Questionhi. My bike maxes out at 55 mph. It's a 400cc 6 speed and should go a lot
faster. I'm wondering what an appropriate course of action might be. There
are no mechanics in my town, but i can get parts.
Thanks
AnswerI had a '78 GS400 so I can tell you from experience that your '77 should be able to go a lot faster than that. It wasn't topped out at 160 Km/h (100 MPH) with a passenger on the back, and it routinely did 140 Km/h (88 MPH) pulling a sidecar with a passenger.
Are you sure it's running on both cylinders? The best way to check is by holding your hand near each header pipe (don't touch them - they are supposed to be really hot). If one is cold (or significantly less hot) that side isn't running.
If one cylinder is dead the most likely causes are lack of spark or lack of fuel. Check for spark by removing the plug, putting it into the plug cap and cranking the engine with the side of the plug touching the engine. If you have spark you probably need to clean your carbs. If there is no spark, make sure the plug cap is screwed firmly into the end of the plug wire - you might need to cut a bit off the end of the wire to get it to contact properly.
If only one cylinder is running and this doesn't solve your problem let me know and we can go into this in more detail.
If both cylinders are running you should go through the basics first: Are they the right plugs and are they gapped correctly? What condition is the air filter in? Check the valve clearances, make sure the points are set properly and the carbs are balanced &c. This stuff is all covered in a shop manual. I kept my GS running for many years with a Haynes manual. You would be amazed at how much difference a good tune up can make.
Just an afterthought: Make sure you don't have a dragging brake. The easiest way is to take it up to speed and then coast to a stop without using the brakes. Immediately after stopping, feel the rear drum and the front disc to see if they are hot. Be careful - a hot disc can burn your fingers. If you didn't apply the brakes they should be cold so any heat indicates something dragging.
Let me know if this helps or if we need to di further.
I recommend joining a good online usergroup like this: http://www.thegsresources.com/ where you can find others with similar bikes who have already had the same problems you are likely to have.
