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Lt80 Hard To Start

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  #1  
Old 03-18-2018, 01:41 PM
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Default Lt80 Hard To Start

I bought a non running lt80 as project. When I got it I drained the tank, cleaned the carb, checked that I had spark, and connected a battery. It would turn over but wouldn’t start. I rebuilt the top end with a cheap ebay kit. When I went to crank it, it fired up and ran for 3-4 seconds then died. After that it would just sputter like it wanted to start but wouldn’t. I put on a new carb and charged the battery up. Turned it over a few times and it finally started. I drove around for less than a minute and as soon as I let off the throttle it died and wouldn’t start back up again. I noticed that when I put gas in it the first time it leaked all over my carport. Could the old carb and the petcock have flooded the cylinder with fuel? If so, how do I drain the fuel out?
 
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  #2  
Old 03-18-2018, 02:39 PM
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"Could the old carb and the petcock have flooded the cylinder with fuel? If so, how do I drain the fuel out?"

The cylinder usually hydraulicaly locks, if it fills with fuel so the engine is seized until you get the fuel out. I do it by removing the plug and turning the engine on the starter, however I have set two on fire doing this, so prudence now dictates removal of the low tension lead to the coil first. As you have had the engine running since flooding it, any excess fuel will have been burnt. The carb will not flood if you don't have the tap on PRIME anyway.

When you work on them you tend to stir up sediment in the fuel tank, so the most likely cause of non starting is dirt getting in and blocking the carb. It may be worth checking compression to ensure you have got that top end rebuild right. Other possibilities are the reed valves faulty, or a blown crankcase oil seal, but these are a lot less likely than dirt in a jet, or an ignition fault.
 
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  #3  
Old 03-18-2018, 03:20 PM
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Welcome to the forums.
Like mentioned, check the carb.
You might want to remove the bolt in the bottom of the pipe. Might be fuel in there plus it'll help see if the pipe is plugged.
 
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  #4  
Old 03-18-2018, 04:44 PM
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So I should start by cleaning the tank, remove and clean out the carb, and check the reads?

Is it possible that the starter isn’t spinning fast enough to start the bike?

Also, what should my compression be?
 
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  #5  
Old 03-18-2018, 07:57 PM
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It's best to clean it all.
If the motor is spinning, it's prolly fast enough.
90 minimum on compression.
 
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  #6  
Old 03-18-2018, 08:14 PM
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Should I have two lines coming from the petcock? I only have one.
 
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  #7  
Old 03-18-2018, 11:29 PM
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Yes, 1 for fuel supply, 1 for vacuum. The rear port on the carb is for vac. Hopefully it's plugged/capped.
You have a simple on/off style petcock. A lot of ppl replace the stock vac petcock with one like that.
 
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  #8  
Old 03-19-2018, 07:32 AM
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The vaccum port is not plugged or capped and my petcock is PRI ON RES
 
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  #9  
Old 03-19-2018, 08:34 AM
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Better plug the port. It'll suck a lil dirty air.
 
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  #10  
Old 03-19-2018, 08:52 AM
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Yesterday it started up again and I drove it around the yard for a minute but it wouldn’t idle and wouldn’t start back up. I drained and cleaned the tank out, removed and cleaned out the carb and it still wouldn’t start it. Just sputters like it’s trying to start. This morning I realized I didn’t have a vacuum line so I tried connecting one and I tried putting a cap on the vacuum port. Still no start. Tonight I’m going to try and new plug and I’m going to check compression. What mm head do I need to check the compression. Also do I need to hold the throttle open?

Could a bad petcock cause these symptoms?
 
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