What is good compression for my 1980 DT175?


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I currently have 130.


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I have zero. 

130 is fine.  Compression readings are a very unreliable indicator in these engines, different gauges and different technique can give vastly different results.  Your bike has 130 with your gauge and technique...  you can use that to compare with your future readings.

130 sounds good without researching it.
I just go by the bouncy feel on the kickstart.
You get a feel of it after years of doing it on any & every size motor.
How does your motor run.
Does it idle nice, & sort of lumpy as it fires through strong compression.
If very low it will struggle & hold a flat line idle while trying to fade out & stop--need the speed screw turned up [in] more than need be--not sound happy.
I'd say ya 'all good'. In saying 'that' i'm sure i remember DT175's at that time coming out with those rings made of something you could just about tie a knot in & flexed without breaking but didn't do a great sealing job that rings should do.
Sorry if that starts worry [correct me someone please if i'm wrong].
I worked for Yamaha locally in those years. [workshop].

And just FYI, Yamaha never published any numbers for these bikes...  probably because of what I just said...  readings can vary widely on the same engine with different gauges and different people doing the test.

Mark T and RT325

Thanks for input. Bike runs and idles strong now.

I had a blown out base gasket. The idle was all over the place.
So I repaired that and put a new Wiseco piston and rings. Bike runs really good and finally idles like it should.


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Cool, base gasket sure upsets carburation.