Pipelinetriker, welcome, but the yt175 came with a suspension front end uless you have changed a bunch of parts over. Cox the yt175 only came out in 82 and 83. If you have 2 81's, more than likely they are 125s. It is also a bit of a pain to put 175 engines in the 80 and 81 frame, it's possible but a pain. Now you can switch the top ends, but the 80 and 81 engines have clutch baskets that take fewer clutch plates and fiber and a 175 top end on an 80 or 81 lower end tends to fry the clutch pretty fast. Maybe you guys ought to go out and check your machines a little more closely.
Nicholson 500x (Project)
Nicholson 185s
Nicholson 110 (That takes an atc70 tank)
Ascott 500 head/350x (Project)
Homebuilt Racer Chromoly Suspension 110 (Ragin Runt)
PK Racing Suspension 70
A+ Inc Suspension 70
AWS Aluminum 90 frame
Hi Performance ATC Suspension frame rd350
Hi Performance ATC Suspension frame 90