ATC 70 running a piranha 90 motor. Can't get new motor/carb to start. Please help

[DRKCYDE]

Working on my first 70 and it has a new 90 piranha motor and new mikuni 19 mm carb(wholesale-cycles recommendation). Have spent the last few nights working on it with a local three wheeler buddy and for the life of us can't get it started.

I have been through out this 70 forms top to bottom and usually the threads about bikes that won't start are put a new carb, or check the points. I can see if I was dealing with the 25 year old stock carb or motor, but brand new stuff?

The details..... Can't get it to really even fire up.

Has great spark. Have tried a couple different new plugs. They seem to get wet and black each time we pull to check. Tried some started fluid and didn't get any results.(down carb, and down cylinder)

Usually the only times I can get it fired (for a few seconds) is starting with full throttle, once full choke, then much later(following week) full throttle no choke. Have been working on it inside the house if ambient temp has anything to do with it.

Checked float level and adjusted a few times without any luck.
Tank is new so it's not from rust clogging anything.
Drained old fuel and replaced with fresh 92 octane.
Did take apart and clean and blow out with compressor just to be safe and try easy things.

Motor has stock exhaust if it matters and uni air filter.
Only have minutes worth of carb experience and seem to not even be close with my attempts.*

Wholesale cycles has offered to send my different jets, but haven't even gotten that far to know if that might be what's off.

I know a bunch of you have tons of experience with these.... Anyone have any advise other then try a new carb, or get a new cdi, stator?

Thank you in advance... So excited to ride this thing for the first time and is killing me to walk by everyday. Grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

[Vealmonkey]

The thread says you can't get it to start, then in your thread you say you got it to fire. Which is it? Have you tried firing it with starting fluid. Have you double checked to make sure you have oil in the engine in case it starts. Sounds like a carb problem. If plug is black, it means your engine has fired and more than likely has too much fuel-flooded and/or too big of idle jet or you keep trying to hold the carb wide open. Are you trying to start with the choke on or off. To spray starting fluid you must have the choke off and the throttle wide open when you spray or no fluid will get in the cylinder. You must have the start switch on and if you are getting spark, it must be wired right. Timing may be off, but couldn't swear to it. Carb problems are the likely culprit. Check to see if needle on the carb is in the middle. Turn the gas off at the petcock, quit flooding the engine out. Don't turn the gas on at the petcock until you can get the engine to fire on starting fluid. Don't use a ton of starting fluid when trying to start the engine. The engine is small and will only use so much fluid.

[fabiodriven]

First and foremost Alex, is there an airbox on it? Those little motors do not like to run without some sort of air filter and they start and run the smoothest with an airbox.

[WIkid500]

Are the valves adjusted? Just a thought, if your valves tight she will never fire no matter how much either you pour in the hole. And for the record avoid using either, it drys out the cylinder and does more harm than good. Figure it out and make it run without the starting fluid, that's how they are supposed to run. If you have good compression try closing the gap on the spark plug, literally damn near smash the thing shut. My old Yammi moped with 180 psi of compression won't run with the plug gaped to spec. Smash the electrode shut and she runs like a champ. Cam timing correct, is the key in the flywheel? All things that will stab you in the back if you "Assume".

[DRKCYDE]

Out of maybe 300 pulls it has maybe fired up 4 times, then died out.

Have tried with starting fluid(didn't use much) and tried spraying into the carb, and down into the cylinder, without luck each time. Had the choke open, but didn't give gas while spraying it. Will check that.
Will try closing petcock too...

Fabio, it has an aftermarket uni air filter. Also tried to start a few times without it on.
I have read that sometimes the stock motors with act up with something as simple as a different filter/cleaner on it. Didn't think this motor, new would be such a handful though.

I decided am going to punish it this weekend though, by dragging in the 200x and 250sx and work on them right in front of it, and not pay any attention to it. You know, basically give it a time out. If that doesn't work, nothing will.

[DRKCYDE]

I also got this emailed to me...

There's an "automatic" fuel shut-off valve on these.
When there's no vacuum, there's no fuel.
Look for the vacuum / fuel control valve and
either by-pass it or supply it with vacuum as
designed.

First I have heard about anything like that. Not sure has any idea what he's talking about but I really don't.

[fabiodriven]

Try taking the air filter off and cover the venturi of the carb 1/2 to 1/3rd of the way with your finger. on the boards here was dicking around with a freshly rebuilt 70 one day at DC's house. He was pulling and pulling to no avail. I pulled in, asked him what he was doing, stuck my finger over the carb and it fired right up. He was in shock.

[AutoXer]

if the plug is wet then it is getting gas and if you have good spark it should run. I am doing a lifan 125 in a 70 and once wired properly it fired right up .... seems to like no choke and a little gas... do you have a stock carb you can try? Have you tried to push start it?

[Mosh]

It is critical on these that you route the fuel lines correctly. Becuase of the way the gas tank falls to the carb. In my experience with them, you have to run the fuel line down from the tank valve underneath the gas tank leaving it parrelell (sp) to the tank. The line has to run forward, then wrap around to the right side of the tank then down to the carb.
If your fuel line drops down the left side of the tank, then back uphill to the carb, they wont draw the fuel right. There cannot be any drops in the line below the level of the carb bowl and then go back uphill to the carb. I have put a few of these in, and that has always been the way I have had to run them to get them to run right and start right.
Put in a new non fouled plug, re route the line and try it again. Also make sure that old 70 cap is venting properly. Alot of them get clogged. Usually those engine packages and carbs from Wholesale cylce are plug and play with the jetting being spot on. At least all mine have been okay.