float levels/ engine starting

Just set the float levels on my carbs, cause I bought new float valves and needles. I think I messed up, because the engine's not firing anymore (it was before I took the carbs off).

I set the levels in the carbs off the bike, on the bike they now seem to be a few millimeters shy of the recommended 3mm below the gasket.

Only thing I can figure is either the carbs aren't getting any gas to the engine or they're flooding it. If they were flooding it, wouldn't the spark plugs be wet? They're not.

Probably just user error/ not enough (good) beer.

 

Yes they should be wet. If the choke is on then they still should be wet despite the low float level. The choke pulls fuel from the botton of the float bowl while the idle jet pulls from the top. Remember that brass tube that sticks into the small hole in the float bowl? That is the feeder tube for the choke. If that hole in the float bowl is clogged that maybe the problem. Most likely it is that the pilot mixture screw is turned in too much and the idle mix is too lean to start the bike.
Remember on the float level you have + or - 1mm. So 4m should be ok but I wouldn't stay with that. I would rather be on the + side than the -. I would also make sure there is sufficient fuel in the tank since some may have been removed for the float level setting. you may need to just set it to pri for a bit to fill the carb bowls and then switch to res to make sure you have a supply of fuel.
The pilot mixture screws should have been set by turning them in all the way gently so as not to damage their delicate tips and then turning out 2.5 to 3 full turns.

 

My levels were all over the place, and the only place they caused an issue was in the fine tweaking.

Did you get the "choke" cable hooked back up? Hardest time I ever had was when I forgot to connect mine.

 

The choke cable is hooked up, but could it be possible that it's too loose, not pulling the cold start plungers up far enough? It's moving them, but maybe not enough. I set the idle mix screws to 3.25 full turns each before I put the carbs back on, that's about what they were when I got the bike.

The brass feeder tube, does it go straight from the bottom of the bowl to the cold start plungers? In other words, could I clean them again without removing the carbs? I'm getting pretty tired of taking the things off.

Could it be a loss of vacuum somewhere, so the cylinders aren't pulling in fuel? I put on new intake boots - maybe they aren't sealing airtight on the carbs...

As a general rule, the float levels aren't critical for starting the bike, just fine tuning it, right?

 

Oh, and the headlight usually comes on only the first time of the day I try to start the engine, after it's been sitting all night. After that, if I turn off the bike to charge the battery, the light doesn't come back on on any of my further attempts to start the engine. The first try is the only time the engine actually sounds like it's going to start, also. Maybe a clue?

What the %$^& is going on? This thing was running before I installed new float valves and changed the level. Now it's not even getting gas in the cylinders.

 

I'll leave the headlight issue to someone who knows the 650 electrical systems. On the carbs you would have to remove the carbs to clean the feeder tube. It requires float bowl removal which isn't possible for all bowls due to the alternator being in the way.
A loss of vacuum is possible. Only location for that is the petcock. There are two lines that attach to it. One is fuel from the tank and the other is vacuum from the #3 intake. If that line is cracked or off then no fuel will flow except with the petcock set to "pri".

 

Yeah, I guess I already knew that I can't clean the cold starts on the bike. I'm just in denial - I've cleaned them already, and taken the carbs on and off the bike half a dozen times in the last two weeks.

My dad stepped in. Being an old school sort of fellow, he unloaded half a can of ether in the airbox and started her up. We both survived the explosion, put out all the fires we could find, and the bike ran nicely after that.

That was a few hours ago. I wonder if we just sidestepped possible coldstart issues by using the starter fluid. Guess I'll see tomorrow.

 

Your headlight won't come on until the alternator starts producing electricity. It doesn't take much so just a single cylinder firing one time will do it.

That's why the light only comes on that first try, when the bike sounds like it wants to start.

So do I understand that your bike ran fine after starting on ether?

 

I wouldn't say fine. We had to work the throttle for a little while before it would idle on its own. After that it idled nicely right around 1000-1100 for a while, maybe two or three minutes, then died. During that time there was some smoke in one of the exhausts. Then it died.

Had a bite to eat, read a good book, came back a few hours later (it was the weekend, no need to rush these things). Again, the bike would not start w/o ether. That time, it would not idle at all. Couldn't get it to fire again after it died the first time. And it was backfiring, I believe.

And now, cause I needed a break, I've been working on that bike for two months to get it to this point, I dropped it off at my local yamaha dealer to have a look. I know, I know. Sellout.