runs on choke only

[Guest]

I've picked up a GS400 with Aussie stamp claiming it's a 1980's model. Owner said it was running just before he garaged it for a decade. Compression test is ok and I've just changed the sparks, oil, brake pads etc.

I fired it up found a hole in the exhaust so it's not running at the moment, but strangely I could only get the bike to start with the choke engaged. I let it run for about 2 minutes then flicked then disengaged the choke and it died. Started with the choke again and gave it some revs and sometimes she stalled and sometimes she picked up.

Am I being too eager with the throttle while it's cold or should 2 mins be enough?

[Steve]

When the carbs are properly cleaned and adjusted, two minutes is WAY too long. My bikes are ready to ride after about 30 seconds of "choke" useage.

Consider yourself lucky that it starts at all, but you will do yourself and your bike a big favor if you remove the carbs and fully dismantle them and clean them properly.

Not sure what you have available for carb cleaner, but I do know that you don't have our favorite: Berryman's Carb Cleaner Dip. GUNK brand has a similar product that also works well, but you probably don't have that, either. How about the stuff that Yamaha sells? It's a concentrate that you mix with water. I have tried it, it seems to work well.

Regardless, it will take more than just spraying around some carb cleaner spray to make them look good. The parts you need to clean are the little passages that are buried deep inside the carb. You also need to replace all the rubber o-rings, but don't get "carb rebuild kits" to do that. Check out cycleorings.com, see if he ships to you. If he does, his kit and the dip will get you on the road rather quickly.

.

[kw86er]

Everything you need to know is on this site already. I started with a bike that wouldn't start... followed the information available on the forum and and got her running. A couple weeks of parts ordering... a couple days of carb cleaning/rebuilding, adjusting valves... about an hour of dialling it in and I have been riding ever since. Still messing with things but she goes allot faster than the suspension and brakes would like her too!

[brettule]

what's the problem with a "carb rebuild kit"? that sounds like exactly what I need.

[tom203]

what's the problem with a "carb rebuild kit"? that sounds like exactly what I need.

The kits often contain inferior parts to Mikuni stuff ; the metal parts in carbs don't usually wear out, they just get gunked up. The o-rings need replacing and hopefully cycleorings.com can supply them to you.

[cowboyup3371]

Carb kits also don't carry all the oring parts you need

[koolaid_kid]

brettule, please listen to these folk. Those carb kits contain everything you do not need. You need to check with your Aussie friends, (pete comes to mind) about what carb cleaner is available there. You need to get an o-ring kit from www.cycleorings.com. I personally prefer to replace the fuel bowl gaskets, they are over 30 years old.
If your carb boots have o-rings you should replace those. Also available from cycleorings. If your carb boots are hard or cracked, you will need to replace those.
Please do not try any shortcuts, they just do not work and only add to the frustration level.
Best of luck, and congrats on your new-to-you bike.

[pete]

Hey mate, yep, definitely carb cleaning time!

O ring kit from Robert Barr (be sure to get the combo kit including O rings for intake boots).

The only good carby cleaner around seems to be ... errr... Yamaha brand

Yamalube carb cleaner comes in a 997cc bottle (weird I know). I mixed it 1:1 with water and let my carbs simmer in it over a gas hotplate for something like an hour each from memory (been a while).

It smells disgusting, so make sure you have plenty of ventilation and keep it away from the house. I mean it really is bad...

If you have the time, don't simmer it, just let each carb soak overnight instead. I couldn't let them sit overnight at the time unfortunately.

The bottle actually warns against heating it up so I didn't tell you to do that ok?

And yeah, my 450 doesn't have to stay on choke long at all before it's warm enough to take me down the road...

[Crage]

Vacuum leaks and dirty carbs will keep the bike from idling correctly.

[BassCliff]

Hi,

Go back to your intro thread. Read the "mega-welcome", follow the maintenance lists, see my little website for "how-to" guides and other documentation. Old bikes love proper maintenance.


Thank you for your indulgence,

BassCliff

[brettule]

Thanks BassCliff. How can I tell if I have a Mikuni BS series or Mikuni VM? My bike is stamped with an ADR plate of Sept 1980 but that just means it's the date it was certified in Australia. The bike may well be a 1979 model.

[BassCliff]

Hi,

Have you had a chance to look at the carb rebuild/clean-up guides on my website? There are "how-to" guides for both.

VM style carbs:



I believe these are VM26SS carbs. (Green arrow points to the vacuum connection, blue arrows point to the vent hose connections.)


CV style carbs (BS3xSS):



(The above is a set of '82 BS32SS carbs, which have a little different choke mechanism than the '80-'81 models.)

Thank you for your indulgence,

BassCliff

[brettule]

Ok, carby rebuild it is. I opened the section of the Suzuki_GS400-450-77-87_Clymer_Manual and it says "All models are equipped with twin Mikuni BS 34 carburetors" so now I know. I ordered the kit from Robert Barr you guys recommended. Tomorrow I'll start the strip down and clean.

THanks.