ET: Engine (Twin) Clogged 276s On My Shadow? Hard To Start and Bap-Bapping At Low Throttle

[CarlHungness]

After reading all the wonderful replies to my post on starting my twin I approached it with trepidation and as
much confidence as I could muster this morning only to wear myself thin. I just could not get the Beast to fire, The only
other time this has happened in three decades is when the original mag went dead.
I did finally get it to run and she was bap-baping at low throttle. I set off and the cut-out continued until I gave it
some throttle and it seemed to clear out. I had a seven mile journey to make and at low speed I got the cut-out again,
then cleared at more throttle.
It has been eons since I've had the 276 carbs apart, and I don't have my diagram handy, so am wondering what can
be clogged. I recall reading about the tiniest hole in the unit that needs to be cleared with a hair thin wire. Rather than
stripping the carbs and cleaning I thought it best to ask the group for advice. I'd hate to clean them, have the bike
run perfectly and not know what it is I've done.
Plus I have a nagging thought that possibly one of my B-TH plug wire connections isn't snug, and I haven't removed
the cowl to check yet either.
Initially, it sure seems as though it is a fuel problem, and my best guess is the problem is surely responsible for my
starting woes.
All advice from the journeymen greatly appreciated. The seven mile journey was just to move the bike to my new
phenomenal workshop. Most every time I ride the machine I'm going to go at least 150-200 miles round-trip. My old
shop was 12' x 28' and the new one is 40' x 30' where I hope to become an accomplished panel beater in the next half
dozen years if I live that long. All of my workshops have had wooden floors in the past 40 plus years, I find it well worth
the time to install them for looks and comfort. I like the sound of an errant nut hitting the floor too as opposed to concrete.
Remember, Henry Ford discovered he could get more work out of employees when they worked on wood. Plus, the location
of this shop looks like it is in the middle of the Cotswolds. I couldn't ask for better.

 

[chankly bore]

Remembering the old adage that 70% of carburation problems are electrical I'd check for corrosion on your B.T.H. connections, since that is the easiest thing to eliminate. Then I'd go to the pilot drilling in the jet block of the carburettors. An indistinct diagram appears in the Rider's Handbook. You'll need a straightened strand of control wire or a No. 76 drill bit, for memory. I think the diameter is about .020". Remove the pilot mixture air screw and blow that out as well, of course. Let us know how you go.

 

[passenger0_0]

Maybe you have the wrong carburetors Carl as Shadows use 289/221 type 1 1/8" not 276 1 1/16".

 

[vibrac]

I do wonder about the effect of oil on wooden floors, however I also remember the exceptional wooden floors on the original Conways in Goldhawk road, they seemed to survive, (They must have been exceptional for me to notice in a room cramed with Vincents!) however they wre probibally 19th century flooring boards not modern 'stuff'

 

[greg brillus]

The new type 289 carb's give significant troubles in the pilot and slide at low running speeds on part throttle..........a couple of fixes sorts them out........Not so much of an issue with the much smaller bodied 276.

 

[CarlHungness]

Maybe you have the wrong carburetors Carl as Shadows use 289/221 type 1 1/8" not 276 1 1/16".

Actually I made a mistake..I do have 289's.

 

[CarlHungness]

The new type 289 carb's give significant troubles in the pilot and slide at low running speeds on part throttle..........a couple of fixes sorts them out........Not so much of an issue with the much smaller bodied 276.

"A couple of fixes sorts them out," which is great to hear if the fixes are explained of course.

 

[CarlHungness]

I do wonder about the effect of oil on wooden floors, however I also remember the exceptional wooden floors on the original Conways in Goldhawk road, they seemed to survive, (They must have been exceptional for me to notice in a room cramed with Vincents!) however they wre probibally 19th century flooring boards not modern 'stuff'

Years ago we could buy 'real' sanding sealer in the US, so I'd always seal the floor, sand it again, and the sealer dust was white-chalky. Today's sealer works to a degree but not as good as the old stuff but I still seal the floor then varnish it. I'd guess my floor will last a few lifetimes with literally anything spilled on it.

 

[CarlHungness]

Remembering the old adage that 70% of carburation problems are electrical I'd check for corrosion on your B.T.H. connections, since that is the easiest thing to eliminate. Then I'd go to the pilot drilling in the jet block of the carburettors. An indistinct diagram appears in the Rider's Handbook. You'll need a straightened strand of control wire or a No. 76 drill bit, for memory. I think the diameter is about .020". Remove the pilot mixture air screw and blow that out as well, of course. Let us know how you go.

The 76 drill bit, if that's it is great info. I'm moving shop to shop and most everything is packed away but the 76 will give me a starting point...just as soon as I check out the BT-H. I cranked on the machine so much my hip hurts today so it'll be a while before I get back to it.

 

[greg brillus]

On the newer 289 carb's the pilot jet bore is generally too small and/or can have swarf in the hole........The jet block needs to be carefully removed and the tiny pilot hole at the front drilled out with not more than a 0.020" drill........any larger and the engine will run too rich. Sometimes the new pilot adjusting screw is not fully seated in the carb body and this gives a false reading. The fit of the carb spiggot on the manifold is important too, as a loose fit here will draw in fresh air that will also cause a lean mixture........The standard number 4 slides can make the carb spit and cough back until the engine is up to opperating temperature......Often I simply trim off 20 odd thou off the base of the slide and clean up the sharp edges with a dremel or similar.........this will simply allow the slide to sit slightly lower in the carb body thus lowering the cut away area and helping give a slightly richer mixture for better running and easier starting. The removal of the material off the slide is done in a lathe.......an internal mandrel is not necessary if the slide is gripped carefully in the chuck.........excess force is not needed, it is only brass, and it machines easily.........you can effectively modify these slides several times without destroying them........new ones are expensive and not needed.........For interest sake, a number 3 slide will be way too rich, and a number 3 1/2 can also be on the rich side as well.......So a 4 with 20 to 30 thou max removed off the base is plenty. The new 276 carbs do not seem to suffer these issues.......the body of the smaller carbs is actually a lot smaller than their bigger brothers........the air flow characteristics obviously plays a big part in it.........Cheers.