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Scott Chapman

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  1. Scott Chapman

    Transmission Oil leaking into engine oil????

    A bit of advice about the Head vent tube: We routed the Head vent tube straight down the back of the engine and not into the airbox. We DNF'ed at an important race when Jon high sided on a off-camber and oil blew off the head vent into the airbox with the engine still running. This fouls the carb up and the only way to start the bike is to bump start it. To prevent this we route it away from the airbox and just straight down the back. Be sure to plug the hole left in the airbox.
  2. Scott Chapman

    Transmission Oil leaking into engine oil????

    Thanks for the info. I will try Rob's fix below first by replacing the main crank seal. If that doesn't work I'll tear it down.
  3. Scott Chapman

    Crank and Counter Balance Shaft Seals

    I'm having a similar problem with my bike, although it is a CRF250. oil is migrating from the transmission to the engine. We rreplaced the counter balance shaft seal and it is still doing it. I don;t think it is the crank shaft seal as the bike runs well. Where else could the oil move through to the engine??
  4. We have a 2005 CRF250R and we are losing transmission oil into the engine oil. The engine level increases until oil blows out the crank case vent (we have the crank case vent hose routed down the back of the engine case and not into the airbox to prevent fouling the bike upon wipe outs). We just replaced the counter weight shaft seal on the left side of the engine. We figured the engine was sucking transmission oil through this seal. But we still have the problem. We lose 500ml of oil in 20 minutes of hard riding. I'm afraid I need to split the case and go in deeper. It's quite obvious the oil is moving over as the engine oil becomes very dark and is obviously contaminated with transmisison oil. Any thoughs would be greatly appreciated??