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1978 GS400X Idles then dies

  • Thread starter Thread starter asletten
  • Start date Start date
A

asletten

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My bike won't idle for more than 5 seconds or so. I had it at the shop recently to clean it up and get it running nicely but it still doesn't idle constantly while in neutral or while the clutch is in. The carbs were cleaned and I guess "had an ultrasound" run on them twice because he wasn't happy with the results of the first.

This is a huge issue for me on this bike since it is kick start only and my first bike. I can't just hold the clutch and hit the start button to start going again. Everytime it dies I have to pull to the side and put it back in neutral and kick start it....not exactly a fun thing to do when on the road so I haven't even taken it out of the neighborhood. And please don't tell me to get over it and keep the throttle going to keep the rpm's up. I have enough to get use to as it is :).

Any suggestions or ideas on what is causing this would be great. I've read a bit and saw that rust in the tank could cause this (as this bike sat for 25 years in a small closed shed, but it's in wonderful shape). I also read that there could be build up in a line choking out the carbs, but the page didn't seem like it was related to motorcycles completely.

I'd like to get riding as soon as I could, but I definitely won't feel comfortable having to think about my bike dieing everytime I pull the clutch in.
 
Sounds like your float bowls are not holding enough gas to keep her running. run her till she dies then open the float bowl drain screw. Is there fuel in there. Sounds like you are starving. The next place to look would be the petcock.
 
Even though the carbs were cleaned, they may have turned out great.
If there was rust in the tank it needs to be fixed. There are chemical kits made to clean, neutralize and seal motorcycle tanks. Most motorcycle shops carry them.

http://www.amazon.com/POR-15-Cycle-Tank-Repair-Kit/dp/B000H9K4JQ
Just reminded myself I need to order one too...
http://www.amazon.com/Stens-Replace...F8&qid=1370934972&sr=1-1&keywords=fuel+filter
I'm running a fuel filter almost exactly like that just in case my tank has any contamination it should be kept in there. I threw my bike together recently and skipped a few steps like checking to make sure the tank was clean :oops:
If the tank has rust in it from storage, it will continually make its way into the carbs. It may even develop an external leak if not addressed soon. I'm pretty sure this is your problem.
The pilot, or idle, circuit is a very small opening where fuel flows through the pilot jet. Any particles going through the fuel from the tank would make happy homes in a pilot circuit.
 
"The carbs were cleaned and I guess "had an ultrasound" run on them twice because he wasn't happy with the results of the first."

The idle circuits in these carbs are tiny and once they get plugged with gunk, you get a lousy idle. It seems his "ultrasound" ( I assume you mean ultrasonic cleaner ) didn't work. Time for your carbs to take a dip; as someone says on here " shortcuts are longcuts"

take a look at this link- there are others at Basscliff's info lodge


http://members.dslextreme.com/users/cbsaunders/gs/gs450_carb_cleaning_guide.pdf
 
What about the choke and the idle adjustment?

Can it simply be that the engine is cold and needs some choke, or that the idle screw isn't wound in enough?
 
Good point Pete.. Sounds like we will need some feedback from the wrencher on this one..
 
Thanks a ton for all of the advice. I will have to take a look over a lot of this as there were quite a few responses. I have also thought about the idle screw but haven't touched it. I highly doubt it's rust in the tank as it was stored very well and taken care of, but this is still something I could check out.

The choke works fine and when on after about 30 seconds-1 minute of running with the choke on (after a cold start) it will rev up to 6k rpm and stay there. Once I turn the choke off it drops down to around 1.2k rpm and slowly lowers and lowers until it dies. As long as I have the throttle going it won't die, only when I let it idle does it die.

So I am pretty sure if it were rust in the tank it wouldn't be running as smooth as it is with the throttle going. It seems as if there is an issue with the amount of fuel it is using to idle. Like it may not be getting enough to keep up the rpms unless I assist it with the throttle.
 
asletten said:
..... Once I turn the choke off it drops down to around 1.2k rpm and slowly lowers and lowers until it dies. As long as I have the throttle going it won't die, only when I let it idle does it die.

S It seems as if there is an issue with the amount of fuel it is using to idle. Like it may not be getting enough to keep up the rpms unless I assist it with the throttle.
Click to expand...

Turning off "choke" forces bike to run on the idle passages very quickly- not enough fuel, engine gets starved. But make sure idle stop screw is actually holding throttle plates open a tad.
 
As long as I have the throttle going it won't die, only when I let it idle does it die.
Click to expand...
Its a lack of fuel issue or an air infiltration problem. There is no mention of the carbs being rebuilt with fresh O-rings or any mention of the state of the intake boots or O-rings under them.

If its not idling right I would always suspect an air problem. Lots of people reuse O-rings because they look ok but if you distort them you may find they are cracked. Its also very likely that air is getting in around the intakes.

Have you looked at the plugs? If they are dry and almost white in appearance you are running lean which again means not enough fuel or too much air.

As a final point don't assume that because a shop did it was done right. Too many of them now do a half assed job and they are not beyond telling fibs to the uninitiated. The only way to know its done right is to do it yourself. Carb cleaning and tuning is not hard and there are excellent tutorials here to help you sort it out.

I would spend some time on a fresh rebuild of those carbs with new O-rings.

Good luck with it.
 
Thanks guys. Is adjusting the idle stop screw difficult and can it really F the bike up? I read that you need to adjust it after the bike is warmed up but that's all I saw about it.

I'm not against learning how to take the carbs apart, clean em, and replace any worn parts, I would like to. Time right now for me is difficult as my wife works a separate shift as I do and we have a one and a half year old son who demands a lot of my attention when I am home. I will look into those tutorials and see if my father in law would be willing to help me out. He's a mechanical tech and initially took the carbs apart and cleaned them out when I bought the bike. So in all reality they have been cleaned up twice already....just not sure how well. I may be able to have him help me with the basics and go more deeply with a tutorial. I would like to know my bike inside and out...guess I gotta start somewhere and sometime!
 
Take your time is the first point.. Clean the cabs.. Basscliff has great tutorials and your father in-law will be able to follow what you cannot.
http://members.dslextreme.com/users/bikecliff/

Once the cabs are clean and the o-rings are replaced. You will need to replace to Intake boots.. Do not skip these parts. Just assume they are bad and replace them. Will save you tons of heartache and time that could be spent riding. Once this is done you will "bench sync" the carbs.

What this really means is that you will insert a set measurement "Such as a straight part of a paperclip" underneath both of the butterfly valves.. You want it so that both valves are lightly touching the paper clips. Basscliff site explains whats screws to adjust to get this..

Once that is done you put the carbs back in and and see how she idles. You can then use this here to adjust the idle screws. I have a 450 and started at 1.5 turns out.. My end adjustment is 2 1/4 turns.. I use this to adjust my pilot screws.
http://www.thegsresources.com/_forum/showthread.php?t=199096&highlight=pilot+screw+adjustment

If your not able to get through these then you still have a fuel/air mixture/idle circuit problem.
 
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