Topic: 73' cb500...filthy rich

[MADMAX]

really enjoying the forum... now if i can make this thing run correctly.

plugs are always fouling with soot.

carbs are clean, set up stock, and synched.  air screws 1 and 1/8 turns out, new K and N filter. 

clean plugs and it runs pretty good.  i still feel a lack of power.  a few minutes later it stumbles from 0 to 1/4 turned throttle range and only has smooth response when running high RPMs (4K-6K)

ive gone through the tune up procedure twice now.  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 readings.  this is the el - cheapo chinese tester from harbor freight. 

just a thought - ive never seen the pipes that i got with this bike on any other 500. 

whats next?

[flybox1]

adjust your air screws to lean you out.
clogged pilot jets and emulsion tubes?
what plugs are you running?

[MADMAX]

emulsion tubes and pilots cleaned 3 times now haha. carbs are about to come back off again so i will check again.

running D7EAs.

thanks for quick reply.

 

[lucky]

The compression is low but even.

When you did the compression test were the throttle open?
Fully charged battery?
Were all of the plugs out?

All of these factors can compromise a compression test.

Now the other problem. Running rich.
Low compression can be burning oil.
Is it burning oil? That will make the plugs look like they are running rich.

FACTS:
1973 CB500.

Mileage???
Intake type???
Exhaust type...Looks like a 4 into 2 system from the photo.
Mufflers or baffles???
Idle jet size?
Main jet size?
Slide needle position.
Float levels can cause rich running if they are off.
Mixture screws 1-1/8 turns

Are the jets stock size?


A lack of information.
Need to get rid of all the question marks.
that way we can just deal with facts.

[MADMAX]

not burning oil.  throttle wide open. fully charged battery. plugs were out.

30K miles, stock intake, 4 into 2.
not certain about mufflers or baffles.  how can i tell?
idle jet - 40, main - 100 (stock)
havent verified needle position
float levels are 2mm below the lip of the bowl after checking with clear hose.

can i check needle position without disassembling the rack?
thanks for the help.

[Stev-o]

Is the exhaust really really loud? If yes, baffles may be out.

[MADMAX]

no, it sounds pretty normal.  i was really just curious if it was a stock setup or something aftermarket. 

this evening i can verify needle position.

[dave500]

if you think you have a crappy guage try and borrow another one and recheck,those numbers are #$%* house.

[lucky]

I am not sure of the specs for that year but I would set the floats as described in the book.

Sounds like the float bowls could be too high.

2mm below the top of the bowl! That is only .078 thousands or just slightly over 1/16 inch below the top of the bowl!  Just seems way too full.
That could  be the problem.

That seems way too full to me.

I would get a float gauge or calipers and measure them the way the book says.

[dave500]

go over your ignition and also check those spark plug caps resistance,sort out your compression test again with a better guage.

[lucky]

There is a LOT of discussion on the internet about this bike and these floats.
(A lot of confusion)


There is a float gauge made for this bike and it reads 1.0236 thousandths
or 26mm when the carbs are right side up and you measure from the bottom of the float hanging down, up to the edge of the carb body.

I knew the floats were too high.
Generally all of these Hondas keep the float bowl about 3/4 full in general.

[Deltarider]

I am not sure of the specs for that year but I would set the floats as described in the book.

Sounds like the float bowls could be too high.

2mm below the top of the bowl! That is only .078 thousands or just slightly over 1/16 inch below the top of the bowl!  Just seems way too full.
That could  be the problem.

That seems way too full to me.

I would get a float gauge or calipers and measure them the way the book says.

No, no NO!
(sigh) This goes on and on and on...

OK, for the very last time. Unless the PO has messed with the floats (That PO MUST be a reader of this forum where false information is echoed and echoed over again), they're right. Have a look at the floats and you'll understand why. If that little tang doesn't show any signs that someone has bent it, it is ALL RIGHT. THERE IS NO WEAR WHATSOEVER, NEVER. PERIOD. Check it for free movement, check that the little tang still runs parallel (tells you nobody tampered with it) and maybe check the seal around the float needle seat. That's it.
Here´s a question for you floatadjust lovers. Why is it, I only read about it in this forum, not on the German forum, not on the French forum, not on the Italian forum and if I remember right, not on the British forum. That tells you. If you find your float tangs bent and not parallel anymore, it's a pound to a penny the PO is a member of this forum. This is the last time I´ve warned you.

[lucky]

I am not sure of the specs for that year but I would set the floats as described in the book.

Sounds like the float bowls could be too high.

2mm below the top of the bowl! That is only .078 thousands or just slightly over 1/16 inch below the top of the bowl!  Just seems way too full.
That could  be the problem.

That seems way too full to me.

I would get a float gauge or calipers and measure them the way the book says.

No, no NO!
(sigh) This goes on and on and on...

OK, for the very last time. Unless the PO has messed with the floats (That PO MUST be a reader of this forum where false information is echoed and echoed over again), they're right. Have a look at the floats and you'll understand why. If that little tang doesn't show any signs that someone has bent it, it is ALL RIGHT. THERE IS NO WEAR WHATSOEVER, NEVER. PERIOD. Check it for free movement, check that the little tang still runs parallel (tells you nobody tampered with it) and maybe check the seal around the float needle seat. That's it.
Here´s a question for you floatadjust lovers. Why is it, I only read about it in this forum, not on the German forum, not on the French forum, not on the Italian forum and if I remember right, not on the British forum. That tells you. If you find your float tangs bent and not parallel anymore, it's a pound to a penny the PO is a member of this forum. This is the last time I´ve warned you.

I completely agree sir.
No need to adjust float tangs. Just install a new float needle .

But the reason you want to measure it is so that you can rule out any
crazy stuff that a PO may have done to it. Thats all.

[lucky]

Now you will have to check the workshop manual but this is a photo of the float gage for the CB750 showing the float hanging down and the measuring tool.

Get the CORRECT measurement for the CB500.

CLick once on the  photo for larger image.

[dave500]

clean plugs and it runs pretty good.  i still feel a lack of power.  a few minutes later it stumbles from 0 to 1/4 turned throttle range and only has smooth response when running high RPMs (4K-6K)

did you clean the plugs or use new ones here?once theyve carbon fouled theyll be unreliable even when cleaned,use new plugs after youve gone right over the ignition,,you will dick around with the carbs forever if your ignition isnt up to par.

[MADMAX]

thanks for the help guys.

float levels are set to stock 22mm using a homemade guage i made.

 i have been using new plugs after i make a change and foul the old ones.  ( i've really got a good collection of used plugs going!)  the timing is set up correctly to stock settings.

today ill be returning my chinese made compression test kit and sourcing a good one.  the readings from that thing made me sweat for a few minutes.

carbs are also coming off today and i will check needle height and make sure all air passages are clean.

[Deltarider]

carbs are also coming off today and i will check needle height and make sure all air passages are clean.

May I advice you first to report to us what you've found, before you alter anything?
The reason is: I have serious doubts about the carbs data as found in that American Honda Motor Booklet (1977). Data shown there conflict with data found elsewhere for the 500. Can someone who has that booklet, please inform us what it says in the third column (CB-550F) under IDLE MIXTURE SCREW INITIAL SETTING. Unfortunately, when I zoom in, I can't see what it says, due to poor resolution of the scan.
I might have a theory about forsaid booklet...

[MADMAX]

started my day off with eggs, sausage, toast, and potatoes.

just got carbs open - jets and emulsion tubes are all still looking clear and clean.  needle is at the fourth position from the top. 

checked voltage at coils and got 11.85 with key on.  battery voltage with key on was 12.3. 

whats next?

[MADMAX]

needles are stamped 272304 also.

plug boots are brand new. 

another thought - my charging system didnt work for a while on this machine and i would trickle charge it and ride it without lights anyway.  would this have some negative effect on coil output voltage now that the charging system is working?

[Deltarider]

Thanks. Do you have the impression the position of the needles is stock? Have your carbs been opened before, you think?

[lucky]

started my day off with eggs, sausage, toast, and potatoes.

just got carbs open - jets and emulsion tubes are all still looking clear and clean.  needle is at the fourth position from the top. 

checked voltage at coils and got 11.85 with key on.  battery voltage with key on was 12.3. 

whats next?

Yes Sausage ,potatoes, eggs!!!
My favorite also.
OK...Now lets fill in the gaps.
See this bike is no different than the same bike with 4 into 1 exhaust.
Not much difference. A non stock exhaust.

BTW the float level on that chart says 22mm- makes sense.
That is .866 thousandths. That has to be finished. Has to get done.

My recommendation.
Intake type???
Exhaust type...Looks like a 4 into 2 system from the photo.
Idle jet #42
Main jet size #110
Slide needle 4th position from the top. EDITmiddle position.

Float levels can cause rich running if they are off. Checked???
Mixture screws Stock says 2 full turns. probably would be 1.5 now.

The reason it stumbles from 0-1/4 throttle is because of the exhausts.
It is lean at idle .
I would go up one step on the main and one step on the idle jet.

Stock main jet was #100mm
Stock idle jet is #40mm

I would put in a #110 main jet.
I would put in the #42 idle jet.

I bet it will have good throttle response from 0-1/4 then!

[MADMAX]

when my breakfast including coffee costs $5 it tastes even better.  if you're ever in indianapolis check out the donut shop.

i hadnt disassembled the slides until today.  everything looked new in there so id assume it hasnt been done in the past. 

intakes are stock and are paired from 1 and 2 as well as 3 and 4 ( photo below ).  they are stock as far as i know.

i would assume exhausts contain baffles because its quiet.  it is a 4 into 2.

wouldn't upping jet sizes increase my fuel in the mix making it more rich?

thanks for your help.

[lucky]

carbs are also coming off today and i will check needle height and make sure all air passages are clean.

May I advice you first to report to us what you've found, before you alter anything?
The reason is: I have serious doubts about the carbs data as found in that American Honda Motor Booklet (1977). Data shown there conflict with data found elsewhere for the 500. Can someone who has that booklet, please inform us what it says in the third column (CB-550F) under IDLE MIXTURE SCREW INITIAL SETTING. Unfortunately, when I zoom in, I can't see what it says, due to poor resolution of the scan.
I might have a theory about forsaid booklet...

Looks like 1-1/4 to me.

[mono]

carbs are also coming off today and i will check needle height and make sure all air passages are clean.

May I advice you first to report to us what you've found, before you alter anything?
The reason is: I have serious doubts about the carbs data as found in that American Honda Motor Booklet (1977). Data shown there conflict with data found elsewhere for the 500. Can someone who has that booklet, please inform us what it says in the third column (CB-550F) under IDLE MIXTURE SCREW INITIAL SETTING. Unfortunately, when I zoom in, I can't see what it says, due to poor resolution of the scan.
I might have a theory about forsaid booklet...

Looks like 1-1/4 to me.

+1 on that - i read somewhere yesterday that the 500 was 1 - 1.25 turns.

[73CB500K2]

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.