Some vague running issues A7 Shooting Star spec

[BSA500]

Did it run ??????

[Peter in Aus]

Did it run ??????

Well no, it had low compression and no spark but all good now

[Slymo]

I've had excellent success rebuilding Amal Carbs (276-376-389's not so much with Concentrics) I've re sleeved the bodies in brass and a bored the bodies and sleeved the slides all with a very satisfactory result. The biggest issue I've had with the Monoblocs is the needle jet wearing out. You can shag around for a lifetime with the idle mixture jet and never get things good if the needle jet is shagged and they do wear prodigiously. With the separate float bowl carbs the problem often comes from the body losing contact with the jet block due to over tightening the big nut at the bottom of the body. Careful scraping and shimming with paper and the idle mixture screw works again and all is happiness. If the British motorcycle industry had been prepared to pay a few pennies more per unit the metallurgy of the Amal carbs (monoblocs and concentric) would have been as good as Delorto or Mikuni or any of the others but a mazac slide in a mazac body was never going to work for more than a year or two.

[BSA500]

some sort of update. Did a leakdown test on it, air getting past the timing side inlet valve and across the headgasket. lifted head and barrels and found the small ends are shot

[muskrat]

G'day BSA500.
Bugga, but at least you found something. You've got a bit of work for the cooler months.
Cheers

[RDfella]

If the BE's etc seem OK, it's possible to change SE's in situ with appropriate collar, mandrel and draw bolt.

[RichardL]

If it was me, with the small ends shot, it would be hard to accept not checking the big ends.

If nothing is damaged inside the crankcase, while not entirely pleasant, the reassembly should go pretty easy. If something IS damaged, well, at least you know you're there for a reason.

Richard L.

[RDfella]

If it was me, with the small ends shot, it would be hard to accept not checking the big ends.

I agree, Richard, but what if it was rebuilt not long ago but the builder neglected to check the SE's? I've seen that done a few times. For some reason they're often considered inconsequential. I note in the early part of the post it was stated the engine had been rebored, BE's done etc not long ago. Like you, I wouldn't consider changing just the SE bushes unless I had good reason to believe the BE's were OK.

[muskrat]

G'day Fellas.
I agree with Richard. If I found that the whole lump would be inspected.
I hope it wasn't Rivet Man that did the rebuild!
Cheers

[BSA500]

Just to reassure the lump is out of the frame and in alot of pieces. Checked the big ends all fine(the rebuild was 7 years age how time flies) all the mains bearings are good as well. The conrods are off as well to get new small ends fitted and honed. The shells looked great,quite surprised I don't normally get that lucky. Pistons are toast mainly due to me knocking a skirt and taking a chunk out of one of them. They looked a bit scuffed as well perhaps due to the slack small ends. Bores are unmarked and when a new set of rings were pushed in the end gap is in spec

[BSA500]

I really suspect the quality of the SE's both worn exactly the same amount so loose they fell out, I bought them off ebay, i know.