I have a 1971 honda ct70 trail bike with engine problems.?

Question

ok so i have a honda ct70 trail bike. (its from 1970 something not sure specifically what year)

i had it running great.

with no problems.

well i turned it off and when i tried to turn it back on, it didnt work.

you can hear the piston doing its job but no exhaust is coming out and i dont think its igniting the fuel.

put a brand new spark plug in. working fine.

all valves are working.

any suggestions?

Answer 1

probably the time chain pull the plug & hold your finger over the & see if you have compression.

Answer 2

How do you know the carburetor is working fine?

One of the jets can be clogged  and the spark plug would still get wet.

Remove the carb, remove the pilot jet (long and thin), hold it up to the light - you should be able to see through it.

Does the battery have a good charge? - it's battery ignition (needs a fully charged battery to fire the spark plug).

Check for spark - remove the spark plug, insert it into the spark plug cap, lay the threads against the engine and try to start the bike - the spark plug should spark.

Adjust the points and timing.

Answer 3

it takes four things to get an engine running.

fuel

compression

spark

timing

just because the engine started once doesn't necessarily mean it's in good condition.

the first thing to do would be to spray starter fluid (found in most gas stations) into the air filter and see if it starts that way.

if yes, then it's a fuel problem. which probably just means that you need to do a thorough cleaning of the carburetor so that you get enough fuel. or if it turns out you're getting too much fuel then your floats might be shot.

if no, then it's either compression or timing.

in that case you can use a compression tester to check the compression. anything over 100lbs should at least start. if it's less then you might have an air leak, or your piston rings could be worn out.

if the compression and fuel are good then it's an electrical issue which can be very annoying if you aren't familiar.

if there is spark and fuel and compression then you probably need to adjust your points so that the spark is happening at the right time (relative to the position of the piston).

you'll probably need some help doing this if you don't know how.

basically you want your points (which are found under the flywheel) to open up when the piston as at TDC (Top Dead Center). there are usually markers on the flywheel and stator plate (what the points and coils are attached to) to tell you when the points are supposed to open. you'll also have to know how far they're supposed to open which varies from bike to bike.