rcfyam Posted July 5, 2010 Share Posted July 5, 2010 Hey guys, I recently bought a 1995 yamah dt125r (2 stroke) which required a lot of rebuild work. I installed new tyres and rims, I had to replace the fuel tank as the old one was rusty, I over hauled breaks and carb and I recovered the seat. After all this work I was glad to get it running. It felt good and I had no problems. That was untill after about about 300 miles of riding and the engine partailly seized on me. Once recovered I went about investigatin the problem and found that the oil in the tank had not been injected at the correct rate therfore the motor was running on no where near enough oil. Once i had replaced piston and rings and rebored the engine I went about sorting out the oil problem. I checked the oil feed pipe for blocks, none I checked the bled screw to see if any air was in the system, none I checked the outlet pipe for leaks and blocks, none I also checked the throttle cable housing and it was running perfectly and finally I acually replaced the pump unit I thought maybe the pump was blocked internally but when I ran the engine it was still only consuming about half the amount it should at about 80:1 where it should be running at 40:1 (I ran premix in the tank to insure it did not seize again) The only thing that I can think of and havent replaced or checked is the gear that the pump runs off in the gear box but I would of thought that if this was worn then the pump would not run at all? The throttle cable is allined correctly. Any ideas because Im running out of them Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 5, 2010 Moderator Share Posted July 5, 2010 is thethrottle turning the pulley ok? try turning the pulley manually when the engine is idling, this allows the oil pump to maximum stroke and the bike should smoke heavily. Link to comment Share on other sites More sharing options...
rcfyam Posted July 5, 2010 Author Share Posted July 5, 2010 I have done this and the pully is turning fine on the cable. The oil is getting to the engine just not enough. When I do this it doesnt smoke heavily but does smoke a bit more than usual. Do you know how fast the pump should move up and down at idle? I did do I little test on the pump where I first of all disconnected the delivery pipe, while engine was running with premix, and at idle no oil seems to exit the pump, maybe not running fast enough. I then attached a clear bit of pipe to the delivery pipe and pump to see the oil and it only seems to be sucked into the engine from vacuum. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 5, 2010 Moderator Share Posted July 5, 2010 The clear pipe is a good way to go, it should definitely pulse through the pipe at idle although the pump stroke is much reduced . But when held fully open at idle the oil should travel around 6/7mm with each stroke of the pump. Nothing to do with the vacuum, it should do this even with the delivery pipe disconnected from the reed block. By the way...could there be an issue with your reed block oil spigot being blocked? Try disconnecting the delivery to see Link to comment Share on other sites More sharing options...
rcfyam Posted July 6, 2010 Author Share Posted July 6, 2010 How can I tell if the reed block oil spigot is blocked? Also if this was blocked wouldn't the oil go down at the correct rate but not enter the engine? Im not sure if this helps but when I leave my bike overnight on my drive I sometimes get a little patch of oil and I haven't been able to trace where it comes from, could this be from the blocked spigot? Thanks Link to comment Share on other sites More sharing options...
rcfyam Posted July 7, 2010 Author Share Posted July 7, 2010 UPDATE: I decided to check the delivery feed today to see if oil was getting pumped into the engine at the correct rate. I found that no oil was coming out at idle and with the pulley pinned fully opened at idle not much oil came out either. The problem must be to do with the drive componants, although the pump has a clear oil feed and is operational. The drive gear and shaft sound like there not completly engaged with the pump, maybe this could effect delivery rate? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 7, 2010 Moderator Share Posted July 7, 2010 these things are silent. can you see the pulley and the shaft it's on reciprocating? have you bled the pump properly until only oil came out? Link to comment Share on other sites More sharing options...
rcfyam Posted July 8, 2010 Author Share Posted July 8, 2010 I have bled the oil and oil is coming out free of air. The pump is moving up and down but the correct amount of oil isn't coming out. Its like the pump is moving up and down but not enough oil is being delivered. Also answering your question about opening the pulley full when idling, the bike does not seem to smoke much more when I do this. Would it be possible for the drive gear to be damaged? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 8, 2010 Moderator Share Posted July 8, 2010 I have bled the oil and oil is coming out free of air. The pump is moving up and down but the correct amount of oil isn't coming out. Its like the pump is moving up and down but not enough oil is being delivered. Also answering your question about opening the pulley full when idling, the bike does not seem to smoke much more when I do this. Would it be possible for the drive gear to be damaged? If the pump is moving up / down in a uniform manner then it looks as though the drive is ok doesnt it? so if thats the case the pump may be faulty. Link to comment Share on other sites More sharing options...
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