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Yet another "starting problems" post....

  • Thread starter Thread starter bexabarr
  • Start date Start date
B

bexabarr

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I?m having a bit of a problem starting my bike. It is a 1979 GS550L with 10,000 miles. I rebuilt the carbs, thoroughly cleaning them and replacing the o-rings. I have also replaced the intake boot o-rings. I have checked the valve clearances, and found a few a bit tight and others a bit loose (nothing that I think will affect the bike starting), I have not got around to changing them because of monetary issues. I have replaced the points and set them correctly (I did not replace the condenser). The spark plug boots seem a little worn, but they still let a nice blue spark through (from what I can tell).

I personally think that it is the carbs. The floats are set at 24mm (as recommended on this site) and the manual says to set them at 26mm. I checked the petcock just in case and it is functioning well. When I drain the fuel from the carb bowl, it seems that there they don?t have enough fuel (but then again, I don?t know how much fuel should be in there in the first place).

The battery has a low voltage and I have to replace it. But I did hook it up to my car battery (without the car running of course) and nothing. I also have a kick starter on my bike? I don?t know if that generates enough current or not, but I?ve also tried starting it with that.

Anyone have any ideas? Thanks!
 
"and nothing"? Do you mean that the starter motor won't run with the car battery jumped to your motorcycle battery?
 
The starter engaged fine... I just can't get the bike to startup. oh and I have VM carbs. Thanks.
 
Turn the petcock to PRIME for 10 seconds or so before you start the bike. This way you know you have enough gas. Unless there are plugged up filters preventing that.
 
Hi, I just checked the carb level (wet method) and they are getting enough fuel. The bike to my surprise actually started, but I had to keep it going with the throttle. When I took the choke off, it got a little better. It smoked a little, not much. I heard a back fire. Then the bike died (run time only about 45 sec) and now It doesn't want to start back up. Ideas?
 
I just went out, and noticed that only cylinders 1 and 2 are warm. umm. what about the fuel screw underneath the carbs?
 
That's your idle adj screw. Has nothing to do with fuel delivery.

This can be different things. Maybe you're not getting a good spark to 3&4, or maybe 3&4 carbs have plugged idle circuits. Maybe the choke is only actuating 1&2. I'd start with the choke.
 
flyingace said:
That's your idle adj screw. Has nothing to do with fuel delivery.
Click to expand...

I meant the screws that come off the carb bowls (I have them turned out 1 turn). I think these screws are unique to vm carbs, and regulate fuel during low rmps. Not sure though.
 
Could be a lot of things, but since you say you did some carb and points work, try these easy/basic things and see what happens.
The most work here is a bench synch for the carbs. This is mandatory in my opinion. A poor synch will not allow the bike to start easily, if at all. The bench synch should then be followed by a vacuum tool synch, but AT LEAST do the bench synch as best you can. Do a search for the VM bench synch and you'll find my detailed post on how to do it.
Pre-set the side air screws to 1 3/4 turns out. If you get the bike running decent later, fine tune them by using the "highest rpm method".
Pre-set the pilot fuel screws (underneath) to 1 full turn out as a starting point. Fine tuning will most likely be necessary later. Never seat these screws tight. Only seat them lightly! Use a good fitting tool to avoid stripping the air and pilot fuel screws. They may be stiff.
Make sure the two floatbowl vent lines are clear and not kinked.
Be sure the air filter is clean.
Make sure your battery is charged well and filled correctly with distilled water. Check the posts for being clean and tight connections.
Be sure plugs are the correct heat range and are gapped correctly.
Remove plugs, slowly rotate the crank and check that you timed the ignition right. You said the points dwell was set I believe.
If you get it running, get a timing gun and double check the ignition timing and advancer mechanism for operation. Check timing/advancer at about 2,500 rpm's so you know the advancer is fully operating.
East stuff to do, though the carb synch requires removal.

And by the way...you mentioned a couple of tight valve clearances but lack of funds to repair. Tight valve clearances, such as less than .03mm (I believe on your model), will cause you to burn a valve down the road. This will cost you much more than a couple of correct thickness shims. You may even be able to swap the tight valve shims with the ones you said were loose. Don't run the bike with tight valve clearances.
 
Thanks Keith!

Your post are always thorough and extremely comprehensive. I did a bench sync prior to installation, but I'm going to do it again. I plan to get my shims changed soon, (sooner now that you have mentioned their importance). I just went out, and found that spark plugs 2 and 3 did not fire, but seemed to be a bit moist with gas. Prior to removing the carbs I plan to switch spark plugs 1 and 2 over to 2 and 3 and see if that shifts the problem. I suppose that the condensers are fine since the bike did start, right?

Thanks again guys, I wish you all the best!
 
well... I switched the spark plugs... and the problem shifted... I should of done this before I posted but I was so convinced it was the carbs, that I did not. I'm going to get new spark plugs soon (I bought some two weeks ago, but I guess they've already gone bad which worries me). The carbs are carbon sooted (rich mixture right?), and the bike blows a bit of smoke. I assume and hope that this is because I'm running it on choke.

Thanks again.
 
If 2 and 3 aren't firing, try cleaning the plugs in case they're just fouled. Check again for spark at 2 and 3. If firing, do the stuff I suggested before and then test.
If not firing, then take the plugs that are firing at 1 and 4 and try them in the 2 and 3 plug caps. If the swapped plugs do fire, then the other plugs need a better cleaning or replacement, unless you have some poor cap connections and just moving things around is giving a temporary better connection. At this time, I suggest checking all the caps for clean/solid connections. Snip off any green/corroded copper ends.
If the swapped plugs (known to fire before) don't fire either, you need to check your coil terminals for clean/tight connections. Check for wire strand breakage at the connector ends. If any problems found, repair and test.
If all connections look good, check for correct voltage at the coil terminals. Check resistance (ohms) across the 2 and 3 plug caps.
Be sure the battery is supplying correct range voltage before taking any reads.
 
Oh. Just noticed your 3:24 post. Didn't see it before, just your earlier 3:22 post.
You can still try what I said though.
 
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