Picked up an 86 250r

[DesertRider]

Brought it home, guy I bought it from had no history, noticed this. Long rod?

[yaegerb]

Brought it home, guy I bought it from had no history, noticed this. Long rod?

Its pretty likely.

[BOB MARLIN]

Yep, looks to be a long rod lower end from a TRX with a ATC top end.

[shortline10]

Or a stroker crank :wondering

[Bernard3rd]

Hi Guys,

Seems like this might be a beginner question, but can someone explain to me why it is called a "long rod", and what externally demonst? It looks like the Bore and stroke for the 85 and 86 ATC 250R's is 66 X 72 mm, and the 86 and 87 - 89 TRX 250R's are also 66 X 72 mm...

What gives it the designation "long rod"

I did a search of the site and came up with nothing which actually explained this.

Thanks,

[Bernard3rd]

Sorry, above should say "and what externally demonstrates this?"...

[atc300r]

The 85-86 250r engine cases have a different cut out at the front mount than the 88-89.First pic 85-86 250r .Second pic 88-89 250r . The early 250r 85-86 has a short rod the piston wrist pin hole is lower than the 87-89. the bore and stroke are the same . If you run the 85-86 piston in the 87-89 motor the piston will come out of the top of the bore by about 5 mill thats why you need the spacer plate. 87-89 250r over bores only go up to about 68-69 mill the big bore 250r kits are kinda based off the short rod motor. 246973 246974

[Bernard3rd]

Makes sense now. Thanks for the clarification.

[BOB MARLIN]

I was told at one time that Honda went to a longer rod to lessen the angle of the rod for dependability. It doesn't seem like that small amount of change would do much though.