1977 vs 1978 YZ Frames

[Tahitian_Red]

All the test articles mention the added chromoly in the 1978 YZ frames, but how much lighter and stronger are they versus the 1977 frames? 

I am assuming they used 70's "Japanese Chromoly". 

[Nathan S]

I strongly suspect that there's minimal actual difference in the material used in D & E frames.

Having had bare 125D & 125E frames together, there's no discernible different in weight, corrosion resistance, difficulty to drill/cut. If anything, I've seen way more cracked E frames than D ones - this is the only sign I've seen that there is actually a difference between them... :/

[LWC82PE]

I have an official suzuki doc where they explain differences between 76 and 77 RM's. They said the 77 swingarm is made from 'high-tensile strength steel' (what ever that is?) and is constructed to weight less and be more rigid than the 76 which was made of 'cro-moly'. When i first held a 76 i thought wow this feels light (compared to a mild steel swingarm) and i knew it was cro-moly by the sound it made when tapping it. But then that feels like a boat anchor compared to some alloy swingarms i have. KG's difference. I have not got a 77 one to compare too though. But I wonder exactly what material the 77 is made from since they say its not cro-moly like the 76.

[shelpi]

just my opinion, I think the RM77 swing arm is made of pressed mild steel sheet metal because it rusts like mild steel, welds like it and feels about right in the weight stakes and sounds like it when belting the piss out of it,
hence why it is box section, dont get me wrong they strong and light enough ish