rebuilt carbs, still hard time starting cold!!

[kvgarrison]

Hello, a few weeks back I posed a question about my 82 gs850gl. I said that it would not start cold, you folks said to do the carb work, so I did. I cleaned the carbs and found that the choke was hanging up so I fixed that. Everything is put back together, tested for air leaks and seals are fine front and rear of carbs, cleaned air filter. The bike will start markedly better now but it is still "hanky". I have to half choke it and play with throttle when it is cold or it won't fire over. Now I got the new battery and I don't want to kill this one so help!!!!! Bike starts and runs fine when it is warm. Any wise GS wizards out there?:?

[Dave8338]

Sounds like there is still a restriction in the choke circuit. You should not have to touch the throttle to get the bike to start. If you do, chances are that there is still blockage in the choke / pilot circuits. Did you dip the carbs or just spray them down? Replace all the o-rings in the carbs? If not...you may end up doing so.

[longgreensilverado]

make sure you clean every single circuit in each carb. then while they are off, take the boots off that connect them to the head and change the o-rings. than check your valves. i had a similar issue and the valves made quite a difference. also check your air filter and make sure your air box is all sealed up properly. oh and put half a bottle of Sea Foam in your gas tank. it may help a bit after you do the first things we have mentioned. it is 6.00 a can at advance auto parts.

[UncleMike]

Valve clearances?

(I'll say that until the day I die.)

[Hammer]

I've got the same problem. Always has been hard starting.
79 GS850G, rebuilt carbs, 57k miles.

I'd like to know more about the valve clearances and how it relates to hard starting.

Thanks.

[pvtschultz]

Lost compression if there has been enough wear of the valve seats so the valves hang open. Also, you to be absolutely certain that the choke circuit fuel path in the bowl is open. There is a path that goes down the side of the bowl, through an oriface, and then into the bowl. This may become plugged up by old/bad gas and it is a huge PITA to clean out IME.

[Nessism]

Bike sounds normal to me. GS bikes are lean from new and always require choke from a cold start.

[Steve]

I'd like to know more about the valve clearances and how it relates to hard starting.

Thanks.

Air flow in the cylinder is controlled by the valves. If the clearance on the intake valve is too tight (and there is not much clearance to start with), the valve will be closing later than it should, and may not close completely at all. :shock: Either way, since the piston is already coming up, some of the mixture that has been drawn into the cylinder might get pushed back through the carb, picking up more gas on the way. Moments later, when the intake valve opens and the piston goes down again, air is drawn through the carb for a third time, picking up even more gas. Obviously, this is too rich a mixture now, even without a choke.

If your valve is not closing completely, there won't be enough compression to light the mixture properly, and some of the poorly-combusted mixture might get blown back through the intake valve, at least until things warm up and maybe seal somewhat properly.

I had this problem on a previous bike (not a GS) to the point that I actually had to use my shop vac in the blow mode to pressurize the airbox to make sure the air only flowed one way. :shock: This worked when the bike was cold in the morning. At the end of the day, when I was ready to leave work, it was a crap shoot as to whether the bike would start or not. Once running for more than a couple of minutes, it would start any time I wanted, until it cooled for several hours.


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