1980 gs850g running lean

[longgreensilverado]

ok here I go beating it to death about jetting. my bike is running lean.
to start my carb boots are all new in and out. also the o-rings are new.
my valves are set right in the specs. my air box is sealed tight.

i have all stock jets except the main which is #120. my plugs are white/grey. otherwise very clean looking. I know the bike is running lean.
i was thinking of going to #122.5 main and go to #45 pilot and then reset my mixture screws.

I have a k&n airfilter which is sinilar to stock. also have stock exhaust set up.

the problem is the bike is running hot and pings when i take off gently. I am using 89 octane mobil gas.

 

[Steve]

A couple of possibilities here. You could be running a bit lean due to the K&N filter. A 122.5 jet might work, might need a 125. 45 pilot should do nicely.

Are you running 89 octane gas because it's pinging or have you been using it all along?
These bikes are designed to run on 87 octane. You do not get more power by merely running higher octane gas. In fact, power will be down a bit and fuel efficiency (gas mileage) will suffer, too. If you have been running 89 all along, there is a chance that there are excessive deposits in the head or on the valves. These deposits will retain extra heat, and this is what will set off the fuel mixture before the spark, causing your pinging. Try running a heavy dose of Sea Foam through an entire tank, but do it all in one day. Run it hard enough to keep things really warm and moving around, it should clean the combustion chambers rather nicely. Refill the gas tank before parking the bike for the night to thin out the strong Sea Foam mixture. Not sure you want the strong mixture sitting in the carbs for more than the few hours it takes to ride your way to RESERVE.

One last thing to check ... spark plugs. Are you using the correct heat range? Correct plug is NGK B8ES.


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[longgreensilverado]

thanks steve. i will try those jet sizes.
I have been running 89 because i thought it might be better than 87.
I run ngk B9ES thinking it would run coler.
I have tried seafoam before and know it contains stuff that can eat a carb for lunch. I will put a can in before going to work tomorrow. (i have a rather long commute 45 miles one way) and will top off the tank with 87 and see what happens. it can't hurt to save a few bucks.

also it's hard to find the pilot jets. you'd think i'd have luck with the (6) bike shops, and the several parts shops I'd have luck.

 

[Steve]

I have been running 89 because i thought it might be better than 87.

Higher octane is only "better" if your engine has been modified with higher compression pistons, cams, etc. and pings in that condition. The higher-octane fuels are harder to light, so they resist the pre-ignition caused by the higher compression temperatures, and wait for the spark to ignite the mixture. The higher octane fuels also burn slower, which is why you have to advance the ignition timing on higher-performance engines. You advance the spark to get the mixture burning in time to burn it all by the time the piston starts going down on the power stroke.

I run ngk B9ES thinking it would run coler.

Spark plugs do not control the running temperature of the engine.
"Hotter" or "colder" spark plugs only refers to its ability to transfer heat from the tip to the outer jacket, where it is cooled by the head. A "hotter" plug transfers heat slower, which is good for maintaining proper tip temperatures to keep the plugs clean. This is good if you do extensive low-speed driving in town or if your engine burns oil, tending to foul the plugs. "Colder" plugs transfer heat quicker, which is good for extensive hard, high-speed running, like racing. "Cold" plugs used in lower-demand driving situations might tend to foul up quicker.

I will put a can in before going to work tomorrow. (i have a rather long commute 45 miles one way) and will top off the tank with 87 and see what happens.

If you are only going 45 miles, you are only going to burn about 1 gallon, so don't use more than the normal mixture of an ounce per gallon. Only use a strong mixture (half the can per tank) if you can go for a ride long enough to burn it all out in one day, then fill it up to dilute the mixture before parking it for the night. The whole idea is to get the strong mixture moving through the jets and passages, not just sitting there.


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[Guest]

Check compression and valve clearance. With a K&N filter it should not warrant a rejetting. Only mixture screw settings.
Don't change the stock spark plug. No need.
I might be off track but I still think you have an air leak somewhere.

 

[longgreensilverado]

thank you gentlemen for your replies. the spark plug explanation was very helpful. I filled my tank this morning with 87 octane and half a can of seafoam. I took the long way to work today. 87 miles to be exact. so i just topped off again with 87. so far so good. oh and also i put a new stock air filter in with a very light amount of air filter oil on it. I also put the ngk b8es plugs back in. i'll check the plugs tomorrow and see what happens.

thanks again i will report on monday