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4 cycle backfiring

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Old 06-15-2003, 10:19 PM
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mndbndr3d
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Default 4 cycle backfiring

I have a saito 180 and I'm using cool power 30% fuel. I've got about 2 gallons thru the engine and it's running great, but once in a while the engine backfires, is this bad for the engine? what's your opinion?

Harold.
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Old 06-15-2003, 11:48 PM
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Default 4 cycle backfiring

If I am not mistaken, it is due to the engine being lean. Richen up the mixture (idle or high end) and you should be fine.
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Old 06-16-2003, 04:23 AM
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Default 4 cycle backfiring

that is true, 4 strokes cannot be run lean for that reason. but, also high nitro content on a hot plug isn't great for that issue either. what plug are you using? because a hot plug on 30% fuel isn't very good.
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Old 06-16-2003, 04:51 AM
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Default 4 cycle backfiring

Backfires will wear out the engine really bad.
I once messed with a YS 53, backfires like 6-7 times
and I loss nearly all compression and have to
replace the cylinder liner, piston and ring.
Be careful with the needle, especially using high nitro fuel.
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Old 06-16-2003, 02:18 PM
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Default 4 cycle backfiring

Back the nitro off to 15% and see if that doesn't cure it. And don't run it overly lean. Also check that your prop isn't too big.
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Old 06-16-2003, 03:56 PM
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Default 4 cycle backfiring

if your four stroke is pumped, than you can run your engine at peak without problems. HOWEVER if your engine is not pumped, you should bakc it down to about 500 below.
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Old 06-16-2003, 05:47 PM
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Default backfire

Thanks for the response. I forgot to mention that I am using a perry pump on my engine and It's running at it's peak without any problems. I'll go ahead and try you guys advice to richen it up.

"high nitro content on a hot plug isn't great for that issue either. what plug are you using? because a hot plug on 30% fuel isn't very good"

I'm using the stock plug that came with the engine. I'm only using the 30% cool power because this is what recommended by saito to get the best power.

Harold
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Old 06-16-2003, 06:44 PM
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Default 4 cycle backfiring

I would give it a try with 15% and see if you notice a big difference in performance. If the plane still has enough power to do what you want it can save you a lot of $$$ and also be a little easier on the engine. Most people have had better success replacing the stock plug with an OS "F" plug.
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Old 06-16-2003, 08:03 PM
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Default 4 cycle backfiring

the best power would be the minimal amount of castor, running the rest nitromethane. that won't happen. basically, what they are saying is that that's the highest amount of nitro the engine can handle. it will also wear out your engine a bit faster. if you MUST stay at 30% nitro, bakc down to a cooler plug and see if that helps. BUT i would reccomend that you go to around 15%- 20% (i run 20 percent) and use the os #F plug. people are really satisfied with this plug. i know a guy who has had one in his engine for 10 years, and it still tunes really well. the only problem is it is a fairly expensive unit
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