Jetstream carb to fit an ASP36?

[Richard Honeywell]

I found a nice little ASP 36 in a late clubmate's 'bag of bits', but the bracket holding the rear needle was broken and the needle missing.  I was wondering whether any of the Jetstream carbs still available would fit.  The 1750, 1851 and 9650A are still available, but I can't find specs for them anywhere on the web.  The carb aperture on the crankcase is 13mm diameter.

Any information, advice or alternative suggestions gratefully received.

[Jon H]

If you can find an ASP needle you can just undo the end cap on the carb and fit the needle directly to the carb at the front. If not, an irvine carb will probably work fine. What size is the carb boss and what is the choke size? i used to have an ASP36 and it was a brilliant little engine. 

[Richard Honeywell]

Thanks for the reply.  I just looked at it again and it's actually an SC 36 but same difference, as I understand it.  The choke size is 7.3mm approx.  Not sure what you mean by the carb boss - sorry (only migrated from electric to IC a few months ago) - could you explain? 

 

I did have a trawl of various spares sites a while ago and a place in Poland had most of the parts for a front needle arrangement, but not all, and the postage was extortionate in any case.   

 

As you will notice from the photos I will also need a new set of cover plate bolts as two of them are too long now that I have removed the broken rear needle bracket, but Just Engines has these in stock.  It is as clean as a whistle inside the crankcase.

[Jon H]

 

35 minutes ago, Richard Honeywell said:

Not sure what you mean by the carb boss

 

 

When you remove the carb from the engine the diameter of the piece that fits into the crankcase. Could be called a boss, spigot, mounting bit, thingy that plugs into the crankcase. names are hard 😉 

 

In any case you need to find a carb with the same size choke and mounting or get the choke right and then modify to suit the mounting. Might be more of a faff than finding a needle

[Richard Honeywell]

Thanks Jon.

 

Is anyone sufficiently familiar with the Jetstream carbs currently available (1750, 1851 and 9650A) to know whether any of them has a boss of 12.5mm diameter (to fit a 13mm diameter hole in the crankcase) and happen to have a choke diameter of around 7.3mm? (approximate measurements from a cheap plastic Vernier gauge).

[Jonathan W]

An OS needle valve assembly will screw directly into the carb, once you have unscrewed the hexagon-headed plug that is presently fitted. That is, the black hexagon next to the fuel inlet nipple. Unscrew that hexagon and then you can screw in an OS needle/jet assembly.

 

I tried in vain to upload an image for you, but it's cranky as hell, so I give up. Here is an example ebay listing, or give Just Engines a call.

 

[Richard Honeywell]

Thanks Jonathan, that is very helpful.  I will get in touch with Just Engines.

 

[Nigel R]

The later irvine carbs you list were all 15mm boss, IIRC. They are all from bigger engines, too.

 

Easiest way forward would be to get a new remote needle, I think.

 

You could certainly source a new perry carb from just engines but don't expect that to be a cheap answer to your problem. You would need a 13mm boss I would imagine, not 12.5mm. 

[Richard Honeywell]

Thank you Nigel, I was afraid that the Jetstream carbs would all be too big. 

I had a helpful reply from Andrew at Just Engines, and have ordered a needle (same as for an O.S. 91 FS Surpass), a silencer and some other parts.

Thanks to all for taking the trouble to reply.