Re-Gearing an R80/7

  • by Airhead Contributer

    • Charles Bachmann, charles_bachmann@mgv.com writes:

    Hi Airheads,

    I am a fairly new owner of a 1978 R80/7. It is a great, fun bike. However, I find that at speeds over about 60 mph, the thing turns higher rpm’s than I would like. I am considering going to a higher gearing.

    Thanks for any feedback/advice!

    Charles Bachmann
    Raleigh, NC

    I know how you feel. I’ll bet you’re always looking for 6th gear.

    A 37/11 drive is the same that came on my ’74 R60/6. At 60 mph I’m showing at least 4000 rpm. Kinda high. But it’s only a R60. On the other hand, it’s the same drive that came on my ’83 R80RT. This was not acceptable to me. I replaced the 37/11(3.36:1) with the next higher-up 32/10 (3.20:1) from an R75/5. The drive housing has a different look & design, but everything fits fine. It was better, but still too revvy for me. Unlike you though, the ’83 R80 has lower compression than your ’78, therefore less horsepower too. I dare not try a higher drive because I have already lost a fair chunk of power.

    PERSONAL OPINION: I would not go with a 33/11 (3.00:1). I think this would be too big a jump for the R80. Remember, the 33/11 was made for the much more powerful R90S & early R100’s. Instead I would try a 34/11 (3.09:1) which was standard fare on the early R90/6. I replaced the stock 32/10 on my R75/5 with a 34/11 & am quite happy with it. It’s more at ease on the road and I didn’t lose enough power to worry about. I suspect the R75/5 and your R80/7 have roughly the same horsepower, so you should have the same results as me.

    I didn’t stop there,though. I own a few Airheads & did the same thing to them:

    ’74 R60/6: has 37/11 (3.36:1) — Left it alone; doesn’t have enough power
    ’71 R75/5: replaced 32/10 with 34/11 — Love it!
    ’74 R90/6: replaced 34/11 with 33/11 — Love it!
    ’83 R80RT: replaced 37/11 with 32/10 — O.K.,but not enough HP for more

    Final note: a friend who owns an R90S rode my Airheads after the upgrades and promptly changed his 33/11 (3.00:1) to a 32/11 (2.91:1) from an early R100RT — LOVES IT!

    UNCLE HOZO…………..15 AIRHEADS FROM 1953 TO 1983!

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