Topic: '78 750F - Points are sparking at lower RPM

[Triffecpa]

Trying to get a friend's CB750F running well.  Seems to have poor throttle response at small throttle openings.  If I run it with the cover plate off on the ignition side, I can see the points sparking at lower RPM's.  I've gone thru the carbs, installed new plugs, set the valve lash, timing and dwell etc.  I'm about to go thru the whole thing one more time.  I've heard that a bad condenser can cause the points to spark, so I swapped in a different one with no different results.

Anyone got any thoughts on this?  I've got an extra Dyna S that I thought I might toss on there to see if that makes any difference, but my firend is only interested in getting the bike running well enough to sell it so he doesn't want to spring for the cost of a Dyna for the bike.

The one item that I haven't checked is the accelerator pump on the carbs.  I would think that would have a big impact on the throttle response on small throttle openings.

Thanks
Tracy

[Crusty_Butt]

The jet needle setting can also have a big impact in that area. I recently bought a cb500 that you had to crack open the throttle to get it to go, gradually rolling on would cause a hesitation. It turned out the PO had raised the jet needlees. I put them back to stock and now it runs perfectly.

Bret

[eldar]

Way off there. Your carbs will not affect point spark at all. You will need to get a POINTS FILE  or a small rat tail and file the points flat so there are no pits. Then you will want to reset your timing and point gap to proper specs.  Do this before even bothering with carbs. There is no point in dinking around with carbs since if the ignition is off, it wont matter anyways.

[oldfordguy]

Don't use a round (rat tail) file on your points, they need to be perfectly flat.  A points file is flat on both sides.
Matt

[eldar]

A flat file is best but rat tail has worked for others around here but it is hardly the best tool.

[Triffecpa]

Thanks guys, I'll give the points a second look.  I realize that carb issues aren't related to the ignition woes, but at this point, I'm just not certain which is giving me the big problems.  I'll double check all the ignition stuff first though.

Thanks
Tracy

[Wheelhorse77]

That's why I bought the entire points and condesor plate from Honda. New p&c and new coils my 77F screams.