Bike will not turn over

[stp1stp]

I don’t think it’s a fuel problem in the crankcase or the petcock. Change the oil and still won’t turn over. I think it’s electrical. I have good compression. I get spark but can you have weak spark? How do you test this? Is there a way to test the coils? Or the Ignite Unit? If they are bad would you get any spark? It cranks cranks, cranks, and just will not turn over. The battery will die after trying too long. Does anybody think it might be my battery but it does charge without any problems? The carbs are primed. The fuel flows with vacuum. I just can’t figure it out. Any help?

[frosty5011]

What's the battery voltage (a few hours after it's charged)?

You say petcock works when vacuum applied...how did you test? Do you have the vacuum hose hooked up to carb #2? (not to #3 as is the case with VM carbs).

Are the plugs wet with fuel after you tried to start it?

Have the carbs been cleaned, or are they all gunked up?

If you are getting spark, even if they're weak, it should still show some signs of wanting to start. From your info above, it sounds to me like it's not getting fuel through the carbs.

[Steve]

All good suggestions, but I will change one of them to what I feel is more important...

what is the battery voltage WHILE YOU ARE CRANKING?

If it is around 10 volts or lower, you are not getting enough power to the coils to fire the plugs. And, yes, you CAN have a weak spark. If your voltage is low, bring your car up to the bike and connect jumper cables to it. DO NOT HAVE THE ENGINE RUNNING. The larger battery in the car will power the bike starter without dropping as much, so it will show you if the bike is working. If that fixes your problem, get a new battery for the bike. I would suggest a sealed battery, they are only about $60 or so from your local Batteries Plus or equivalent.


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[stp1stp]

I sucked on the vacuum line myself and the fuel starts to flow. The lines are hooked up right. I completely clean the carbs. I’m fixing to take them off and check them to make sure nothing changed. Them bike was running for three straight days after changing all the gaskets and o-rings. Went about 20 miles each day. On the fourth day them bike just would not turn over. I took off the cam cover to discover that all the head bolts were loose. I don’t know how that happen, but it did. I torque them to specs. Do you think it could be the valves? If the valves were off would that keep the bike from starting? I don’t think the plugs are getting wet after I try to start it. I just checked and they didn’t seem to be getting wet. Maybe it is in the carbs but I don’t know how. It was running great until the fourth day. Back to the battery, I connected it to my truck and the same thing. For a second there I thought it turned over but I think it was my imagination. The battery voltage is 12.somthing.

[Steve]

I think you have solved the problem yourself. Look at the third sentence in your last post: "I completely clean the CRABS."

Loose head bolts are not a good sign. Depending on just HOW loose they were, you might have blown a head gasket.

Valves? If they are too loose, they are not open long enough to allow the proper amount of mixture into the cylinders. They would be noisy and not make much power, but it would at least run. If they are too tight, it won't be long before the valves get burned. The valves are not closed long enough (if at all) to transfer heat to the head, so they soften enough for damage to occur.

Battery. Was that 12.something volts while cranking while connected to the truck, or just with the bike. It is unusual for a bike battery to stay that high while cranking. I just tried to start my 850 to see what it does. Before turning on the key, the battery showed 12.6 volts. (This is a new sealed battery, purchased in May, this year.) I left the choke off so I would have to crank it for a while. While cranking, the voltage dropped to 10.7, then came back up to 12+ when I let go of the starter button. I had to leave the choke off as the bike usually starts VERY quickly. When going down the road, the voltmeter shows 14.3, so it charges well, too.


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[stp1stp]

Another thing I just tought of was that the air box was loose. Will too much air into the carbs keep it from starting? I check the battery at a stand still without cranking. I will check it cranking tomorrow. I don't know about everybody else but I hate with a passion putting back the carb and airbox into the frame. Why the hell did they make that area so damn tight?

[nabrams]

There is zero chance of the bike running properly with an airbox that's not installed properly, but it should at least start up. When you say the head bolts were loose (I'm assuming you don't mean the bolts for the cam cover) that could mean that a leak in the head gasket has developed (not the cam cover gasket). When I had a leak in my head gasket the bike was nearly impossible to start. When I replaced the gasket, the bike started instantly. See my other posts about how to detect a leaking head gasket.
Improper valve clearances (no clearance at all) will lead to very hard starting.
Have you actually checked/verified compression?

[stp1stp]

I checked compression on all cylinders and all were at about 160 to 150 psi. I went ahead and lifted the jig up and reapply gasket sealant to the crankcase gasket and the head gasket. And yes the head bolts were loose not the cam cover. My book says to be around 128 to 171 psi.

[nabrams]

Your compression numbers rule out the possibility of a significant head gasket leak. They also rule out insufficient valve clearance.
Now, you say the bike ran fine for several days before the problem.
Was that with a loose airbox? If that's the part of the equation that's changed then I'd fix that first and see if it solves the problem.
In any case, you can simply spray starter fluid into the carbs while cranking (via the airbbox, with air filter removed). If the bike roars to life, runs for a few seconds and then dies, then you'll know it's a fuel delivery and/or mixture issue.
And YES, it is possible that with the airbox disconnected the mixture is just too lean to have any hope of igniting.
Oh, and one more thing that may have suddenly changed: The cam chain may have jumped a tooth (as a result of being too loose), thus messing up the timing.

[stp1stp]

I’ll try the starter fluid tomorrow. I retimed it when I reapplied more gasket sealant to the crankcase gasket so it can’t be that. Maybe it’s the air box? Maybe it came loosen on the fourth day? I never did any adjustments to the air screws yet also. I’m also going to take off the fuel bowls and see if there is any visible change to the carbs. Thanks for the info everybody.

[stp1stp]

Update

\\/ Well everybody, finally got the bike to turn over. It must have been the air box. Air was getting around the air box side of the carbs into the carbs. The clamps were not tightening enough to get a good seal around the carbs. Thanks for everybody’s help. I try everything and never notice that the air box came off the carbs until I was ready pull the carbs out. I never knew that could cause the bike not to start until somebody mention it in the forums. I guess it was too lean. Now all I need to do is change the petcock because it’s leaking a little through the vacuum line. Then adjust the carbs and I should be good to go.
Thanks:-D