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Author Topic: 1981 GS450 Tracker Project  (Read 227 times)

Offline CupidsDeathDay

  • Posts: 185
1981 GS450 Tracker Project
« on: Aug 08, 2019, 02:53:04 »
Hey guys. I will be posting pictures of my project soon, but i have a few questions about an issue i am having. Hoping someone may have some input.

I was working on cleaning and prepping the carbs, cylinders, tank, electronics, etc. to get my bike road worthy again after a 2 year hiatus. But i seem to have come across an unusual issue with my scoot on my first drive attempt.

After getting everything cleaned, and tank was cleared of the surface rust after sitting for a while. Cleaned the petcock, carbs, and gaslines. All of this seems to be clean and seals are all good that i can tell. I have good compression from the cylinders and good spark on the plugs on both sides. But there seems to be an issue with one cylinder firing really lean. The idle is super high when i start the bike, and really low after warming up. I cleaned up the spark plugs and verified again that spark was good. Both carbs are getting gas and i know the floats are working. But when i hit the throttle it accelerates very slowly. Once i get moving its as if one side is not firing as i get no acceleration. But then *BOOM* it accelerates hard for a split second, and bogs right back down to the slow acceleration again. I cannot find any airleaks that i can see. I tried spraying the boots connecting the carbs to the engine, but it does not rev when sprayed from either side.

So i accelerated, the best i could, downhill and dropped the throttle closed and came to a halt to check the plugs. One is white(the problem cylinder), and the other is almost a perfect Tan/brown.

Could this still be an air leak on that carb that i am not seeing, or could this be a timing issue?

Fully open to suggestions as this has just become a frustrating pain in my ass. I checked and verified i have all matching jets(in case i put the wrong size in one). The diaphragms for the slide has no holes and the needles are all straight. This bike ran great before i stopped riding...

P.S. I am running a 2-1 exhaust, and dual 2-stage UNI's for the filters on stock Mikuni CV carbs. For my jets, as a starting point, I am currently running 35's on the pilot, and 145's on the main. Could it just be that i need a Higher pilot jet?

Offline CupidsDeathDay

  • Posts: 185
Re: 1981 GS450 Tracker Project
« Reply #1 on: Aug 08, 2019, 22:09:44 »
I think i may have figured out the issue. I don't like what i found, but i found it.

Looks like i have a head-gasket leak on the left cylinder side of the engine. I plan to retest the spot i found with the starter-spray test. If it fails the test, I will pull it apart this weekend to verify. Gaskets aren't old, but this has been sitting dry for a while, so i guess i am not surprised. Updates to come. Hopefully will be uploading pics soon too. If anyone else has any suggestions while i am tearing into the top end, let me know.

I plan to go ahead and have the sleeves honed, and probably clean the intake/exhaust ports of any carbon and such. Also will be making sure timing and valve clearance is all good, while i am in there.

Offline CupidsDeathDay

  • Posts: 185
Re: 1981 GS450 Tracker Project
« Reply #2 on: Aug 15, 2019, 03:12:14 »
So after doing some testing i found that there is a small break in my head gasket on the Left side Cylinder. So it looks like a top-end "Rebuild" is in order. New Gaskets, shims, possibly valves, and honing of the cylinder/sleeves. So this is going to be a fun fall/winter for me...