WTF

So:

Xj750 41y was running fine with exception of leaking inlet boots.

My inlet boots were leaking at the joint between cylenders and boot. so i put loctite gasket maker on the inlet gaskets.

Put everything back and now cyl 2 and 3 are not running!!??

-changed coils but no difference
-cleaned carbs (maybe gasket sealer got into the jets)

But still 2 and 3 are not running.

What the hell could have happened? The cyl 2 and 3 were running fine before putting gasket maker on the inlet seals..

 

could be the leaks made fuel mixture correct to run.
check mixture screws for adjustment . try syncing carbs or start with re bench syncing carbs.
turn in idle adjustment

maybe some gasket got between the valve seat and valve

 

Could be the leaks made fuel mixture correct to run.

I had not thought of that, good point a vacuum leak with mixture screws incorrectly adjusted and correcting the leak throws the mixture off. I was thinking perhaps there was a loose ignition wire on the low tension side of the coil for 2-3 unlikely if it was running before and he changed the coils.

 

Is there still spark? 2/3 share the same coil so it seems like an odd coincidence to me.

 

Yep still a spark, i checked that.

I checked the mixture screws, they are the same for all carbs.

Carbs were rebuild 100km before anyway.

Really weird..

 

Are the spark plugs on 2 and 3 wet with fuel? If so you could try drying them off and refit them in case they are fouled?