PR: Proprietary Items Amal jets

[vibrac]

I read in the VOC mag (the other VOC...Fishtail) that the main jets of the carbs on the original series B & C bikes (289 etc) are the same as UK gas cooker jets as they are made by amal and were calibrated on the same machine (except they are pointed at the end)
if anyone has access to those domestic things it may be worth a look certainly a lot cheaper...

 

[mercurycrest]

I read in the VOC mag (the other VOC...Fishtail) that the main jets of the carbs on the original series B & C bikes (289 etc) are the same as UK gas cooker jets as they are made by amal and were calibrated on the same machine (except they are pointed at the end)
if anyone has access to those domestic things it may be worth a look certainly a lot cheaper...

Looks a bit "iffy". Maybe they could be drilled to fit?

Gas Jets | AMAL Carburetters

Shop the AMAL Carburetters range of Gas Jets online.

amalcarb.co.uk

 

[bmetcalf]

Is the base of a needle jet tapped 1BA to match those jets?

 

[Nigel Spaxman]

The main jets on the B & C bikes are exactly the same as the main jets that fit in the Mikuni VM series carburetors. Mikuni once made licensed copies of Amals and they continued with this style of jet for a long time. I am using a Mikuni jet inside the timing chest of my twin to meter the oil to the cams. Or is that jet for the big end I forget but anyway it's a Mikuni part in there.

 

[ClassicBiker]

The main jets on the B & C bikes are exactly the same as the main jets that fit in the Mikuni VM series carburetors. Mikuni once made licensed copies of Amals and they continued with this style of jet for a long time. I am using a Mikuni jet inside the timing chest of my twin to meter the oil to the cams. Or is that jet for the big end I forget but anyway it's a Mikuni part in there.

Thank you for that info. I thought I was delusional in that I read that Mikuni VM carbs were based on Amals. I forgot where I read it and haven't been able to find it again. Further to the point the jet numbering system is the same as Amal, it is the number of CCs of paraffin flowed at 68F (20C) with 12" of head pressure. The basis for the number system for the height of the cut away on the slide is also the same on Mikunis and Amals.
Steven

 

[oexing]

Imperial threads on Mikunis for Amal copies ??

Vic

 

[ClassicBiker]

No, I think you will find that the threads on the jets are the dreaded "M" word.
But I shall have to check to be certain.
Watch this space.
Steven

 

[Magnetoman]

The main jets on the B & C bikes are exactly the same as the main jets that fit in the Mikuni VM series carburetors.

Athough they're "the same," they're not exactly the same. The calibration of the flow rate of the jets uses a rig with a specific pressure head, and where the flow depends on, among other factors, the ratio of the density to the viscosity of the gasoline used for the calibrations. In turn, both the density and viscosity depend on temperature. As a result, it would have taken very little difference in composition of the fuel used by Mikuni along with temperature of their laboratory (a rather chilly 15 ℃ was specified for Amal's) to account for the 18% difference in flow rate. Note that Mikuni's jets actually hit the numbers they should (e.g. 300 cc/min. for a #300), whereas Amal's aren't exactly the same.

The 18% difference in flow rate is important for anyone who decides to cross-thread a Mikuni jet into an Amal carburetor, since a significantly larger number Mikuni would need to be cross-threaded to give the same mixture strength.

 

[bmetcalf]

FWIW, I think I remember buying Mikuni jets with the same hex section length as Amals.

 

[Robert Watson]

I run 34 mm flat slides on one Rapide and all the Mikuni jets I have purchased are the same length as the Amal ones. I have not seen a shorter one. I probably have a few hundred carb jets in various stashes around the shop, and I do mean hundreds, and the small jets are either Amal or Mikuni and one needs good eyesight to distinguish between them, as in you have to read all the little numbers and letters on them! Having said that I have somewhere what appears at first glance to be a pre-monoblock small Amal carb. On close inspection however it is very clearly cast in the body MIKUNI. I'll have to find it and look at the main jet in there........