Can any one give me any ideas on my problem? I have lost all top end power on my son’s 1975 DT 175 bike. I've been through the Carburetor about six times making sure everything is clean and adjusted. I've cleaned the piston and the head. The compression is a little low but it starts great and ideals great. It’s got a magneto and the points look good and adjusted. It’s like the timing doesn’t advance when I rev it up. I’m at a loss does anyone have any idea??

CHP4JC

When my old IT-175 used to get weak up top, it was always either worn rings or clogged exhaust. If your silencer is clear (no packing wadded up in there) then it sounds like a wornout set of rings. Wouldn't hurt to check that the reed valves are not chipped and seal against the intake cage well. If the bike still has stock-type steel valves, get some good fiber reeds. Longer life and better performance.

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No Witnesses....

Thanks alot! I'll pull the muffler off and I’ll check the compression. I'll let you know what I find out. Thanks again.

I found some time to work on the yamaha last week end. I check the Muffler and the compresion. Muffler was clear and the compresion was a little low but ok. I took the carbs off and took the gas take off. I was getting ready to take the cylinder off to measure it for a ring. I found a fuel filter built in to the petcock and took it apart. wow, I found rust setament. it was resticting the gas flow. I just had to put it all back together after i cleaned it and try it. It fired up on the first kick like normal. Got it out into the yard and I gave it the onion, the front tire came off the ground and it took off!! that was it, it was starving for fuel the whole time. I got to get the blinkers working and it will be road worthy. Thanks for the help!