Question about 1976 Honda CB 100

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My 50cc 2 stroke engine won't start, it has fuel flow into the carb, and decent spark, and good compression, how would i check flowing into the cylinder, and repair it if it's not? (not the right category...didn't have what i have.... it's a generic 2 stroke, piston at the front with a bowl carb at the back...)

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Hi and welcome to FixYa,

A couple of ideas:

  • fuel to the carbs - as you posted checks good;
  • fuel inside the carbs - loosen the drain screw at the bottom/bowl. Check for quality / quantity of fuel;
  • fuel into the combustion chamber - check the plug (would be wet).
For a no start 2 stroke engine with your described condition, a possibility to consider is too much / unburned 2T oil in the lower combustion chamber; remove sparkplug, air dry (or use compressed air).

Good luck and thank you for asking FixYa.

Posted on Sep 09, 2009

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2 Answers

What should I check to repair this problem? Vehicle has spark and gass flow, but will not fire.


that leaves compression

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Does a ***** boy 50cc have a reed valve? Bike


Hi first thing what is the bike second thing is the engine a 2 stroke, if it is 2 stroke it most prob. has a reed valve, check that the carb needle valve is working as it should, then drain the cylinder and crank of fuel check the plug sparks, leave the carb off and put a small amount of petrol in it, try and start it if it fires once or twice, then it should start with the carb on it, if not there is a problem with the carb. good luck.

Sep 12, 2014 | Motorcycles

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50cc mini atv wont start


do a compression check if its under 100 psi could be piston rings are bad or leaking gaskets.

Mar 26, 2012 | Cycling

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I have spark and getting fuel won't start


if its a 2 stroke then you need fuel spark and air to get the bike to start have you got compression? check it by removing the spark plug and put your finger over the hole air try and start the bike your finger should be pulled into the hole if not then a piston ring is either cracked or broken

open the air box and check the filter then clean the carb thats all you need for a 2 stroke

if its a 4 stroke then again check the air filter and compression remember that a 4 stroke doesnt have the oil with the fuel it goes in a separate chamber

hope this helps


John

Jul 06, 2011 | kawasaki VN 800 A Vulcan Motorcycles

1 Answer

My TE 450 worked fine for 2 years and when I tried to start it this year it does nothing. Does it have a fuel filter or something else I should check?


Typically on these machines, it is the carburetor that causes most of the problems. Along with deteriorated fuel lines, carbon build up and some other 2 stroke issues. The ethanol that is added to our gas nowadays is one of the biggest culprits. Our machines ran FINE without it and no small engine likes it. It is damaging and not necessary. Your machine has to HAVE these things to Start and to Run 1. Compression (around at least 90 PSI on a 2 stroke like yours) 2. Clean Air
3. Strong Spark 4. Correct Fuel Mixture (fresh, not over 30 days old). All of these work in unison and are even MORE important for a smaller engine because any problem with ANY of these things negatively affects the performance of the machine. The carburetor is very touchy and temperamental. The least little dirt or gum and varnish can lead to a no-start condition. A carburetor that is in bad need of an adjustment can also cause this.
We can try "coaxing" the machine into running. Remove the air filter. Get a can of spray carb/choke cleaner (auto parts store). Open the choke on the carb. Open the throttle all the way. Spray a couple of good shots of the cleaner thru the throat of the carburetor. Immediately choke it and attempt to start it. Try this a couple of times. If the engine "pops", then that is a good start. If you can entice it to start running it will draw the fresh fuel you put in it (right?) from the carburetor and run. Further carb adjustments may be needed if and when you get it running.
Or if you prefer, remove, disassemble and clean the carburetor. It is a great learning experience and not that hard. As far as checking your fuel filter, it is in the fuel tank and kind of hard to see, so, you check it by observing if the MAIN fuel line from the tank is allowing fuel to flow to the carburetor, The primer/purge bulb assists in this matter and ethanol destroys it too. Very small check valves in the carb help keep the fuel flowing in the right direction. When they fail, ( I have one now doing this), the fuel flows backwards, the engine floods and it won't start at all.

May 27, 2011 | Poulan 25cc 2-Cycle Gas Powered String...

1 Answer

Bolens 5.5-Torque 21


Does it have compression? If not.. remove the spark plug and squirt some WD 40 in large quantities into the spark plug hole. You may have a valve stuck open. Let it sit for a while with the plug removed for the WD 40 to soak. Then turn it through with the recoil. After that Place your thumb over the spark plug hole and check for compression.
NO compression... soak with WD 40 again let it sit then turn the engine thru for sometime. At least until your arm gets tired. Check for compression again.

Once you establish compression....

Fill gas tank and make sure the fuel selector is ON. BRIEFLY Remove the fuel supply hose from the carb connection and check for fuel flow. If you have flow then reconnect the hose.

Remove the Oil dip stick and make sure the OIL level is FULL. Service if necessary... the LOW OIL level sensor will kill the ignition if the oil is low.

Still no start?

Spark YES

Remove the air cleaner and add some gas into the throat of the carb. Attempt a start. If it starts then dies the carb needs serviced. If you have a bowl type carb:

This is how to clean the fuel passages in the carb.
Here is what you need to do:

1. Fuel selector off
2. Remove float bowl mounting screws and nut
3. Remove the BRASS Jet / Orifice in the very bottom of the venturi tube inside the pickup tube. (Flat blade screwdriver) Hold the Orifice up to the light. You should see a pinhole. If it is not clear clean the orifice but do not force anything through the hole.
4. Underneath the Orifice there is yet another BRASS tube that you need to remove. (Flat blade screwdriver) Make sure all of the holes in the tube are clear. The tube will be over 2 inches long. Clean it and reinstall it.
5. Reinstall the Orifice.
6. Using a catch fuel container turn on the fuel selector. Fuel should flow at a good rate. GENTLY lift the float assy level and make sure fuel flow shuts off. When you drop the float again fuel should flow.
If you do not have fuel flow at this point the needle and seat will need to be inspected. Fuel selector OFF.
(The following procedure is to be done only if there is no fuel flow with fuel selector on.)
a. Remove the silver float pivot pin retaining screw
b. Drop the Float down (The needle will come off with the float. NOTE the position)
c. Inspect the tapered rubber of the needle If should be pointed. If it is not pointed then the rubber tip is stuck inside the seat.
d. Clean the seat hole ONLY if obstructed. (Easily damaged)
e. FUEL Selector on then off fuel should rapidly flow through the needle seat.
f. Renistall Float and needle making sure to get the pivot / hinge pin installed correctly and reinstall the silver retaining screw.
g. Fuel selector ON. Raise and lower float checking for free movement and fuel flow.

7. If there still is no fuel flow at this point remove the fuel hose from the carb and check fuel flow. If no flow check that gas tank exit hole, fuel filter (if installed) and the selector valve assy for obstructions. Reassemble connections.

FUEL FLOW IS GOOD

8. BEFORE you install the float bowl inspect the bowl nut. There are 2 holes in the side of the nut where it screws in to the bottom of the carb that must be clear.

9. Install Float bowl mounting screws and nut. Check for leaks.

10. Test engine.

That should do it. (carb cleaning 101)

Thanks for using FixYa.

Kelly

Apr 14, 2010 | Poulan "Poulan" Push Mower

1 Answer

Starting a lawn mower that sat for the winter


Hi and welcome to FixYa. I am Kelly

I am wondeing if this was just a seasonal session that the mower was idle? Having said that...

First remove the spark plug and spray wd 40 in generous quantities into the spark plug hole. Turn the engine through slowly 3 or 4 pulls on the recoil. Let it sit for 15 mins. Then pull the recoil rapidly (Spark plug is still removed) Use your thumb over the spark plug hole and have someone pull the recoil. (Your checking for compression)

Compression established...

Recheck the oil level to make sure that the oil level is all the way to the top of the full mark.

Before you install the spark plug connect it to the high voltage lead and ground the base to the cyl. head. (Check for spark!)

Spark extablished

Install the spark plug and attempt a start. If it starts GOOD JOB!

If not.... time to do some carb maintenance below.

This is how to clean the fuel passages in the carb.
Here is what you need to do:

1. Fuel selector off
2. Remove float bowl mounting screws and nut
3. Remove the BRASS Jet / Orifice in the very bottom of the venturi tube inside the pickup tube. (Flat blade screwdriver) Hold the Orifice up to the light. You should see a pinhole. If it is not clear clean the orifice but do not force anything through the hole.
4. Underneath the Orifice there is yet another BRASS tube that you need to remove. (Flat blade screwdriver) Make sure all of the holes in the tube are clear. The tube will be over 2 inches long. Clean it and reinstall it.
5. Reinstall the Orifice.
6. Using a catch fuel container turn on the fuel selector. Fuel should flow at a good rate. GENTLY lift the float assy level and make sure fuel flow shuts off. When you drop the float again fuel should flow.
If you do not have fuel flow at this point the needle and seat will need to be inspected. Fuel selector OFF.
(The following procedure is to be done only if there is no fuel flow with fuel selector on.)
a. Remove the silver float pivot pin retaining screw
b. Drop the Float down (The needle will come off with the float. NOTE the position)
c. Inspect the tapered rubber of the needle If should be pointed. If it is not pointed then the rubber tip is stuck inside the seat.
d. Clean the seat hole ONLY if obstructed. (Easily damaged)
e. FUEL Selector on then off fuel should rapidly flow through the needle seat.
f. Renistall Float and needle making sure to get the pivot / hinge pin installed correctly and reinstall the silver retaining screw.
g. Fuel selector ON. Raise and lower float checking for free movement and fuel flow.

7. If there still is no fuel flow at this point remove the fuel hose from the carb and check fuel flow. If no flow check that gas tank exit hole, fuel filter (if installed) and the selector valve assy for obstructions. Reassemble connections.

FUEL FLOW IS GOOD

8. BEFORE you install the float bowl inspect the bowl nut. There are 2 holes in the side of the nut where it screws in to the bottom of the carb that must be clear.

9. Install Float bowl mounting screws and nut. Check for leaks.

10. Test engine.

That should do it. (carb cleaning 101)

Thanks for using FixYa.

Kelly

Apr 13, 2010 | Toro Lawn Mower With Toro Power Tools

1 Answer

My 22" Model # 20067 won't start, I don't think it is getting spark. It is two year old and ran find when i put it away last fall. Any idea what might be the problem.


Hi and welcome to FixYa. I am Kelly

First remove the spark plug and spray wd 40 in generous quantities into the spark plug hole. Turn the engine through slowly 3 or 4 pulls on the recoil. Let it sit for 15 mins. Then pull the recoil rapidly (Spark plug is still removed) Use your thumb over the spark plug hole and have someone pull the recoil. (Your checking for compression)

Compression established...

Recheck the oil level to make sure that the oil level is all the way to the top of the full mark.

Before you install the spark plug connect it to the high voltage lead and ground the base to the cyl. head. (Check for spark!)

Spark extablished
Ensure that most all of the WD 40 you sprayed into the engine has purged.
Install the spark plug and attempt a start. If it starts GOOD JOB!

If not.... time to do some carb maintenance below.

This is how to clean the fuel passages in the carb.
Here is what you need to do:

1. Fuel selector off
2. Remove float bowl mounting screws and nut
3. Remove the BRASS Jet / Orifice in the very bottom of the venturi tube inside the pickup tube. (Flat blade screwdriver) Hold the Orifice up to the light. You should see a pinhole. If it is not clear clean the orifice but do not force anything through the hole.
4. Underneath the Orifice there is yet another BRASS tube that you need to remove. (Flat blade screwdriver) Make sure all of the holes in the tube are clear. The tube will be over 2 inches long. Clean it and reinstall it.
5. Reinstall the Orifice.
6. Using a catch fuel container turn on the fuel selector. Fuel should flow at a good rate. GENTLY lift the float assy level and make sure fuel flow shuts off. When you drop the float again fuel should flow.
If you do not have fuel flow at this point the needle and seat will need to be inspected. Fuel selector OFF.
(The following procedure is to be done only if there is no fuel flow with fuel selector on.)
a. Remove the silver float pivot pin retaining screw
b. Drop the Float down (The needle will come off with the float. NOTE the position)
c. Inspect the tapered rubber of the needle If should be pointed. If it is not pointed then the rubber tip is stuck inside the seat.
d. Clean the seat hole ONLY if obstructed. (Easily damaged)
e. FUEL Selector on then off fuel should rapidly flow through the needle seat.
f. Renistall Float and needle making sure to get the pivot / hinge pin installed correctly and reinstall the silver retaining screw.
g. Fuel selector ON. Raise and lower float checking for free movement and fuel flow.

7. If there still is no fuel flow at this point remove the fuel hose from the carb and check fuel flow. If no flow check that gas tank exit hole, fuel filter (if installed) and the selector valve assy for obstructions. Reassemble connections.

FUEL FLOW IS GOOD

8. BEFORE you install the float bowl inspect the bowl nut. There are 2 holes in the side of the nut where it screws in to the bottom of the carb that must be clear.

9. Install Float bowl mounting screws and nut. Check for leaks.

10. Test engine.

That should do it. (carb cleaning 101)

Thanks for using FixYa.

Kelly

Apr 10, 2010 | Toro Lawn Mower With Toro Power Tools

2 Answers

I have a kiddies 50cc two stroke no name brand bike there is spark, and petrol flow into the carb the reed valves is working well but still wont start


Hi and welcome to FixYa,

Your post, there is spark, there is fuel to the carb; additional initial checks:
  • determine if their is fuel inside the bowl of the carb by loosening the drain screw and determining the quality and quantity of the drained / collected fuel;
  • determine if there is suction/vacuum by closing the carb opening with your palm. it should get wet with fuel on cranking/starting;
  • check for compression. Temporarily remove sparkplug, replace it with compression gauge and crank/start engine with throttle wide open (WOT);
  • check if the sparkplug gets wet with fuel.
Another possibility is that there is stale 2T oil in the crankcase below the piston. This would prevent ignition as the air/fuel mix inside the combustion chamber would not fir.

Good luck and thank you for asking FixYa.

Nov 24, 2009 | 1976 Honda CB 100

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