Bike not turning over

[stp1stp]

About 3 weeks ago I replaced all the gaskets and o rings in the engine. Clean the carbs. Put new sprocket and chain on. When I was all done the bike started right up. A little back firing that I think is coming from cy. 2. I think the petcock is bad and is pulling a little fuel through vacuum. I rode the bike about 20 miles for there days strait. On the fourth day the bike would not turn over. Went ahead and checked to see if the timing is still right. Notice when I was taking the valve cover off that the bolts were a little loose. Further inspection and all the head bolts were loose. Went ahead and lifted the jig up a little and reapply gasket sealant to the crankcase gasket. Torque the head bolts down to specs (again). Put it all back together and it still will not start. Any suggestion?

[chef1366]

Check compression. You have an 80 petcock which requires vacuum to run on prime and run. Slot up and down is prime, back and forth is run. Check your gas flow on prime and run while applying vacuum to your petcock. I had to replace mine because it was a pos.

[stp1stp]

I just bought a compressin gauge yeasterday. It came with no instruction and I never used one. Does the bike need to be running the check it? Do you just screw the hose into spark plug hole?

[stp1stp]

The petcock works great. I disconnect the fuel line and suck on the vacuum line and gas started pouring out. I hooked up the vacuum line to the carb and gas came out. Fuel will not flow without vacuum. But after a 20 mile run I disconnect the vacuum line and there will be a little fuel in the line. That is where I think the back firing is coming from and why I think the petcock is bad. But that should have nothing to do with it not starting. The fuel bowls are full.

[chef1366]

Your bike doesn't have to be running to check compression but it really should be warmed up. But if it won't start you can only get a rough ideal if the bike has compression or not. Take out the spark plugs and apply the compression tool to spark plug hole and twist the throttle open all the way and hit the starter button until the guage needle stops rising.

[relic-rider]

Check your oil in the crankcase. Does it smell of gas? If the petcock leaks or the needles don't shut off completely, you will get raw gas into your engine. Sometimes if there is too much leaking into the combustion chamber or crankcase, the engine will hydro lock. That will make it stop dead and not crank over as the liquid gas does not compress. I had this happen twice and had both a bad petcock and a couple of leaky needles and seats. Something to check. If there is gas in the oil , change it, and fix the problem or it will happen again.

[stp1stp]

Just finish checking compression. Did not have the throttle open though. I Should read the replies before going outside. They were all at 160 except cy. 2, it was at 150. I think it's in pounds. There might be gas in the crankcase. Can you just pour a little oil in a jar and the gas will be noticeable? If that is the case that really sucks seeing how I just put in Rotella 5w-40 Synth Oil which was twice as much as any other oil.

[relic-rider]

Sucks doesn't it. Three times I went out to the garage and found my bike wouldn't crank over and 3 oil changes with 0 miles. I cry when I throw away new oil, but if you run it like that it will wreck the seals and engine. I just smelled the oil. It gets pretty thin with gas in it, but if there is only a little you might not notice. Change the filter after you get the problem fixed. I put all new needles and seats in, and a new petcock repair kit. The diapraghm in it was pretty cheap looking compared to the original, and a short while after installing I found a piece of the spring steel on the back of it broken off. So I put an inline shutoff valve after the petcock, so I have no more worries. Been good ever since.

[Suzuki mad]

My GS(1000) can be a pig to start. If you touch the throttle at all when turning her over she won't start. I then have to take the tank off and suck the fuel lines to get the tap to start working again then refit the whole lot. Hit the button and away she goes! It didn't make any difference if I used another tank and petrol tap!

More of a problem if you got petrol in the oil though.

Suzuki mad
GSX1100ESD 1983 restored and running in
GS1000E 1981

[stp1stp]

Sorry for just now posting. 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. I see all the bikes on the road and I just get so bike sick. I haven’t got to ride much at all this summer.