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need help to diagnose problem

Old 05-07-2016, 10:51 AM
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nitrosportsandrunner
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Default need help to diagnose problem

I picked up a exceed barca 30cc buggy yesterday.
It was cheap guys, $200!

Now, the owner said he had driven through a puddle with it and water got sucked into the carb. He said it had run since then but not as well. The guys got money, no time, just wanted it gone.

He tried to start it for me and it did fire once.

I tried yesterday for 20 minutes, couldn't even get a pop!

I checked, have spark. Tried a new spark plugs as well.
It has compression (maybe not enough)
The carb likely has an issue, but even if I put fuel through the spark plug whole, I get nothing.

I took the head off last night but nothing jumped out at me (except for the head having a good amount of carbon buildup.


Is it possible to have compression, but not enough? I have a compression tester, but it wont fit this small engine. Is there some other way to test for bad compression? I keep thinking compression cause I have a strong spark and even fuel right into the motor wont cause it to fire.

I did just order a new piston ring online. But wanted to see if you guys could come up with anything else to check or try!
Old 05-07-2016, 06:59 PM
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Originally Posted by nitrosportsandrunner View Post
I picked up a exceed barca 30cc buggy yesterday.
It was cheap guys, $200!

Now, the owner said he had driven through a puddle with it and water got sucked into the carb. He said it had run since then but not as well. The guys got money, no time, just wanted it gone.

He tried to start it for me and it did fire once.

I tried yesterday for 20 minutes, couldn't even get a pop!

I checked, have spark. Tried a new spark plugs as well.
It has compression (maybe not enough)
The carb likely has an issue, but even if I put fuel through the spark plug whole, I get nothing.

I took the head off last night but nothing jumped out at me (except for the head having a good amount of carbon buildup.


Is it possible to have compression, but not enough? I have a compression tester, but it wont fit this small engine. Is there some other way to test for bad compression? I keep thinking compression cause I have a strong spark and even fuel right into the motor wont cause it to fire.

I did just order a new piston ring online. But wanted to see if you guys could come up with anything else to check or try!
Did you take the muffler or header off? I asked because sometimes the exhaust port can get carbon built up plugging it up.
Also check the flywheel key ,an make sure that it didn't shear off ,that would throw the ignition timing off.

Last edited by cbaker65; 05-07-2016 at 07:08 PM.
Old 05-07-2016, 09:13 PM
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nitrosportsandrunner
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just took the exhaust off and checked. no carbon build up or blockage.

I did turn over the motor with my drill and put my hand over the exhaust and noticed that while air is being moved, there isn't much force. I can cover the exhaust and it doesn't push my hand away.

The inside of the cylinder looks good, not all scored up and I cannot see any damage to the piston ring, but I still kind of think that it may have low compression. I know there is spark...and even if it were weak I should at least get a pop every now and then.

I bought a new head gasket and ignition coil tonight. I bought a piston ring last night. Hopefully when those parts arrive, I can get it running. I know for sure the carb at least lets fuel get to the motor...so if I can get good spark and compression it should fire.
Old 05-08-2016, 06:22 AM
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Originally Posted by nitrosportsandrunner View Post
just took the exhaust off and checked. no carbon build up or blockage.

I did turn over the motor with my drill and put my hand over the exhaust and noticed that while air is being moved, there isn't much force. I can cover the exhaust and it doesn't push my hand away.

The inside of the cylinder looks good, not all scored up and I cannot see any damage to the piston ring, but I still kind of think that it may have low compression. I know there is spark...and even if it were weak I should at least get a pop every now and then.

I bought a new head gasket and ignition coil tonight. I bought a piston ring last night. Hopefully when those parts arrive, I can get it running. I know for sure the carb at least lets fuel get to the motor...so if I can get good spark and compression it should fire.
Usually with low compression ,it should atleast fire though.
But yea,it sounds like low compression ,might be a leaky head gasket or worn out ring.

If you had the measurements of the piston ,you can try to find a dual ring piston that would fit ,your compression ratio
will increase dramaticly ,you will get better performance out of the engine!
Old 05-18-2016, 10:09 AM
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nitrosportsandrunner
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well, I am officially 100% stumped.

I have replaced the piston ring, spark plug, ignition coil, head gasket and the carb. And I get, nothing. not even a pop! There is compression, fuel does go into the motor and there is spark. Ive never had a motor act like this. It sucks cause I don't have $100+ to buy a replacement motor. I have $250 into it now, so Id probably take a loss if I sold it. Ugh!
Old 05-19-2016, 03:47 AM
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Mudgy
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It's a 2 stroke.... compression, spark, fuel. is all you need.
Did the carb check out OK? have you had it apart? What are the needle settings?
Spacer block on the carb ok?
Inlet manifold leaks?
just going through things in my head is all...

your finger in the spark plug hole should be a good enough indicator of compression.

coil to flywheel can be spaced with a business card.. most are usually 0.3mm thick, and make a quick handy gauge for air gaps.

sometimes I've had debris in the needle seats.... I just wound the needles open to let the junk through, then wound them back in to tune L & H.
Old 05-19-2016, 05:59 AM
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after posting my frustration yesterday, I got motivated to go back out and work on it again.

I pulled the motor...cleaned the surfaces the head gasket mates to better and spaced the ignition coil and put it all back together. BAM, runs now. I had installed the head gasket with the motor still in and may not have cleaned the old gasket off well enough...add to that the ignition coil was rubbing the rotor and it likely had low compression and poor spark.

After a little tuning I got it running pretty decent. Pretty happy, especially since it only cost me $250 to get a running 1/5 scale.
Old 05-19-2016, 11:38 AM
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Originally Posted by nitrosportsandrunner View Post
after posting my frustration yesterday, I got motivated to go back out and work on it again.

I pulled the motor...cleaned the surfaces the head gasket mates to better and spaced the ignition coil and put it all back together. BAM, runs now. I had installed the head gasket with the motor still in and may not have cleaned the old gasket off well enough...add to that the ignition coil was rubbing the rotor and it likely had low compression and poor spark.

After a little tuning I got it running pretty decent. Pretty happy, especially since it only cost me $250 to get a running 1/5 scale.
Awsome man!

Yea,there shouldn't be no reason why it wont fire!
All it take is a hole in the block or leaky head gasket or a sheared key way in the magneto flywheel!

Glad you got it going!...Also ,you gained some experience!....

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