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14672Re: [Small4-strokeEngines] Re: motorcycle engines

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  • ron ohler
    Sep 1, 2014
      I flew 2 strokes for nearly 20 years. Some 650 hours on several engines. 3 hours on a 277 that came on a Falcon before I transferred a Cuyuna ULII-02 onto it from on of my Pterodactyls. I've owned a number of Pterodactyls. All had Cuyuna's. One came with an engine that didn't run right - wouldn't idle properly. I figured out it had bad crank seals - something the previous owner didn't figure out and seized the engine a couple times. The other planes - one came with a points ignition. It ran fine. I sold it after about 5 hours of flying. All of the other hours were put on 2 engines - a 430 with CDI and the ULII-02. I've had a few engine out landings. First one was caused by fuel stored in the tank over the winter settled out some goo that was drawn up by the fuel pickup and plugged the small sintered metal fuel filter. I cleaned the filter and used the fuel line as a syphon to vacuum the rest of the goo off of the tank bottom. I then flew home where the tank was removed and thoroughly cleaned and a larger filter installed. Then an electrical connector on the ignition failed and put me down. I cleaned the connector - crimped the female ends a bit and reassembled it and flew. I later soldered the connections. Next one was one where I scuffed a piston because I put a different muffler on - an automotive glasspack - and flew without thoroughly testing for any changes in jetting requirements. The engine did not quit - I could hear that it did not sound the same while flying and when I tried to restart it to leave the destination field I could feel there was a loss of compression on one cylinder. I raised the jet needle and flew home. Rebuilt the top end and put a proper muffler on it. Next was a forced return to the field by failure to produce enough power to maintain flight. Bad ignition coil. Next forced landing was because the belt reduction drive tensioning cam backed off - I was able to keep the engine running at very low throttle settings and get some thrust. I then flew from farm field to farm field sniffing out every thermal and using them to gain altitude and then power glide to the next field. This went on for some 10 miles until I was able to get to a private airstrip where I barrowed a few wrenches to tighten the belt again. Next was intermittent severe power losses. The engine kept running fine but something was definitely wrong. I landed in a farm field that was a bit rougher than it looked. I found that a screw had come out of the magneto breaker plate and was caught inside the flywheel where it was stuck to the magnets. It would move around and bind between the flywheel and the coils. It was this binding that was slowing down the engine. Takeoff from the field was rough - breaking a cable that braces the nose boom tubes from the nose gear. Result was that the tubes flexed more which was rather disconcerting with the canard wobbling around in the afternoon thermals. I few for years without more problems until a fuel problem gave me several forced landings. A primer bulb was found to be too hard for the fuel pump to draw fuel through. A couple T's and a short bypass line corrected that. Then more intermittent fuel issues - one resulting in an aborted takeoff - was finally found to be a cracked compression nut inside of the fuel tank. Then a couple engine stalls on final glide into a couple airfields on a trip was traced to a carb float valve that was starting to fail resulting in too high a fuel level in the carb. Then - a sudden stoppage of the engine on takeoff - only 50ft off of the runway - was the hardest to determine a cause. It was finally traced to a bad ignition switch. A replacement switch corrected that. The last and final one was caused by a fuel line failure resulting from poor maintenance and the earlier primer bulb bypass. I had gone to using the blue urethane fuel line sold by CPS. This is decent stuff for what it is - but needs to be replaced every 2 to maybe 3 years. When I fitted the bypass on the primer bulb I used a 3inch piece between the bulb and one of the bypass T's. It was not new line It had been used for about one year. I replaced all of the rest of the fuel line when looking for the air leak that was finally traced to the inside of the fuel tank. I missed changing this 3 inch piece of fuel line and it spontaneously broke shortly after takeoff. My landing in a corn field damaged the plane. I have not flown since as the plane needs repairs and I lost my hanger.
       The CPS fuel line is an issue. It is quite tough when new. However - when used for 2 to 3 years it discolors and takes on a greenish tint as it looses it's transparent blue color. At this time it is full of tiny micro-cracks and tears easily. I could cut this short piece in half with a thumbnail. It was about 5 years old and had been used for about 6 months and then removed and placed in inventory. It was then retrieved and put back on the plane and used for about 3 years before failing. I still have a partial coil  of new line in inventory where it looks as good as the day I bought it over 12 years ago. I have used it for other things where it does not appear to suffer from storage. I did find out that it can not be used in contact with used vegetable oil. The oil destroys the line within a week.
      I don't blame the engines for any of my engine out's/forced landings. Except for the scuffed piston - which did not result in an forced landing - all were caused by things other than the actual engines. I blame myself for trying a Cherry bomb type glasspack for that one. Some failures were correctable by better methods (locktite on magneto screws) maintenance (periodic replacement of serviceable components - fuel line for instance) or mechanical failure - ignition coil and switch. The carburetor float valves have always been a wild card. I've had valves last 60 hours and others that only lasted 7 hours. Most failed in 20 to 40 hours. I tried float valves made by Grose but did not have good results. Most float failures were noticed by hard starting or idle mixture changes. None were significant enough to effect powered flight. Only landing glides or ground operation. While I have kept float valves in service after noticing changes in ground operations - I quickly came to realize that it is far better to just change the valves than change carburetor settings. I believe that many folks who have problems with 2 strokes just can't get the carbs set right in the first place and then change things without understanding that if you change carburetor settings and then later - a float valve - that you must plan on reversing all of the changes you recently made on the carburetor to compensate for the leaking float valve - possibly before you realized the float valve was the problem. If you don't - the carburetor is likely now set too lean and you will likely find out when it really matters - while flying.


      From: "'George Bearden' gab16@... [Small4-strokeEngines]" <Small4-strokeEngines@yahoogroups.com>
      To: Small4-strokeEngines@yahoogroups.com
      Sent: Monday, September 1, 2014 3:50 AM
      Subject: RE: [Small4-strokeEngines] Re: motorcycle engines

      > getting tired of misinformation about 2 strokes
      I'm glad you have had good luck with 2-strokes. It is encouraging to hear. Like you, I have heard pilot after pilot report engine failures in their 2-strokes forcing an off-field landing. It doesn't take too much of this to undermine my confidence. Natchurley these reports come from quite a wide sampling of pilots, experience, engine knowledge and now maybe honesty. Some pilots assert their engine savvy when saying they treated the 2-stroke right. But I'll never know. I have no way of checking that. Plus- do they have an agenda and are being dishonest about the incident somehow? I can't know. Sitting here in my seat I have people claiming 'misinformation', over there are people swearing at 2-strokes with vivid accounts of premature failure, over and over.
      Two things I can know; 1) you can't claim misinformation with integrity until you KNOW all the particulars in each case, 2) good results on your part with 2-strokes doesn't imply lying on the part of others with bad results. Because each of us have honor and integrity until proven different, I would encourage you to re-read your msg before posting in order to avoid unnecessary inflammation of the topic.

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