1981 Yamaha XJ650LH Maxim Carburetor Flooding (Hitatchi HCS 32)

I have a 1981 Yamaha XJ650LH Maxim that I'm working on for my neighbor. The bike was expelling fuel out the rear throats of the carburetors. I immediately looked to the float needles and seats. The bike appears to have aftermarket needles and seats, and they do seal when the floats are lifted with my fingers. I'm at the point where I don't think the plastic floats have enough buyonacy to lift the float needles to shut off fuel flow. I went so far as to individually dunk the floats in gasoline. I was not impressed with the buyonacy of any of them. Even after excessively lowering the floats, it's hit or miss. There's absolutely no consistency . It's also worth noting that the floats seem to have excessive play side-to-side.

I'm not new to this nor is my friend who I called in to assist. We've both worked in dealership service departments for many years. We've checked for damage, corrosion...you name it. This is the first time a set of carburetors have seemingly defeated either of us. Floats aside, I'm not too keen on aftermarket parts. Unfortunately, Yamaha offers nothing in the way of parts any longer.

I was wondering if anyone else has had a similar problem and if a solution was found.

 

Get correct one from chacal @xj4ever, Len has the correct ones on hand at all times and gets them to you fast. That goes for any parts for an XJ. If he doesn't have them you probably can't buy them anymore.
Baseline float level is 17mm from mating surfaces carbs tilted at 45*

 

Only to add to what toomanybikes replied, be sure to wet set them after assembly as well. Out of 8 floats I only had to adjust 2 during the wet set but I was glad I checked them

 

I have yet to see an OEM Hitachi float fail (the construction of them precludes failure). The float height is likely off, or they are not the correct floats for the carbs (likely due to the excessive play).
Wet set is required.
Setting the fuel levels

 

maybe in upside down?

 

One of the few carbs on the planet that floats will fit upside down.
Have seen that a few times

 

I'd like to thank everyone for your responses. I'm going to take a photo of the current set-up. Is there any way to verify if the float assemblies are correct, e.g., a stamping? Also, my brother owned a 1982 model with YICS. If I recall correctly, it had the same carburetors. Whatever the case, I remember the float pins (looked a bit like a nail) being almost a tolerance fit, and having to had to remove them with kid gloves as not to brake either or both arms where the float pin sits.

I see very inexpensive float needle and seat sets on E-Bay. I can't help but wonder if inferior or incorrect parts were installed. Well, I'll be off to the shop tomorrow to take some pictures and do some more studying.

 

this link has photos of upside down and correct install of floats


Setting the fuel levels

 

IME, slightly press-fit float pins are in the Mikunis. The Hitachi ones are loose.

 

so loose the move back and forth on hatachi carbs

 

Sometimes.

 

Yes. They are held in place by the float bowl wall, and, once the bowl is off, they just drop out. For the Mikuni ones, I made a special pair of pliers to press them out and in.