Removing a 389 is there an easy way?

[a101960]

My bike is fitted with an Amal 389. I thought that it might be wise to change out my throttle and choke cables because they have both been on the bike for some while now. It is always a bit of a problem to do this task due to the lack of clearance between the top of the carb and the frame. (Not one of BSA’s most successful design features). I assume that everyone else has the same problem as me, in that it is necessary to remove the carb from the manifold studs before there is enough room to separate the top from the body, and getting the carb off of the studs can often  be problematical. As for getting it all back together it is even worse. Anyway leaving all that aside, has anyone got a solution to the issue of routing the cables neatly so that they are not strained and distorted by the close proximity of the frame top tube? Also can anyone tell if a concentric 900 pancake air filter will fit a monobloc 389?

John

[Greybeard]

I have bolts rather than studs holding my carb on to the manifold; this makes it easier to remove and get the, (standard) air filter rubber located when refitting. My cables are loosely held against the top tube by cable ties.

[bsa-bill]

know what you mean, did see some right angle bends that thought might help but never tried them.
another thing I aint tried but thought about is replacing one of the carb/head studs with a setscrew (if those are the correct terms), would allow the carb to swing on the other stud once removed - hah just read Greybeard's post but I'll post anyway

[Topdad]

John, would it be easier to remove just one stud and loosen the other to remove slide and choke and then just pull the body off ! I had a 389 fitted for a short time and I think that's how I did it . I removed the gearchange side stud ( to avoid another right left fiasco ) and did it. My cables are also held in place along the top tube, regards Bob

[a101960]

Thanks for the replies chaps. All useful suggestions. What size bolts would I need, and where could I get them from?

[Greybeard]

Thanks for the replies chaps. All useful suggestions. What size bolts would I need, and where could I get them from?

I got most of my rebuild parts from Draganfly. The bolts have a fine thread.

[duTch]

 I think GB means a 'fine' (cycle) thread on the outer end....at a guess I'd say 1/2" WW(screws into manifold) + ~3/8"unthreaded + 1/2" BSC (Cycle thread)=1-3/8" overall (min.) Just a suggestion, make the outer BSC end long enough to get a locknut on so you can undo one easy...(~5/8" ?) which makes the studs; 5/16  x ~1-1/2".... plus nuts

[Greybeard]

Dutch, I have bolts with fine, (cycle?) thread into the head inlet casting.

[bsa-bill]

Can John clarify - we're talking alloy head (don't think cable run is an issue with cast heads ? )

makes a difference to studs used alloy - Whitworth , cast - cylcle

[duTch]

 

Dutch, I have bolts with fine, (cycle?) thread into the head inlet casting.

makes a difference to studs used alloy - Whitworth , cast - cylcle

  Ok, points noted, hadn't considered that

[a101960]

Can John clarify - we're talking alloy head (don't think cable run is an issue with cast heads ? )

Yes Bill, it is as you surmise an ally head

[Greybeard]

I have an iron head; and so does my motorcycle!

[Johnny J]

Mines more like a wood-sponge alloy....

[bsa-bill]

mine is full of stuff (careful) others don't know - like what is a cylcle thread

[beezermacc]

I stock both types of bolts/ studs for alloy / iron heads. Send me a PM if you want some.