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vernonf · 03-04-2007, 04:54 PM

Well , I found out today why the engine is hard to start. I have zero compression on the rear most cylinder. It has a melted 3/8in hole in it after the first 15 minutes on the test bench. I am feeling sick.
I ran the proper breakin oil mix and recommended prop. I warmed the engine up a couple minutes and mid range for 1 minute cool down 1 minute then ran it up to Tached 6100 to 6200 rpm for breakin. It started slowing down , so I thought it was overheating, then when it went to idle, it blew out a white puff of smoke out the left exhaust. I pulled the plugs , the right plug looked great, brown and a little fuel/oil residue, but the left plug showed signs of being Lean, clean . I put the fat finger over the plug hole , no compression. The right side great compression. I pulled the exhaust off and the right piston shows oil / fuel residue on the piston and sleeve. The left piston is dry as a bone. The carb setting were verified . Low was 1 3/8 and High was 1 1/2.
I am shipping it to DA tomorrow.

What could cause the rear cylinder only to run Lean enough to melt the piston?

03-04-2007, 04:54 PM	#1 (permalink)
vernonf Super Contributer Join Date: Jan 2006 Location: Phoenix, Az Age: 46 Posts: 129	Test Bench Break in DA 100 Big Problem Well , I found out today why the engine is hard to start. I have zero compression on the rear most cylinder. It has a melted 3/8in hole in it after the first 15 minutes on the test bench. I am feeling sick. I ran the proper breakin oil mix and recommended prop. I warmed the engine up a couple minutes and mid range for 1 minute cool down 1 minute then ran it up to Tached 6100 to 6200 rpm for breakin. It started slowing down , so I thought it was overheating, then when it went to idle, it blew out a white puff of smoke out the left exhaust. I pulled the plugs , the right plug looked great, brown and a little fuel/oil residue, but the left plug showed signs of being Lean, clean . I put the fat finger over the plug hole , no compression. The right side great compression. I pulled the exhaust off and the right piston shows oil / fuel residue on the piston and sleeve. The left piston is dry as a bone. The carb setting were verified . Low was 1 3/8 and High was 1 1/2. I am shipping it to DA tomorrow. What could cause the rear cylinder only to run Lean enough to melt the piston?