FIRST... get a compression test, or you may do it all for nothing. I purchased a motorcycle compression test kit on Ebay, very easy to do, but beware of the fact your spark plug are inserted at a slight angle toward front (practice this with a plug you insert rolling with your fingertips first). Otherwise, you or a mechanic may cross thread your spark plug, which will require a major repair or replacement of the engine head (I've been through it). You also need to adjust the valves every 8000 miles, or they may burn and cause major damages to your engine (especially if you are running with an overrich mixture).
I suggest you get your muffler pinhole soldered, replace your jets and perform a carburator synchronization.
Your carb is a Constant Velocity type, 30mm, from Keihin, model number VB22A
Primary jet is a 72, secondary is a 118. Initial pilot screw adjustment is 2 turns out (if you must replace it). It would be smart to get new carb bowl gaskets and replace both float needles too. This can be done without much risk for damaging your carb. If you notice the rubber plug next to the jets is degraded, you may replace it too as a precaution.
After 28 years, It would be smart to replace the original rubber gas line with a new one to make sure you don't get rust or rubber debris into your carb after you cleaned it. 1982 and up versions already have fuel strainer (rough screen filter) into the petcock valve. Get the same benefit by adding one now !Personnaly, I also added a small transparent conical fuel filter between the petcock and the carb fuel intake. This is cheap insurance and it allows you to monitor fuel flow problems instantly.
You may want to have a look at this site to get an idea on what you are dealing with: http://www.gadgetjq.com/keihin_carb.htm Yes, Keihin carbs are used on Harley Davidson bikes too, so it is easy to find someone who can help with a complete overhaul.
I strongly suggest you get a copy of "Clymer Honda 400-450cc Twins 1978-1987". It contains basically all the procedures you want to do. Honda's OEM shop manual is useful for some specifications, but information is scattered and explanations are very limited.
I don't recommend you completely dissassemble your carb as on
http://dirtbike.off-road.com/dirtbike/a ... ?id=413750 because yours appears to simply be off because the jets are damaged.
One last critical detail: Make sure you use carb cleaner that is SAFE FOR RUBBER!. Stay away from GUNK unless you are replacing all rubber parts, they will swell and desintegrate.
Have fun !
Martin
system9 wrote:The bike is a 1981 CM400T
The one thing i'm not familiar with, are the 2 screws that sit on the bottom of the carbs. They are adjustment screws, but i'm not sure where they should be at. There is also a rather large knob type screw, that directly adjusts the throttle, i guess its for setting the idle? or is it some kind of air/fuel setting? see, between the 3 different screws, there is plenty of head scratching.