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beastly

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Hi all,

Im new to the forum, and I need help with my crf50 clone engine. It is a 50cc 4 stroke fully auto. It doesn't have gears or a kickstart, so I am relying on electric start to turn it over. I kinda bypassed some of the electrical, but it gets spark and turns over. I checked for compression by putting my thumb over the spark plug hole and cranking it, and it pushed my thumb out of the way a LITTLE bit. Timing is good, and I cleaned the carb totally including the jets, although I did not check the clearance of the float. The carb is a PZ19. Mixture screw is 2 turns out from being lightly seated. Air filter is clean (I am trying to start without air filter). I am going to clean the fuel pet**** tomorrow. It turns over and sometimes sounds like it wants to start, but it never does. I have sprayed starting fluid into the carb and it still does not start (I have also tried spraying into the spark plug hole). I also adjusted the valves at TDC to .0025 with the engine cold (NOTE: I originally forgot to set it to TDC and I adjusted the valves, but later I corrected this and adjusted them at TDC, does this matter?) I'm sorry for the long post, just trying to be as detailed as possible :).


Here are my questions:

1. It didn't start with the original exhaust, so I tried a header from a similar bike, but it didn't fit, so the header is pointed forwards instead of backwards, is this bad?
2. How can I check for engine gasket failure without just rebuilding everything (last time I rebuilt a motor, it never ran again).
3. Does the flywheel case gasket matter?
4. Will the engine start without and exhaust gasket (copper ring)?
5. When I removed the carb and pulled the throttle cable, it did not spray gas, should it?
6. Is there a way to completely bypass the electrical so I just have the battery, starter, and coil?
7. Any ideas on why it won't run?
 
what exactly did you bypass in the wiring loom and why?
1.... sholdnt matter to just get it going
2....if your unsure on re building it just take it to a shop, not worth killing another one
3.... shouldnt do, all of the long engines i have worked on havnt had one at all (in sayng that i havnt played with one of these)
4.....should start, but will run like a dog, will also be running very lean
5.....carb unlikely to spraY gas without airflow as well
6.....why???

thats my 2 cents worth anyway, my67xr is far more versed in these things than i, and will not doubt be along to help when he can lol
 
welcome to Miniriders,

here's a couple of questions for you,

have you fitted a new spark plug ? NGK C7HSA
do you have spark ?
and what colour is the spark ?


when you adjusted the valves the first time, did you turn the engine over after doing them ?
how many times approx ?

cheers, craig
 
Thanks so much for the replies! I bypassed the loom because a lot of the lights and things on the bike I'm working one are not working. Newer NGK plug, installed about 1 week ago, but it has black soot on it from another bike. The spark color is white/bluish if I recall correctly. I spun the engine over about once or twice before adjusting the valves, should I have spun it more?
 
ok, the valves might be alright.
adjusting them with the engine not at TDC can cause the valves to touch the piston and bend the valves


try putting the palm of your hand over the intake/filter end of the carby and try starting it up
it will create a big vacuum and can help to clear any blockages in the ports of the carby.

try it a couple of times, your hand should get wet with fuel, that's normal.
now try starting it again, no throttle etc
if it fires and wants to start try it with a touch of throttle
let us know how you go
 
It happened as you described. It created a vacuum and gas got on my hand. It also started to sound like it wanted to turn over. It almost sounds like it is running when you try to start, but it never starts. Once, i sprayed a little starting fluid into the cylinder from the spark plug hole and it ran for about 3 seconds. When I tried doing this again, it wouldn't start like it did. Tried starting with throttle, no throttle, and choke. Spark is bluish white. The plug is blackish and gets wet (I think it is gas). Needle is in middle position and mixture screw is 2 turns out. Also, I tried installing a carb from a running bike, but it did the same thing. Then, I took the carb from my bike and put it on the other bike, it started up for a few seconds, but then it would die. Timing is good (I rechecked). Also put on a new intake manifold gasket.
 
i would be double checking the carby.
take it off, pull the fuel bowl off and remove the Pilot Jet
check the the holes that run across the jet are all open, poke some wire through them
then look at the bottom of the carby where the pilot jet screws into
if you hold the manifold side opening up to the light, you should be able to see light if you look through where the pilot jet screws in.
poke some wire though to make sure it hasn't got gum etc built up in it.
 
if that doesn't make a difference,
then take the Mixture screw right out of the carby and blow compressed air through the 2x small ports on the air filter side, it may have a blockage somewhere in one.
you should be able to feel air coming out the pilot jet hole when you blow through one of the small ports
the other port is for the main jet
 
what about a blockage in the fuel line? if you pull the hose of the carby and turn your fuel tap on do you get heaps of fuel or a slow trickle? just wondering if there isnt enough fuel flow to fill the bowl properly, would explain why it ran with the other carby for a few mins and then not running after that........
 
Okay will try and do these things tomorrow. Do you think it could maybe have a bent valve or bad valve seals?
 
if there is a bent valve, it will hiss out the carby/air filter when you kick it over
 
I don't hear a hiss. Today I and triple checked the carb. All jets, and the passages you told me to check were clean and I could see daylight through them. Gas flow to the carb is good. I took off the head today, and everything looked great. Sprayed a little wd40 on the piston and went on. Valves look like they seat good. I redid the timing, and even looked through the spark plug hole to make sure the cycles were correct. Timing lines up good. Still does not start. Sometimes, it sounds like it is going to start when you are cranking it, but it never does. Thanks for the replies, my patience is waring thin and I'm about to toss this POS in the dumpster.
Questions:
1. The TDC happens twice on the cam sprocket for each flywheel revolution, does it matter which revolution the cam sprocket is on when you check the valve clearances?
2. I turned the valves so that when I set the timing to TDC, the valves were able to spin freely (I believe they could spin 180 degrees as I read online), is this the proper setting?
3. When I spray in starting fluid, and crank it, it just spurts black fluid from where the exhaust mounts in on the head.
 
to have your engine at TDC,
you need to have the TDC mark on the flywheel pointing at the mark inside the top of the case at 12 o'clock
and the timing mark on the cam gear pointing at the mark in the head at 9 o'clock


the both the lobes of the cam will be pointing back towards the engine
 
I have them lined up as you say, but does TDC mean that the thing the cam sprocket bolts to can move freely?
 
no the cam wont move, the timing chain hold's it still.
that's unless you turn the flywheel
 
I mean when the cam timing chain is off, along with the sprocket and at TDC, should you be able to rotate the plate that the cam sprocket bolts onto? The plate I'm taking about rotates the rockers and the valves.
 

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