Odd jets from PO

Hi,
PO seems to have gone smaller than stock on the pilot and emulsion tube.
Before I bring it back into line, can you think of any reasons why they might have done this?

Current:
Main Needle Jet: 517[]0-6
Main needle: 4chp3
Main fuel jet: R[]112.5 (N100.604)
Pilot fuel jet: []30 (N151.067)
Pilot Air jet: R[]125

Main Needle Jet/emulsion tube stock is: 0-8
Main needle stock is: 4GZ11
Pilot fuel jet stock is: []35
Pilot air jet stock is: []170

Bike is from Pennsylvania, now on the south coast of England.
No idea when the jetting changed.

 

what bike do you have. some had different jet in the us to help meet emissions standards.

 

'82 xj550 seca.
Sry, thought i had that in my signature.

 

in 1982 the air in Pennsylvania wasn't really air as most people know it

 

One reason that comes to mind is they sourced the wrong carb.
That's an awful lot of jets to purchase.

 

Yeh it's odd. The carb is correct for the bike, so maybe they were confused or maybe they were trying to correct a problem.
The carb boot rubbers look pretty shot, but I cant see how this kind of re-jetting would help.

confused. and anxious.

 

Looks like you could drill out some of them

 

Examine the carb bodies closely and see if there is a "5K5" stamped anywhere.

 

Yamaha made a "400" version of the "550"
I don't know what the jets are in that,
but it's an example of something that would "drop in place"

 

I think you're right about donor carbs, my choke lever is different to all the secas and maxims I've seen.
Instead of being cable actuated, its thumb actuated.
Instead of a little shelf coming out of carb 1, there is a screw hole

I tried searching the carb type by the main needle (seems the kind of thing that you wouldn't replace). no luck yet but got this info:
Mine: 4CHP3, 5 slots, 46.5 L, K1 14.5, K2 30.500, K3 38, A1 0.45, A2 2, A3 4,
Stock: 4GZ11 1 slot, 43.5 L, K116.2, K233.7, K3 0, A1 1.45, A2 8, A3 0.

I dunno what most of that means, I'm assuming milling angles but either way its well different.
This is hard enough without having the wrong carbs.

They look the same in every other way, do you think I can re-jet to Seca stock or will that likely make these mystery carbs run like shit?

 

You MAY have even had a set of carbs that got swapped in from a Honda or something other than Yamaha....................

Dave F

 

If there is, then we know they're from a Maxim.

The goofy choke arrangement makes me tend to agree with Dave though; if they were off a 550 Max, the choke and throttle setup would be the same as the 550 Secas.

I recommend you get a set of actual XJ550 carbs, Max or Seca, and re-jet THOSE to "Seca" spec.

 

Take a close look at the bottoms of the carb bowls. See if you can see any series of letters/numbers there. You may have to play with lighting and angles a bit. They were originally stamped on, but subsequent cleanings may have removed them. If you get the light right, sometimes you can see remnants of it, and sometimes you can read them clearly.

Let us know if you see anything.

Also, if you're able to get a couple pics for us that might help.

Dave F

 

Cheers all,
I checked all over for 5K5, but saw nothing.
One side of the carb says Mikuni corporation, the other says made in Japan.
Inside carb bowls has "P 2-1"
There is a kind of sideways "H" underneath where the choke gets its fuel from

It looks exactly like the normal bs28's except for the missing shelf that sticks out of carb 1 (for the choke actuating lever)

In the meantime, I am delighted to discover that during my attempts to fabricate a choke actuator finger thing, I've lost the screw for another.

Anyhow, lemme know what you know.
Pics: http://exjayarrjey.tumblr.com/post/6724 ... jbikes-com