Help! Instaleld 75cc upgrade, now bike will only start if i hold throttle

[shroomigator]

Put a ruima 75cc upgrade kit in my zx50.  Now the bike will only start if i hold the throttle at max, and if i release the throttle it stalls.  Played with the screws on the carb, does nada.  What do I do?

[ophelia]

Did your ZX50 run well before you put the 75 cc kit in?

[245luigi]

Did you only install a cylinder + head or did you make other changes/add other parts? If you took off the carb, did you allow the carb bowl to fill with fuel?

[shroomigator]

Did your ZX50 run well before you put the 75 cc kit in?

no, I was having a lot of problems with not getting enough power.  cleaned the carb, and found a blown head gasket... when i took the cylinder off to put the kit in, I found that the bottom gasket was completely missing.

I did take the carb apart, and didn't put fuel in the bowl... how do I do that?

[ophelia]

Your carb float bowl should fill up once you've kicked the engine over a few times if the fuel tank is hooked up correctly to the petcock and to the carburetor. If you were running it just fine at full throttle, it's likely full.

What kinds of problems were you having before with not enough power? Did your ZX50 idle smoothly before the upgrade? Are all the hose and intake connections secure? Is the auto-choke attached correctly?

[shroomigator]

Always idled smoothly and always started right up.... then one day I gave my coworker a ride to work and i'm pretty sure that's when I blew the headgasket, because it went from a top speed of 43mph to around 30.  I asked around on these boards, was told to replace the roller weights (i did) and clean the carb (likewise done) performance dropped steadily until finally she wouldn't go faster than 15, at which point I took the head off and found the busted gasket... tried to use a silicone gasket, but couldn't get any compression (still started right up and idled smoothly).  Bought the upgrade kit and during the install became aware that I had been riding the thing with no bottom cylinder gasket all along (which would explain why the silicone gasket  on the head didn't fix the problem)...
so now, upgrade kit is installed, but no start unless I hold the throttle.

[ophelia]

Is the auto-choke installed on the carb and connected?

What kind of idle mixture screw is on your carb? Is it a pilot air screw or is it a pilot fuel screw? Usually an air screw is mounted close to the intake side of the carb and a fuel screw is mounted close to the engine side of the carb.

[LoveMyKymco]

The stock carb isnt giving it enough fuel to keep it running.
You definitely need to upjet or get a bigger carb and intake. I suggest doing the latter.

[JJJoseph]

Never mind upgrading your carburetor.  This problem likely has nothing to do with the carb.  First things first with 2-strokes: Check the ignition/shut-off switches are OK; then check compression.  Compression should be at least 90psi to run, maximum ~ 120psi.  If it's below 60psi, it won't start, and there's a problem with rings and cylinder walls.  Check all gaskets for integrity, and make sure the reed valve is clean and in one piece.  Check for a spark (there's no timing to adjust on scooters), and the plug is gapped to 0.7mm.  THEN, after all the above, check the carb and fuel supply, and air filter.  Most scoots won't run without a stock air filter.  The carb is the last thing to check.

[LoveMyKymco]

Ok I was being nice first but now its just funny. First things FIRST, the ignition switch OBVIOUSLY works or it wouldnt even start. 2nd 90 psi is barely enough to pass a fart through a 75cc set up, 3rd if you had an airleak your bike would idle high after starting if you could get it to start, not barely idle like someone with no experience with a 2 stroke would assume, 4th Id start with the carb first since youre trying to feed a cylinder that is effectively 50% larger with the exact same jetting and carb. Anyone with common sense of 2 strokes would tell you this is where to BEGIN, not lead you on a wild goose chase. 
JJ you really shouldnt give so much advice when you yourself know nothing of building a proper 2 stroke. Most scoots will run without a stock air filter, its called properly tuning your carb. For someone who cant properly tune a carb for an open air filter you sure are full of something and its not knowledge. 
All you have to do is click on the link in my signature to see ONE of my 11 built scoots. If you want to see more you can always check out my youtube videos or my photobucket. I dont day dream about what could or couldnt happen, Ive been there and done it and know the right way to do things.

[ophelia]

I'm sure both of you know how to diagnose and tune two stroke bikes your own preferred way and Shroomigator could benefit from your knowledge, but be nice to each other. Maybe there's something both of you can learn from the other too.

[JJJoseph]

Ok I was being nice first but now its just funny.

Oh, calm down, LoveMyKymco!  I was talking to Shroomigator about the sequence to go through when your 2-stroke is having a fit.  Go ahead now, you can talk about your 11 tiddlers, show your pictures,  and tell us how clever you are, we'll just sit back and listen.

[shroomigator]

Is the auto-choke installed on the carb and connected?

What kind of idle mixture screw is on your carb? Is it a pilot air screw or is it a pilot fuel screw? Usually an air screw is mounted close to the intake side of the carb and a fuel screw is mounted close to the engine side of the carb.

Carb has two screws, one for air and one for fuel, the air screw is just above and offset from the fuel screw...

Fiddled with em both, tried both wide open and both closed, and several steps in between, this seems to have no effect.

The auto choke is clean and moves smoothly, as does the carb float, the entire carb is just clean as a whistle and everything seems to be doing what it's supposed to...

I have to agree with the notion that the carb just isn't supplying enough fuel to the upgraded cylinder... I ordered a jet kit from 6sigma. hopefully that will solve the problem without having to replace the carb.

Anyone here have experience with 6 sigma?

[LoveMyKymco]

I own the 6 sigma for the zx50 and its not the correct kit. Heres a pic of the kit they sent me.

You know JJ the reason I post pics is because I dont want any misconception of what I have done or not done. I dont lie nor do I guess if its going to cost someone else time or money. Unlike some people who post things to just see themselves on paper I actually want people to succeed with as little resistance as possible. Not go on wild goose chases because some guy wants to be seen. Every one of my scooters, motorcycles, quads, trikes, and sleds runs. I spent my youth blowing up engines and thanks to that I earned a lot of knowledge of what you can or can not do. All I ask is you do a little research before you spout something as absolute.

[LoveMyKymco]

I did how ever run the needle they sent me in the kit. It was worth the sticker I guess, I won the kit for 5$ on ebay.