Problems with Carburator GS450L

[Dutch-Martin]

First of all: A hello from overseas!
Im from Holland, so forgive any spelling mistakes...

I hope that someone can help me with my GS450L from 1987 (USA Import) with about 20.000 Miles on the clock. Except for the collor and some electric extras, this bike is mostly original.
Most Motor-shops rather see me leave than come with an oldie... so im trying my luck in this GS-site i came by.

Problem:
Bad starting, and when she runs she runs pretty good, but at a traffic-light she starts to rev high to about 3000-3500 rpm... and people look at me like im nuts...

What did i do 1e attempt:
I cleaned the carbs like 10 times (also ultrasonicly), added an feul filter (other owner spray-painted the tank without covering the filling hole, so some paint is in the tank and is disoulving), serviced the engine.
Changed the o-rings between the intake-manifolds and the cilinders. Synced the carbs, checked for false air ( you call it that to? ) with can of brake cleaner while running. etc.

It ran pretty good for a while but the problem came back after a while...

What did i do 2e serious attempt:
I bought a pair used carbs, they look almost brand new, cleaned it ultrasonicly, changed the intake manifolds and the o-rings...

And still she wants to rev at 3000-3500 rpms while idle`ing... ( sometimes she idles ok, but if i even look at the throttle she revs to high again...


Some tips??? Thanx! Greetings Martin

[Mr. Sinister]

Does the choke operate correctly?

[JEEPRUSTY]

Hi Martin welcome to the site.

Is it possible that your throttle cable is sticking?

[Dutch-Martin]

Hi all,

good questions, i should had mention that:

I have changed the choke-cable, and checked the choke-chaft working in the carbs, it works fine.

And the throttle is the first thing i looked at, seemed the obvious reason to high rev, but the the cable works perfect.

When i stop the bike for a traffic-light, the engine idles fine for 5 seconds and out of nothing she starts to rev to 3000 rpm...

With the old carbs it helped a bit to clean the stationairy jets, i had the feeling that the engine got a to lean mixture... or false air, but checked it all...

( hope your`all making sense out of my attemt to write english )

[Mr. Sinister]

Your English is fine!!
Have you checked the operation of your petcock?

[Larry D]

The difficult starting is likely the valves needing adjustment. As far as the high idle...are you certain you have NO air leaks anywhere ? Do you have the stock air intake system...airboxes, filter, etc... ? Also, where are the idle mixture screws set ? They should be around 2 1/2 turns out (this is a variable and may be a bit more or less) from lightly seated.

[Dutch-Martin]

Thx, i had to google the word Petcock though, haha.
Translated we call it a Tank-Faucet.

Yes, in the beginning i had some problems with it, but i cleaned it, and even on the PRI-setting the problems occure. And on the PRI-set the feul runs perfectly when i remove the feul-hose.

[Dutch-Martin]

Ok, the valves, thats an idea... I did remove the valvecover, but there were no adjusters that i saw, so i guess it has to be done by filler-plates. I didn`t had the material so i left it at that... maybe its worth it to get it checked...

And the only thing a wanted to try if i had the time is to sync the "new" carbs again and set the stationairy jets indeed... I didn`t understand how to adjust them with that feul-tank above it...

I borrowing a small feul-tank so i have a feul-resource i can hang above it, and i can reach all the screws...

[Dutch-Martin]

O, and the air filters are completly stock.
And i set the screws to about 2 turns out..

[Larry D]

Sounds like you're close to getting it right.
The first thing you should do is check our BassCliff's site. He had compiled a huge amount of info for our bikes. His site has been down lately, but, you may be able to access some of the info until he gets it fixed back up.

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

There are instructions for a valve adjustment for 8 valve engines and procedures for tuning the idle correctly. Be prepared to spend some time there, its' a treasure of information.

[tom203]

So you have a vacuum operated petcock- no leaks in the vacuum hose itself or at connections??
The o-ring at cylinder head interface needs to be high temp resistant- ordinary plumbing fitting would fail quickly and leak.
As mentioned you need to check valve clearances ,even if you don't have "filler plates" (shims to us) - you'll need some tiny gauges .030 mm. Carb sync would come after the valves are properly adjusted.

[Dutch-Martin]

Ok, thx for the link, thats a lot off info indeed! Have some homework to do. I have an workshop-manual, but its for the first models, not everything is the same, and i didn`t get the info i hoped for...

Yes its a vacuum-petcock, the hose/tube is new. also checked it with carefully spraying some brake-cleaner on in while running.
In fact i had the whole "california-emisions-free" version with all of the extra carb-vents and some other vacuum tubes and hoses collected to some sort off collector-box above my tail-light... it was already cut off and disconnected when i bought the bike. My new carb is off an "normal" version, so a lot less hoses/tubes...

The valve clearance is something i didn`t payed a lot off attension to... Mainly because off the amount off miles it has run..

Its on the top off my list now! Thx!

[Dutch-Martin]

update

Hey all,

finally had some time to check the valve-clearance of my GS450L that doesnt want to run ok; al valves were to tight by a 0.05 mm exept for the cilinder 1 outtake valve, that one was 0.1 mm to tight...
So i think you guys are right about the valves...

My local Suzuki Dealer had the shims on stock, but i ordered some parts to revice my camchain-tensioner that needed some work to, so have to wait a few days to test the bike again...

I already bought an Suzuki valve-push-tool ( what ever its called in english... ) and a vacuum-synq gauge set, to synq the carbs again...


So i hope ill get the parts soon, havend found a dealer or repairshop nearby that is happy to help me with my old GS, always have long delivey times on parts... All ready waiting 2 weeks.

As soon as i get the parts and can test the engine, i hope i can bring some happy news and start the painting and the big clean up... (hopefully with some help here )

For all GSèrs, take care and enjoy the rest of christmas!

Martin

[barnbiketom]

merry Christmas Martin.

I've had a number of these and if they're not synched close to each other that can cause problems ..

assuming the carb internals are perfectly clean, intake boots are soft and pliable and valves set.. maybe the synch is off bit?? a synch tool iis the best way to verify!!

[Steve]

First of all: A hello from overseas!
Im from Holland, so forgive any spelling mistakes...

Martin, your mastery of the English language is remarkable, better than many of the regular American posters here.

Sure, there are some spelling differences (feul should be fuel), but we know exactly what you mean.
I wish that all of the posters here were as clear in their explainations as you are.

So i hope ill get the parts soon, havend found a dealer or repairshop nearby that is happy to help me with my old GS, always have long delivey times on parts... All ready waiting 2 weeks.

Don't worry about the 2 week wait. Most of us have to wait about that long, and our sources are right here.

You would have to check with other GSers in Europe to see where they buy their parts. I would imagine that some of our American sources would ship over there, but prices (and import duties) might increase the prices quite a bit.

.