Time to replace the coil packs?

Shdwdrgn post=927688 userid=41747Think the carbs are ready to test, but when I went to check the (dry) float heights, they're supposed to be at 18.6mm, however every one of them was actually about 5mm higher than that.  I have had a constant issue with fuel flooding into the air intake chamber and suspect this could be a cause?  However when I first built the bike I did in fact have a rig on the workbench and took the time to adjust the floats using a clear tube from the drain nipple.

I can't find the old coffee can I had rigged as a temporary gas reservoir, so I'm getting a small fuel tank ordered off Amazon that has the same 1/4" connector on it, hopefully will arrive tomorrow.  Then I can see where the fuel actually sits (and confirm all of the valves are still working correctly).

   That sounds like the tiny spring loaded pins in the float needles are stuck in the depressed position.  Confirm that the needle pins are free to move before proceeding with clear tube adjustment.

   That said, we don't pay much attention to float height measured on a scale.  Those crude old floats with flexible metal frames don't have the consistency of stiff, modern floats that are relatively quite precise by comparison.   +/- a couple mm at the dry float bulb should be well within in range of clear tube fine tuning.  "...supposed to be at 18.6mm, ..."  Trying to split into tenths of a mm seems futile.  The differences in stationary fuel level will be insignificant between say, 18.5mm and 18.6mm dry float height.  Fuel is constantly moving around in the bowls when being ridden, so a rough average is the best that can be expected.

   Aftermarket float needles and needle seats can have a surprisingly large effect on fuel level too.

   No one has mentioned choke plungers yet.  Plungers leaking when closed will contribute to rich running when when fuel level is correct.

   Vintage carbs offer many lessons for the vintage bike enthusiast.  Patience and tolerance of frustration have been two of the most important for us.

   We documented our development over the past few years of a process that eases setting wet fuel height.  It's a variation of clear tube fuel level tuning that makes fuel level easy to visualize and adjust and, adds safety by using a less-volatile gasoline substitute when working in an indoor shop.  It's a fairly long thread.  Something within may be of help:
www.kzrider.com/forum/3-carburetor/61368...n-setting-fuel-level

Good Ridin'
slmjim & Z1BEBE

bound wrote:

I believe that an old bike just needs some time and elbow grease. I really hope that you are able to get the float levels figured out. I had the same problem!!!

Looks like my browser crashed before it saved my reply here last night...  But yeah, it's a good old bike, I practically scratch-built it combining parts and frames from two bikes that had been chopped up, so I already adjusted the floats once years ago.  I don't know if I simply didn't do it right or if the valves needed time to "break in" to get an accurate measurement, but I was surprised at how far off they seemed to be.  I'll get it figured out though.

@slmjim+Z1BEBE Yeah I also thought it was odd that this would be given in fractions of a mm, especially when the tolerance is supposed to be 1-3mm below the gasket?  So it's not THAT critical and I'm certainly not going to get them accurate down to 0.1mm  I save that nonsense for the 3D printer where 0.02mm actually makes a difference.

Anyway, just came back in from checking the fuel level in the bowls.  All four valves seem to be working correctly and shutting off the flow when full.  I thought it was odd the measurements were all in a line but the last one broke the trend.  In order from left to right they measured at 1mm, 2mm, 3mm, -2mm (this one was above the gasket line).  But that means the roughly 22-23mm height the floats were originally at is definitely way above the line.

So now the bowls have been drained again and I left the bank of carbs laying on its side to air out, and tomorrow after work I'll try to get the bowls off again so I can make a final adjustment of the floats.  I think #1 and #2 are in pretty good shape, just need to touch #3 and #4.

And maybe someone can check my process here, but I think it's pretty straightforward?  On each bowl I hooked the clear tubing and opened up the bleed screw a couple turns while keeping the other end of the tubing above the carbs.  This allowed a little fuel into the line but trapped an air bubble each time right at the drain nipple, so I raised up the end of the tubing a little which forced the bubble back up into the bowl.  Then as I dropped the tubing back down again making sure it stayed full of fuel with no air.  At this point I held the ruler up to the side of the carb and dropped the end of the tubing down another inch or so, then held it in place for a moment as the fuel level filled up and stabilized, and that's what I measured against the bottom side of the gasket.  Does that sound about right?

   If the results are repeatable over multiple tries you're on the right track.

Good Ridin'
slmjim & Z1BEBE

Huzzah!  Finished checking the float levels then fought with getting the carbs back on the bike again.  Those rear rubber boots are always such a pain.  I used my temporary tank to supply the engine, and it just started right up without so much as even being choked.  Ran it for a couple minutes until it started warming up and it just kept going smoothly.  Seriously, it has NEVER run like that before, especially not from a cold start.

So I had to shut it down because the old fuel filter (or possibly the line?) was leaking gas onto the engine and I forgot to pick up a new one.  Will try to remember to stop on my way home from work tomorrow.  I want to keep the small temporary tank on the bike for the moment because I'm sure I'll need to readjust the idle screws again and I need to find that article from here on how to do that process with a single vacuum gauge.  I suspect that will go a lot easier this time as well -- then it'll be time to put the tank back on and see how she performs.

Fall is here, but I'm still really excited!

[EDIT] Found it!!!   kzrider.com/forum/3-carburetor/593426-ca...-single-vacuum-gauge

Grabbed a new filter today and ran the bike for a few minutes after resetting the air mixture screws all back to 2 turns (hoping to sync them tomorrow, but they ranged from 2.5 turns to 5 full turns open, which is probably another indication of how badly things were sitting before).  Once again it started easily without even being choked, so we'll see what that means once I get the engine up to full temperature.

Meanwhile, a bit of disappointment.  As the bike was heating up, it started to do the same thing as at the beginning of this thread -- the throttle climbed up to about 3000rpm and it started backfiring again so I started adjusting the idle screw to bring it down, and once it got below 2000rpm it died.  It's like once the engine warms up it simply doesn't want to run at a low RPM, and yet when I first started it and it was still cold, it ran nice and smooth at 1000rpm.  At least now it is starting under its own power without jumper cables, and I can immediately restart it, but what gives?  Does this type of operation tell anyone anything?

I'm not surprised by the throttle increasing as it warms up.  I fully expect that the idle screw is set too high now, and when I can properly set it back to a correct level I will once again need to choke it for cold starts.  However I do not expect the engine to just suddenly die as I try to bring the speed back down.  I'm tempted to throw some seafoam in the gas to see if it flushes out anything still gunking up the carbs but I wanted to check here first for other ideas.

Did anyone ever mention checking for air leaks? On my 550 when I had an air leak it had very similar symptoms. It would heat up then it would start revving up then when I tried to lower the idle the rpms would just plummet and barely idle. Popping and backfiring are symptoms of running lean. If you have propane laying around you could check that way by spraying it around the carb holders. Sometimes you can even hear it.

Hmm I do have one vacuum line open right now (the one that is supposed to go to the gas tank) but I wouldn't expect that to affect the other three cylinders.  Hopefully not an air leak around the rubber boots since I completely pulled and re-seated the carbs.  I also don't currently have an air filter in place, but the previous air filter was so plugged up that I thought maybe it wasn't pulling any air at all.  Going to give it another test run at lunch to see what happens.

Shdwdrgn wrote:

Hmm I do have one vacuum line open right now (the one that is supposed to go to the gas tank) but I wouldn't expect that to affect the other three cylinders.  Hopefully not an air leak around the rubber boots since I completely pulled and re-seated the carbs.  I also don't currently have an air filter in place, but the previous air filter was so plugged up that I thought maybe it wasn't pulling any air at all.  Going to give it another test run at lunch to see what happens.

All vacuum ports on the carbs need to be plugged otherwise your bike will otherwise run like $#@+!!!! No air filter will make the bike run lean.
 

Wow I didn't realize it was so sensitive to the vacuum.  While I was running it and checking things tonight it started revving up again and I realized I forgot to reattach one of the lines.  Running somewhat ok with everything plugged up now.  I managed to run it up and down the street a little with my temporary tank, I'm sure that was quite a sight.

And then the clutch cable broke.  <groan>  Well I suspected it had been stretching out so I was terribly surprised, and I guess I couldn't have asked for any better timing then when I was headed right for my driveway anyway.  Good news is I actually had a spare left over from the original build, so if I can get it on the bike tomorrow then I only need to put the gas tank back on again and I'll be ready to ride around town and see how it runs.

Sat-Sun are the last days of 80s in the forecast, then it drops into the 60s next week, so this is my last hurrah for a nice ride, even if I don't expect to go very far.

Shdwdrgn wrote:

Hmm I do have one vacuum line open right now (the one that is supposed to go to the gas tank) but I wouldn't expect that to affect the other three cylinders.  Hopefully not an air leak around the rubber boots since I completely pulled and re-seated the carbs.  I also don't currently have an air filter in place, but the previous air filter was so plugged up that I thought maybe it wasn't pulling any air at all.  Going to give it another test run at lunch to see what happens.

Is the air box installed with the element removed or are the carbs running open ?

At the time I posted that, the airbox was installed but there was no air filter in it.  I have everything back in place now.