Topic: Bench syncing/slide height

[jwurbel]

Starting to set the slide height,  does it matter where the idle screw is at?  Should it be turned all the way out?  Or turned in a few turns?  This is a k2 with 657A carbs

[newday777]

All right here.....

http://www.hondachopper.com/garage/carb_info/tuning101/carb_tips.html

[Floshenbarnical]

Oh my god, that's a great explanation. I'm going to have some fun this summer ...

[jwurbel]

Appreciate the response. However I am talking about the idle screw controlling all 4 carbs not the individual mixture stews. I have taken it out to where it just touches the rack and set the height from there but I don’t know if that is where I should be. Or should I turn it in to some point and start measuring height from there.

[MauiK3]

The idle screw on racked carbs has little to do with it. Just be sure, as a starting point, that you get the slides as matched as you can, you will likely have to fine tune with gauges later.

[Bodi]

This depends on the slide adjustments. If you have a fixed reference carb (no adjuster) then it's not hard. You want that slide to just close fully without torching the idle screw, it doesn't matter if its out all the way but you should have quite a bit of "rpm up" room available. Then you can use it to set the bench sync on that carb, and proceed to the other 3.
Without the master non adjustable one, it gets trickier if anyone has been messing around since it left the factory. I don't think the K2 had a choke throttle advance, that thing makes it more complicated.
You want all four slides to fully close with the idle screw out a bit. That's about it. Then raise the idle to where they are close to where your desired bench sync opening is and adjust three to match one. Confirm the slides completely close with unscrewing the idle screw.
With a choke advancer, you need to get the slide adjusters to where the advancer cam is not touching with slides closed and choke wide open. There may be a spec on that spacing?.

[jwurbel]

Kinda of what I thought. No Master carb, all adjustable.

One last point. I can’t get them to completely close. I can still see the notch but barely. Is that an issue?

[Floshenbarnical]

This depends on the slide adjustments. If you have a fixed reference carb (no adjuster) then it's not hard. You want that slide to just close fully without torching the idle screw, it doesn't matter if its out all the way but you should have quite a bit of "rpm up" room available. Then you can use it to set the bench sync on that carb, and proceed to the other 3.
Without the master non adjustable one, it gets trickier if anyone has been messing around since it left the factory. I don't think the K2 had a choke throttle advance, that thing makes it more complicated.
You want all four slides to fully close with the idle screw out a bit. That's about it. Then raise the idle to where they are close to where your desired bench sync opening is and adjust three to match one. Confirm the slides completely close with unscrewing the idle screw.
With a choke advancer, you need to get the slide adjusters to where the advancer cam is not touching with slides closed and choke wide open. There may be a spec on that spacing?.

Can you go into more detail on this?

[jwurbel]

When backing off idle screw, slides will drop.  However they don’t full close.  The photo shows what I am referencing.

[smee]

Starting to set the slide height,  does it matter where the idle screw is at?  Should it be turned all the way out?  Or turned in a few turns?  This is a k2 with 657A carbs

Slide heights are adjusted on the top of the carbs. You will see the lock nuts on the top. I use an 1/8 drill bit for spacing on mine for a bench sync.

https://www.google.com/search?client=firefox-b-1-d&q=hackaweek+bench+sync#fpstate=ive&vld=cid:09084fa3,vid:aVe7TmvAots (14 min mark if you are a visual person).

[jwurbel]

Past that.  Photos show result.

[jwurbel]

To clarify the last comment, photo shows result after the bench sync with the idle screw backed off.

[PeWe]

After a bench sync, verify that you can close throttles completely with the idle screw.

There is a risk that you have set throttles too high and idle will be very high.

I've done that mistake.

[pjlogue]

What PeeWee said.  You need to have the single idle screw engaged about 1-1.5 turns which raises the gang of four fingers slightly.  Then do your bench sync using a 1/64" drill bit using the shank end, not the fluted end as a "feeler gauge"  The tops of the adjusting rods (four of them) should show about 1.5-2 threads above the top of each locking nut.  Once this is done you should be in the ballpark of having your carbs synced enough and you will be able to adjust your final idle speed properly.  You can then sync your carbs using sync gauges.

-P.

[jwurbel]

 This is the same procedure I followed.  When done I ended up with treads even with the top and slides exactly like the photo.  Not sure what or if I’m doing wrong.  Appreciate the clarification. 

I am going to do a start and see what happens.

Will post results.  Hopefully they are positive.

[Bodi]

I haven't done this in a while. But probably the edge of the cutout is showing when the slide is fully down.
For the choke advance... hard to explain. But after having to reset and resync the slide adjusters after doing this wrong following a full rack disassembly I assure you it needs to be considered.

[jwurbel]

Synced with a Morgan Carbtune and was able to balance all 4 carbs.
When I slowly increase the speed and then let go, it returns to an acceptable idle of 1200 rpm’s.  However if I blip the throttle, it wants to drop to a point where it will stall unless I increase the idle screw by turning.

Haven’t touched the air mixture screws, still at 1 out.  Plugs not fouled or showing over lean condition except #2 might be trending towards lean

Had a problem with hanging idle before. Clipped  one half of advancer spring per HondaMan and that issue is gone.
 
Any ideas are appreciated as I think I am close but don’t want to screw it up.

[dave500]

bench sync gets the bike running,you must vacuum sync to get it correct,be sure the ignition is squared away but perfectly first!

[jwurbel]

Were vacuumed synced after resetting points and timing with strobe.

Dropped idle doesn’t slways go to stall when blipped but it does.

If all else fails, will go through every thing again.  One thing, when starting, choke only used to start.  If left on after, it dies.

[smee]

Were vacuumed synced after resetting points and timing with strobe.

Dropped idle doesn’t slways go to stall when blipped but it does.

If all else fails, will go through every thing again.  One thing, when starting, choke only used to start.  If left on after, it dies.

Sounds rich on the pilot (classic sign is dipping RPM below the idle baseline setting). What are your carb settings? Real Honda brass? Can you post some pictures of your plugs during idle?

[jwurbel]

All Honda brass.  40 on the pilots 110 on mains, needle in 4th position, exhaust HM 300.

[newday777]

One thing, when starting, choke only used to start.  If left on after, it dies.

That is how it should be, fire it up with choke on, once started move lever down to off as needed and slowly blip the throttle a little bit to keep it running until warm enough to atomize the fuel properly on it's own at idle.
I don't let mine set idling more than a minute unless it's below 70°(to fully warm up before riding) I start off slowly as I have a long driveway and then a short distance on the road to a stop sign, then once on the main road, speed limit through town is 30 so I can take my time warming it up for a mile going easy.