Topic: carburation/timing question

[stay youth]

hi everybody, i have a 1975 cb400f, im running emgo pods, and a dunstall exhaust. lately i have been having issues with the bike being sluggish and un responsive. I rebuilt my carbs a few months back and made the mistake of using a sealer on the carb bowls. naturally that sealer broke down and proceeded to clogs jets. I had a feeling this would be the cuase of the sluggish and non responsiveness. So i removed my carbs and cleaned out the gunk from the sealant(never use sealant!!!!!) and cleaned my jets. I put the carbs back on the bike and when i kicked it over a loud popping sounds came from the exhaust also included was blueish smoke.  SO i figured i might have fouled plugs . put in new ngk d7ea plugs and the bike would roughly idle but still would have occasional loud pops. i pulled the plugs they were black and wet with gas. I took it to the shop about 3 weeks ago and i thought they did the timing. My thoughts are; i might have a airleak around the intake manifold, bad piston seals or timing issues. i dont think its piston seals cuz its seems odd that they would all just go at once. does anybody have a any thoughts? thanks in advance

[eldar]

Well you can pretty much rule out an airleak. Airleaks can cause idle issues but usually in the lean direction.

make sure your cam chain is adjusted right and check your timing.
from there, make sure your carbs are assembled right. and make sure you can see light through your slow jets. also make sure you have your idle mix screws set to factory default.

start there and let us know what happens

[kghost]

If there was gunk in the bowls there is gunk in the jets.

[stay youth]

yeha i cleaned out the carbs and its tuned to factory specs. guess i'll be checking my timing soon. thanks

[kghost]

When you "cleaned the carbs" did you pull the jets?

Or just clean out the bowls and remove any obvious gunk?
 

Guess thats what eldar and I are wondering.

If you didn't pull the carbs, remove the jets, and clean them out.....just cleaning the bowls does sweet F all to fix the problem.

It is possible that the shop did not get all the timing screws tight and something has slipped.

Its easy to check even statically it should be close. Did the shop set the dwell? Use a timing light? Any ideas?




May we ask what prompted the use of sealer in the first place?

[stay youth]

yeah i completely went through each jet soaking them then cleaning them out so i could see daylight, im going to check my timing tomorrow. might my timing result is gas on the plugs? thanks

[750goes]

Even though you cleaned the jets to perfection, if the sealant has been sucked through into some small orifices it will be difficult to remove -

It may have passed through the JET but NOT passed through the carb body.. I think you need to at least confirm that ALL passageways are clear of sealant not just the jets for some peace of mind before you go looking at other possibilities...

Do these carbs have emulsion tubes as well  - if so some clogging there will definitely affect running..

what sort of sealant was it - can you dissolve it with carb cleaner or some spray cleaner ??

[eldar]

yeah, your best bet is to remove the jets and pull the carbs off the racks and clean all fuel passages. Fuel from the bowls goes through these passages. if some are mucked up, it will try to pull thru the mains and that just does not work too well.

[tmht]

Even though you cleaned the jets to perfection, if the sealant has been sucked through into some small orifices it will be difficult to remove -

It may have passed through the JET but NOT passed through the carb body.. I think you need to at least confirm that ALL passageways are clear of sealant not just the jets for some peace of mind before you go looking at other possibilities...

Do these carbs have emulsion tubes as well  - if so some clogging there will definitely affect running..

what sort of sealant was it - can you dissolve it with carb cleaner or some spray cleaner ??

Yes the 400 carbs have emulsion tubes. They are great fun to remove and clean... Ask me how I know. 

What I want to know is what the plugs looked like before hand and if you are using the stock #75 jets. The bike simply will not run right with pods and the stock jetting. Hell, the 400 is so picky it runs like crap if the cover to the airbox is missing. Also the stock plug should be a D8EA, if you are having to run D7's to make it run right there was already something not right with your state of tune.

[kettlesd]

So i removed my carbs and cleaned out the gunk from the sealant(never use sealant!!!!!) and cleaned my jets. I put the carbs back on the bike and when i kicked it over a loud popping sounds came from the exhaust also included was blueish smoke.  SO i figured i might have fouled plugs .

Anyone else pick up on the blue smoke? What kind of fouling were your plugs - gas, oil or light,fluffy carbon?

[stay youth]

thnaks for the feedback. so how do i clean the emulsion tubes? thats weird about the spark plugs those are what i have been using for a while i believe. my plugs were lighty carbon fouled before my problems , then they were fouled with gas on them. what are the differences between the plugs? just heat ranges? how do i know what number of jets im using, im not sure if there 75's

[tmht]

thnaks for the feedback. so how do i clean the emulsion tubes? thats weird about the spark plugs those are what i have been using for a while i believe. my plugs were lighty carbon fouled before my problems , then they were fouled with gas on them. what are the differences between the plugs? just heat ranges? how do i know what number of jets im using, im not sure if there 75's

The stock Main Jet is a 75... it should be etched somewhere on the side of the jet.

To clean the emulsion tube you need to remove it from the carb. This is going to require you to pretty much disassemble the carb entirely. You need to take the top cap off of the carb and remove the throttle valve (I have heard that this can be done with the carbs still on the rack, though I haven't tried it myself. I always disassemble the rack.), then open up the bottom of the carb and remove the main jet. The emulsion tube sits in the same hole as the main jet but must be pushed down from the top of the carb. If you are really lucky you will be able to tap the carb body (facing upright) gently on the bench and it will come out... more likely you will have to find a phillips head screw driver that is every so slightly larger than the opening in the top of the emulsion tube and push it out.

I don't personally run pods on my 400 and don't actually know anyone who does, but I would put a question out there for some personal experience with tuning the bike with the pods.

And yes, the D7 is a hotter plug than the D8.