gs450 idle and sync

[gs450]

I just bought a 1980 GS450E with 12,000 mi. It runs great down the road with plenty of power. The compression for both cyl is 150 psi. The valves are in adj. and timing is on. Plugs are new.
The Clymer's manual indicates the carbs are BS34SS. There is no model no. on the carbs that I could find. They are Mikuni. They do not look like the diagrams I have seen for that model. The idle and main jets are in the float bowl as opposed to the main body.
When I first got it, it idled at 1200, but after riding it and it warmed up good the idle speed increased to 3000-4000 rpm. Checking the balance indicated it was running on the left cyl. Balancing only increased rpm.
I removed the carbs and cleaned them. The idle and main jets are clean as well as the passages in the body and float bowl. I made these adjustments before replacement:
1. Backed off the idle stop till it didn't touch the linkage.
2. Backed off the balance screw till it didn't touch and back till it just did.
This left both butterfly valves closed all the way and balanced, for idle anyway. I thought on starting they would be balanced. I started it with the "choke". It would not run without it. Using the sparkplug grounding method I found that it was running on the left only. I have not ridden it to warm it up, but based on previous experience with it the balance will not change once the "choke is off.
What next?

[bmac]

You might try taking off the spark plug boot from the right side wire and put that on the left side and try it. The spark plug boot may be bad. Also, try cutting off some of the lead and refasten it to the boot. Clean the leads at the coil and all other connections. Just throwing some things out there. Bob

[gs450]

Bob - thanks for the reply. It is not spark. it runs too well on the road.

[bmac]

Sorry, I misunderstood your thread. Did you replace the intake boots and or o'rings. Where the pilot jets removed and cleaned. Those are under the plugs in the bowl? How thorough of cleaning did you do. Complete tear down and soak? Bob

[cowboyup3371]

What kind of voltage are you getting on your coils? You could have a bad boot with the way I am reading like Bmac said, a bad coil, ignitor, or even carb problems themselves.

Basscliff will be along later with his mega-welcome and I strongly recommend you read through everything. Trust me when I say that the guys and gals here have seen about every problem you could imagine and the tips you'll get will work if you try them.

[kelticsol]

Got a picture of the carbs? Some could probably id them by sight.

Good luck. The guys here will get you sorted out.

[Steve]

If your carbs are not synchronized, you could still be running on just the left one. You may have spark in the right cylinder, but with nothing in there to light, there will be no fire until you twist the grip enough to finally open the throttle on the right carb.

Grounding the spark might work if EVERYTHING ELSE is working perfectly, but is not a valid test if you have multiple problems. In this case, you can't be sure if it's lack of spark or lack of fuel (due to closed carb). A proper vacuum sync will get them properly adjusted.

.

[gs450]

It is not spark. When I gave it a little throttle and grounded out each plug, both cyl ran at same rpm. Then back to idle and both cyl were ok but rpm's were 3000-4000. The linkage is not hanging on the throttle cable. Do I need to take the carbs back off and get into the fuel enrichment mechanism?

[cowboyup3371]

If the rpm's stayed up then you have a hanging idle which means intake boots or orings could be bad, air box needs to be sealed or something in that respect. Just because everything started running after giving it throttle doesn't change the fact you could have a synch issue.

[gs450]

Thanks for all the input, everyone.
I did not replace the intake boots and orings. I don't remember seeing orings. Are there supposed to be orings between the intake boots and carbs?
I did clean the pilot and main jets and squirted carb cleaner through all the passages in the body and bowl to clean and check for blockage. I did not remove the tops or the enrichment devices.
I will try to upload a photo later.
I really believe the carbs are in synch with each other, at least at and near idle, because they are both completely closed and they open together when the linkage is moved. I don't have a manometer. I have to use the spark plug ground out method. I will do that when I can.
The idle is not up due to a too tight or sticking throttle cable and the throttle stop is out far enough so it is not touching the linkage.
Again I do not think there were orings between the carbs and the intake boots. The boots don't seem to have any cracks. I do have the metal clamps on them very tight. I'm sure if air is leaking in there it could be the cause and would explain different results with different engine temps.
I will get back on it when I get a chance and rep[ort back whatever I find.

[bmac]

It sound's like you have work to do. The o'rings are between the head and intake boot. They seal the mating surface of the two ( head and intake boots). If you research carb cleaning thread's you will find the correct procedure for carb over hauls. Replacing the intake boots and or o'rings are pretty much a given if not knowing the history of the bike in some cases. Once again, the carb's should be dismantled and dipped completely. You are going in circles if you do not address this and other related maintenance items to make this bike perform to it's expectations. Take your time and do it right the first time and you will have a sound machine until you have to maintain it again. Oil, filter, brakes, wiring, battery and so on. If you own one be prepared to repair it. But, do not take it to a shop unless less you have a lot of disposable income or allergic to a little grease and oil. Bob

[pete]

First off, let me just confirm that it sounds like you have the right carbs for your 450.

The 80 - 82 are all pretty much the same, and my 82 has the pilots and mains in the float bowl like yours.

Have a browse through my rebuild thread in my sig. and you'll see where I cleaned mine and where my jets are etc.

Also, I can definitely confirm what the other guys said that the O rings are between the boots and head, mine were so brittle they cracked when removed.

Go to www.cycleorings.com and get Mr Robert Barr's 450 combination kit, you won't regret it. He's a member here too.

Also jump onto BassCliff's site and read through the 450 carb cleaning guide by Flaming Chainsaws, his pic's are far better than what I took of mine.

http://members.dslextreme.com/users/bikecliff/

[Steve]

When I gave it a little throttle and grounded out each plug, both cyl ran at same rpm.

When you "gave it a little throttle", you opened up the carb that is lagging a bit behind the other one.


Back to your original post:

Using the sparkplug grounding method I found that it was running on the left only. I have not ridden it to warm it up, but based on previous experience with it the balance will not change once the "choke is off.
What next?

You can NOT check carb sync (balance) with the "choke" still engaged.

The bike has to be fully warmed up and the "choke" turned OFF to make any sync checks.
Yes, the balance can change quite a bit once the "choke" is turned OFF.

.

[gs450]

Well guys, I certainly see why anti-seize compound is recommended for the intake boots! I finally got them off after buying a baby vice grips. And, there were no orings. I can see the groove where they went, but obviously someone didn't think they were important. I'll get a new pair and get back to it. I'll let you know. I understand that a vacuum leak can cause weird and variable performance due to extra air. What I still can't figure out is where the gas is comming from since at idle a vacuum leak at the intake boot would raise pressure in the throat. Both butterfly valves are closed as much as they can. Any insight would be appreciated. In the meantime I'll get some orings for that and the carbs and get to work.

[BassCliff]

Greeetings and Salutations!!

Hi Mr. gs450,

It sounds like I'm a little late to the party. Oh well. There is a 450 carb cleanup guide on my website if you'd care to take a look. There's also a valve adjustment video link for the GS twins. Most of the other information on my little website will apply to your bike, just cut everything in half.

Anyway, let me dump a TON if information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff