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Old 05-04-2012, 08:46 PM   #16
wirewrkr
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Old 02-05-2013, 06:00 AM   #17
tomjrtsmith
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Quote:
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.

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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.
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Old 07-01-2014, 11:35 PM   #19
Larry Landes
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R80 to R100 advice

Seems I found the right thread, so I have a question...

My brother and I both own '81 R80GSs. We used to ride them a lot but then he broke a valve. Since I'm the mechanic of the two and because he didn't have money at the time, I pulled the right head off of my GS and gave to him, thinking I was going to upgrade to 1000cc.

It never happened and my bike has sat for far too long. But now he and I want to ride them from California to the East Coast and back, so it's time to get the old girl going again.

Long ago I bought a really rough parts bike '83 R100GS. I've never touched it, but it's available for parts.

So the question is, which option do I take:

1. Get a right side R80 head and put my bike back together.
2. Take the top end off of my parts bike R100GS and put that top end on my R80, along with the larger Bing carbs. (that was the plan, but now I hate to disassemble a good R100 motor in a rough, but complete R100GS)
3. Keep the parts bike as is for a potential project down the road and buy used R100 pistons, cylinders and heads but use my 32mm R80 Bings.

I guess what I'm asking indirectly is do I want my R80 to be 1000cc and if so, do I use option 2 or 3 above?

Thanks for any advice/input.
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Old 07-01-2014, 11:57 PM   #20
Larry Landes
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Here's the parts bike I've never touched. The Red Baron.
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Old 07-02-2014, 02:21 AM   #21
Rob Farmer
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Looks just fine as it is.

Don't sweat the 40mm bings. I've had a US bike with 32mm carbs and it ran much better than the 40mm carbed bikes. Cleaner bottom end and stronger midrange with no discernible difference at the top end.

Given a choice I'd take the 32mm carbs every time.

For my Moorespeed engine I bought 800cc heads and had them machined to 1000cc. The usual thing to do with barrels is buy 800cc and have them bored to 1000 and then re nickasiled. It works out to 140 a barrel so only 15 more for starting with 800cc. google threw up these guys in the states offering over boring and replating for $240 http://www.lukesracing.com/luksr/np.html obviously there's pistons on top of that. Probably cheaper to buy the power upgrade kits from Motobins

Rob Farmer screwed with this post 07-02-2014 at 02:31 AM
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