Topic: Pods Thread

[neil young]

thank you sir

[rlarkin70]

with the pods did you make any modifications to your choke lever?

maybe it was just the pods that were on my bike, but you basically have to take off the #1 pod to choke the carbs. then start it. then put the pod back on.  At least, thats what the PO did. I am thinking about going back to the stock airbox.

-Ron

[edbikerii]

I recently had this discussion with another list member via PM.  That member realized that the tapered pods that I used on my 1977 CB550K don't work well on the pre-1977 CB550s because of interference with the choke lever and the frame tubes.  That member was going to use smaller, flatter pods available elsewhere on their 76 CB550K.  I don't know how that turned out.

with the pods did you make any modifications to your choke lever?

maybe it was just the pods that were on my bike, but you basically have to take off the #1 pod to choke the carbs. then start it. then put the pod back on.  At least, thats what the PO did. I am thinking about going back to the stock airbox.

-Ron

[Rsnip988]

has anyone done this for a 750k?

If not i may have to document my own struggle with the jetting/tuning

[750essess]

To avoid further frustration dont tune with stock jets and dynojet jets. A jet mark 104 in a keihin jet and the same in dynojet is not exactly the same size. Use either all stocks or all dynojets.

[cb750frank]

What type of oil are you guy using on your pods? And how much should I use? Also people mention clip position when they discuss tuning carbs. I have a 1975 cb750k5. Where are they located on my carbs and what do they fine tune. thanks!

                                                                                            FRANK

[Terry in Australia]

G'Day Frank, you can buy filter oil from most bike shops for you pods, K&N make it of course, and I've got some Shell filter oil in my garage too.

The "clip position" refers to the notches on the slide needle in your carbs, the needle position (there are 5 notch positions that your needle can be adjusted up and down) determines the fuel/air ratio, or the mixture. If you have the clip in the middle notch, or position (usually the factory start point) and you raise the needle a notch by dropping the clip position, you'll have a richer (more fuel to air ratio) "mixture". Similarly, if you lower the needle (by installing the clip on a higher notch on the needle) you'll run a "leaner" fuel/air ratio "mixture". Cheers, Terry.

[TwoTired]

Uni sells both a foam filter cleaner and filter lube in spray cans.

To add to what Terry said.  The slide needles (with the Clips) effectively fine tune the mixture from about 1/4 to 3/4 throttle positions.  Higher throttle positions are primarily metered by the main jet, and lower positions the slow jet/circuit.

Cheers,

[obnoxshuz]

If I go the pods route on a 78 750K ( will put in a mac 4-1 exhaust ), do I need to change the slow jets from the stock #35 to something bigger ? I see that we are all trying to figure out the correct size Main jets ( somewhere around 120 -140 ) but no discussion about slow jets...

[edbikerii]

The guy at a local shop said the same thing.  However, in theory at least, a 104 is supposed to have a 1.04mm hole, whether it is Dynojet or Keihin.  I don't know where this concern came from, but I have heard it repeated many times.

In practice, I went from 106 Dynojet to 105 Keihin main jets and accomplished exactly what I was hoping for.

Of course, I have not "flow tested" identical jets side-by-side, nor have I verified the hole sizes with 1.05mm and 1.06mm drill bits, nor have I purchased Dynojet 105 mains (they only sell even sizes 104 and 106).

To avoid further frustration dont tune with stock jets and dynojet jets. A jet mark 104 in a keihin jet and the same in dynojet is not exactly the same size. Use either all stocks or all dynojets.

[edbikerii]

The small amount of air you pull at idle should not be affected by whether you run airbox or pods.

You always start out by tuning the mains first at WOT, then the needle positions for mid throttle openings, and finally the idle for both idle and slightly off-idle throttle openings.  Usually just the idle screws will allow you to adjust adequately.

If I go the pods route on a 78 750K ( will put in a mac 4-1 exhaust ), do I need to change the slow jets from the stock #35 to something bigger ? I see that we are all trying to figure out the correct size Main jets ( somewhere around 120 -140 ) but no discussion about slow jets...

[rugger81]

I have a 77 750K that I put pods on.  You don't have to change the slow jets, which is good because they're press in and would be a pain in the ass to change.  Also for what it's worth, on my bike with the uni pod filters and a mac 4 into 2, I found that the bike ran too rich with 127.5 jets and the needle at the leanest clip setting.

If I had to guess, you're not going to go higher than 125 main jets, probably even lower depending on your clip setting.

[ekim98]

I just put 120 mains in my 78 750k and I'm running emgo pods and a Mac 4 into 1 exhaust. I still need to double check my carbs sync. but it seems to be running pretty good. I haven't messed with the slow jets at all. It might make a differance what kind of pods you use. I think th K&N pods are just a bit more restictive than the Emgo's.

 And to change the needle setting on the 78's you have to shim I believe.

How can I make my motor a little more warm blooded, it's a pain to wait as long as it takes for it to warm up enough to ride. 

[edbikerii]

I made the idle one turn richer to help with warmup.  This is typical practice on many newer bikes, too, but you have to pull the brass EPA plugs to do it on them.

How can I make my motor a little more warm blooded, it's a pain to wait as long as it takes for it to warm up enough to ride. 

[TwoTired]

How can I make my motor a little more warm blooded, it's a pain to wait as long as it takes for it to warm up enough to ride. 

On the CB750, change your spark plugs to D7EA for cool weather use.  Go back to D8EA for the hot summers.

Cheers,

[ekim98]

I made the idle one turn richer to help with warmup.  This is typical practice on many newer bikes, too, but you have to pull the brass EPA plugs to do it on them.

How can I make my motor a little more warm blooded, it's a pain to wait as long as it takes for it to warm up enough to ride. 

I'll have to look again about the brass plugs - I assume your talking about the 750 and not your 550 or do they both have the plugs?

[edbikerii]

I meant more modern bikes, not SOHC4s at all.

I made the idle one turn richer to help with warmup.  This is typical practice on many newer bikes, too, but you have to pull the brass EPA plugs to do it on them.

How can I make my motor a little more warm blooded, it's a pain to wait as long as it takes for it to warm up enough to ride. 

I'll have to look again about the brass plugs - I assume your talking about the 750 and not your 550 or do they both have the plugs?

[ekim98]

I meant more modern bikes, not SOHC4s at all.

I made the idle one turn richer to help with warmup.  This is typical practice on many newer bikes, too, but you have to pull the brass EPA plugs to do it on them.

How can I make my motor a little more warm blooded, it's a pain to wait as long as it takes for it to warm up enough to ride. 

I'll have to look again about the brass plugs - I assume your talking about the 750 and not your 550 or do they both have the plugs?

Good, cause I thought I was going crazy here - well I am but you know what I ment.

[750essess]

The guy at a local shop said the same thing.  However, in theory at least, a 104 is supposed to have a 1.04mm hole, whether it is Dynojet or Keihin.  I don't know where this concern came from, but I have heard it repeated many times.

In practice, I went from 106 Dynojet to 105 Keihin main jets and accomplished exactly what I was hoping for.

Of course, I have not "flow tested" identical jets side-by-side, nor have I verified the hole sizes with 1.05mm and 1.06mm drill bits, nor have I purchased Dynojet 105 mains (they only sell even sizes 104 and 106).

To avoid further frustration dont tune with stock jets and dynojet jets. A jet mark 104 in a keihin jet and the same in dynojet is not exactly the same size. Use either all stocks or all dynojets.

I called dynojet and asked them, cause i also thought it was unfounded. They said that there jets are drilled to a certain size and keihin jets are drilled for a certain flow.

[TwoTired]

They said that there jets are drilled to a certain size and keihin jets are drilled for a certain flow.

I think you'll find the Mikuni jets are flow sized.  Keihin, at least for our vintage carbs, are sized for orifice diameter. A #100 would be  one millimeter.

Confusion abounds...

[tsp37]

Someone asked the question that I've always wanted to ask - what influence does the exhaust setup on a 4 stroke engine have on carburation?  Rejetting is frequently said to be necessary when the exhaust is modified.  I say horse $hit, it don't make no difference.

[Soos]

They said that there jets are drilled to a certain size and keihin jets are drilled for a certain flow.

I think you'll find the Mikuni jets are flow sized.  Keihin, at least for our vintage carbs, are sized for orifice diameter. A #100 would be  one millimeter.

Confusion abounds...

Exactly.
I KNOW that 98 keihin jets are .98mm for older jets, the new ones they make may flow rated, but not the older jets.

l8r

[paulages]

Someone asked the question that I've always wanted to ask - what influence does the exhaust setup on a 4 stroke engine have on carburation?  Rejetting is frequently said to be necessary when the exhaust is modified.  I say horse $hit, it don't make no difference.

 
do a little research, and i think you'll quickly find how wrong you are. that's not theory, it's proven. 4 strokers may not benefit in the same way as 2 strokes, but the back pressure of a restrictive exhaust has an impact on scavenging at lower RPM's, just as a less restrictive exhaust can benefit a high revving motor.

[seaweb11]

When I first  got my 750, I replaced the worn out 4 x 4 exhausts with 4 x 2Mac. No jetting changes were required, but the carbs certainly needed adjustment. 3 months later I put on the pods and main jets needed to be switched out to larger.

So......  changing exhausts might not require re-jetting   at least not on a 78K from stock to 4x2 Mac

[TwoTired]

Someone asked the question that I've always wanted to ask - what influence does the exhaust setup on a 4 stroke engine have on carburation?  Rejetting is frequently said to be necessary when the exhaust is modified.  I say horse $hit, it don't make no difference.

Based on what evidence, theory, or placement of a wild hair? 

Compare a restrictive exhaust to free flowing.

Restrictive exhaust generally has a higher muffler/pipe chamber pressure.  This leads to less complete evacuation of exhaust gases from the combustion chamber. The fresh charge from the intake stroke then mixes with the leftovers. And, the available oxygen must be matched in correct ratio to the fuel.  This mixture will be leaner than if a complete evacuation of the exhaust gas was made as some hydrocarbons remain from the previous combustion cycle.  A more open exhaust generally requires a richer mixture to compensate for the lack of back pressure.

A 4 into 1 is supposed to use the exhaust velocity of other cylinders, to help evacuate the cylinder currently in the exhaust stroke, creating a scavenge effect.  This is usually tuned to have an effect at the higher RPM range.  Again the more complete change of combustible charge requires a fuel ratio enrichment to go along with the higher availability of oxygen in the chamber.

Since the SOHC4 carbs have no information about what is in the exhaust stream (like an Ox sensor in modern computer controlled systems) the carburetor must be adjusted to provide the correct mixture with the given engine breathing parameters.  This generally involves jetting.

I could, of course be wrong (along with a lot of other carb tuners).

But, I'm willing to hear explanations of why exhaust changes do not have a jetting repercussion.

Cheers,