981 GS650.

The GS550 is very close to running while the GS650 is more of a parts bike and would need a lot of work to get running. When I purchased the bike the seller said he was tired of working on carburetors and wanted to get rid of them.

Everything on the bike works, aside from the charging system and the carburetors. New chain, front tire, clutch cable, and a bunch of cleaning to the carbs. The charging system I suspect the stator as I've heard these go bad. The carbs are their own story.

After completely taking the carbs apart, carb dipping, blowing all the passage ways out, fitting new orings in all the critical areas, choke, fuel lines, and fuel/air screw, and reassmbling I am able to start the bike and with a little finesse on the choke, can get it to idle. The problem I am having is that the bike dies as soon as I push the choke back in. When starting hot, choke fully pulled, the bike will start and rev high and stay at about 3 rpm. Finesse brings it back to idle but wont idle on its own. So i figure it needs fuel at idle and I test by turning each carb fuel needle out a half turn at a time all the to about 4 turns out and starts to help. I know 4 turns is too much so I figure it must be my jet sizes. The guy before me "worked on" the carbs. What this consists of I did not think to ask at the time. These are Mikuni BS32SS carbs with jet sizes as follows

Main Jet 110
Pilot Jet 42.5
Needle Jet x-5
Air Jet 160

My questions are about jet sizes, which jets to adjust for idle, and where to buy. Does bigger the jet size mean more flow or less? Do I need more fuel flow at idle? What jets do I change? Or are the jets even my problem?

I apologize if this was posted somewhere else but my search of "GS550 choke" came up with nothing.

Thanks and intelligent input is much appreciated

wheelzz
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Snod Blatter
Crazy Courier



Joined: 21 Nov 2014
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PostPosted: 10:17 - 19 Sep 2015    Post subject: Reply with quote

Idling seems to be a problem, a little help here and here although they both seem to boil down to "clean them some more".

Did you check the float levels? Are the jet sizes correct? Do you have a manual to hand to check these things? Are all the diaphragms okay?
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1994 CB250, 1984 CBX250RS-E, 1989 K100RS, 1995 TRX850, 2016 Z250SL
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A100man
World Chat Champion



Joined: 19 Aug 2013
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PostPosted: 19:48 - 19 Sep 2015    Post subject: Reply with quote

Are they in fact the right carbs ? My XJ550 of the same era has BS28s only the later are rather more powerful XJ600 used BS32s and then with smaller jets than you have! (Mains 105 pilot 40). Lot of dedicated GS forums out there to help..

https://www.thegsresources.com/_forum/index.php
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600
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wheelzz
L Plate Warrior



Joined: 19 Sep 2015
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PostPosted: 21:55 - 19 Sep 2015    Post subject: Reply with quote

Floats levels were checked and are correct. Diaphragms have no holes or cracks. Yes BS32SS carbs are for the GS550. I just think I need bigger jets for the idle system. But I have no experience with different jet sizes so I was wondering if anyone has changed jets before and the outcomes of doing so.
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A100man
World Chat Champion



Joined: 19 Aug 2013
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PostPosted: 22:46 - 19 Sep 2015    Post subject: Reply with quote

Are all the idle paths clear ? About 3 pin-prick holes on the 'roof' of the carb out near the butterfly ?

Can't find GS550 jet sizes but the 850 with teh same carb has a 115 main and only a 40 pilot.. An internal passage somewhere blocked in one or more carbs would be my best guess - they can be minute.

Even if you cleaned them thoroughly there's no telling if some small cr@p from teh tank has found its way in.
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600
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Casper
World Chat Champion



Joined: 12 Jul 2010
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PostPosted: 12:04 - 20 Sep 2015    Post subject: Reply with quote

A100man wrote:
Are they in fact the right carbs ? My XJ550 of the same era has BS28s only the later are rather more powerful XJ600 used BS32s and then with smaller jets than you have! (Mains 105 pilot 40). Lot of dedicated GS forums out there to help..

https://www.thegsresources.com/_forum/index.php


Same question ^^ I am sure they should be BS30 carbs. I have had two GS's. The E and Katana and i am sure the main jets were smaller (under 100) but one higher for some reason. I am sure you running that with the 650 carbs. Now some 650 top ends fir the 550 bottom. Has the previous owner did this swap hence the larger carbs? Get over to the Old School Suzuki forum and ask as that lot have forgotten more than i know and get the manual.

OH they were renowned for Reg/Rec burning out. Run with lights on was meant to help. I put a GSXR600 one on my last 550.
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