Frozen engine or piston

dnecca

New Member
Jul 4, 2020
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I have an 80cc 2 cycle [I assume] motor and the engine would freeze up only when the spark plug was inserted . I was able to freely pedal the bike without the spark plug .
I have never got to ride it motorized, because of this problem of it freezing with the spark plug .
I checked the spark-plug- and it was good+ with a spark when disconnected from the engine and with the rear wheel turning.
So, after reading on here of a similar problem I took of the piston head cover[?} and looked at the piston . Although it was clean, there were cracked plastic like type rings [see pics].
Do I need those? Or can I put it all back together and hope it works.
I'm asking because it was tedious to take it apart in the first place.

20200704_203447.jpg

Otherwise the piston head cover looked clean...
20200704_203459.jpg

This is the bike .. [mountain bike] and it is my first motorized bike.... I bike ..about 20 to 30 miles every stint and a couple or more times per week.

I went for a mountain convert my first time.
Any help is appreciated.
20200704_152105.jpg
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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If those rings aren't in one piece....they're broken. You need to get a new set and put the on the piston without breaking them, then get the jug back on without breaking them.
 
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dnecca

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Jul 4, 2020
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Thanks for responding.... I don't know the manufacturer but it was in China [not sure about the dirt floor or even if they wore sedge straw hats when they made this...], Would you know of any other reason that the bike wheel would freeze only when the spark plug is in?
 
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mapbike

Active Member
Mar 14, 2010
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The engine only has compression when spark plug is installed, rear wheel isnt supose to be easy to turn unless clutch lever is pulled all the way back assuming clutch cable is adjusted correctly.

Dont be affended by what Im gonna day next here please..... but it seems that maybe you dont understand how these engines work on the bicycle.
 

mapbike

Active Member
Mar 14, 2010
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If clutch cable is adjusted correctly, you should be able to roll bicycle around with only a slight bit of resistance while spark plug is in engine head and engine is correctly setup to run.

These bikes need to be pedaled up to 6-8 mph and then while still pedaling forcefully we release the clutch lever to tranfer the force / inertia of the rear wheel to the engine through the chain and sprocets, thos force is what will ovecome the compression of the engine and get it spinning over inorder to get it started up.

If all else is correct, once the engine fires off you just apply some throttle and your riding under the powet of the engine then.

Some good pics of your engine setup on the bike may be helpful also, this way if someone notices an issue, they could pointnit out to help you know what you maybneed to do to get your bike setup right so you can ride it under engine power.
 
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dnecca

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Jul 4, 2020
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If clutch cable is adjusted correctly, you should be able to roll bicycle around with only a slight bit of resistance while spark plug is in engine head and engine is correctly setup to run.

These bikes need to be pedaled up to 6-8 mph and then while still pedaling forcefully we release the clutch lever to tranfer the force / inertia of the rear wheel to the engine through the chain and sprocets, thos force is what will ovecome the compression of the engine and get it spinning over inorder to get it started up.

If all else is correct, once the engine fires off you just apply some throttle and your riding under the powet of the engine then.

Some good pics of your engine setup on the bike may be helpful also, this way if someone notices an issue, they could pointnit out to help you know what you maybneed to do to get your bike setup right so you can ride it under engine power.
Thanks , I'm not offended. I don't know the mechanics of a bike or engine too well. So, that said. I did find out that the resistance was from the spark insert and it was as it should have been (and the clutch needs adjusted) . [from an "advance auto" tech.] Now I need to buy Small piston rings. Have any advice or knowledge on where?
He told me to check online or a gas mower store.
I'll put up pics but they are of the motor dissembled, although on the body.
Here the pics:
Motor:
20200704_203423.jpg

Position of motor:
20200705_164900.jpg


Other side of motor:
20200705_164850.jpg
 

mapbike

Active Member
Mar 14, 2010
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Thanks , I'm not offended. I don't know the mechanics of a bike or engine too well. So, that said. I did find out that the resistance was from the spark insert and it was as it should have been (and the clutch needs adjusted) . [from an "advance auto" tech.] Now I need to buy Small piston rings. Have any advice or knowledge on where?
He told me to check online or a gas mower store.
I'll put up pics but they are of the motor dissembled, although on the body.
Here the pics:
Motor:
View attachment 105129
Position of motor:
View attachment 105130

Other side of motor:
View attachment 105131
Well glad you got some things lined out now... great to hear.

As far as the piston rings go, thats an easy find, I dont want to step on the toes of any sellers on the forum here, but I can leave you an ebay link here to where you can get them very inexpensively.

I haven't been active on the forum in a long time and have just very recently eased back in to play catch up on whats new nd who's still around since I fell off the forum map a few years back.

OK, based on what I believe I can see in your picks I believe your engine has the piston with lower wrist pin placement, so here is a very inexpensive kit that gives you some extra gaskets as well as new rings, piston and new wrist pin, so for less tyn $9 you get new rings plus some handy spare parts for later if you should need them.



I hope this helps and best wishes getting your bike ripping down the road very soon.

I look forward to your success with it, they're a lot of fun if you like to tinker.
 
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mapbike

Active Member
Mar 14, 2010
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Central Texas
Great ... thank you and I bought it on ebay ... hope it works! Super thank you!

excellent.... just make sure you're super careful installing rings and you make sure to get ring gaps oriented right at the retaining pins that are in piston ring grooves.