Idle mixture/etc one rich plug

[Mjpcarbon]

Bonz, you mention an oring on the pilot adjustment screw ? I dont have any orings on those screws, never did !

[bikerphil]

On 78-79 carbs, no O-ring is used, 80-82 carbs use pilot screw O-rings. They have a different type pilot screw.

[Mjpcarbon]

Ahh ok thank you

[Bonz]

Disregard my PM response, I did not know what year bike you had.

Any success getting it figured out?

[Mjpcarbon]

It is better but idle still fluctuates sometimes it is 2000 then at idle will drop to stall. Chasing my tail

[Bonz]

Lots of good posts and info. You mention "It is better", does that mean the black plug on #1 has been rectified? Have you done a second sync to verify all is good in that regard?

I just finished a major refurb of carbs (and fork seals, steering head bearings, brakes, etc) on a Gen 1 V Max for a friend. The idle was decent after bench sync, then spot on after Carbtune sync. But went downhill after a few rides. The braces that hold the carbs in the racked formation had loosened and were allowing the carbs to move around a bit, causing holy heck with the idle as now the sync was off big time. As an aside, getting those carb braces off between the racks needed an impact driver because they were so stuck after all those years on the bike. I out-thunk myself and put a bit of anti-seize on each screw holding the braces to the carbs on reassembly. Anti-seize also means anti-grip. Every damn screw had loosened up to finger tight lol. Thoroughly cleaned the threaded holes in the carburetors and the screws themselves. Put everything back together and they stayed solid like they should. After a fresh sync, they have stayed where they should.

In any case, are the carbs solid in terms of the braces that rack them together? Just taking a stab at this since it's been such a tough go.

[cajun31]

what kind of spark plugs are you running and how old are they?

[Mjpcarbon]

NGK and new
Bonz, #1 is still rich, float height is proper
I did get a colortune just for fun and machining an adapter to go from the 10mm to 14mm they didnt have anymore when I ordered.

Have not done a second sync, I was hoping to get #1 a little closer, dont know what is causing the overrich condition

Idle still hangs at 2000 then slowly drops to a stall, to me indicating a lean mixture aside from #1

[cajun31]

NGK and new
Bonz, #1 is still rich, float height is proper
I did get a colortune just for fun and machining an adapter to go from the 10mm to 14mm they didnt have anymore when I ordered.

Have not done a second sync, I was hoping to get #1 a little closer, dont know what is causing the overrich condition

Idle still hangs at 2000 then slowly drops to a stall, to me indicating a lean mixture aside from #1

What NGK spark plug? Are you using resistor or non resistor plugs? If your idle is not holding then you either have a vacuum leak somewhere or the jet/jets are not right or good. I had a problem with a set I was rebuilding that no matter what I did I could not set the pilot jet screw properly. Not talking about the pilot jet itself but the pilot jet screw setting. I removed that pilot jet and inspected it closely and didn't seem to have any problems. I ordered a new mikuni jet and replaced it anyway and the problem went away. On these carbs at different rpm ranges different circuits in the carbs come into play. Doesn't sound like you have the bike running good enough yet to actually be out riding the bike bringing the main jet circuit into play yet. When you cleaned the carbs did you replace the butterfly shaft seals? If they have never been replaced they can be a source of a vacuum leak. The carb intake manifolds can also leak where they bolt onto the engine. If there are paper gaskets in use you should remove them clean the surfaces and mount them with a small amount of yamabond. Solves any leak there.

[Mjpcarbon]

Sprayed carb cleaner all around checking for leaks, no changes so leak is doubtful
where can I get just pilot screws ? Don’t want eBay parts, looked at Mikesxs but could not find just pilot screws

[bikerphil]

Genuine Yamaha....

https://www.partshark.com/oemparts/p...0/-screw-pilot

This is for the screw only, the spring is a separate part #.

Beware of the cheap Chinese ones, the threads are sometimes the wrong size.

[Mjpcarbon]

Perfect thank you

[DEEBS11]

Don't forget to look at the air jets. #1 could be wrong sized or clogged if you have this type.

[Mjpcarbon]

I know it is open but perhaps the wrong size

[cajun31]

I know it is open but perhaps the wrong size

If you have that hole on your carbs that Deebs pointed out then I am now confused about which carbs you actually have. On the earlier carbs there is no hole there. Any way you can post a picture or two of the carbs you have?