Hello, I have recently also purchased a Yamaha DT 175 MX. Year 1981, credible 6,800 KM, two previous owners, really good original condition. The following problem: I now have to renew the spark plug for the 3rd time after only 100 kilometers of driving distance. Each time the gkeiche, new spark plug in (last also with new plug), starts immediately and has great performance. After only 50 KM the power decreases and a few kilometers the engine stops the service and does not jump more on. Spark plug bolted out, held to the cylinder head and kickstarter operated: As with the previous spark plugs, there is an ignition spark, but at the thread of the candle and not where it belongs. I have screwed the prescribed spark plugs of NGK (B8ES) and also once by BERU … with the same result! Can someone give me a tip where it is in the Ekektric or Ignition???? Greeting