Carb linkage play - recommendation to fix

[Gra900]

Im just statically settingup carbs before refitting. I was getting the butterflies to open at the same time and noticed play where the actuator arm joins the butterfly spindle.
When open there is about 4 mm play in the butterfly. See photos
It looks like this a problem with where the bit circled in blue joins the shaft.
This sure ain't going to make it run smooth.
Any ideas on a good repair? Peen over, braze, solder ?
Thanks
Graham

Graham

 

[xschris]

Shouldn't be any play if they are assembled correctly.

 

[Gra900]

So I stripped the pair and found that where the bracket is joined to the butterfly shafT there was about 3mm play. Fixed it it by multiple centre punch points, seems ok now.
Bike started up this afternoon, but there was intermittent running on left cylinder, and right cylinder plug was very pale grey when chopped. I set the floats to 23mm but now think that was wrong and will switch to 26mm. The pilots were 3 1/2 turns out, but I feel they are a bit lean. it’s an 82, SE, with the 28 bhp cam shaft which was fitted with 125 main jet and 42.5 pilots. Stock filters and h pipe, 2 into 1 with quiet exhaust (restrictive).
And last, when on side stand petrol came out of the air filter on that side which makes me think float heights first thing to change, then tweak pilot screw, then look at pilot jet size. nice big chunky sparks!

 

[xschris]

I would start with stock 28hp jets and go from there. 3 turns out on the pilot mix screws is a good start maybe less for the 28 hp motor. If you have brass floats 26mm is a good setting. If you have the black foam ones 22mm is what those use. If you carbs are over flowing still you my need to replace the float valves. Be careful as a lot of the cheaper aftermarket ones are an incorrect length and size. I had a set never seal and had to clean an old mikuni set which still works fine years later.

 

[Gra900]

Hi Chris, that’s really interesting. I have the black foam floats and have recently replaced the float valves (which were metal tipped ) with the ribber tipped version. I also replaced the original pilot jets. The replacements were not OEM, but measured up the same as the old ones.
I’m very tempted to put the older ones back in.

 

[xschris]

Yamaha used the rubber tipped ones from 80-82 here in the u.s. Do your carbs have screw in float valves or ones that press in with a o-ring.

 

[Gra900]

The float valves press in with an o-ring

 

[xschris]

Those need the rubber tip ones. Make sure yours are for the 80-82 sohc xs400 as the 82-84 dohc ones are different. Best to buy them in a matched set rather than getting just the needles.

 

[Gra900]

Yep will do. Just made sure the drilling’s from the reservoir to the pilot jet were clear.
Several photos may help.
1 block up air jet. NB picture shows wrong hole blocked, moved it down later
2 instal needle jet
3 remove pilot jet, turn around and feed into closely fitting tube. I used some leftover shrink fit
4 screw pilot and tube back into pilot jet,
5 fill syringe with vinegar and squirt through to where pilot injects into carb just by butterflies. There are 3 tiny holes near butterfly and the one the pilot jet uses
6 make sure there’s plenty of flow through

just need to put back on bike , again, and see how it goes

this is a long and smelly proces