Engine won’t start! HELP!! Rovan 5sc

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Zach619

Zach619

Member
Messages
22
Ok so I bought a rovan 5sc with the 36cc 2 stroke 2 months ago. It ran fine until about 2 weeks ago. I couldn’t get it to start but it sputtered. I swapped spark plugs and it started but did not want to stay running. Once I got it started I ran it full speed down the street to try to get it warmed up. Halfway down the street the engine died. Not sputtered and shut off but died entirely. Something got into the engine and scarred my piston and cylinder. So I bought a top end rebuild kit and put it on there. I now have compression and air. Now to the fire. I have a factory replacement spark plug. When I take it out of the head and ground it to the head while turning over the engine it sparks. I cannot however tell if it is firing at top dead center. I read that coils can go bad and still spark but the timing be off so I replaced it. The car still will not start. The flywheel is keyed so it can’t be off on the timing. Top end is fresh rebuild so I have compression. I figured maybe it’s my carb so I took it apart and cleaned it and reinstalled it to factory settings on the high and low. Still can’t get this to fire. I took the carb off and sprayed starting fluid into the intake slot in the engine while turning over the engine and couldn’t even get it to start like that. I can’t even get a sputter. Does anyone have any clue what I need to do to get this car running again. In theory there is absolutely no reason why it will not run. PLEASE HELP!!
 
Welcome Zach.?? Sorry you are having issues with your Rovan. Believe me there will be more knowledgeable people that will be chiming in shortly. Its Friday so it may take a little time, but I'm married with children so I don't have anything else to do.? There's one thing I didn't hear you say you did....gap the coil to the flywheel. Did you do that?
 
crucialRC said:
Welcome Zach.?? Sorry you are having issues with your Rovan. Believe me there will be more knowledgeable people that will be chiming in shortly. Its Friday so it may take a little time, but I'm married with children so I don't have anything else to do.? There's one thing I didn't hear you say you did....gap the coil to the flywheel. Did you do that?
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Yes that is one thing I did. I used a business card to set the gap cause that’s the best I could find online as to what I should use to measure my gap on the coil.
 
Zach619 said:
Ok so I bought a rovan 5sc with the 36cc 2 stroke 2 months ago. It ran fine until about 2 weeks ago. I couldn’t get it to start but it sputtered. I swapped spark plugs and it started but did not want to stay running. Once I got it started I ran it full speed down the street to try to get it warmed up. Halfway down the street the engine died. Not sputtered and shut off but died entirely. Something got into the engine and scarred my piston and cylinder. So I bought a top end rebuild kit and put it on there. I now have compression and air. Now to the fire. I have a factory replacement spark plug. When I take it out of the head and ground it to the head while turning over the engine it sparks. I cannot however tell if it is firing at top dead center. I read that coils can go bad and still spark but the timing be off so I replaced it. The car still will not start. The flywheel is keyed so it can’t be off on the timing. Top end is fresh rebuild so I have compression. I figured maybe it’s my carb so I took it apart and cleaned it and reinstalled it to factory settings on the high and low. Still can’t get this to fire. I took the carb off and sprayed starting fluid into the intake slot in the engine while turning over the engine and couldn’t even get it to start like that. I can’t even get a sputter. Does anyone have any clue what I need to do to get this car running again. In theory there is absolutely no reason why it will not run. PLEASE HELP!!
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Is the spark plug a ngk or a off brand China special that some rovans come with? Also is the spark plug gapped correctly? Is it getting fuel?
 
Z.hb71 said:
Is the spark plug a ngk or a off brand China special that some rovans come with? Also is the spark plug gapped correctly? Is it getting fuel?
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The plug is ngk and so was factory on my car. The gap the plug came with matched the gap of my factory plug so I’m assuming it’s correct. Yes I am getting fuel. I even tried starting fluid with no luck. Not one fire.
 
crucialRC said:
That should get you close enough. DDM sells a gapping tool but the business card should get you close enough. ?You also didn't mention whether or not you have a killswitch. When you pulled the plug was it wet?
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Yes the engine has a kill switch attached to the coil. I tried to start the car with and without it attached. Even with it attached I am getting spark. If the kill switch was bad it would be grounding my spark. And with the plug wet or not that is a yes and no question. Throughout trying to change settings on the carb and from spraying starter fluid in there I have pulled the plug out dry at times and wet at other times. In both cases it will not even sputter.
Z.hb71 said:
Ok. I really stumped right now. I'll tell you if I think of anything
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Thank you!!!
 
I gonna take a wild guess and say you may have installed your piston 180 degrees off and you're losing compression through the ring gap at the exhaust port. To verify piston orientation, remove the exhaust and rotate the crank until you see the ring. If you see the ring gap there's the problem.
 
Check your clutch are you sure you put the piston in correctly and ring it goes a specific way go on YouTube but I would check everything again
 
Top Dead Center said:
I gonna take a wild guess and say you may have installed your piston 180 degrees off and you're losing compression through the ring gap at the exhaust port. To verify piston orientation, remove the exhaust and rotate the crank until you see the ring. If you see the ring gap there's the problem.
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Piston is directional. It has an arrow stamped on the top of the piston for direction of flow. The arrow points towards the exhaust. The old piston was orientated that way and also from what I read online that is the correct direction. That is the direction I installed it. Unless the stamped arrow is backwards from the factory the piston is in the right direction.
crucialRC said:
?check carb insulator for a crack?

+1 on the clutch.
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No damages to that and I tried starting fluid with the carb completely off. Can’t get even a sputter.
 
It sounds like your troubleshooting methods are spot on. So, I'm making guesses at extraordinary issues. First would be a sheared keyway and your ignition is out of time. Second would be crank seals (highly unlikely on a two month old engine).
 
Top Dead Center said:
I gonna take a wild guess and say you may have installed your piston 180 degrees off and you're losing compression through the ring gap at the exhaust port. To verify piston orientation, remove the exhaust and rotate the crank until you see the ring. If you see the ring gap there's the problem.
Click to expand...
If you getting spark but not firing and you were just in there??
crucialRC said:
?check carb insulator for a crack?
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+1
 
Top Dead Center said:
It sounds like your troubleshooting methods are spot on. So, I'm making guesses at extraordinary issues. First would be a sheared keyway and your ignition is out of time. Second would be crank seals (highly unlikely on a two month old engine).
Click to expand...
The keyway is intact. No issue there. I don’t know how the seal on the crank shaft could be bad cause it’s a new engine like you said. Any other ideas?
 
Z.hb71 said:
Blocked air filter? Possibly?
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I took the entire carb off at one point and sprayed starting fluid into the intake port to see if I could even get a sputter that way with no help. Also intake is clear through carb. No blockages.
 
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