First timer troubleshooting

Mgb2504

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May 30, 2021
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Hey all. So I’ve got an 80cc 2-stroke kit on a road bike. My main issues remaining are getting the chain tensioner lined up, not sure why it doesn’t line up with the engine sprocket, will just require some precise bending. The real drag is that I can get the clutch dropped in and the motor running but only for about ten seconds at a time, at which point it burps back asleep.

Possible causes are, I spaced the magneto with a business card but forgot to put the paper gasket back and one of the “super high quality improved” hex bolts completely stripped so I’ll need to reverse drill bit it out, and then find a new bolt. Would the paper gasket for that part make me lose pressure? On other engines I’ve worked on the magneto is not part of the pressurized crankcase. Is this type of engine a sort of two stroke four stroke hybrid?

I also am waiting on a gas tank in the mail
A967DB06-95D7-43A5-AE74-F887941884B1.jpeg
. I’ve got the fuel valve screwed into an upside down Pepsi bottle currently, the fuel tank that came with had a bent bolt and when I tried to weld it it got holes. I tried it with the Pepsi bottle as is and then got better results with a hole poked in the top as a vent. Yes I know that it’s no great mystery that this system is faulty but I wanted to solve some problems before the gas tank got here.
 

Greg58

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That looks like a standard 2-stroke engine, it should run without the mag cover on it, if you’ve got pressure leaking from the cover you have a blown crankshaft seal.
 

Greg58

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It’s not a Hybrid, four strokes have valves in the block or in the head, the engine you have is a piston port two stroke. Some people add reed valves and modifications to the piston for better performance.
 

Mgb2504

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Thanks @Greg58, when you say Mag cover are you referring to the cover for the magneto that I spaced and then forgot to put the gasket back? Just want to be sure I can rule that out.
 

Greg58

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The only cover that has to be on while testing is the one over the chain sprocket, it should run normal with either of the other two off, just beware of moving parts that can catch clothes.
 
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Mgb2504

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@Greg58 Do most new bicycle engines have trouble getting fired up at first? Like the break in period I know is five tanks or so but is there a good demo on how to adjust a bowl carb? I’ve only adjusted Weedeater carbs with the diaphragm.
 

Greg58

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A lot of engines are hard to start at first, you will have to learn a routine to start it. I've had a couple that were very hard to get running and some fire right up. Looking at your carburetor it's not tilted too bad so as long as you have fuel in the bowl or it's not leaking the float should be ok to start.
 

Greg58

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The only adjustment is the idle, you'll have to change jets to adjust the mixture. I break mine in at two tanks of 24/1 mixed with a good oil, then switch to 32/1.
 

JerryAssburger

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You probably know this already, but don't overlook compression leaks or intake manifold leaks... they plagued my new build to the point that the engine would start and run, but wouldn't move the bike without pedal-assist. Being new to ChinaGirls, I almost thought that's how they were supposed to run! Glad I didn't settle!
 
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Mgb2504

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You probably know this already, but don't overlook compression leaks or intake manifold leaks... they plagued my new build to the point that the engine would start and run, but wouldn't move the bike without pedal-assist. Being new to ChinaGirls, I almost thought that's how they were supposed to run! Glad I didn't settle!
Cool I have a compression gauge
 

Greg58

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I remove the head and true it before I ever run a engine, actually I disassemble the engine and deburr the ports and clean up everything before I run it. In the early engines piston skirt trimming was needed to get the performance desired.
 

Greg58

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I true a head by taping sand paper to a true flat surface like a piece of glass and sand the gasket surface of the head till I get a even surface.
 

Mgb2504

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I true a head by taping sand paper to a true flat surface like a piece of glass and sand the gasket surface of the head till I get a even surface.
Makes sense, I’ve got some gasket in the tube maybe I’ll give it a shot, certainly put it on the troubleshooting list.
 
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wrench

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Makes sense, I’ve got some gasket in the tube maybe I’ll give it a shot, certainly put it on the troubleshooting list.
Gasket in a tube should not be used for a cyl head gasket.
If ya read the directions it probably says so right on the tube.
Not compatible with gas
 

Mgb2504

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Tbh I’ve never even looked at it, it was in a box I inherited from my uncle it’s probably hard as a rock lol.
 

Mgb2504

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Update, the bike ran for a few minutes without Interruption today, then the loose chain ate two of the back tire spokes. Decided to go ahead and get a Nel Lesso for the fat tires and spikes and because I know people have successfully mounted an engine on them. Apparently my engine was out of alignment and no chain tensioner did not work for this build. So I’m switching everything over to the new bike and am going to sand and paint, possibly weld a bracket for the gas tank (Walmart only had the girls cruiser but idgaf). Will post pics soon.
 

JerryAssburger

Active Member
Mar 11, 2017
179
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28
Salem Oregon
Update, the bike ran for a few minutes without Interruption today, then the loose chain ate two of the back tire spokes. Decided to go ahead and get a Nel Lesso for the fat tires and spikes and because I know people have successfully mounted an engine on them. Apparently my engine was out of alignment and no chain tensioner did not work for this build. So I’m switching everything over to the new bike and am going to sand and paint, possibly weld a bracket for the gas tank (Walmart only had the girls cruiser but idgaf). Will post pics soon.
It's amazing how the supply of bicycles and most things related to them have gone to s#$% lately.
Regarding your chain issue, if at all possible , most try to run the chain without a tensioner- (if you're lucky enough to get the chain-length right, that is.)