guestion on the adjustment section of the carb guide...

[jonandjones]

I have read the carb bible a few times over. I have a question, under post 5 section 2. It talks about adjusting the mix screws. It says to warm bike up, then set the throttle stop to 1500. Then it goes through all the dead cylinder stuff... Then it says to lower the idle till its lowest steady idle.Then begin adjustments. I'm not understanding the 1500rpm if your just going to lower it. I love the carb guide!! Just alittle confused on that part.

 

[weekendrider]

When you start you have 2 cly. running. Using the dead method you take one cly out and the rpms will drop from the 1500. Now you drop the idle till it will run at the lowest idle.

If you start too low it may not run well on one cly. Then you would be "hunting" the sweet spot but is it up or down?
So start high and work to the low spot.
Hope this helps.

 

[5twins]

Yes, when you disconnect one plug and your idle speed drops, the bike may stall if initial idle speed with both running is too low. That's why you turn it up 1st before pulling the plug wire.

 

[pamcopete]

Caution: Do not run the engine with one spark plug wire disconnected, especially with the TCI or other electronic ignitions that use a dual output coil. Read the note on page 150 of the Haynes manual.

The problem with dual output coils is that there is no internal connection to ground or the primary of the coil, so the very high voltage will find a path to ground through the insulation and leave a carbon track behind that basically shorts out the coil.

You should always connect the plug wire to a spare plug that is secured to the engine or frame.

If you have vacuum barbs, then it is easier and safer to just pull the vacuum hose off of one carb at a time. The resulting very lean mixture will kill the cylinder for the dead cylinder test.

 

[retiredgentleman]

Further to what Pete was saying, this is the simple set up I use. Just an alligator clip to clip to an engine fin and a hose clamp to the plug body.

 

[jonandjones]

Oh man! Very obvious now...thanks guys! I did ground one plug and I turned on the screw but couldn't get the idle to change. I need to go up a size on pilot correct...

 

[weekendrider]

If you can't get the idle to change there is a problem in the metering.
Not jet size. It should go down as you squeeze down the size of the hole with the mix screw. Up as you open the hole giving it more gas.

 

[jonandjones]

Metering you mean the needle. There bs34 carbs. Up or down the idle didn't change. Expect when I screwed the needle all the way in for the hell of it the idle whent up just a bit. Then I backed it off to 3 turns again...any ideas what that is
Bs34 filter pods 2into1 exhaust. I have 42.5 45 pilot, 132.5 135 145 mains

 

[5twins]

If you get no response from the mix screw adjustment, the idle circuit may be plugged. Your float levels could also be off. Or maybe the mix screw assembly is incorrect or it's o-ring is bad. The BS34 mix screw assembly consists of several parts (spring, washer, o-ring) and they need to be assembled in a particular order to work correctly. And, as mentioned, the o-ring needs to be in good shape .....

 

[jonandjones]

If the idle curcuit was plugged it would run lean In that cylinder?

 

[5twins]

Yes, at least at idle anyway.

 

[weekendrider]

And real crappy at any other rpm.

 

[jonandjones]

They idle good just really hot! Not red hot but blue. I have the carbs off and apart I will clean them again. At least idle curcuit. The mix screws r together right and the o rings good.

 

[5twins]

Check the float levels while the carbs are off. If they're wrong, particularly too low a fuel level (higher measured number), the mix screw adjusting will have little or no effect.

 

[jonandjones]

The floats are set to about 26.2 w/gasket. I suppose I should check both side of the float itself one might be higher then the other. I have adjusted the floats a few times maybe there tweeked a bit.

 

[5twins]

1980 BS34s with brass floats?

 

[jonandjones]

Yeah 5twins I have this going in another thread. But what if somewhere down the line someone put the wrong style pjs in my carbs. Sinse the metering orfices r different maybe that would make the mix screw have no affect??

 

[5twins]

Well, if that was so, things should right themselves when the proper pilots were installed. You do have the rubber plugs in place over the pilots, right? That makes them pull their fuel supply from the needle jet area (as this carb was designed to do). Speaking of needle jets, have you pulled them to make sure they and the hole they fit into is clean? If that area's all gummed up, the pilot may not be getting enough fuel no matter what size it is.

 

[jonandjones]

The pj on the left is the style that came out of my bs34. I think wrong and the needle and needle jet r clean as far as I can tell.

Posted via Mobile