I have a 1970 125cc 2 stroke dirtbike that I just cannot get running. I adjusted the points, it now has spark, compression is good (from what I can tell), fuel is good, I tried the carb that came with the bike as well as the original, still nothing. I have read things about gaskets going bad and letting air in. Is there some way to try to get it to at least fire. There was a youtube video of a guy using zippo lighter fluid. I need suggestions please.
2 stroke engine problems..
- Thread starter DANP
- Start date
Jared
...Try the morphine, it's excellent today!
Sounds like vacuum leak issues to me. Check all of the intake components and make sure there are not any cracks in any rubber parts. Another thing to check is if the reed valves are bent or not sealing properly. Two strokes rely on both high pressure and vacuum pressure to run. I wouldn't suggest using Zippo fluid as a means of trying to get the bike to fire, because it could damage the crank seals and bearings. If you pull all the intake components off, you should be able to use a flashlight and see if the cylinder or piston are scored or burned up.
rufio
Been Around the Block
Even with worn seal it should at least fire at one point but maybe not keep an idle. Premix or oil injected?
I'm also thinking top end. If you have gas and spark it should fire unless loss of adequate compression. Its easy though. 2 strokes are great in the sense you don't have to deal with cams, timing chain, tensioner and all the other normal 4 stroke stuff. Check the head and look for those scores.
I'm also thinking top end. If you have gas and spark it should fire unless loss of adequate compression. Its easy though. 2 strokes are great in the sense you don't have to deal with cams, timing chain, tensioner and all the other normal 4 stroke stuff. Check the head and look for those scores.
Jared
...Try the morphine, it's excellent today!
The best way to see if it'll run in my opinion is to make sure everything is sealed, and none of the gaskets are leaking. I would also pull the float bowls off the carbs and see if the float needles are sticky or gummed up and that the jets don't have varnish in them. After that see if the points are worn or dirty and that the spark plug is putting out a hot spark when it is supposed to. If all of this is within spec, pull off the stator cover and see if the crank seal has oily residue around it that might indicate a leak. If everything is good, (hot spark, fuel delivery, no vacuum leaks) then it isn't a bad idea to pull the head and cylinder jug off and look for any scoring or burned spots (especially on the exhaust side of the piston). These little bikes are usually ran pretty hard and require rebuilds kinda often due to inadequate fuel/oil ratios and overheating issues.
Gaskets all seem to be in check. I rebuilt the carbs and all looks good. points were just cleaned and adjusted to .016 gap. The spark from the plug seems to be OK but I don't know. Looks to be a little weak but I am relatively new to this so I don't know what a "hot" spark looks like. The piston looks very good. Could not running an air filter be an issue? I have a small 6.5hp clone motor that would not start without the filter installed. I have two of these little 2 stroke engines and one runs fine with no filter.
Jared
...Try the morphine, it's excellent today!
Sorry, I'm on my phone and its taking me a little while to type out responses.
-If the top end is in good condition then check for vacuum leaks, and make sure that the carb isn't gummed up. After that check the points for correct ignition timing, gap distance, and that the voltage output is adequate.
-If the top end is in good condition then check for vacuum leaks, and make sure that the carb isn't gummed up. After that check the points for correct ignition timing, gap distance, and that the voltage output is adequate.
Jared
...Try the morphine, it's excellent today!
That sounds like it might've created ground issues. This is probably going to sound like a silly question, but when you test the plug for spark, are you grounding the end of it to the head or does it still make a spark without touching any part of the engine?
