Motorcycle Repair: 1970 honda sl-350 idle adjustment, honda sl350, adjustment screws

Question
fires up with choke on, but when i bring the choke down it dies, im sure the idle adjustment screws (inside) the crabs need adjustment, but i would have to take the carb apart an adjust blindly with the engine off...my guess is i have to back the screws all the way down then bring them back a turn 'n a half...sound right??

Answer
David, carburetor adjustments are the LAST thing to do after you have performed a complete tune-up on the bike.

Adjust the valves, check compression... looking for about 175 psi. If good, then move onto

Ignition system... Remove points plate, check function and lubricate the mechanical spark advancer.
Replace point plate and check point gaps, when the points are opened at the widest part of the points cam ramp. Set gap to .014-.016 after you have cleaned the point contact faces to nice shiny surface with no grit or debris left behind. Rotate crankshaft to F mark and using a 12v test light watch when the points on the right side just begin to open (light comes on). If the F marks are not where the light turns on, loosen and rotate the points plate until it does and then go back to check the point gap again, to ensure that it hasn't changed beyond specifications. Then do the same thing with the left points and the LF timing marks.

NOW the fuel system.

There are NO adjustment screws inside the carburetors. You have external idle mixture screws, which are set about 3/4 to 1 turn out from lightly seated. The other two screws are for the idle speed adjustments on each carburetor.

http://www.cmsnl.com/honda-sl350-motosport-350-k0-usa_model732/partslist/E++18.h...

Due to age and unknown history, you probably should remove the carburetors for cleaning and replacement of the o-rings. The idle jets are probably plugged which makes the engine hard to start and then it won't idle if you want it to afterwards.

The carb diaphragms need to be inspected for tears or pinholes. I am assuming that you have an SL350K0, as the K1 carbs are totally different. If the intake manifolds are cracked/torn, you will have to replace them, as well.

With the ignition timing dialed in and cleaned carbs, it should fire up fine, assuming that the engine is sound to begin with...

I do have a compilation of Honda 350 tech files available on CD, which may be helpful for you.

Bill Silver
www.vintagehonda.com