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Old 05-04-2012, 08:46 PM   #16
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Old 02-05-2013, 06:00 AM   #17
Joined: Feb 2013
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Originally Posted by BeemerShop View Post
If you don't like the 9.5:1 compression ratio of the Seibenrock kit, install one low test base gasket per side part number 11111335650 and that will drop compression to 8.8:1. The Seibenrock kit is the ticket.

Seibenrock has a kit designed for the R80 with pistons machined to fit the heads so no head modifications necessary, makes it a bolt on kit. We sell and install a lot of them with great results.

Ted Porter
Hey Ted,

I'm thinking of this upgrade for my 1988 R80RT. I do a lot of highway miles and already find the fifth gear quite short. What would you suggest as the best final drive ratio to accompany the upgrade kit? I'd ideally like to sit at around 60mph somewhere around 3750 rpm but at present the motor runs around 4200 at this speed. There seems to be a huge amount of debate around how to go about this. Can you buy different drive ratios from BMW without having to change the entire final drive housing? This would seem to be the easiest option. It seems odd to me that there is every aftermarket accessory under the sun for airheads except for final drive ratios, which from the look of things is what many owners seem to end up wanting.
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Old 02-05-2013, 07:11 AM   #18
Airhead Wrangler
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You can buy different gear sets, but once you include the labor of swapping it into your housing, you're better off just looking for a good used final drive from an R100 mono. Your other option is the 5% taller 5th gear available through various sources. Moorespeed also does a 10% higher 5th.
R80ST Gets The HPN Treatment
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Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.
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