Topic: Pilot air jet arrangement on Keihin PDs

[cjg1245]

Hi, am stripping/cleaning/rebuilding the carbs on my 1977 750A. Anyone know if the tiny metal washer on the pilot air jet is essential ? One was missing from my carb set, and looking for a replacement from a spare set of carbs I have, there were none fitted.  Am wondering what the metal washer actually does, and if it is necessary.

Info gratefully received. Thanks in advance.

[flybox1]

yes, it is essential.
It keeps the spring from tearing up the tiny o-ring.

contact member harisuluv.  he has a plethora of carb parts.

[drumstyx]

Are the carbs on the '77 A the same as the '78 K? If so, it's a pilot FUEL screw, and all the little washer does is press evenly on the o-ring so it's not the spring right up against it. I'm positive it'd run without it, but it's not the right way to do it. That said, it's just a washer, not a shim (someone correct me if I'm wrong) so if you can find something that fits -- i.e. from other bikes, other years (looks the same as a '78K to me...), etc.

[flybox1]

Are the carbs on the '77 A the same as the '78 K? Yes for the most part.... small differences, needle adjustibility If so, it's a pilot FUEL screw, IMS= Idle Mixture Screw is the proper term, but yes, it does meter fuel during idle.  IN is leaner, OUT is richer  and all the little washer does is press evenly on the o-ring so it's not the spring right up against it. I'm positive it'd run without it, but it's not the right way to do it.  Certainly dont, as, over time, small bits of the oring can wear off and clog the circuit  That said, it's just a washer, not a shim (someone correct me if I'm wrong) so if you can find something that fits -- i.e. from other bikes, other years (looks the same as a '78K to me...), etc.

[cjg1245]

yes, it is essential.
It keeps the spring from tearing up the tiny o-ring.

contact member harisuluv.  he has a plethora of carb parts.
[/quote

Thanks for the info. I thought it might work like that, but then saw on the schematic that it fits ABOVE the rubber ring and not between the spring and the rubber ring. That confused me a bit ! Since my post I have found a washer in my bits and pieces box.

[cjg1245]

Are the carbs on the '77 A the same as the '78 K? Yes for the most part.... small differences, needle adjustibility If so, it's a pilot FUEL screw, IMS= Idle Mixture Screw is the proper term, but yes, it does meter fuel during idle.  IN is leaner, OUT is richer  and all the little washer does is press evenly on the o-ring so it's not the spring right up against it. I'm positive it'd run without it, but it's not the right way to do it.  Certainly dont, as, over time, small bits of the oring can wear off and clog the circuit  That said, it's just a washer, not a shim (someone correct me if I'm wrong) so if you can find something that fits -- i.e. from other bikes, other years (looks the same as a '78K to me...), etc.

Thanks for the reply. Problem solved I think.

[cjg1245]

Are the carbs on the '77 A the same as the '78 K? Yes for the most part.... small differences, needle adjustibility If so, it's a pilot FUEL screw, IMS= Idle Mixture Screw is the proper term, but yes, it does meter fuel during idle.  IN is leaner, OUT is richer  and all the little washer does is press evenly on the o-ring so it's not the spring right up against it. I'm positive it'd run without it, but it's not the right way to do it.  Certainly dont, as, over time, small bits of the oring can wear off and clog the circuit  That said, it's just a washer, not a shim (someone correct me if I'm wrong) so if you can find something that fits -- i.e. from other bikes, other years (looks the same as a '78K to me...), etc.

Thanks guys, good info. Happily, problems sorted now.

[Jnel]

A plethora.    Very good word

Sent from my SAMSUNG-SM-G935A using Tapatalk

[flybox1]

A plethora.    Very good word

Sent from my SAMSUNG-SM-G935A using Tapatalk

Definitely more than a gaggle.