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Discussion Starter · #1 ·
I'm new to the forum and this question has possibly been asked before, but is there a major difference (reliability, performance, aftermarket parts, etc) between the 1975-1978 and 1979 Bonneville engine with and without the splayed heads? I have access to a 90% complete 79 Bonneville (a true barn find) for almost zero money, but I can't seem to find a Mikuni conversion for that year, only for 78 and older. I'm thinking of using the frame and motor for a custom project. Thanks!
 

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Cylinder heads with splayed inlets were used up until '78 ish for T140V which had two Amal Mk1 concentric carbs. These carbs were (are) prone to wear, which is probably why some people choose to fit Mikunis. (but Amals are cheap to rebuild / replace).

Cylinder heads with parallel ports were used from '78 onwards for the T140D & E and subsequent bikes, which were fitted with Mk2 concentric carbs - much better devices. Much later on ('83? onwards) Bing carbs were fitted. Cylinder heads on Bing carb'ed bikes had parallel inlets, but the inlet stubs were a little shorter than the Amal Mk2 inlets.

A '79 bike should have Lucas RITA electronic ignition, which is good. Doing away with mechanical auto advance and points ignition gets rid of a major source of buggeration.
 

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I'd stick with the Amal 2's.

If you don't want the 79 " for no money" I'll have it!

You can get Mikuni conversions for about £500 v £150 each for new Amals
 
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