Topic: 73' cb500...filthy rich

[lucky]

I didn't like the sound of the clip being down 4 from the top. 3 from the top should be the middle and that's supposed to be the stock setting. Where its at now, as you mentioned would hold your main jet needle up to high and give you the rich mixture you are having a problem with. Move the clip up one to the middle and try there that's where I run mine.

That chart that was shown showed that 4th from the top.
I would move it to the middle position too.
I will go back and see where that data came from.
Yes Deltarider posted that chart and it does not say where it came from. It is not clear.

But it is normal to see the clip in the middle position from the factory.

[MADMAX]

thanks guys i am currently setting the needle clip up one position.  more information as it arrives.

[lucky]

Yes i agree about setting the needles in the middle position.

You reported the the exhausts are quiet, and that is hard to quantify
with words, but we will assume it has some sort of baffling.

That would make me want to keep that clip in the middle position for now.

Did you check the floats as shown in a Clymers ' manual???
What's going on with that?

Thanks-LUCKY

[lucky]

Remember how i was saying moving the clip position on the slide needle will make a very dramatic change. Well that needle could have been the problem or an attempt to make the bike to have better throttle response by a previous OP/

Anyway you could just put it all back together with no changes on the jets and see where you are at.
But if it still stumbles you need to take it apart once more at least.

Did you verify the jet sizes while you have it apart?

BTW..I was born in Indiana. Mishawaka Indiana.
Got transplanted.

Changing to larger jets will make it richer but just in one area.
Changing the needle on the slide richens up the ENTIRE 1/4-3/4 throttle.
basically almost every part of the throttle.

If you just enlarge the idle jet it just increases the first 1/4 throttle.
If you increase the main jet there is some cross over into the mid range but
main jet mostly controls WOT. There is some crossover into mid range near the top.
But you know the needles cannot raise up do far that they come out of the main jet.
So the main jet is always partly blocked.

There is some cross over between all of the jets but it is not dramatic as what a needle repostioning will do.

[MADMAX]

yes jet sizes are stock - 40 idle and 100 mains. 

i made a float height tool with a credit card.  i will make sure they are all correct once more.

[lucky]

yes jet sizes are stock - 40 idle and 100 mains. 

I made a float height tool with a credit card.  i will make sure they are all correct once more.

Great!
Sounds like everything is getting tightened up. Not so many unknown facts.
Just do not get discouraged if it runs leaner but still stumbles.
It may or may not happen and it all depends on the amount of back pressure the exhaust is influencing how much air and gas can come into the engine.

Wait a couple days to make sure of how it behaves.

Good idea with the credit card.
I just thought they were to make guitar picks.LOL...lol

[MADMAX]

that good idea came right from this forum! seems to be full of them. 

[Scott S]

 You're doing all the right things....keep at it.

 Have you checked the advance springs? Are they weak? Do they snap back or kinda hang open a little?

 Did you trim the spark plug wires and install new caps? That's cheap enough to do....

[73CB500K2]

Remember:

After all the changes you have made to the carbs ie: needle jet clip change, you will have to re synce the carbs again and double check the idle mixture screws, my bike likes them at about 2 turns out.

It will run, idle and behave differently so you will need to do some road testing to fine tune.

I also agree with the previous post to check your advance unit and make sure its free and advances correctly. After sitting they can corrode and become sticky.

[Scott S]

 Or weak...the springs should snap back and close completely.

[MADMAX]

 i verified that all carb passages were clear and changed the needle clip position from #4 to #3.  went for a quick ride around the block and it felt good through the throttle range although i did use brand new plugs.

when i checked the advance before it was hanging up terribly.  after cleaning and lubing, it still hangs up the slightest bit. maybe new springs are in order.

 i checked plugs when i got back and found cylinders 1 thru 3 were black and number 4 showed white.

 i heard a valve tapping also that came from the number 4 area. i suspect this to cause the lean condition?

this ride was a lot of starts and stops so i guess this could cause the rich look of plugs 1 thru 3?

i was pooped for the day so i will do some more chasing tomorrow.

[73CB500K2]

Sounds like a valve adjustment is in order and remember you will have to re sync the carbs after your needle clip adjust.

[lucky]

My interpetation of this:

Quote:
"went for a quick ride around the block and it felt good through the throttle range."

Need to find out why plug#4 is white.

 FIRST..Take a timing light and clip it onto plug wire # 4 and see if it has consistent timing strobes.

Since all passages and jets are clean,  I will open the drain on float bowl#4 (if it will unscrew),Or else I will sit the bike level, turn on the gas,then turn off the gas and remove the float bowl carefully and see how much gas is in the float bowl.

[lucky]

Sounds like a valve adjustment is in order and remember you will have to re sync the carbs after your needle clip adjust.

A valve adjustment will not cure a lack of fuel.
A valve adjustment will not cure no spark.
A carb sync will not cure a carb.
A valve adjustment will only make the valves within spec of being too loose or two tight.

[MADMAX]

i will double check valves and fuel level in bowls tomorrow.

[MADMAX]

after rechecking valves and another ride around the block i found plugs 2,3, and 4 looking lean haha.  plug number 1 was soot black like always.  only difference with this carb is the solder repair i did on the overflow tube.  i wonder if this has some negative effect. 

still havent carb synched again but i didnt understand the urgency when i changed needle clip position.  if i changed the clip from the top of the carb without disassembling from the rack would a carb synch be necessary? someone school me on this. 

lucky - the effect of the needle clip was very dramatic!

thanks dudes.

[lucky]

after rechecking valves and another ride around the block i found plugs 2,3, and 4 looking lean haha.  plug number 1 was soot black like always.  only difference with this carb is the solder repair i did on the overflow tube.  i wonder if this has some negative effect. 

still havent carb synched again but i didnt understand the urgency when i changed needle clip position.  if i changed the clip from the top of the carb without disassembling from the rack would a carb synch be necessary? someone school me on this. 

lucky - the effect of the needle clip was very dramatic!

thanks dudes.

MADMAX...

OK..You changed the clip from the top without taking the carbs off. NO problem.
You do NOT need to take the rack apart for that.
But there is one concern to check on.
When you put the clip holder back down in the slide you have to make sure the spring is lined up over the clip needle. I will post a photo.

If you soldered the overflow tube and it was blocked completely it would still run as long as your float bowl vents are still working.
Over the long term some gas could get sucked into the intake system via the vents from that #1 bowl it it over flows.

But to check it just take the overflow the coming from #1 and see if you can blow through it at all. If you can, then it is not blocked.

If you have good float needles and you set them using the proper gauge it will work fine.

The fact that #1 cylinder spark plug has soot on it all the time since you first started working on it means that either something is different about that carb.
Or something is blocking the intake.

I am just wondering if a squirrel nut or something is jammed in the intake.
The nut would not go all the way in the combustion chamber because the valve guide would stop it if it is too large. Maybe a waded up towel or rag. LOL..lol Just covering all the bases.
ALSO what about something blocking the intake of #1 cylinder INSIDE the air box?
There have been several photos on this forum of nuts inside of air boxes.

Could the slide needle be the wrong one??? You know a PO ?
You said the compression values were almost even so I do not think it is a broken piston ring.

In the first post you said QUOTE:
"just ran a compression test and came up with 80, 80, 80, 72 respectively.  after adding a little oil number four came up to 76.  i read the test equipment can cause low ...."

Makes me wonder if you know that #1 cylinder is on the left side of the bike and #4 is on the right side as you sit on the bike? Just asking..

Think about this..

You have ONE cylinder #1 that has soot on the spark plug. On the compression test you have ONE cylinder low on compression and that cylinder is one of the outside cylinders.. See what I mean?

BTW HOW much soot?? Maybe it is not that bad? Wish we had a photo.

[lucky]

One more thing IF the cylinder #1 IS the one that had lower compression
( and lets not forget 76 or 80 is splitting hairs), IF it is #4 that had the 76 lbs. compression, I would not even be wondering about that small of a difference.

I would focus on that #1 CARB and the AIR INTAKE of the AIRbox.

Let us know.. Thanks MADMAX.

I know you will find out.
If you were a dealership mechanic you would HAVE TO find out.
Many times in a motorcycle shop on difficult mysteries all of the mechanics try to help the mechanic having the problem by offering ideas.

ITs like you have many people on this forum offering ideas.

[TwoTired]

still havent carb synched again but i didnt understand the urgency when i changed needle clip position.  if i changed the clip from the top of the carb without disassembling from the rack would a carb synch be necessary? someone school me on this. 

Must re-synch carbs after changing slide needle position, as you have disturbed the actuating arm position.

I wouldn't do ANY more carb fine tuning until the plugs display the same deposit pattern on all four.  Something amiss with the oddball, which may only be carb sync, but that must be squared away first.

Did you put in a new air filter for the fine tune adventure?
Between the air filer and the carbs is an air plenum distributing air to each carb.  Tell us about the drain tube hose that is on bottom of that.  Style, routing, termination, etc.

Cheers,

[MADMAX]

thanks again guys for the help.

lucky - number one ( first from left when im on the bike ) is the fouled up one now. number 4 had the lower compression reading.

going to re-synch the carbs here shortly.  the drain tube on my air plenum is new from honda.  i will check routing today.  air filter has no more than 500 miles on it. 

more details as they arrive.

[MADMAX]

today i synched carbs again.  it gave me hell this time but after enough patience i got them looking good.  tube from air plenum runs under battery box and out near the back tire.  rode the bike for a few minutes and it felt pretty good, not stumbling, just slightly underpowered. 

i was in a neighborhood and was able to get it into fourth at WOT, pulled clutch and killed it.  the plug deposits are shown below are in order as sitting on the bike. (top is #1) as you can see number one is more rich than the others.

then i cut my thumb pretty good.  my worked stopped here for the day!

[lucky]

today i synched carbs again.  it gave me hell this time but after enough patience i got them looking good.  tube from air plenum runs under battery box and out near the back tire.  rode the bike for a few minutes and it felt pretty good, not stumbling, just slightly underpowered. 

i was in a neighborhood and was able to get it into fourth at WOT, pulled clutch and killed it.  the plug deposits are shown below are in order as sitting on the bike. (top is #1) as you can see number one is more rich than the others.

then i cut my thumb pretty good.  my worked stopped here for the day!

Sorry you cut your thumb!
Did it require stiches???

Fourth WOT in the neighborhood!!! WOW!!
Be careful.

[cgswss]

I'm sorry but from what I'm hearing the bike is running rich.There is no way I would go richer unless I had some indication of lean. 

High RPM mixture is controlled by your main jet.  From what I get your running good at high RPM
The needle setting effects about 1/4 to 1/2 throttle.  You seem to be rich in this area.  I would drop the needles one slot

Once you get it back together, I would play with the air screws and fast idle stops

I guess I'm the only person on here that uses plug chops to see inside the engine.  But I would recommend you do a WOT plug chop to see exactly where you are on the main jet.   I have also used a plug chop to get information about running around at a consent lower RPM  The reasion for a plug chop is that if you just pull the plugs and look at them, you are looking at the results of wide rang of conditions,  With a WOT plug chop you are looking at JUST the main jet.

[TwoTired]

I wouldn't do ANY fine tuning until I found out why # 4's plug is devoid of deposits.  What is different for that cylinder or carb?

[lucky]

I wouldn't do ANY fine tuning until I found out why # 4's plug is devoid of deposits.  What is different for that cylinder or carb?

I agree. Something is wrong with that carb or with the intake.
It is not getting enough air??

The compression values are not that different from each other.