Topic: '79 CM400T questions: CV Carb Conundrum

[Pinhead]

Here's another pic of the 400 with a likeness to the "F" bikes.

[Pinhead]

I did a little work to the 400 today to make it ride a bit better. The squishy ride had to be remedied so I added front fork oil (they were completely empty) and replaced the rear shocks with the stock shocks from my '79 CB650. This added a bit of stiffness and height to the rear-end which made the bike handle and ride much better.

[Pinhead]

I made a strange discovery today... The engine will idle with the tops of the carbs, springs, and slides completely removed. 

[crazypj]

I've posted that several times, the butterflies control air flow and fuel goes through bypass port.
 You could remove slides and it will still start and idle OK
 It will probably cut out if you try and rev it because it goes too lean (never actually tried that  )

PJ

[cheseburger]

Got a 1980 cm400t. have cone air filters , cleaned carb pretty good and used air to smoke out rust from tank.  Have 2 into 1 exhaust welding up one side of the crossover.  20 inch baffled cheap muffler. It is still loud.  Now I need to have a good idea where to start with main and piolet jets. Any help would be wonderful.  Stock I believe is 72mains.

[Pinhead]

Believe me, it's not loud. Loud is if you remove the crossover and run straight pipes. I'm not even driving my bike until I get new mufflers installed. My straight-piped CB650 sounds stock compared to the straight'd 400T. The 400 makes Harleys sound soft.

[Alan F.]

Got a 1980 cm400t. have cone air filters , cleaned carb pretty good and used air to smoke out rust from tank.  Have 2 into 1 exhaust welding up one side of the crossover.  20 inch baffled cheap muffler. It is still loud.  Now I need to have a good idea where to start with main and piolet jets. Any help would be wonderful.  Stock I believe is 72mains.

I looked up some stock jetting info, it's posted here:
http://forums.sohc4.net/index.php?topic=59429.0
-Alan

[cheseburger]

[quot[/quote] i started out with a 120 main and 72 piolet jet.  this should let me know at least if im to lean or to rich.  stock was 112 to 118.  it has a 118 stock main jet.  at least i can drill out jets.  how many thousands is a jet from one size to another? thanks for the help

[tbpmusic]

[quot

i started out with a 120 main and 72 piolet jet.  this should let me know at least if im to lean or to rich.  stock was 112 to 118.  it has a 118 stock main jet.  at least i can drill out jets.  how many thousands is a jet from one size to another? thanks for the help
[/quote]

The jet sizes are in millimeters.
EG: A 150 jet has an orifice that's 1.5 mm in diameter. A 100 jet is 1.0mm, a 72 is 0.72 mm, etc.

I don't know what that is in inches, sorry.........

[Crash007]

I got a CM400T recently and the carbs are in bad shape.

I have the repair manual so I will try to take apart and clean up.  What do you recomend for a cleaning solution?

Also, what other bike model's can I pull the carbs off as a replacement?

Thanks

Crash

[Alan F.]

Berryman's is good stuff, simple green or purple power will work, boil the carb outdoors in 1/2 lemon juice and 1/2 water will work, there are many good ways to clean your carbs.
Become proficient with the search function on these forums and you'll learn everything you'll ever need.
-Alan

[cb650]

Nieghbor while growing up had one with just "HAWK" on the side covers and was a auto.

[Crash007]

Question on carb sync.  I have the carbs off the CM400T, got the bowls off needles out etc for cleaning.

Looking at the carbs, when I pull on the throttle, the 2nd carb is not in sync with the first.  Like at idle the first is closed the 2nd is about 15% open.  I found the screw between the carbs to adjust and now when i open the throttle, both will open up to the same level.

Then problem is, when it goes to idle, the 2nd carb wont close on its own.  It now has the free play to shut, but I have to push it shut with my finger to see.

The rods and springs connecting the 2 are very gunked up, I have not cleaned them yet.  Do you think they are just rusty or loose or something?

THanks

C.

[Pinhead]

I had the same exact problem with my bike. I sprayed the hell out of everything with WD-40 and worked it back-and-forth to get it to work right. I haven't taken them apart to clean them yet, though, so that's probably what needs to be done.