Another "my bike doesn't start" thread.

My 81 xj650 ran ok last winter when I parked it (outside). This spring, I decided to clean the carbs again. I usually do them every spring, but I missed last year, and the bike was starting to act like it.
So I cleaned them like I always do. This time around, I opted for new throttle shaft seals, and all new stainless hardware. I wet set the float height, and here is where I have my only real clue: The fuel level in all the carbs was too high. I had to bend all the tangs about 1/16" to get the fuel level in spec. I opted for the lower side of spec, closer to 4mm, because I live at higher elevation. Still in spec, just on the low side. The only other things I can think of that's different now than when I took them apart is I set the pilot mixture screws all to 3 turns out, and of course the sync has been tampered with; I did a look-at-the-holes bench sync.

So I got the whole thing back together, expecting it to fire right up, and nothing. No pops, no wheeze, no backfire, just nothing.

I sprayed some starter fluid into the airbox and it fired up, and I could ride it around running on the starter fluid. When the starter fluid was mostly used up in the airbox, I could ride it around and the choke almost acted like the throttle, which seems odd to me. Choke closed (warm engine) was like 0 throttle, and opening the choke would add power. Then all the starter fluid would be used up, and it would die with no signs of life.

I checked the compression and did a leak down, 1, 2, and 4 are perfect. 3 is crappy, but it's always been. With 3 good cylinders, I'd expect there being some signs of life. Plugs look good, nice purple spark. Tonight I had the realization that the gas may have gotten water in it, sitting outside all winter. I drained the carbs and put new gas in, and still nothing. I thought the symptoms sounded like lean running (only would run with choke) so I pulled off a carb-to-airbox manifold, and I tried covering the intake with my hand. This draws a lot of fuel into the engine, but there was still nothing! I put a spurt of starter fluid right into the carb there, and that made the one cylinder fire perfect.
I guess I should've already pulled the carbs off before writing all this, but I'm 99% sure I got them together right. Or at least I was when I installed them haha.

 

4mm would push bike to the lean side

sounds like pilot jet circuit is clogged if it will run on choke

does bike respond to throttle when it is running?
how far did you dissemble carbs? all fuel jets removed?
air jets removed?
mixture screws removed?

read this
Setting the fuel levels

 

I agree that 4mm would be leaner, but I still expect it to run, at least with the choke on. I can't believe that all 4 pilot circuits would be clogged that it wouldn't run, and also it only runs with the choke on if there's starting fluid. It wont run or even show any signs of life with just the choke. The bike doesn't run on only gas, but when it was running on starting fluid, throttle barley made any difference. The only thing that affected engine RPM was the choke.

I've verified that the choke and throttle cables are installed correctly.
I completely disassembled the carbs, so that I could change the throttle shaft seals.
The air jets were removed. I'm aware that the haynes manual has them incorrect; I'm 99% sure I reassembled them correct. Main, small, goes in middle of the 3 holes.
The mixture screws were removed and I replaced the O-Rings. They're all set at 3 turns out.

I'm pulling my hair out, I guess the last thing I have to do is to put the fuel level at the higher side of spec, closer to 2 mm.

 

you did a bench sync sounds like you got it right.
you know you have fuel to carbs because you drained the bowls.
bike starts on starter fluid so battery should be good.
3 things that have changed wet set and mixture screws set to 3 turns from soft bottom.
oem or aftermarket throttle shaft seals? if oem ,Installed correct direction?.These V-shaped seals are installed with their open “face” facing away from the carb throat. The OEM seals (HCP6838B) have one open face and one closed face, while the aftermarket HCP38B seals are like the original-installed seals, and have an “open” face on both sides (and thus for these aftermarket seals, it does not matter in which direction they are installed!).
Replacing your Hitachi throttle shaft seals
are throttle and choke cables in correct location, not reversed?


did you make sure the enrichment wells were clear in the bowls?

how much fuel in the tank?

fuel filter?

 

I pulled the carbs back off tonight to check my work, and I think I may have my answer.
First picture is verifying the float height with the tube I used when I set the float heights. It's a smaller diameter tube, and I believe the capillary action causes the fuel level to read higher.
Second is a vent tube off of an old battery. The float tang wasn't adjusted between the two pictures.
https://imgur.com/a/W8dtMFc

If the diameter of the tube matters this much, perhaps we should hunt down an original yamaha special tool, and see what the ID and material is. The haynes says to use a 6mm tube, which is about 15/64. I wonder if the brits refer to the tube ID or OD when describing it's diameter...

I'll update this when I get the fuel levels set with the bigger diameter tube, and everything reinstalled. I'm going to the stealership tomorrow to check out an R1, so it might be a few days

Thanks for your help XJ550H

 

www.xj4ever.com sells the fuel level tube with graduations on it. fuel lines are 6mm id so it would stand to reason that 6mm id is the size

tubing is generaly listed by id