Rough running and starting, way too rich

JoeyDuino

New Member
Apr 6, 2019
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Hey everyone, im new to this whole motorized bicycle world, and im also new to this forum, so forgive my naivety, as well as the long story lol. So, a few months ago I got one of the 2 stroke motorized bike kits to put on my mountain bike. It all worked great and I got the bike running great for a long time, and I even got a smaller sprocket for better top end speed. Unfortunately, just recently I started it up as usual and it was having some trouble getting going. Definitely not normal because my bike would always start up pretty much instantly before. When I finally got it going, it would not want to stay running, and it would not idle. I revved it up a little to keep it going so I could inspect for any issues when I heard and saw a little poof of smoke and a little bang come out of the top of the crank case area. (right under where the carburetor sits) I thought it was over at that point so I opened up the motor and didnt find anything crazy, but I did find a slight bit of scoring on the piston. I was going to split the case to inspect the crankshaft and crankcase gasket, but I decided to put the motor back together after cleaning it up a bit. (I didnt have the proper puller tool at the time) I turn it back on and it worked, but it was running crazy rich, like we're talking the ground was soaked with oil and gas rich. Still had bad starting problems and wont idle. Then I move the c clip on the slide up a couple notches and it seemed to run better but something still wasnt right. SO, could I have blown my crankcase gasket, and if so, would it cause the issues im having? my intuition would say no, but I am an amateur mechanic so I honestly dont know for sure. Is there anything else that could be causing my problems? Feel free to ask any questions about my situation as im not sure if this is enough information to diagnose my engine. Thanks for your time.
 

Greg58

Well-Known Member
May 1, 2011
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Welcome to the forum, I would start with the carburetor, make sure you don't have debris in the jet or needle and seat. What fuel ratio are you running? If you're running the 16/1 that is recommended by most kits you may have a fouled sparkplug, 32/1 is a good ratio for a 2 stroke. If it were the case gasket or a air leak the engine should rev and idle high so start with the basics first.
 

JoeyDuino

New Member
Apr 6, 2019
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Welcome to the forum, I would start with the carburetor, make sure you don't have debris in the jet or needle and seat. What fuel ratio are you running? If you're running the 16/1 that is recommended by most kits you may have a fouled sparkplug, 32/1 is a good ratio for a 2 stroke. If it were the case gasket or a air leak the engine should rev and idle high so start with the basics first.
I ran 20:1 in the break in, and now im running 32:1 all the way. I checked the carb, and there was some dirt around the needle valve and in the fuel inlet nipple, so that probably wasnt helping. Also the jet was completely clean. I think my spark plug is fine because I took it out to test it, and I had a pretty good spark, so what else should I look for?
 

Greg58

Well-Known Member
May 1, 2011
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Set the spark plug gap at .26-.28, that works good for mine. Try the e-clip in the top notch on the needle, last check all connections from the magneto to the cdi and kill switch.
 

JoeyDuino

New Member
Apr 6, 2019
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Ok, I will try all of that when I can. I have another question: I am planning on replacing the crankcase gasket anyway because I think it might be on the way out so, would I be able to use gas proof gasket maker to seal the cases? Or would it just be better to get the proper gasket?
 

Greg58

Well-Known Member
May 1, 2011
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Full engine gasket set are available from the company’s that advertise on the sides of the forum. You will have to totally disassemble the engine to replace the case gasket so I would try to tighten the case screws first.