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Popping/carb question.

  • Thread starter Thread starter satchmo
  • Start date Start date
S

satchmo

Guest
Keith Krause wrote:

If a bike starts and idles at 1100 rpm and then reaches 2500 rpm after it's warmed up,then the bike is running lean because of an air leak. Too much air increases the rpm's
Click to expand...

Then does it follow that if the bike (mine) starts and idles at 1200 rpm and then after it's warmed up, the idle dives below 1000rpm and continues diving until it stalls (only when it's really warm) ...does that mean the bike is running rich?

I'm just curious, I know it's running rich because I'm only getting 18mpg and the plugs are really wet. But until I can afford four carb kits then I'm stuck with it.

I'm just wondering if that phenomena with the idle is caused by the bike running rich. I also get some popping on acceleration, and idle as well.

Satch

1977 GS550
 
It's not really a phenomena. If you start a cold engine that is actually running over-rich,the engine may be able to handle the rich condition until it reaches normal temperature.That's why the choke can be used.But once everything is warmed up,the engine runs better with a balanced mixture of fuel and air.If you take a perfectly running,warmed up motor and turn IN the side air screws(less air-richer)the idle will drop. If you turn OUT the screws(more air-leaner)the idle will rise.Sometimes the rpm's will rise a lot,such as broken o-rings in the carb intakes.The bigger the opening or crack,the more air enters and the rpm's rise accordingly.If you start a cold engine that is actually running lean,you will find you have to use more choke to warm up.You may notice only a slightly higher idle than normal,but as soon as the engine clearances tighten up you will see the rpm's rise according to how over-lean conditions are.Sometimes a motors timing can be so far off or have such a weak spark that it can be confused with being too rich.A weak spark will not ignite the mixture properly.This can also cause a wet plug,popping,(which means your plugs are near fouling) and poor mileage.More often though,it's carburetion problems.Their are a lot of things in the carbs that can cause your bike to run rich.There may be dirty or blocked passages/jets inside.O-rings need to be in good shape.Any part that can wear such as jet-needles,needle-jets,float valves and seats,etc,need checking.Float height needs checking.If you have pilot screws,they need to be adjusted right,and also the side air screws.The carbs also need to be reasonably balanced with each other.The air filter(s) need to be clean.What's the background on your bike?Is it stock?Has anyone possibly changed the jetting before you got it?Was it running this way when you got it,or just start happening?Are all 4 plugs wet,or just 1 or 2 ?Are they wet with fuel or possibly oil?Check your timing first,make sure it's right,then start on the carbs.What makes you think you need carb kits?Maybe a simple cleaning or the pilot screws adjusted will fix it.
 
Earl was giving me a hand with this earlier, but I ran out of cash to fix, and time as well as I was working on my thesis. I've got more time now, but still not so much cash.

Here's a complete history of the bike (as far as I know, which isn't much).
I bought the bike in march of 2002. It's my first bike. I didn't pay very much as she was pretty rough looking.

A 1977 GS550, I got her home, and she wouldn't run. I took off the carbs and attempted to clean them myself. I put them back together (with new gaskets of course) stuck them on the bike, and started her up. She went, way to fast. RPMs up there like crazy and spewing smoke out the exhaust. Also leaking oil like a seive from under the engine somewhere.

So I called the shop and had them fix her up for me as this was too much for me to handle, and I'm not very mechanically inclined (although I'm trying now)

They replaced the chain, which was completely stretched out, added a chain adjuster nut and bolt which were missing. And replaced my exhaust (not with OEM) because one of the original exhausts was cracked. They also boiled the carbs or something like that to clean them all up and stuck 'em back on. They fixed a leaky o-ring which was causing the oil leak.

Then I took her back, she ran much better than before, no leaks, at least none visible. The problem is that I'm not really sure what an engine should sound like, so it's hard for me to tell if mine is running right.

Anyways, at the end of last fall, I realized my mileage sucked and when I mean sucked I mean it's getting 18mpg which it still does. I took it back to the shop, and they fiddled with the airbox (new air filter and whatnot) but didn't really fix my problem and I didn't have the money for a carb rebuild. They didn't even tell me what's wrong (that's why I'm trying to do it myself).

So here I am in the same condition. I know that I need new exhaust ring gaskets because I'm losing some exhaust out of the front of the bike. My plugs are all nearly fouled, very very black. Upon Earl's instruction (thanks man) I got a multimeter out and checked the electrical, I'm losing a volt between the battery and the coils. So I'm going to clean the electrical connections, today actually.

I've been thinking about the jetting, I'm not sure what exhaust are on it, the shop just threw on the cheapest things around, because I didn't have money for pricier ones, I'm wondering if that could have screwed around with the system.

Besides the exhaust I think the bike is all stock.

Satch
 
Satch.A quick note 'cause I'm running late.Before playing with the carbs,you need to tell us if the ignition is timed correctly and if you're getting a good blue spark (clean up the plugs first before checking the spark).Try to get back with you on this to-nite.
 
even if the ignition timing was a little retarded the bike shouldn't have plugs soaked that bad. i think your pilot screws on the bottom need to be closed about a 1/2 turn.

my older 550 ran pretty rich...about 30 MPG around the city and barely 40 on the highway. plugs would always be black...which was no biggie because i was just happy it ran. i just put the carbs on my other 550, and closed the pilots about 1/4 a turn on each...and its running very sweet.

~Adam
 
I'll check out the spark issue today as well.

How do I check the timing? I'm not really good at these things. And also, where on the carb body is this pilot screw located? do I have to take the carbs off the bike to mess with it?

Satch
 
yes, unlcess you have a very short screwdriver.

the pilot screw is located on the bottom of the carbs...whereas the air screw is located on the side of the carb body.

i would suggest closing them 1/2 a turn each, and seeing if that helps. removing the carbs isn't a total chore, unless you have the stock airbox in. in that case, it sucks.

~Adam
 
Yeah I have the stock airbox. I've taken 'em off before. It's not the taking off, it's the putting back on.

I'll check the timing and spark first :D

Satch
 
putting the carbs back on for me wasn't too bad...AFTER i figured out spraying the boots with a little WD40 made them slip right in. :oops:

i have never wrestled the stock airbox and put carbs back in...i threw my airbox across the parking lot and vowwed to never use it again. :D
 
satchmo said:
I'll check out the spark issue today as well.

How do I check the timing? I'm not really good at these things. And also, where on the carb body is this pilot screw located? do I have to take the carbs off the bike to mess with it?

Satch
Click to expand...
Satch. Since all 4 carbs are too rich,I don't think it's likely that several parts just wore out.It's possible that someone played with the carbs.You say the carbs were cleaned inside and the air filter is OK.So we'll rule those out?The cheapest and easiest thing you can try is adjusting the pilot and air screws.If you have never turned these screws,be carefull if they are tight.The heads can strip off(especially the side air screws.)The factory puts a coating on them that can gum up the threads.If this coating is still on them,try to clean it off with a toothpick and spray.The pilots are underneath and in front of the float bowls.Try turning all 4 of them IN(clockwise)about 3/4 of a turn.You will have to find a short screwdriver or a flathead bit and a small wrench if they won't turn with your fingers.Be sure to get a good fit.If you should notice any screw bottom before you get to 3/4,stop,DO NOT tighten them.The tip can break off inside.Now the side air screws.The small brass screw on the left side of carbs 1 and 2, and on the right side on carbs 3 and 4.Start the bike and let it reach normal temperature.If it will idle,turn the side air screws OUT until you hear the highest idle.On 1 side of the bike,try to turn 2 screws out at a time at 1/2 turn increments.This makes it easier to hear the rpm's.Once you've got the highest rpm,go do the same to the other 2 screws.After all 4 are done,if you have too high of an idle(over 1200 rpm)then just re-set the carbs idle knob to get it to 1100 rpm or close.See if this helps.If not,I would take out the side air screws(don't lose the o-ring or small spring) and spray some carb cleaner into the holes.I would also spray the air-jet in each carb.You have to take off the air box to reach them.They are on the side of the throat but to make it simple,look into the carb throat and spray any hole you see.Make sure you use a tube on the spray can.Watch the eyes! I know you said the carbs were cleaned,but this is a simple job.Re-start the bike and see if this helps.You still should do the timing check FIRST.Do you still have points?I have never done points but I have a manual for '78 and'79 GS1000 and I think your procedure to set would be the same,except the actual degree of timing.I could give you the info if you don't have a manual.They do it using a test light. Let me know.
 
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