GS850 post rebuild issues

[Guest]

I recently did a top end rebuild on a 1980 GS850 -first experience with an engine rebuild. Valve job was done by S&k racing who came highly recommended. A friend who used to run a bike shop helped me rebuild the carbs, which we also rejetted for the full length open pipes that were on the bike when I acquired it. The rest of the rebuild I did myself in my shed with the advice of my friend along with all the info I've acquired from GS Resources! 23 miles on the rebuild, everything was going ok, had power through all gears, but seemed to be running lean. I had been trying to correct the leanness with my carb mixture screws but this week some other issues came up. Started up fine but after running for a few minutes I noticed exhaust for 1&2 getting hot quick and 3&4 pipes remaining cold. I shut it off, then started it up again, ran for 3 or 4 more minutes again same inconsistent heating of cylinders, then I started getting white smoke from pipe for 1&2 so i shut it down. Again this is a new development and was sudden. I'm getting spark for all four and I've got fuel in all four carb bowls. S&K racing shimmed valves for me, but I did not check clearances before initial startup. Checked cam chain tensioner(which I also rebuilt) action is good. Pulled the valve cover-cam timing is good and so is crank position. No visible damage up top and no valves appeared to be sunk..cams and cam lobes look undamaged. I checked all valve clearances twice and I only have one that is under .10 mm, with clearances ranging from .09 to .15 mm! So i know I need to re-shim the valves, but could loose valves cause the sudden inconsistent heating of cylinders and the smoking? I know that straight pipes are frowned on in general on this forum and for good reason. I plan to get some slip on mufflers and hopefully just go back to stock jets after I sort out this other issue..kinda wish I had in the beginning.. I'm sure they are contributing to the leanness and they are annoying at over 1/4 throttle! I know it's a lengthy post but I figured the more info the better. I've put a lot of hard work and $ getting this bike to this point so any advice is appreciated. Just hoping I wont have to pull the top end off again to find the answer!

[Steve]

I am one of those who does not appreciate straight pipes and don't usually help anyone that admits they have them, but I will say this: adjusting the mixture screws does NOTHING for adjusting the jetting you need for compensating for the pipes.

Get some mufflers on there, then do the jetting necessary for them. No point in going through all the hassle of jetting now, then doing it all again later.

No, your extra valve clearance would not cause the symptoms you are talking about, but should be adressed soon. You won't hurt anything in the meantime, but do keep the RPM down well below redline to prevent valve float.

If you had valve seat work or valves refaced, you essentially have a new head. Suzuki recommended a first service at 600 miles, mainly to check the valve clearance, which usually tightened up. Yours might come into the "tolerable" range if you wait that long.

.

[JHook]

Again, the straight pipes were the hand that I was dealt when I picked up this bike and I plan to remedy the situation..please don't judge me! Do you think the issues could be because of a blown head gasket? I saw no oil leaks around the head externally. It just seems strange to me that all four cylinders were affected in this way all the sudden.

[Steve]

Not sure exactly what the problem is, but running lean is not helping anything.

If it's a bad head gasket, you would see that with a compression check.

.

[JHook]

I should also mention that spark plugs for 3&4 were not fuel soaked but the pipes were cold, so that must mean I'm not getting fuel to those cylinders? Unless something randomly clogged jets for both carbs, I don't know where that could happen because they are surgically clean at this point otherwise. I checked the float bowls and fuel is getting to them..stumped!

[Big T]

Well, you answered your own question right there

1. Gas in float bowl
2. No (or little) gas at plugs = gas is not getting from bowl to combustion chamber

Something got loose and plugged up the carbs

How does the inside of the fuel tank look? Rusty?

[JHook]

So, compression check shows about 140 psi across all 4 cylinders, with little or no difference between each one.It does seem strange that 2 and only 2 carbs would not be getting fuel to their cylinders all the sudden. I really appreciate you guys chiming in with advice. If anyone has any ideas as to what else this might be, before I pull the carbs again and check the passages? Carbs have not been vacuum synced yet, so could that simply be the issue here?

[JTGS850GL]

BINGO!! Get those carbs synced up first before you start to tare into things.