Looking for a bit of mechanical help (GS400)

[VTNewb]

I don't suppose I could ask for some opinions about a problem I've been having on my 77 GS400? Can't get any answers from anyone

If your all strictly GS500 I understand  

[mjm]

I don't suppose I could ask for some opinions about a problem I've been having on my 77 GS400? Can't get any answers from anyone

If your all strictly GS500 I understand  

Hey, it is a GS Twin - and about 95% of the engine is the same as ours - (of course that is also true of a GS1000) what is the problem?

[VTNewb]

Well it is of the CV carburetor persuation, carb slides and diaphragms.
When the idle is set low enough to to brink of stall no problem happens, but if I set it to idle at 1.2-1.5k and I rev the engine it will either fall very slowly from 4k down to idle or get stuck at around 3k, the thing is this happens only sometimes. If It is at idle and I pull the throttle as hard as it can go it will pop very loudly and rev up or it will stall.

[Blueknyt]

sounds like Vacume leaks, spray wd-40 all over the Rubber boots that hold the carbs on, more then likely your sucking air from somewhere between the throttle plates, and the intake ports of the head.

[JLKasper]

My first road bike was a '78 GS400 purchased new, so I feel your pain with the carbs.  This could be caused with float height, or the cracked manifolds mentioned in another post, pilot screw o-rings, or simply clogged jets.

The layout of the engines are the same, but the older GS4 had a roller bearing crank, compared to the GS5's shell bearings more commonly in use today.  Aside from that, it also had wimpy fork springs, overoptimistic speedometer, and ridiculously lean jetting.  I do like the choke better on the 500s.  Before the seat self-destructed, I thought the 400 was more comfy than the 500 is now.  

[scratch]

In addition to checking for leaks, if your carbs are similar to ours, adjusting the mixture or pilot screws richer may help.

[500rider]

What no GS400 forums?  Weeeellll ... ok ... since it is a GS ....

Just in case you didn't get the WD40 reference, I guess you spray it while the bike is running and if you notice a change in rpm, then you know there is a leak.  Maybe u knew that already.  

It does sound like there is a lean condition.  Adjusting the idle speed higher I would think would make it even more lean thus making the  idle "stick".  Do you know if there is a pilot valve on those carbs?  On ours, there is one but it is hidden behind a brass plug that you have to drill out in order to adjust the screws.  Not sure why they did that but ...

Hope you get some help.  Just keep posting and you will get some.

Rob

[VTNewb]

Was gonna try that WD-40 test today, but when I kickstarted the damn thing it only ran on one cyldiner, after playing musical chairs with the sparkplugs I found out the left spark plug wire isnt delivering electricity anymore. Unfortunatly this might be the end of my 1 week motorcycle excursion, bought the thing with the help of a mechanic saying its an easy and cheap fix and it's all going downhill.

[500rider]

Well don't give up ..  must be a Buddha Loves You to have to try and get the bugs out while having to kick start.  like I wrote before. Keep posting and you will get some help ..  by those more knowledgeable than I.

Rob

[VTNewb]

Oh it has a button, the battery was just low from a lot of starting with no riding

I'm gonna talk to a freind of mine that just got back from a few years at motorcycle mecahnics institute, hopefully he can fix this spark plug issue.

[VTNewb]

I'm now considering selling it with its high idle issue save some cash then financing myself a GS500. Something new and working would be much preferable now.

[JLKasper]

The GS400 is a sweet bike , once everything is sorted out.  The major difference in maintenance between the two is between ingition systems.  The 500 has electronic ignition, while the 400 makes do with points and condenser for each cylinder.  With a manual, it's pretty easy to sort out.

On the other hand, a 500 outshines the 400 at nearly every turn, while giving up the kickstarter and digital gear indicator.  Wider, tubeless tires, brighter headlight, more powerful brakes, stronger chassis, more trouble-free ignition and parts availability are just a few of the many advantages the 500 offers.

Should you decide to stick it out with the 400, I'll give you a tip that'll help keep the battery charged up.  The hi/lo dimmer switch has a tab underneath it that prevents it from being slid into an "off" position.  If you remove the screw on side of the switch actuator, it'll pull off.  Just cut the tab off and you can turn the headlight off while you're troubleshooting.  I have a Clymer for the 400, but it's not for sale.  If you pm me, I can talk you through some procedures.  I'll also say a prayer for you when you need to remove and reinstall the carburetors.

[VTNewb]

I might need some tips when testing points and condensers for this spark plug wire As for the carbs I've taken em off around 10 times now, bleh.
Well see how it goes. My best buddy is a harley mechanic and ill see if he can pull some magic and fix this thing to ridable.

[Greg Gabis]

Have you checked your valve clearances recently?

[Blueknyt]

if you deside to trash it, yank, kickstarter stuff off the engine, including gears,cover,springs, i would love to incorperate it back into the 500 platform.