Engine bogging

F

FlyingSchwinn

New Member
I have been having this issue since the motor was new, let me explain. Engine will start out fine, lots of power, etc and then after a while will develop a severe lack in power all the way through the power band. It will happen after running over half throttle and going up hills; both are situation when more air and fuel are needed. I thought I solved the problem with the change to an NT Speed carb because the motor is a 66cc. I was thinking either a warped head, bad plug, wrong jet size, or an air leak. Before troubleshooting I need opinions. These engines are cheap and poorly made and I wasnt expecting much but they are simple to repair. Any input is appreciated, thx.
 
are you sure its not 4 stroking....that happens when the engine cant get enough air to fire every rotation.....it will fire everyother rotation....there is a great sticky thread about how to solve it on this site....there is also a great video showing a 2 stroke 4 stroking
 
I pulled the head today and HOLY S*** the head was warped!! It took me 15 minutes of wet sanding to get the surface flat. I used 220, then 320 and then with 400. NOCO, if it was "4-Stroking" would it do it all the way through the powerband or just at the low end?
It just bogged, ran solid, bog, stall, idle high, run solid and repeat this patern. Hopefully this takes care of it and now I can check warped head off the list.
 
I don't know if the problem is fixed because I got a flat tire the same day I popped the head off . The rim is a Schwinn S-7 and tires are really easy to find. I will post results when I get tires in a week or so. Also, does anybody know if a steel lined cylinder can be had for a 66cc and if so, where?
 
Head did not fix the problem, neither did cleaning out and setting the float bowl, a new ngk plug, and fixing a potential air leak. I did notice, however, that now there is oil spitting from the front of the engine where the head meets the jug. I am sure that the problem is now the head gasket. Are there any known materials that can be used in place of the aluminum hg or is getting one from boygofast the only option. I am one step away from turing my motor bike back into a pedal bike.
 
Listen to me here. Take the air filter off and try to run it with the air filter off. If it runs well, your air filter is either dirty as heck or filtering not only dirt, but air and in that case you need a lighter filter.

I've seen this a million times on motorcycles and had the same issue with my motorized bicycle.

I recommend to anyone from now on that after a carb tuneup you should run the engine without the filter for a test to see the performance difference. I did this with my motorized bicycle and realized the filter was choking the darn thing!

As far as the oil leak, did this occur after you adjusted everything inside there? If this is the case I'll bet you caused this problem yourself and that it isn't a part of your original issue. But, since your compression is now shot, you'll have to fix this issue before anything else. Are you sure you torqued the head correctly? 9-12 ft/lb is what you're looking for--cold engine only.
 
Last edited:
speedster239 said:
Listen to me here. Take the air filter off and try to run it with the air filter off. If it runs well, your air filter is either dirty as heck or filtering not only dirt, but air and in that case you need a lighter filter.

I've seen this a million times on motorcycles and had the same issue with my motorized bicycle.

I recommend to anyone from now on that after a carb tuneup you should run the engine without the filter for a test to see the performance difference. I did this with my motorized bicycle and realized the filter was choking the darn thing!

As far as the oil leak, did this occur after you adjusted everything inside there? If this is the case I'll bet you caused this problem yourself and that it isn't a part of your original issue. But, since your compression is now shot, you'll have to fix this issue before anything else. Are you sure you torqued the head correctly? 9-12 ft/lb is what you're looking for--cold engine only.
Click to expand...

Speedster, you hit the nail on the head with that one, I was running two filters because of the inferior filtration of just one and it was choking the motor at speeds. I am not going to use a filter for now because it is so easy to rebuild the top ends on these engines. I also just installed a new head gasket with ultra copper sealant on it because the thing was spitting oil at the seam. Hopefully takes care of that problem! usflg
 
If you do not use an air filter on a 2-stroke engine, when it comes time to rebuild you will need to rebuild more than just the top end. Yes, the top end will wear quicker, but since the intake fuel/air charge first enters the bottom end before transferring up into the cylinder, any of the dirt and dust ingested that will accelerate wear will affect the bottom end bearings as badly at the top end.
 
Hello, i don't know if u've solved this , but i think i got your answer , i had the same problem for some months now and i had tried everything , the problem though was more simple , the engine had moved from its original position , the carb was tilted towards the back thus the gas instead of going into the engine it went out of the carb intake due to the angle.
Before a week or so i repositioned the engine the carb has a slight angle towards the engine , problem solved, it runs as it did.
Hope i helped
 
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