Topic: 1979 CB650 Pilot Screws

[barber1303]

Can anyone with a 1979 CB650 tell me how many turns out your pilot screws are?

I don't have a "portable tachometer" as referenced in the Clymer manual pilot screw setting procedure, so I kinda had to improvise. 

I achieved the best operation at 4 turns out, which seems excessive to me (compared to other bikes I've had), but this is the first Honda (and 4 cylinder) I've owned.  It starts great with the choke on, but needs to be ridded about a mile or so before the choke can be turned off.  It then pulls great through the throttle range.  Does this sound normal?

Thanks for the help,

Chris

[Zeke]

Chris:

I measured my #1 pilot screw at 1.5 turns out.

Now, the Honda shop manual says to start at 1-5/8 turns out, prior to performing the "Idle Drop" Procedure.

I haven't done this yet -- still trying to find a choke arm to replace the one I broke on Saturday.

Not sure how you can improvise on this without the dwell tach -- it looks like a very tedious procedure but it seems like you need to do it right if you'll have a smooth idle at the right mixture -- not too rich, not too lean.

I bought one some years back for about $20 -- seems like it might be worthwhile since this part of the tuning procedure should remain correct unless you overhaul again.

Zeke

[cb650]

Around 1.5 sounds good.  I only have one of the 79/80s that I have ridden very much and its been parked for years.  It is the next one to work on.
Zeke The only chock arm I have is one a complete set of carbs so dont really want to pull it off.
I'll keep lookin or if you get some made at cnc shop I might be interested in spares.



                     Terry

[barber1303]

1.5 turns sounds like what I'm used to, but I don't see how you could possibly end up there if you follow the idle drop procedure.  The LAST step of the whole deal is to back the screw out an additional 7/8ths turn from where the procedure ended up (which started at 1 5/8ths turns out)...

Chris

[Zeke]

Around 1.5 sounds good.  I only have one of the 79/80s that I have ridden very much and its been parked for years.  It is the next one to work on.
Zeke The only chock arm I have is one a complete set of carbs so dont really want to pull it off.
I'll keep lookin or if you get some made at cnc shop I might be interested in spares.



                     Terry

Terry:

Thanks anyway.  I'm working on a more rudimentary version that will make it cheaper to make.  I'll post a pic of it on my AHHH!!! thread.

Zeke

[Zeke]

1.5 turns sounds like what I'm used to, but I don't see how you could possibly end up there if you follow the idle drop procedure.  The LAST step of the whole deal is to back the screw out an additional 7/8ths turn from where the procedure ended up (which started at 1 5/8ths turns out)...

Chris

Hi Chris:

Well, the 1.5 turns was from my #1 cylinder -- I forgot to record the remainder of them.  I haven't actually done this yet, so I guess it's probable that they will all end up different.  So my only point is that if you set them all the same, it probably won't be smooth.

Anyone?

Unfortunately, because our bikes are in the minority not too many of the 750 guys pipe in on our 650 problems, and I don't know any tricks.

[Ibsen]

The pilot screw adjustment is a rather time consuming procedure on the 650. It is done in several steps. And you really need a manual to get the correct description. If you haven't got the manual, let me know, and I can scan that part from mine and send it to you in a mail.

[barber1303]

I've got the manual, the only problem is that the procedure relies on being able to detect a 50 rpm rise/drop in engine speed.  A "portable tachometer" is required because there's no way to discern a 50 rpm rise/drop using the bike's tachometer.  I don't currently have such a device, nor do I know where I would get one...

Has anyone every used a frequency counter (on a multimeter) as a portable tachometer?

Thanks for the continued help!

[Ibsen]

Ok.
I don't have the portable tach either, so I have relied on the one on the bike and my ear. I know it isn't accurate enough, but it worked out in a way.

And it's nice to see you aboard this site aswell.

[Zeke]

Here's a few for sale on Ebay:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=4541729828&category=43989

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=43989&item=4542886335&rd=1

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=43989&item=4542809579&rd=1

Any one of them will work, All less than $10.

If you want to look elsewhere, search for "dwell tach".  You won't need the dwell function just the low rpm monitoring.

Pretty much any auto parts store will sell them, I'm guessing that a chain store like Kragen Auto or Autozone will have one for $25 to $35.

Zeke

[DRam]

Started at 1 7/8 turn out as specified, then adjusted by ear, finished with 7/8 of a turn on all when done.  I don't think there were more than 3 turns out when done, but don't know for sure.  By the way, a mile for a warm up seems about right. Mine has been like that since I bought it new.