Topic: Bike won't start

[Wayne Meuir]

Bike is a 78 750F.  I rebuilt the carbs and put them back on the bike and it fired right up but was running pretty ragged because the carbs were not synced, timing and stuff not done. I actually rode the bike but it was really not running very well.
I discovered the old hardened carb boots were leaking, so I bought new ones, set the timing, adjusted the timing chain, adjusted the valves. Compression is between 142 and 147 across all 4 cylinders. Dyna S Ignition. That was a couple of weeks ago.

Today I reinstalled the carbs and hooked up the Morgan Carb Tune guages so I could sync the carbs and the bike will not start. Pulled one of the plugs and checked to see if it is firing, and there is a bright, strong spark. When I operate the throttle, the accelerator pump squirts fuel in all 4 carbs, and if I give it a few shots of fuel like that with the accel. pump, it will start immediately and then die just as quickly. 
Any suggestions?

Wayne

[KingCustomCycles.com]

Drop the bowls (again) and look for dislodged sediment.  These carbs need cleaned many times if the galleys had dried gunk in them and you missed it.  I vote for plugged idle jets.  Your ability to start with accel pump fuel and then dying speaks of fuel starvation at idle.

[mattcb350f]

Is zee choke cable hooked up? gotta ask um anyway  

 Matt.

[OldSchool_IsCool]

blocked/kinked fuel line or filter?  Petcock turned on?  No fuel in tank?  Sometimes its the simple things.

[Wayne Meuir]

I am using a remote take with brand new fuel line, no kinks.  I have an inline filter that I put on when I first rebuilt the carbs, but I don't think that is the problem since the squirters on the accel pump are working, I have to assume gas in getting into the carbs.

I guess I will have to pull the sob's back off again and pull the float bowls and pilots out.  I already removed the sync guages and put the vacuum plugs back in the carbs just to be sure it was not a vacuum leak.

Wayne

[scondon]

Your carbs have drain screws. Switch your remote tank off, and open those drain screws one by one. Catch the gas in a measuring cup and see if you have equal fuel in all of them. The way you describe your bike dying instantly I would guess that one or more of your bowls have little to no gas in them at all.

      It may be a float level or clogged jet problem, or it may just be a fuel delivery issue. Be good to know if it's just a fuel delivery issue before going through the trouble of yanking the carbs off

[scondon]

 Also, I've learned an easy trick for removing those float bowls without yanking the carbs.

Tools: A socket wrench, a short extension, a 1/4" socket(5/16"? I forget), and one of those interchangeable phillip bits you find in electric or multi-purpose screwdrivers.

   Assemble the wrench, extension, and socket, then place the bit in the socket.  Voila! a right angle screwdriver. Make sure that the bit you use fits the phillip heads nice and snug. If it's a sloppy fit you may end up stripping your screw heads

[Hush]

Or do what I did and replace them all with hex nut screws, damn easy to drop the bowls when you only need an Allen key.

[Wayne Meuir]

Thanks, guys, I will drain them and see if one of them is not getting fuel like it should.  If I use clear tubing to check the setting on the floats, should the fuel level be just below the bowl parting line?

These carbs have the pressed in pilots, but I pulled them out with pliers and cleaned them.  They felt tight when I reinstalled them, but I guess its possible that thye came loose and are laying in the float bowl.  Still looks to me like the bike would run at high rpm even if the pilots were stopped up, AND, what are the chances that all 4 of the pilots suddenly got stopped up at the same time?

Wayne

[scondon]

Still looks to me like the bike would run at high rpm even if the pilots were stopped up

 This is what lead me to think that it was something other than pilot problems. "dies at idle" "hard to keep running at low rpm's" would describe a pilot problem. "Won't run at all unless fuel is sprayed directly into carbs" sounds like something else

 I set my levels at 1/16" below the bowl gasket line and have good running results. When they were set lower, around 3/16", I had problems. Much higher than the gasket line and rich mixture or overflow troubles may occur.

  The floats in these carbs are kind of counter-intuitive. The flat side faces down into the bowl/fuel, and the curved side faces up. If any were installed upside down then that would certainly explain things and be an easy fix.

[Duke McDukiedook]

How is that inline filter oriented? vertically? Do you have a clean tank (lined?) Petcock filter? If you have the latter two you don't really need the inline filter.

[Wayne Meuir]

Scondon, I will check the fuel level first, then pull the bowls and see what I find.  I know the floats are not upside down becasue I used the flat bottom to set the height when I had them apart.

Dukiedook, I am using a remote plastic tank that I bought for just this purpose.  it is perfectly clean and simply has a ball valve for a cut off.  Using clear line so I can see it flow.  The stock tank, however, is perfectly clean.  When I first got the bike I pulled the old petcock off because it was leaking and there was not even any sediment collected around the inside of it.  I flushed the tank anyway and drained everything into a plstic bucket so I could see what was in it and it was clean as a whistle. 

WAyne

[Wayne Meuir]

OK here's where I am now:

Using clear tubing I checked the fuel level.  On all four carbs, it was right at the bottom of the flange on the float bowls gasket surface which is about 1/8" below the parting line.

I pulled the carbs off, float and everything intact, floats are in correctly, needles and seats seem to be working as they should to open and close fuel flow.  I pumped the accelerator pump by hand with fuel in the float bowl and it squirted fuel out the feed hole in the top of the float bowl (where the small o-ring sits)as it should.  Pulled and inspected the mains and they are clear.  Have not pulled the pilots again because they are the pressed in type and I already took them out once, don't know if I can get away with doing it again and have them still fit tight enough to say in place.

I took the bowls off with the carbs setting straight up so I could see the fuel in the bowls after I got them off and everything was perfectly clean with no sediment in bowl at all.

Soooo-what do I look for now?

Can I get away with pulling the pilots and reinspecting them?

These carbs suck!  Or I suck!  One or the other!!!

[scondon]

 Everything sounds good Wayne. You can pull those pilot jets and clean the passages again while your in there just to be sure.

Only other thing I can think of is to make sure that your overall idle speed screw is tightened in somewhat. If it's backed out too much then the bike will die as soon as the throttle is released. I usually crank mine in a lot when starting a bike w/carb work for the first time.

 I'm kinda stumped too

[mattcb350f]

One thing I noticed Wayne about the F2 is that it is incredibly lean to start with. Compared to starting my 350F, the 750F2 needs a lot of choke and persuasion to get running, especially when it's cold out.

I started my fathers F2 a while back when it was about 28F out and it was all it could do to idle with full choke and I still had to pump a bit of fuel into it with some throttle blips to keep it running. Once it warmed up after about 5 minutes I could start to take the choke off. There is nothing wrong with this bike, it's just that the mixture is leaned soo much on these bikes which is why they use an accelerator pump.

If it's cold out, even if the carbs are working, it probably won't want to start up and idle nice like you think it should 

At least now, you know the carbs are in good order.

 Matt.

[Wayne Meuir]

Well, I could not find anything wrong with the carbs, so I put them back on the bike and it fired right up.  It is idleing pretty rough, but will idle at about 1100-1200 RPM with out dying.  It is sorta spitting back on #4, don"t really know why, compression on #4 was 147, so I think the valves are holding fine.  The timing chain is really noisy, I hope its is not loose enough to make it run out of time but that is almost what it sounds like.  I adjusted the timing chain according to the manual and gave the adjuster just a slight amount of help to get it just a little tighter, but its still raising hell.
I will sync the carbs tomorrow and see if that smoothes it out and/or quitens it down.

Thanks for the help, guys.

Wayne