Older style carbs

[DGXSER]

Working on my first set of the 78-79 version of the carbs. How can I tell if it is a 78 or 79 setup? Did they use different needle jets or emulsion tubes from 78 to 79?

The air, pilot, and mains are not right at all. look to eb aftermarket and 40 pilots with 130 mains, and 180 pilot air jets. So I am trying to figure if I should jet with 42.5 or 45 pilot jets. Plan is to clean them up and get them setup and ready to run, then send to a new owner yet to be named or determined. They have the plastic floats, so going with the XV920 float valves. So I could go either way, but if the needle and emulsion tubes determine a setup, that is the way I want to go with it.

[petejw]

hey dgxser,

heres a good link from the uk site with carb specs
for all the models.

http://www.benefiscal.co.uk/forum/in...p?topic=3775.0

[natemoen]

Didn't the 79 have 180 air jets? 78 had 210.

[geobiker]

Carbs

DGXSER:

According to my Clymer Manual, the 78E and 78F had the same main jet (137.5), the same needle jet or emulsion tube (X-2), same pilot jet (42.5) and same air pilot jet (180). The jet needle is a 5GZ6.

Don't know if this helps.

Geobiker

[skids]

The air, pilot, and mains are not right at all. look to eb aftermarket and 40 pilots with 130 mains, and 180 pilot air jets. So I am trying to figure if I should jet with 42.5 or 45 pilot jets. .

Maybe the pilots were downsized to compensate for being the wrong type and resulting previous probs with being too rich? The right type has a small oriface at the upper end (as installed). I never owned a 79, but the 78 does have 210 air's.

[natemoen]

DGXSER:

According to my Clymer Manual, the 78E and 78F had the same main jet (137.5), the same needle jet or emulsion tube (X-2), same pilot jet (42.5) and same air pilot jet (180). The jet needle is a 5GZ6.

Don't know if this helps.

Geobiker

this is one of those situations where the clymer manual is wrong.

[bikerphil]

If you follow the Clymers recommendation for the 79, you should be good. This would be for a stock setup, of course.

pilot jets 42.5/180
main: 137.5
float level 25.7mm

The 210 air jet setup is for the 78 and very early 79 models with the hot cams. IIRC, they also used a 45 pilot.

[crazy steve]

this is one of those situations where the clymer manual is wrong.

Even the factory manual is wrong; my '78 FSM calls out a 180 pilot, but my unmolested-since-new carbs had 210s in 'em...

[81xsproject]

The only difference I know of is that the 78 has a larger Starter Jet size in the bowl. But, this won't help identify one from the other. On a more positive note, it doesn't matter which is which because everything else is the same.

[yamahansolo]

My 79 made in april 78 came with 140 mains 45 pilots and 210 airjets. There are a few older posts about this. I don't think the 78's were 210 air though. If you look at some of the parts fische you will see two different jettings for 79 search for one of my previous threads

[DGXSER]

Looking over all the great input, gives me plenty to think on. Most likely go with the 42.5 pilots, looks like they have the correct pilot air jets for that and get new mains the right size. Especially since my test bike is the 81 model, (have to test them before I'd send them to a new home) it might run like crap on those large pilots and air jets with the milder set up.

Thanks for all the great input!

[bikerphil]

Also, needle clips should be in the 3rd (center) position.