help save another GS500e!!

[BSloss13]

Hows it going guys, this is my first bike (coming from a few years of serious 90's BMW car work), I picked up a 1992 gs500e with 12k on it for 350$... It was clear that it had a rod knock due to a virtually nonexistant main bearing, so I bought a crankshaft with 17k on it along with the rods, swapped that in and the bike ran but not flawlessly. Had barely enough power to move, so I did a little tuning, bought a new air filter, spark plugs , cleaned the carb thoroughly, made sure those little o-rings under the vacuum ports were there, installed 40 pilot jets and 125 mains & adjusted mixture screws to 3 turns, and cleaned resealed the intake boots with Suzukibond to the block thinking this would fix the problem.... The bike for sure runs better now, but still, NO POWER!! The top speed I can get to is 25-30 at WOT, in the two times I have tried to ride it, something seemed to click and I got a jerk of power, but the revs started to hang at 5k with no throttle input... so I ripped apart the petcock, tested the vacuum and everything is fine there, drained the gas tank of old gas, checked the tank valve for clogging, there was only a few particles of rust which I removed.... Next I synced the carbs, still barely an improvement except at idle.... Another weird symptom I am having, is that the bike idles flawlessly and will do so for an hour if I let it sit there, but 70% of the time if I give it a little throttle the rpm's jump to 4-5k and will just hang there.... I just noticed a slight knocking that seems like it is coming from the valve cover, with a rhythm of 1,2,3,4 then it goes away for a couple seconds then repeats. The throttle seems bogged down before 4-5k but when it is hanging there it doesn't seem to have any hesistation whatsoever, and will even rev all the way to 10-11k and sounds great when it does. Guys I have like 50 hours into this freaking thing and I love how the bike looks, sounds, I am proud of ripping the engine apart and successfully putting it back together, but I am at a crossroads and I think I am going to sell.... Anybody have any other ideas? Im going nuts here I really want to keep this thing.... The only last thing I can think of is that I forgot to shim the carb needles, but I am at the point where it almost seems like a waste of time to put any more money or effort into this thing.... Help me save it!

[burnchassis]

the carbs are finicky to say the least ..if they are not perfect the bike will stumble.
-CS

[utzguy]

Having just brought a '91 back to life I can understand your pain. I have played with several GS500's in the past, but they really don't like to sit around.

A couple things:
When you cleaned the carbs, did you pull the jet tube out? It's the brass tube in the bottom of the plastic part that the main jet threads into. Mine were really nasty looking and had several of the holes blocked.
When adjusting the air screws make sure you have the idle adjuster turned all the way down. If not you may end up with a climbing/hanging idle.

I had my carbs apart too many times to count before I got it (mostly) working right. I would have given up and taken it to a shop if I had one I trust and had money.

Hope you get it going. It's a great bike when it's working and once you getting it going right it should run forever.

[007brendan]

If the knocking is only around at idle, and not too loud, it's probably just camshaft float.

[piresito]

Most certainly you have a vaccum leak! Spray wd-40 or starter fluid around the boots of the carbs and see if the idle changes. Those leaks can be microscopic!!

Also, just to be sure, recheck you timing.

Changed cranckshafts...you must be mad! You're probably a microstep away from getting it running perfectly!
Look to the bike as if you just got it, and toubleshoot it as you just got it, or as an outsider getting to the bike for the first time.
I think our brain starts to stop working after putting a finite amount of effort in a project....really!

[noiseguy]

something seemed to click and I got a jerk of power...

First part makes me think that you have an ignition issue... that when running only one bank of carbs is firing. I had similar issue with a 4-cyl missing on one cylinder... would be even more exagerated on this bike.

but the revs started to hang at 5k with no throttle input

Second part is hanging idle. Check the FAQ for how to fix this.