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Post by barriew on Aug 15, 2023 7:25:02 GMT
Good morning, I've recently join the club & been reading through the copies of the Independent I was sent in my welcome pack. Lots of interesting articles, well done on a good read. In particular I've been interested in the Amal carb article by Peter Mays. I have a Bantam D14 & currently a Greeves 2t sport in the process of restoration. Over the years, although spending my working life in car workshops, motorcycle carbs have been a bit of an unknown. Peter's article explains a lot, far more than I've found previously. Although aimed at a monoblock it could equally apply to the concentric on my Bantam. As part of the restoration on my Bantam I had used a carb overhaul kit from Amal with parts to spec as per their manual suggests. It has always had a big flat spot on progression that seemed to elude diagnosis. In desperation I bought a Mikuni intending to fit that in the hope of a cure. For some reason I started going through all the old parts I'd removed & noticed that the original slide was 2½ as against the spec of 3½. Light bulb moment, It's too weak. Changed to the old slide & what a difference. So, back to Peter's article & it's easy to see that the smaller numbered slide has richened the mixture & got over the flat spot. So, a happy new member, looking forward to what the club has to offer & maybe participate a bit. Barrie.
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Post by buttybach1932 on Aug 15, 2023 9:02:00 GMT
Hi Barrie W Welcome to the forum. You say that you had a flat spot in the carburation on your D14/4 Bantam and fitted a 3½ cutaway slide to cure it. I will just point out that a 3½ slide is weaker than a 2½ slide not richer. The carburettor settings on Bantam Concentric carburettors are a bit odd. You would expect the Bantam to use two stroke parts in the Concentric carburettor but they used a four stroke needle and needle jet. Many years ago I questioned Barry Lines ? of Amal about this anomaly and he advised that under testing the four stroke parts worked better. I have also noted that some modern re-build kits for Bantams are supplied with a two stroke needle and needle jet. I have tried both and to be truthful I did not notice much difference, but I still use the four stroke parts. The biggest difference is getting the correct sized main jet if it is a bit rich the engine will not rev. It's a case of how weak dare you go without risking an engine seizure at high revs. Regards Butty Bach
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Post by barriew on Aug 15, 2023 16:32:38 GMT
Thank you for the welcome. Re the slides, the spec is 3½ but my Bantam had 2½ when I acquired it.I fitted a new 3½ thinking that was what was needed but have been fighting a flat spot & stutter since. Changing to the original 2½ ( richer ) seems to have overcome the problem. It's odd that the D14 runs a 2 Stroke carb where as the B175 engine, which my bike has, uses 4 stroke settings. Thanks for your interest. Barrie.
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Post by smokiejoe on Nov 16, 2023 22:24:17 GMT
Greetings all, I'm Joe from Guildford, I recently joined BTSC when showing one of my bikes at the Popham mega meet. I have a 1986 350 Kawa 638, the same as the bike I passed my test on back in 1978, but then I had a chair on it. I have just taken it off the road for some winter tlc, it has a rather nasty vibration at around 3.5-4 rpm, iv'e been told it could be the clutch Oring or even a defective clutch. The bike also smokes quite badly, so I'm going to check everything out from the crank seals to a full decoke.
Joe
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