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Old 15-01-2013, 07:26 PM   #1
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Yamaha v4 2stroke 140 problem

Posting for a friend.

Re.140hp yamaha fault = loss of spark on number 1 cyl, upper stb. If I swap the black and white primary feed wires, (from the CDI box to the coils), the loss of spark follows the swap over, so you could say the 4 coils, leads, 4 new suppressor/caps and plugs are ok. Checks are made using a spark tester set at 10mm @ cranking speed. I haven`t yet checked the resistance on the charge coil under the flywheel or the 2 pulse coils. On 4 or 5 outings during the year, the engine has had intermittent slow/idle and acceleration issues, but over 2000rpm and WOT, 5600rpm, it ran fine. During the last outing I made, the engine ran fine in all aspects, ie; idle, hard and soft acceleration, mid rpm speeds and seemless high speed. The outing lasted 2hrs continuous, faultless running. However, recently, I ran the engine at home on a hose flusher and it again was idling on 3cyls not 4. A spark test reveiled no spark at cranking speeds on cyl. number one, upper stb. Cylinders 2, 3 and 4 sparked ok with or without over/rev wire connected. Early during the season, I have checked fuel filters, new plugs, new suppressor caps, new themostats, idle mixture scew settings, new fuel line with primer. On all the info I have picked up recently it would seem I have a faulty CDI/switchbox but at £400 plus, I`m reluctant to buy, untill I`ve checked all the coils under the flywheel. Any help/advise etc. gratefully recieved, regards, Steve.
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Old 15-01-2013, 10:33 PM   #2
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Quote:
Originally Posted by gap52 View Post
Posting for a friend.

Re.140hp yamaha fault = loss of spark on number 1 cyl, upper stb. If I swap the black and white primary feed wires, (from the CDI box to the coils), the loss of spark follows the swap over, so you could say the 4 coils, leads, 4 new suppressor/caps and plugs are ok. Checks are made using a spark tester set at 10mm @ cranking speed. I haven`t yet checked the resistance on the charge coil under the flywheel or the 2 pulse coils. On 4 or 5 outings during the year, the engine has had intermittent slow/idle and acceleration issues, but over 2000rpm and WOT, 5600rpm, it ran fine. During the last outing I made, the engine ran fine in all aspects, ie; idle, hard and soft acceleration, mid rpm speeds and seemless high speed. The outing lasted 2hrs continuous, faultless running. However, recently, I ran the engine at home on a hose flusher and it again was idling on 3cyls not 4. A spark test reveiled no spark at cranking speeds on cyl. number one, upper stb. Cylinders 2, 3 and 4 sparked ok with or without over/rev wire connected. Early during the season, I have checked fuel filters, new plugs, new suppressor caps, new themostats, idle mixture scew settings, new fuel line with primer. On all the info I have picked up recently it would seem I have a faulty CDI/switchbox but at £400 plus, I`m reluctant to buy, untill I`ve checked all the coils under the flywheel. Any help/advise etc. gratefully recieved, regards, Steve.
Almost certain to be CDI !! Is it the one with screw connections ? email me ocrda@btconnect.com and i will send you one but wont be till end of month.

Bob
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Old 16-01-2013, 01:38 PM   #3
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Yam 140

Thanks Bob , i thought you might answer. Have passed details on.
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