Help! Cannot get fuel to go to the engine

[holypotatoes]

:helpsmilie: I've been trying to get my Chaparral ST 80 (Fuji engine) started for months to no avail. The spark plug is remaining bone dry and I can't figure out why. I've replaced the spark plug, coil, point (the condenser is fine so didn't replace) and I have spark. Not the problem. I've checked for compression, and it's 110+. So not the problem either. I redid the gas tank, cleaned the inside, POR 15'd the inside, replaced the petcock and filter, and gas is easily flowing to the carb. I originally tried cleaning the Mikuni carb that was on it, multiple times, and when gas was still not getting to the engine, I just decided to buy a brand new one that is the exact same model (Mikuni VM18-144 Round Slide). And yet gas is still not getting from the carburetor to the cylinder. I bought a NOS exhaust pipe that was for the Chaparral and put that on there as it didn't have an exhaust when I bought it so I can't imagine that's causing any problems either. The only thing that is not stock and that I make shifted is the air filter. The one thing I can think of as being the issue is maybe too much air is getting into the carb and not creating enough vacuum, so this weekend I tried blocking things off and only allowing a small amount of air to go through and still nothing. I've tried push starting this thing and nothing, and kick starting has been a complete failure. I've gotten a few pops out of it (like one) each time I've dumped gas into the spark plug hole directly but nothing more than that. At this point I'm at a complete loss as to what's going on. Fuel is definitely getting to the new carb as it now keeps leaking out of the overflow/air tube on the bottom of it which was also happening with the old carb as well, but it never seems to be making it to the engine itself to actually ignite. And FWIW, I don't have any wiring hooked up either. I've been attempting to get wiring to work with a switch that I had but that hasn't worked out so nothing's hooked up. There is no kill switch.

If any of you have any tips on what else I could try it would be greatly appreciated because at this point I'm at a complete loss. :cursing:

 

[electrathon]

Almost everything you have done is not fuel related, but you said you think it is a fuel problem. Pull the plug, and prime it. See if it starts. You will know in a few minutes if it a fuel problem or not.

 

[holypotatoes]

Initially it started as a spark problem hence the many spark fixes, but now that it's been fixed the only thing left is fuel really. I was just trying to give a run down of everything I've done to rule out what it's not.

And I know this is a stupid question but what should I prime it with? Just regular gas?

 

[electrathon]

what should I prime it with? Just regular gas?

Yes

 

[jim85541]

Keep in mind the old mikuni carbs do not "choke" but enrich the fuel. A separate jet is engaged to let more fuel in when cold and you push the choke lever. But it will not work unless the throttle is closed, forcing the engine to suck thru the enriching jet. A common problem was people would crack the throttle while choking and not getting enough fuel while cold. Also make sure the throttle cable is loose enough to let the slide go all the way down and the groove on the slide is engaged in the little knob in the bore.
Worse case if priming doesn't make it fire, try holding your hand over the end of the carb while cranking motor, forcing it to suck gas. If that fails then check to see if piston was installed correctly, arrow goes forward. Could be the piston skirt is not letting fuel in. Or crank seals are so bad as to not suck in fuel, but still give good compression. If I recall these do not have reed valves so that isn't an issue.

 

[holypotatoes]

So I've been priming and kick starting the last 45 minutes and still nothing. It pops once, then does nothing, until I re-prime. I've held my hand over the carb to suck fuel and it didn't make any difference. I'll check the piston next Jim. Thanks for the help you guys.

 

[gumpit]

Key

 

[danford1]

If it only pops once when primed you either didn't put enough gas down the spark plug hole or you don't have good spark.
My guess is you don't have good spark. You may have some spark but not good enough.
You said you didn't change the condenser yet if it only sparks once, that is a sign of a bad condenser.
It show start and run a second or two when primed.

Pop in a new condenser and make sure the points are very clean and dry and have the proper gap.
Gumpit made a good suggestion. Your flywheel key could be sheared or buggered up.

Danford1

 

[holypotatoes]

If it only pops once when primed you either didn't put enough gas down the spark plug hole or you don't have good spark.
My guess is you don't have good spark. You may have some spark but not good enough.
You said you didn't change the condenser yet if it only sparks once, that is a sign of a bad condenser.
It show start and run a second or two when primed.

Pop in a new condenser and make sure the points are very clean and dry and have the proper gap.
Gumpit made a good suggestion. Your flywheel key could be sheared or buggered up.

Danford1

I'll double check all of this again. The spark seemed decent enough. Initially before I changed the point I was getting minimal spark, then when I changed the point you could see the spark plain as day in the middle of the sunlight in the spark tester so I'd be shocked if there wasn't enough spark at this point. But I do have a new condenser so I could easily throw it on and see what happens. Thanks

 

[jim85541]

Make sure the plug is good. I have seen them fire outside the head, but not fire under compression. Should be timing marks on the flywheel where the points break open. An ohm meter hooked to the coil wire will tell you when it breaks. Or an AM radio tuned between stations will pop when they break. Easy way to check keyway. Holding the plug away from the head while kicking engine, the spark should just 1/4 to 1/2 inch from plug to head. should be a pretty blue spark. also while dad is holding the plug the neighbor across the street should hear him yell when you kick it over. ask me how I learned this one! It could be by now it is so flooded it wont fire. Is the plug wet? Oh be careful checking spark as sometimes spilled gas can ignite and cause spontaneous lessons on how to Irish Jig. Go back to the basics. Engine needs 3 things to work. Compression, and enough of it, fuel, the right amount, and spark at the right time. two strokes also need vacuum in the lower end to suck gas/ air mix.