The usual advice I've seen is to get it running with what you have first, then read the plugs to determine what, if anything, needs to be changed. It usually doesn't take much. The various 400 models use primaries ranging from 65 to 75 and secondaries from 110 to 118 (yours should be 70 and 112).

I'll be watching to see how you come out.

 

Be patient; it'll be a while before I do any thing!

The bike in my sig blog has priority.

 

The usual advice I've seen is to get it running with what you have first, then read the plugs to determine what, if anything, needs to be changed. It usually doesn't take much. The various 400 models use primaries ranging from 65 to 75 and secondaries from 110 to 118 (yours should be 70 and 112).

I'll be watching to see how you come out.

I already have a swee 78' 400 i've been minimalizing. Have my pods and nice cutoff ex. - increased my jets from 70/110 to 75/115, also shimmed my needle with one washer. Can't get her started - plugs are black - super rich. Other posts have said that the larger jet (115) should be threaded into the emersion tube with the hex top and the smaller jet (75) should go into the carb body nearest the pilot jet. Is this right? My 75 is in the emersion tube and 115 is in the other place above the slow jet with the little rubber stopper. Should I take out the needle shim?

 

I posted in the other thread, but the big jet (115) goes in the hex tube, the other one goes straight into the carb. Also, the Keihin CV puck carburetors are almost impossible to get to run with anything free-flowing. As they wear, they need more intake resistance to lift the pucks, so you can try temporarily covering most of the pod filters with masking tape to see if that gets the bike to run, as well.

 

I posted in the other thread, but the big jet (115) goes in the hex tube, the other one goes straight into the carb. Also, the Keihin CV puck carburetors are almost impossible to get to run with anything free-flowing. As they wear, they need more intake resistance to lift the pucks, so you can try temporarily covering most of the pod filters with masking tape to see if that gets the bike to run, as well.

Well that's sucky news, lol. I'll try the masking tape trick tomorrow morning - my "slides" (pucks?) slide well - no sticking or catching at all. Do the slides effect start up?

 

I posted in the other thread, but the big jet (115) goes in the hex tube, the other one goes straight into the carb. Also, the Keihin CV puck carburetors are almost impossible to get to run with anything free-flowing. As they wear, they need more intake resistance to lift the pucks, so you can try temporarily covering most of the pod filters with masking tape to see if that gets the bike to run, as well.

Well that's sucky news, lol. I'll try the masking tape trick tomorrow morning - my "slides" (pucks?) slide well - no sticking or catching at all. Do the slides effect start up?

Here's the thing: if they slide TOO well (ie, they are maybe a bit loose, or the CV cap is out-of-round), then there are essentially air leaks around them, which is why it requires a higher vacuum to lift them. If you clean them with car polish, sandpaper, or even a plastic abrasive sponge to get them to slide freely (a common occurrence on these old carbs with dirty/frozen pucks), you take away material from the edges of them, increasing the air gap, and making them, again, require more intake resistance.


Give the masking tape a shot.

 

The slides should not affect start-up or even performance a little above idle. Having the main jets reversed will cause it to run rich as it progresses above idle.

 

Even at idle, the pucks lift just a teeny tiny bit - I have confirmed this with a mirror on the intake. It's not much, but enough that a loss of intake vacuum/negative pressure will affect idle. But you're right - switching the two main jets will drastically affect how it runs all over the place.

 

tried the masking tape but still couldn't get it started. I can't imagine that I've changed the air-fuel ratio so much that it wont start - I'm not sure where to go from here.

 

I'm sure you can use pod filters fine. While it's true the stock Keihin CV carbs aren't the best for open filters, many people have done it. Check it out.

http://www.dotheton.com/forum/index.php?topic=26184.0

Getting the jets reversed is a common thing. If my '82 Hawk is anything like yours it would run very lean with pod filters, as my bike is already overly lean on the needle stock.

 

From my experience, you will need quite a bit bigger in the jetting range for pods and a free flowing exhaust.

from personal experience and research I have found that the 400T with pods and a 2 into 1 exhaust should be in the nieghborhood of 78/138 for jetting, maybe up or doown a size from there.

To clarify, the larger jet goes under the needle in the brass jet holder/emulsion tube, the smaller jet threads into the aluminum body of the carb.

The pods should operate fine, if you find they are not working or you have flat spots, be sure that your "pucks" pass the straw test (blow into the holes of the pucks with a straw, make sure they go up and down at approximately the same rate) if they do, and they don't seem to be opening properly while riding, increase vacuum inside the pods by blocking off some of the filters surface (tape works well for this). once you discover how much to block off, you can cut aluminum soda can to the right size sheet and put it inside the pod to block the filter and still look stock.

The aluminum wont be sucked into the engine because it's rigid enough to resist the vacuum inside the pod filter.

As for idle, pods or no pods, it should start and idle with stock jets. if it isn't starting, check fro compression, fuel and spark. if you have all three, it will run. (make sure your jets are in the correct places as I mentioneed above in the third paragraph)

 

From my experience, you will need quite a bit bigger in the jetting range for pods and a free flowing exhaust.

from personal experience and research I have found that the 400T with pods and a 2 into 1 exhaust should be in the nieghborhood of 78/138 for jetting, maybe up or doown a size from there.

To clarify, the larger jet goes under the needle in the brass jet holder/emulsion tube, the smaller jet threads into the aluminum body of the carb.

The pods should operate fine, if you find they are not working or you have flat spots, be sure that your "pucks" pass the straw test (blow into the holes of the pucks with a straw, make sure they go up and down at approximately the same rate) if they do, and they don't seem to be opening properly while riding, increase vacuum inside the pods by blocking off some of the filters surface (tape works well for this). once you discover how much to block off, you can cut aluminum soda can to the right size sheet and put it inside the pod to block the filter and still look stock.

The aluminum wont be sucked into the engine because it's rigid enough to resist the vacuum inside the pod filter.

As for idle, pods or no pods, it should start and idle with stock jets. if it isn't starting, check fro compression, fuel and spark. if you have all three, it will run. (make sure your jets are in the correct places as I mentioneed above in the third paragraph)

Where did you get the jets from? any place online? I have checked locally and can't seem to find the jets for these carbs here. also are the primary and secondary jets the same length, width and pitch?

 

From my experience, you will need quite a bit bigger in the jetting range for pods and a free flowing exhaust.

from personal experience and research I have found that the 400T with pods and a 2 into 1 exhaust should be in the nieghborhood of 78/138 for jetting, maybe up or doown a size from there.

To clarify, the larger jet goes under the needle in the brass jet holder/emulsion tube, the smaller jet threads into the aluminum body of the carb.

The pods should operate fine, if you find they are not working or you have flat spots, be sure that your "pucks" pass the straw test (blow into the holes of the pucks with a straw, make sure they go up and down at approximately the same rate) if they do, and they don't seem to be opening properly while riding, increase vacuum inside the pods by blocking off some of the filters surface (tape works well for this). once you discover how much to block off, you can cut aluminum soda can to the right size sheet and put it inside the pod to block the filter and still look stock.

The aluminum wont be sucked into the engine because it's rigid enough to resist the vacuum inside the pod filter.

As for idle, pods or no pods, it should start and idle with stock jets. if it isn't starting, check fro compression, fuel and spark. if you have all three, it will run. (make sure your jets are in the correct places as I mentioneed above in the third paragraph)

wow, been awhile and I've been working through the non-winter winter here in good ol' PA. Got the bike running again finally after using starter fluid. Did a sweet paint job on my gas tank, but after sitting with nothing in it for so long it rusted and then was throwing nasty crud into my poor carbs. Did the BB and lacquer thinner clean out and that seemed to help but also messed up my great paint job quite a bit (its been a long day).

Anyway, I'm now up to 82/132 with my jets in both carbs. The bike starts and idles great, but after about 1/4 throttle it starts to cut out - i'm guessing I need to go up even more like previously said on this thread. I haven't checked the color on the plugs yet, but my prediction is white (hopefully). Bike also seemed to start and idle fine with 75's and 78's for small jets. Comments?

 

The bike starts and idles great, but after about 1/4 throttle it starts to cut out - i'm guessing I need to go up even more like previously said on this thread. I haven't checked the color on the plugs yet, but my prediction is white (hopefully). Bike also seemed to start and idle fine with 75's and 78's for small jets. Comments?

Given the 1/4 throttle cut out I think your problem is still tied to not enough restriction to lift the pucks properly. Here is a photo of what another pod tuner has done to restrict air flow.

This is the place most stop messing around with pods and reinstall the stock air box. It was designed specifically with all this in mind and it works. Don't get me wrong pods are great for the right application. A CV carb just isn't the right application though. If you want to achieve the best performance possible with stock carbs stay with the box. I think it must be said that the whole routine of restricting air flow so you can use pods seems insane and more related to looks that actual performance.
If you want max performance out this engine then you'll have to invest real $ and go with both a freer flowing exhaust AND smooth bore carbs like these:

 

From my experience, you will need quite a bit bigger in the jetting range for pods and a free flowing exhaust.

from personal experience and research I have found that the 400T with pods and a 2 into 1 exhaust should be in the nieghborhood of 78/138 for jetting, maybe up or doown a size from there.

To clarify, the larger jet goes under the needle in the brass jet holder/emulsion tube, the smaller jet threads into the aluminum body of the carb.

The pods should operate fine, if you find they are not working or you have flat spots, be sure that your "pucks" pass the straw test (blow into the holes of the pucks with a straw, make sure they go up and down at approximately the same rate) if they do, and they don't seem to be opening properly while riding, increase vacuum inside the pods by blocking off some of the filters surface (tape works well for this). once you discover how much to block off, you can cut aluminum soda can to the right size sheet and put it inside the pod to block the filter and still look stock.

The aluminum wont be sucked into the engine because it's rigid enough to resist the vacuum inside the pod filter.

As for idle, pods or no pods, it should start and idle with stock jets. if it isn't starting, check fro compression, fuel and spark. if you have all three, it will run. (make sure your jets are in the correct places as I mentioneed above in the third paragraph)

wow, been awhile and I've been working through the non-winter winter here in good ol' PA. Got the bike running again finally after using starter fluid. Did a sweet paint job on my gas tank, but after sitting with nothing in it for so long it rusted and then was throwing nasty crud into my poor carbs. Did the BB and lacquer thinner clean out and that seemed to help but also messed up my great paint job quite a bit (its been a long day).

Anyway, I'm now up to 82/132 with my jets in both carbs. The bike starts and idles great, but after about 1/4 throttle it starts to cut out - i'm guessing I need to go up even more like previously said on this thread. I haven't checked the color on the plugs yet, but my prediction is white (hopefully). Bike also seemed to start and idle fine with 75's and 78's for small jets. Comments?

The 1/4 throttle issue you're having doesn't sound like a jetting problem to me. I would suspect some sort of fuel circuit transition problem.

 

I'm still interested in making this work out before giving up. I'm interested in testing the pucks out for sliding capabilities and you guys mentions blowing in with a straw. Can you elaborate on this - where am I blowing? a normal straw? what am I looking for (how much movement?)? What constitutes a pass/fail?

 

Hello everyone. First time, long time. I have a 1981 cm400t that I have tricked out. I am running pods and straight pips with the CV carbs. The bike runs excellent. Everyone says you can't do that with those carbs. The pucks were designed to work on high vacuum and as everyone knows doing those mods changes it to lower vacuum. The thing to do is modify the carbs to work on the lower vacuum. I accomplished this by cutting 2.5 loops off the springs. I'm running 122 mains and 75 idle. The air/fuel screws are 2 turns out. The plugs are a nice brown. I am going to try 120 mains and 72 idle. I've gone one up on the front sprocket. I can cruise at 70 and still pull away. Pods and pipes WILL work with CV carbs.

 

Welcome to the group. You might post in the member introductions section.

That's a different approach than most folks here have used but, as you say, it can be done.

You might find this interesting:

~http://www.hondatwins.net/forums/63...ums/63-fuel-supply-carburation/23714-cb400-cv-carbs-pods-how-make-them-work.htm

 

Minor correction in terminology since these use a primary and secondary main jet. Your "idle" jet is the primary. Idle mixture is handled by the slow jet

 

Obviously an old thread, but... Same bike here and same carbs. My carbs are currently running 70 and 112 jets (and in good condition). The rebuild kit has 65 and 110 jets. Should I stick with the original 70 & 112 or replace them with the new 65 & 110? Is there an advantage or disadvantage to the new sizes?

Thanks!

 

Those jets a way too lean. Run a #72 and #112. You can run a #115 if you want

 

Leave the originals. IMHO, the 65 is way too lean. I replaced my 70 with a 72 and find it runs much better.

 

Aftermarket carb kits often have inappropriate parts for the application. Another common issue is for the float needles to not fit properly. Hopefully the soft parts will work but the original Honda gasket sets are the best bet. Did your kit include the slow jet plugs?

 

No slow jet plugs, but I replaced them last season along with the needle valves. I'm gonna stick with the original 70 & 112 for now. I might try some 72s later to see what they do. Bike is running fine and nothing worn. I was replacing the carb insulators so I thought I better go thru and clean them while I had them off.