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My office bought recently F150B Yamaha 2 x 4-stroke OBMs. They have so far done around 100 hours. All of a sudden one of the motor started running erratically and would not idle. Fuel lines, filters were checked/replaced. Spark plugs were removed and to my great astonishment, out of 4, on 2 spark plugs, the outer electrodes were bent and touching the center electrodes. Its was like as if someone had dropped them or intentionally bent them but the mechanic swore nothing of that had happened. Replaced the plugs and ran the motors for about 30 minutes and again we were faced with the same problem, i.e. bent outer spark plug electrodes. Checked with Yamaha dealers in Thailand and they suggest using highers (92+) octane fuel. I am not convinced that the bending of the outer electrodes has anything to do with the fuel octane rating as I believe use of lower octane fuel would have an impact of the efficiency of the OBMs and perhaps result to unusual amounts of carbon deposits. And none of this is evident. These OBMs are used in Myanmar and quality of fuel is always questionable. Having said that, however, our 2-stroke Yamaha OBMs (several of them) are actually doing fine - running for years on fuel of same quality!! Any suggestions/advise would be greatly appreciated. Thank you.
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My office bought recently F150B Yamaha 2 x 4-stroke OBMs. They have so far done around 100 hours. All of a sudden one of the motor started running erratically and would not idle. Fuel lines, filters were checked/replaced. Spark plugs were removed and to my great astonishment, out of 4, on 2 spark plugs, the outer electrodes were bent and touching the center electrodes. Its was like as if someone had dropped them or intentionally bent them but the mechanic swore nothing of that had happened. Replaced the plugs and ran the motors for about 30 minutes and again we were faced with the same problem, i.e. bent outer spark plug electrodes. Checked with Yamaha dealers in Thailand and they suggest using highers (92+) octane fuel. I am not convinced that the bending of the outer electrodes has anything to do with the fuel octane rating as I believe use of lower octane fuel would have an impact of the efficiency of the OBMs and perhaps result to unusual amounts of carbon deposits. And none of this is evident. These OBMs are used in Myanmar and quality of fuel is always questionable. Having said that, however, our 2-stroke Yamaha OBMs (several of them) are actually doing fine - running for years on fuel of same quality!! Any suggestions/advise would be greatly appreciated. Thank you.
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spark plug electrodes dont just bend,, something has to bend them, possible contact with the piston,, look inside at the top of the piston with a bore scope for evidence of contact. are you in fact positive those are the correct spark plug.. maybe the reach is to long.. -
Thank you for you advise.. Will be back after checking.Comment
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You prob have been rods and busted pistons. You'll have to rebuild your power head. This happened to me last year.Comment
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