Topic: 72 750k keeps fouling plugs help!!

[CBcafeJunkie]

Maybe you didn't see, but I am not convinced you have 750F carbs, those settings are pretty irrelevant to your K0 engine anyways.  You need to tell us the stamp on the carbs.  Someone listed where it is located up a few posts.

Got it, I just know I put a 75f carb rebuild set in them. I'll check the stamp when I get home. Thanks a ton man

[CBcafeJunkie]

They don't look like 75 750F carbs, the backplate is K style and the casting on the side is not "F".  I would guess 657A or very early 657B, educated guess.

The air screw when turned out to about 1-1.5 is usually about flush with the opening, looks like you are turned in a bit past that. 

Here's a question, did you oil your pod filters?

No oil on filters
657A carbs (would not have guessed as both bikes I grabbed up were 75f bikes.)

[seanbarney41]

They don't look like 75 750F carbs, the backplate is K style and the casting on the side is not "F".  I would guess 657A or very early 657B, educated guess.

The air screw when turned out to about 1-1.5 is usually about flush with the opening, looks like you are turned in a bit past that. 

Here's a question, did you oil your pod filters?

No oil on filters
657A carbs (would not have guessed as both bikes I grabbed up were 75f bikes.)

657a, 657b, and 086a are all completely interchangeable, just different jetting and fuel inlets

[CBcafeJunkie]

Thanks a ton for all of the diligence with this issue I'm hoping to get it on the road by friday well see

So far here's my to do list

Air screws
Check voltage at coils
Check fuel level with clear site tube (not sure how but sure I can find)
And possibly float height.

[harisuluv]

657a, 657b, and 086a are all completely interchangeable, just different jetting and fuel inlets

Yes, but he thinks they are F carbs and also jetted them as F carbs.  Yes, the casting on the number doesn't matter, and I never said that it did.  But I believe he is mistaken.

[seanbarney41]

657a, 657b, and 086a are all completely interchangeable, just different jetting and fuel inlets

Yes, but he thinks they are F carbs and also jetted them as F carbs.  Yes, the casting on the number doesn't matter, and I never said that it did.  But I believe he is mistaken.

not at all argueing with you Hari, but I really doubt the slight difference in jetting between f and k carbs is gonna foul his plugs

[CBcafeJunkie]

657a, 657b, and 086a are all completely interchangeable, just different jetting and fuel inlets

Yes, but he thinks they are F carbs and also jetted them as F carbs.  Yes, the casting on the number doesn't matter, and I never said that it did.  But I believe he is mistaken.

Nope they are 657a that's what I was trying to clarify in last post sorry for the bad communication
And yes I prepared them as 75f carbs

[HondaMan]

Then the only real calibration difference, if they are set as "F" carbs, and IF the needle is the 271307 needle on the center clip notch, if to install #27201 needles on the 4th notch (2nd from bottom) and set the air screws to between 7/8 and 1-1/8 turn out. The 2 turns out setting you had before will DEFINITELY foul plugs, and quickly.

The bikes before K4 also have smaller, weaker spark advance springs than in later ones. The springs were stiffened in the early K4 bikes to generate more low-end heat (i.e. retarded timing) until 2500-2800 RPM, which helps keep the plugs cleaner. Today, also use less octane, like mid-grade fuel. to match the burn rate of the 1970s-era premium. This will also raise the burn temps and keep deposits lower.

I advise cutting off at least 1/2 turn of at least one of the spark advancer springs. I usually do both on the bikes I overhaul. The heat and the years weaken the springs a lot, letting full advance come on as early as 1500 RPM in some cases, and this early advance disturbs the incoming airflow by spitting back into the carbs. This causes a very "wet" intake tract, which then makes for rich mixtures, until the engine its about 3500 RPM and starts cleaning it out. If allowed to idle very long, the plugs will just get wet and foul.

[ekpent]

Here are two observations I notice on your carb settings as mounted on the bike from your pics.
  In the first picture you have posted below it looks like your idle adjustment screw is backed way off, almost falling out to where the spring is not even touching. Does it idle there ?
   In pic #2 there are quite a few threads showing through the nut on the slide adjusters or vac adjusters on carb top which when set too high can cause the idle screw adjustment to not function correctly.
   Again these are not directly related to fouling plugs per say but add to them possibly being out of tune.

[CBcafeJunkie]

Then the only real calibration difference, if they are set as "F" carbs, and IF the needle is the 271307 needle on the center clip notch, if to install #27201 needles on the 4th notch (2nd from bottom) and set the air screws to between 7/8 and 1-1/8 turn out. The 2 turns out setting you had before will DEFINITELY foul plugs, and quickly.

The bikes before K4 also have smaller, weaker spark advance springs than in later ones. The springs were stiffened in the early K4 bikes to generate more low-end heat (i.e. retarded timing) until 2500-2800 RPM, which helps keep the plugs cleaner. Today, also use less octane, like mid-grade fuel. to match the burn rate of the 1970s-era premium. This will also raise the burn temps and keep deposits lower.

I advise cutting off at least 1/2 turn of at least one of the spark advancer springs. I usually do both on the bikes I overhaul. The heat and the years weaken the springs a lot, letting full advance come on as early as 1500 RPM in some cases, and this early advance disturbs the incoming airflow by spitting back into the carbs. This causes a very "wet" intake tract, which then makes for rich mixtures, until the engine its about 3500 RPM and starts cleaning it out. If allowed to idle very long, the plugs will just get wet and foul.

Well that is a ton of information.  TY
What needle would I have since the needles were not changed?

[CBcafeJunkie]

No idle at this point I was messing with the screw blindly, apparently I was turning the wrong direction I'll add that to list

[CBcafeJunkie]

So the list as it stands

Check voltage
Clip springs
Readjust idle screw
Re bench sync and sync ( to fix all the threads showing on needle holders)
Check float height
Check fuel level with clear tube method

Anything I missed? And do all agree with the order of priority listed?

[harisuluv]

Sir, we have been discussing the F/K differences, and while the bodies are the same, the innards are different.  It was pointed out that the needles are one of those things that's different. 

..... it's important.  The number will be on the needle.  I would ask Bill if he can give you most of this info, he is the person with the most knowledge about your set of carbs on this earth.

[ekpent]

So the list as it stands

Check voltage
Clip springs
Readjust idle screw
Re bench sync and sync ( to fix all the threads showing on needle holders)
Check float height
Check fuel level with clear tube method

Anything I missed? And do all agree with the order of priority listed?

Don't focus for now on the threads showing above the needle adjusters unless there is no adjustment range with the idle screw. I was just going by what you had taken pictures of and assumed that it was idling with the screw in the position the picture was taken..

[CBcafeJunkie]

So the list as it stands

Check voltage
Clip springs
Readjust idle screw
Re bench sync and sync ( to fix all the threads showing on needle holders)
Check float height
Check fuel level with clear tube method

Anything I missed? And do all agree with the order of priority listed?

Don't focus for now on the threads showing above the needle adjusters unless there is no adjustment range with the idle screw. I was just going by what you had taken pictures of and assumed that it was idling with the screw in the position the picture was taken..

Got ya

[CBcafeJunkie]

Talked to bill he said carbs were set up with the F needles and center clipped. He said he accounted for all of that. Only thing he didn't account for was the K0 engine and said may need to up the jets

[mrbreeze]

Here are two observations I notice on your carb settings as mounted on the bike from your pics.
  In the first picture you have posted below it looks like your idle adjustment screw is backed way off, almost falling out to where the spring is not even touching. Does it idle there ?
   In pic #2 there are quite a few threads showing through the nut on the slide adjusters or vac adjusters on carb top which when set too high can cause the idle screw adjustment to not function correctly.
   Again these are not directly related to fouling plugs per say but add to them possibly being out of tune.

That picture of the slide adjustment screw prompted me to roll out to the garage and look at mine. They are as I thought they were....1-2 threads showing. It appears that these carbs in the picture have the slides way too far open.

[CBcafeJunkie]

Then the only real calibration difference, if they are set as "F" carbs, and IF the needle is the 271307 needle on the center clip notch, if to install #27201 needles on the 4th notch (2nd from bottom) and set the air screws to between 7/8 and 1-1/8 turn out. The 2 turns out setting you had before will DEFINITELY foul plugs, and quickly.

The bikes before K4 also have smaller, weaker spark advance springs than in later ones. The springs were stiffened in the early K4 bikes to generate more low-end heat (i.e. retarded timing) until 2500-2800 RPM, which helps keep the plugs cleaner. Today, also use less octane, like mid-grade fuel. to match the burn rate of the 1970s-era premium. This will also raise the burn temps and keep deposits lower.

I advise cutting off at least 1/2 turn of at least one of the spark advancer springs. I usually do both on the bikes I overhaul. The heat and the years weaken the springs a lot, letting full advance come on as early as 1500 RPM in some cases, and this early advance disturbs the incoming airflow by spitting back into the carbs. This causes a very "wet" intake tract, which then makes for rich mixtures, until the engine its about 3500 RPM and starts cleaning it out. If allowed to idle very long, the plugs will just get wet and foul.

Ok so I took the spark advancer springs and cut at the base of the part that attaches to the arm that moves then bent the spring too so I could reattach it. I did this for both springs.

[CBcafeJunkie]

Besides cutting springs I started to re bench synch the carbs to make sure needle height is correct

[CBcafeJunkie]

Got it idling more than I had in a while. It will idle slightly but really needs to be sync he's as the needles are loose and the RPMS run a little crazy

[Duke McDukiedook]

How would adding ze podz determine if you have an air leak problem like you stated in your pictures?

[HondaMan]

Then the only real calibration difference, if they are set as "F" carbs, and IF the needle is the 271307 needle on the center clip notch, if to install #27201 needles on the 4th notch (2nd from bottom) and set the air screws to between 7/8 and 1-1/8 turn out. The 2 turns out setting you had before will DEFINITELY foul plugs, and quickly.

The bikes before K4 also have smaller, weaker spark advance springs than in later ones. The springs were stiffened in the early K4 bikes to generate more low-end heat (i.e. retarded timing) until 2500-2800 RPM, which helps keep the plugs cleaner. Today, also use less octane, like mid-grade fuel. to match the burn rate of the 1970s-era premium. This will also raise the burn temps and keep deposits lower.

I advise cutting off at least 1/2 turn of at least one of the spark advancer springs. I usually do both on the bikes I overhaul. The heat and the years weaken the springs a lot, letting full advance come on as early as 1500 RPM in some cases, and this early advance disturbs the incoming airflow by spitting back into the carbs. This causes a very "wet" intake tract, which then makes for rich mixtures, until the engine its about 3500 RPM and starts cleaning it out. If allowed to idle very long, the plugs will just get wet and foul.

Ok so I took the spark advancer springs and cut at the base of the part that attaches to the arm that moves then bent the spring too so I could reattach it. I did this for both springs.

That's an early advancer, so you did the right thing: they often have the loosest springs these days.

The needles & jet question: the 'normal' needles for the K0 diecast through the K6 are the #27201. The mainjet size (assuming stock airbox inlets) vary according to the cam (not so much per the exhaust): the early-open cams of the K0-K1 engines take the #115 or even #120 mainjets. The later cams use less: the K2 Old Factory and some K3 used #110 jets, the rest all used #105 size until the end of the K6. (Then some things changed...).

Generally, if the inlet cam opens at 0 BTC, you would use the #105 jet. As the cam opened earlier, the jet got a little bigger (going backward in time, that is). At 5 BTC openings the #115 works pretty well, while the #120 tends to run pretty wet.

[CBcafeJunkie]

Then the only real calibration difference, if they are set as "F" carbs, and IF the needle is the 271307 needle on the center clip notch, if to install #27201 needles on the 4th notch (2nd from bottom) and set the air screws to between 7/8 and 1-1/8 turn out. The 2 turns out setting you had before will DEFINITELY foul plugs, and quickly.

The bikes before K4 also have smaller, weaker spark advance springs than in later ones. The springs were stiffened in the early K4 bikes to generate more low-end heat (i.e. retarded timing) until 2500-2800 RPM, which helps keep the plugs cleaner. Today, also use less octane, like mid-grade fuel. to match the burn rate of the 1970s-era premium. This will also raise the burn temps and keep deposits lower.

I advise cutting off at least 1/2 turn of at least one of the spark advancer springs. I usually do both on the bikes I overhaul. The heat and the years weaken the springs a lot, letting full advance come on as early as 1500 RPM in some cases, and this early advance disturbs the incoming airflow by spitting back into the carbs. This causes a very "wet" intake tract, which then makes for rich mixtures, until the engine its about 3500 RPM and starts cleaning it out. If allowed to idle very long, the plugs will just get wet and foul.

Ok so I took the spark advancer springs and cut at the base of the part that attaches to the arm that moves then bent the spring too so I could reattach it. I did this for both springs.

That's an early advancer, so you did the right thing: they often have the loosest springs these days.

The needles & jet question: the 'normal' needles for the K0 diecast through the K6 are the #27201. The mainjet size (assuming stock airbox inlets) vary according to the cam (not so much per the exhaust): the early-open cams of the K0-K1 engines take the #115 or even #120 mainjets. The later cams use less: the K2 Old Factory and some K3 used #110 jets, the rest all used #105 size until the end of the K6. (Then some things changed...).

Generally, if the inlet cam opens at 0 BTC, you would use the #105 jet. As the cam opened earlier, the jet got a little bigger (going backward in time, that is). At 5 BTC openings the #115 works pretty well, while the #120 tends to run pretty wet.

Good to hear that was the right thing with my advancer

Since Bill did account for use of all 75f parts on the carbs I know he also used the 75f needles just center clipped. With this in mind it seems all I would need to do is re-jet at 115 and use stock airbox instead of pods correct?

[CBcafeJunkie]

How would adding ze podz determine if you have an air leak problem like you stated in your pictures?

Used butane blow by on my intake to check for rising RPMS before it stopped running. Just to be clear I had it running and rode around with no fouling but came out the next day and #2 was fouled and I started having troubles again. So I started posting about my issue again hoping to resolve all problems; which seems not so far away as I need to sync,re-jet and put on stock air box to check.

[neilc]

Noticed on your sync screws that you have alot of threads showing,  i believe you should only have like 1 -2 threads exposed