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Thought It Was the Idle Air Screw. . .

  • Thread starter Thread starter suzukigirl
  • Start date Start date
S

suzukigirl

Guest
New to the forum, lets see what happens :)
I bought a '78 Suzuki GS400 in parts. Put it together, everything was running great. . .noticed the idle out of wack - one of the carbs (2 carbs) was missing the idle air screw. I've exhausted my resources to find the correct screw (bike bandit, carb specialists, dealership, specialty shops, etc.)- no luck. Put a different screw in from a 450, the bike ran ok, but it's not right.

Now new problem, the bike is running on one carb, totally messed up. Is this in relation to the one screw? Is this unrelated, a problem with the valves? Have I created a new problem and now need to rebuild the engine?

Any advice, this is the first bike that I've built and I can't believe I got so far to be stopped by one screw!
Thanks
 
Have you pulled the plug on the bad side to check for fuel? Have you confirmed spark on both sides?
 
Lots of possibilities, including valve adjustments and carb synchronization. How long did it run great? Check the Bike Bandit fiche to see if the idle screws for the 400 and the 450 have the same part number.
 
Bike ran ~100 miles, first time out; was great. On the return trip it started having trouble idling, that's when I noticed the absence of the screw - fell out?? Rigged a screw from a 450, this is NOT the same screw as stock for the '78 400!!!
Will probably replace the carbs with a set off a '81 450 I'm using as a parts bike, hope they'll be ok. . .I think I may have to get dirty with the valves, if not an engine rebuild.

Spark is fine
 
Chances are, you WON'T need to rebuild the engine...

I did a little research on this, and it seems that Suzuki made some changes to the carbs during the model year, though I don't know WHAT specific changes were made. The change affects all '78 GS400s from frame number GS400-44110 and upwards, so at least part of the answer to this might depend on whether or not you have the old carbs, or the newer version... Wish I could be more helpful, but until we know the last five digits of your frame number, we might not be able to advise you further...

Please check this diagram:

http://images.powersportsnetwork.com/fiche/images/Suzuki/1978/Motorcycles/2089_12.gif

Is the (missing) screw shown there? Is it # 13? If not, can you tell us which one it is? If it isn't shown in that drawing, let me know, and I'll try to find another one...
 
Frame number is 33494. Yes Sir, I believe that would be number 13! That's the diagram I have in my book for the bike, but I'm not sure that it's really correct because the screw that I do have for the left carb doesn't have a spring though the diagram shows there should be one. I ordered #13 from the dealer, employee one said "it's back ordered, it'll take a while to come in." Employee two said "when it says b/o, they really mean discontinued, the screw may never come in." Thanks for your help
 
Ok, so now we know that you have the ORIGINAL version of the carbs, not the newer version... The drawing I linked to is for the NEWER carbs, but I'm pretty sure this link will show you the carbs on your GS:

http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=993797

Here's another image, but I don't know if this is the older carb, or the newer one:

http://alpha-sports.com/spst/1978 GS400/07.gif

As much as I hate to tell you this, Employee Two was correct; you won't be getting the part you ordered from Suzuki in this lifetime, so you'll have to switch to Plan B...

IOW, you'll have to find another (hopefully complete) carburetor which uses the same parts, and scavenge whatever you need from it. Or, you MIGHT be able to track down a parts supplier who has the individual parts you need, but I wouldn't count on it...

Your best bet might be to call some motorcycle boneyards to see if they can sell you another carb, or even TWO complete carbs, since they might not be willing to sell an individual carb...

The one place I've had a lot of luck with is located in southern California; they have some really hard-to-find stuff... They're honest and helpful people, and I call them first when I need something Suzuki says is "backordered"...

You can contact them through their website:

http://www.tricountymotorcycles.com

or call them @ (800) 398-7426, or (805) 648-4167...

They have a LARGE inventory of parts... They usually ship same day, or the next day via UPS ground, though if you want it right away, you can pay extra for overnight or second-day air...

Wish I could be more helpful, but finding such an obscure part just doesn't seem likely to me... Chances are, you could order a pair of carbs; as long as you have a matching pair, it probably wouldn't matter which version (original or newer type) they were.

Hopefully, someone else will see this and have the part(S) you need; if not, I've tried to provide you with an alternative resource...

Before you order ANYTHING online or over the phone, you should post an ad in the "Wanted - Parts, Misc." section of the forum, to see if you get any replies:

http://www.thegsresources.com/_forum/forumdisplay.php?f=112

Best of luck with this; let us know how things turn out.
 
If its on backorder then that's not discontinued
good god what nonsense to be spouting to a paying customer.
I have waited weeks for backordered itmes but if it is showing up in a database in this day in age then it is most definitley festering in a dank bin in Yokohama or some such place.

Alpha sports shows the #13 part for about 10 USD.
and I assume that is alos what you ordered form you shop.

is it?
 
OK, Blackmore, since you THINK you know something about this subject, let's see how much you REALLY know about Suzuki parts...

Calvin Blackmore said:
If its on backorder then that's not discontinued
good god what nonsense to be spouting to a paying customer.
I have waited weeks for backordered itmes but if it is showing up in a database in this day in age then it is most definitley festering in a dank bin in Yokohama or some such place.

Alpha sports shows the #13 part for about 10 USD.
and I assume that is alos what you ordered form you shop.

is it?
Click to expand...

As the former parts department manager of a Honda / Suzuki dealership, I stand by what I've already posted; THE PART IS DISCONTINUED! One know-nothing employee (probably a summer-hire in the parts department) told the OP that the screw she needs is "backordered", the SECOND employee told her the TRUTH, whether you agree with that or not...

The part shown as number 13 here:

http://images.powersportsnetwork.com/fiche/images/Suzuki/1978/Motorcycles/2089_12.gif

is for a DIFFERENT set of carburetors, NOT the ones installed on this particular GS400, according to the FRAME NUMBER... I originally referred the OP to that drawing simply for convenience, because the screw shown in that diagram is numbered, while the screw in the diagram which shows her ACTUAL carburetor is NOT numbered...

You ONLY bothered to look at the Alpha-Sports diagram, which ONLY applies to the NEWER set of carbs, NOT the ones on this particular GS400! You obviously DIDN'T take the time to check any OTHER sources, such as the databases at BikeBandit and MRCycles, which show BOTH versions of the carburetor diagrams; the CORRECT diagram for the earlier carburetor is located here (from MRCycles):

http://www.mrcycles.com/fiche_image...i&category=Motorcycles&dc=792&name=CARBURETOR

and here (from BikeBandit):

http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=993796

If you look closely, you'll see that in EACH of those diagrams, the screw in question HAS NO PART NUMBER, because it IS in fact DISCONTINUED and NOT available from Suzuki!

I'm willing to bet that you ALSO didn't take the time to call your local Suzuki parts department, to verify ANYTHING you posted. I didn't call either; I drove to the local dealership on my lunch hour today and asked an old friend (now the assistant parts manager) to double-check my research. He VERIFIED that those particular screws are NOT available from Suzuki AT ALL!

Admit it, Blackmore, you didn't bother to verify ANY of these details with ANYONE... you simply decided to post ACTUAL nonsense, which DOESN'T help the OP, or anyone else, for that matter...

Got any MORE nonsense for us, Blackmore?
 
Last edited:
Thanks

Thanks

Thanks for all your help guys, glad to know I'm not insane that I couldn't figure this out quite too easily.

I do believe the screw will not come in - to appease lets say (to quote employee #2) that the part is permanently on backorder , and figure that something is still fishy with the spring. . .(see last post).

Will contact sources in CA and see what turns up; and will let you know if a carb swap from a '81 450 fixes the problems - looks like it'll correspond to the pipes/engine/everything

Oh my Kingdom for a Screw!!!
 
Ah poor king Richard III he was the last british King to die in battle when his suzuki 400 developed carb problems..........


Good luck on finding alternates hope the links I posted might help.
The ebay item is pricy but it seems to be the same set of carbs as are on your machine. You would know better than me though.
 
Well whoda thunk!

Well whoda thunk!

The Screw Came in at the Local Dealer after 2 Weeks
 
Must have been on permanent backorder...or maybe the wrong screw? I think that we should maybe tone this down a bit, this is after all a family environment...
 
suzukigirl said:
New to the forum, lets see what happens :)
I bought a '78 Suzuki GS400 in parts. Put it together, everything was running great. . .noticed the idle out of wack - one of the carbs (2 carbs) was missing the idle air screw. I've exhausted my resources to find the correct screw (bike bandit, carb specialists, dealership, specialty shops, etc.)- no luck. Put a different screw in from a 450, the bike ran ok, but it's not right.

Now new problem, the bike is running on one carb, totally messed up. Is this in relation to the one screw? Is this unrelated, a problem with the valves? Have I created a new problem and now need to rebuild the engine?

Any advice, this is the first bike that I've built and I can't believe I got so far to be stopped by one screw!
Thanks
Click to expand...

Did you put an o-ring on that screw?
 
suzukigirl said:
The Screw Came in at the Local Dealer after 2 Weeks
Click to expand...
Thats cool. Sometimes you just have to wait, as there ARE parts still lurking out there in bins that sometimes aren't on national databases. Sure is quiet around here now, huh, Mr PL. chirp...chirp. Please keep your personal attacks on members off of this forum. Some members do know more than others, but none know everything.
 
Yes I did put an o-ring on the screw. I looked through several carbs for a screw that matched mine from similair models and years and couldn't find anything. I was lucky the dealer was able to provide the correct screw.

I'm going to rebuild the carbeurator, seems like it'll run great and then get clogged, start a run great again, then get clogged. Glad I have all the parts now
 
This is great news for you. I am very glad to hear you got your parts as I have been prusing ebay with a handy stored search and have found nothing since you last posted. so these are rare birds or maybe the barn owners that are storing them have no internet?

Cleaning carbs is a fun experience what with the little parts and the carcinogenic chemicals.

Im a lazy man so I would try dumping an appropriate amount of seal safe injection fuel system cleaner in my tank.
 
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