Hi Guys,
Been trying to get this motor running right for a yr now.
Replace the ignition, rebuilt the carb, and had the best of the best work on it and still a no brainer thing going on with it.
It runs real good for the first 5 minutes and after that it starts to burgull real bad, then finally it just quits when I throttle up.
It just seems like when it gets warm up something goes wrong
The only thing I have'nt change is the spark plug and thats because it starts right up and runs good for 5 min.
Could this be the problem.
This motor has only 5 gal of gas ran threw it.

Rod</p>

when it gets warm, how hot is that? Does the engine get cooling? In the plane or on a test stand?  Needle settings? fuel used? muffler system used? Which prop?
Setup pictures perhaps?

These are a lot of questions, but remember that we can only provide answers if you give us some data we can go by.

Hello Sir,
The motor gets plenty of cooling in the plane. The needle setting is not very clear in the manual(or we just dont understand what they mean. All the guys I fly with are DA or DL guy, not that theirs anything wrong with that, but the settings in their motors are a little different.
Dont understand what you mean by(fuel used), unless you mean what grade,(93 octane, 90 to 1 syn.
The muffler is the rap around Evolution.
The prop was a 24x8 but I wipe it out on a land so now I have a 22x10. both props made the motor run the same.
2 yrs ago I had a bad crash I look the motor over real good, but.
I guy told me today that I might have a crack in the carb throat or maybe the reeds are crack, is this possible.
Rod

Thanks for the extra info.
The fact that this all happens after about 5 minutes leads me to thinking heat issues. If reeds are bad, the engine will run crappy from the first flip, which is not the case.
It is possible that the rear carb gets real hot, and vapour lock occurs. Also it is possible that the ignition gets too hot. Both these devices need cool air to work well.
It also is quite possible that there is a  general lack of engine cooling. I have seen too many baked engines where the owner said he had good cooling, so can you please take pictures of how your engine is built in the plane? That would realy help me to evaluate your problem.
BTW, Do you use baffles to guide the cooling air to the cylinders? How is the hot air extracted from the cowl?

90:1 oil is way too little. Factory data: use 40:1 oil. This is as important as good cooling.

The manual states carb needle opening "by clock hands" This is the large hand of course , so "one and a half turn" open is same as "one hour thirty minutes"
Have you checked the plug colour?
How is the plug gapped. Gap should be 0.5 - 0.6mm.

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Hello Sir,
I think, well almost sure that we found the problem.
That line that runs from the back of the motor to the fuel pump I ran it out and around to long(8inches), I did this a while back because the factory line had a kink in it.
A guy at the field today said it probaly was'nt pumping right.
Bad thing about it is I couldnt mount the motor back on cause my stand offs are messed up. I order new ones so when they come in I'll let you know how things work out.
Keep your fingers crossed.
Rod

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Please check your tank. You have to have open one tube. Maybe you have vacuum in your tank. System tank must be open.

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Just wanted to let you folks know that the 58 is fix and running great.
The vacum line was to long, very fast fix once we figure it out.
Thanks for all the help.
Rod

Glad you found the cause.

So the too long vacuum line got hot in 5 minutes and started stretching too much under pressure?