1981 GS450L Acceleration issue

[rathi]

I recently acquired a gs450l that had sat indoors since '92 and had been put into storage. It didn't run at all when I took it out, (For the record I changed the oil, gas, and airfilter [more on that in a minute!] prior to attempting to start). After removing Death itself from the airfilter box and ordering a new airfilter it still wouldn't start. Long story short after trying a bunch of things it turns out the diaphragms where frozen as I found when I tore the carbs apart. SO I cleaned everything out and put it all back together, and low and behold: It Runs!
... well Idles.

No matter what I do I can't seem to get it to really run. a breakdown of what I am experiencing is sort of like this:

-The bike will start cold with the choke on, however it immediately sky rockets to 5000+ rpms
-Once I turn the Choke off I can't get it to go above 2000 rpm's for several minutes.
-Once I can break 2000 rpm's it will go as high as I want, however it will stall at 2600 or so and drop before continuing on, and once it gets where I want I can't keep it there very long.
-If I restrict the flow into the airbox moderately it runs beautifully.
-And ignoring everything previously stated if it gets HOT, as in I forgot I was letting it idle and it idled for 45 minutes, it runs exactly as it's supposed to.

This is really confusing me, is it just running super lean and when it gets hot enough it runs with the correct richness? Why does the throttle have zero response, even if I manual up it at the carburator?

I'm willing to bet it is a carb issue but I have already torn it apart twice... speaking of which, when I took it apart the first time I couldn't get one of the Needle jets out and cracked the tip of it. it's back to round but there is a crack could that be part of my issue? although wouldn't that up the gas flow, not decrease it?

Thank you for your help and advice, any would be gladly accepted!

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. rathi,

It sounds like you are off to a pretty good start, but there are more maintenance tasks to accomplish and a "proper" cleaning of the carbs should be done. Below you will find all of the information needed to get you started in the right direction.

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

 

[Guest]

Welcome to the forums Rathi!

Firstly, go through BassCliff's site, you won't regret it.

Read carefully through the 450 carb cleaning guide on there by Flaming Chainsaws.

That crack on your needle jet won't have any affect on idle as they only come into play from about quarter throttle, but of course when revving to quarter throttle and beyond it may affect it for sure.

One thing you absolutely must do is a valve adjustment, there's no sense finalising carb sync or anything without doing the valves first, and they can seriously impact how well it runs.

Good luck and keep us up to date with how you go, and there are plenty of guys on here far more knowledgeable than me as well, so you should be able to get it purring quite happily.

 

[terrylee]

After doing all that and replacing o-rings in carb. boots to engine and sealing airbox top. Clean and check all the electrical connections, especially ones to ignitior and signal gen. I had a similar problem with my wife's 450 and part of the problem was those connections. terrylee

 

[rathi]

Thanks for all the help! I have one question about the valve adjustment before I open the engine up: all the manuals call for a Suzuki tappet depressor with a specific part number, is this tool vitally necessary? or can the probable shim replacement be done without it?

and Pete fuel is sucked through the needle valve by the diaphragm, correct? so the alteration that damage does should lead to a richer mix when throttle is upped to 1/4 or beyond correct?

 

[mike_of_bbg]

Go visit BassCliff's site and you'll see a page about doing valve adjustments, and a "zip tie supplement". I use the tool (Motion Pro makes one), but some members eschew the $15 investment and some even prefer the zip tie method. Make sure you use strong zip ties so the valves don't cut them (one member recently had that happen and had to go fish it out of his intake tube), and don't turn the motor without all of your shims in place.

 

[Guest]

Thanks for all the help! I have one question about the valve adjustment before I open the engine up: all the manuals call for a Suzuki tappet depressor with a specific part number, is this tool vitally necessary? or can the probable shim replacement be done without it?

and Pete fuel is sucked through the needle valve by the diaphragm, correct? so the alteration that damage does should lead to a richer mix when throttle is upped to 1/4 or beyond correct?

As I understand it yeah, the diaphragm lifts the needle assembly up allowing fuel to run through the needle jet, and yeah I expect that would allow "too much" fuel for that throttle opening.

I'm not a carb guru though so I wouldn't rely 100% on what I say, it just seems to make sense

As to the valve adjustments, as Mike mentioned above I used the cable tie method and I had a reasonably large thick one I used. I've seen the tools others have used and I think in future I'll stick with the cable tie, but that's just my personal preference.

There's a video floating around somewhere of the cable tie method's inventor (Steve, *very* knowledgable and helpful bloke) doing valve replacements too which is invaluable if you have to take the head off for any reason...