[kevelev]

Hi, I have a Z50R (1990-1999?, not sure the exact year) but it has a Chinese 86 cc engine on it. I'm not sure the brand of the engine, all I know is that it says "RCM" on the side. Anyway here's the problem. It has developed a crack in the bottom of the engine and started to leak oil. It would still ride fine, but we would have to check the oil more frequently. We haven't ridden it in about a month. Now when I try to start it it never fires. I cleaned the carb and it was dirty, but that's not the issue. It gets gas and the spark system works fine. I read on here that squirting a bit of oil inside the cylinder (after removing the spark plug) can help create a better seal and get the right compression for it to fire. I did that and it worked, but not for long. I started it up and drove about 100 feet then it died and wouldn't start again. I also don't have the idle screw, that got lost but it ran perfectly for years after that. Sometimes it fires at the wrong time it seems, and there is a flame that leaks out the exhaust head while other times a squirt of gas shoots out the carb. All of this started happening after we didn't ride it for a while. Any suggestions?

 

[sh0rtlife]

sounds like a very neglected motor that need money thrown at it...or a new engine...if it only runs with a lil oil..your compression is shot....likely rings..and with the burp of the carb and the flame out..sounds like your valves are out of adjustment as well

 

[xr1million]

My suggestion is take it to a mechanic.
Explain what part of the carb you cleaned please.

 

[HondaFiddyMan]

Replace motor with a 90cc piranha and call it a day.

Not sure where the crack is but that compounded by the likely need for a serous Tune up and a new carb, a new motor setup would likely be easier and cheaper for you.

-HFM

 

[kevelev]

I took the carb apart and noticed that the smaller of the two jets was clogged so I cleaned it out with a small needle, even though its probably been that way forever and it always worked without any problems. The crack in the motor is at the very bottom of the engine, where you mount the bar for the foot pegs. I never touched the timing or the valves, just cleaned the carb and took off the plug and cleaned that.

 

[spiz5]

If you used a small needle on the pilot jet, you probably plugged it up worse than it was.

 

[spiz5]

Forget that, just reread first post, Im with the others. Scrap it.

 

[xr1million]

The passages in the stock carb are so tiny, and with not being able to remove the pilot jet, the passage way is probably still plugged. Your only hope with the carb is an ultrasonic cleaner... maybe.

 

[dventu]

An old throttle cable will clean the jet. Take a strand of it then straighten it then pass it through the passage.

 

[sh0rtlife]

carb clean and 120 psi from an air comp will useualy do it too

 

[kevelev]

Guys the carb is clean and in good working order. I didn't clog it up more by using a needle, I took out the jet, looked down it, it was clogged. I used a tiny tiny wire to thread through each hole, blew through it with an air compressor, and all the holes were clean. I took off the cylinder head and now am concerned that the valves aren't seating properly. I saw on youtube that you can check it with compressed air and water, to see if bubbles pass through. I did that and there were bubbles on both intake and exhaust valves. But I'm not sure if that guys method is actually good because its blows the air the wrong way.

 

[kevelev]

So really my question is how do I get the valves out without special tools? Can I just remove the nuts on the ends of the rocker arms?

 

[tmas]

You need one of these unless you rig up something.
tmas

Valve spring compressor tool - W-57-8011 - Cylinder Heads & Parts - Pit Bike Engine Parts - TBolt USA, LLC

 

[xr1million]

You can use a socket and a hammer to get the keepers out but you are going to need a special tool to get it all back together.
The nut and bolt on the rocker don't hold the valves in.
GET A SERVICE MANUAL!

 

[xr1million]

Stock carb does not have a removable pilot jet. You were not able to see through it!
#17 and 2 are part of the main jet circuit, The brass tube that is pressed into the carb body next to the main jet is the pilot jet. (non removable)
http://planetminis.com/forums/attachment.php?attachmentid=18439&d=1327005910

 

[kevelev]

What kind of compression should I get when doing a compression test for my 86 cc four stroke (in psi)?