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Thread: Siebenrock Big Bore Kit

  1. #1

    Siebenrock Big Bore Kit

    I have a '92 R100R with 40K miles that I want to have (more) (reliable) fun with. My intention is to install a Siebenrock Bog Bore kit, which seems to be a lot like opening a can of delightful worms?. I am looking for advice on several points. I should also say that I am aware that I don't have to do this, that I am tampering with a great system, but on the other hand, I hope not to do any harm. And I suppose I could revert if this doesn't work.

    It appears that there are three versions of the kit: replacement, touring, and performance. I am thinking of the touring version as that's what I do AND I would see a torque and HP bump, which is more or less the point of this exercise. According to what I have read, there are other changes that should be done at the same time. It's which of these and which ones best fit together that I am unable to figure out. There must be at least a dozen riders out there who have experience with this. I would love to hear from you. Larger oil cooler? Dual ignition? Different carburetors? GS2 exhaust?


  2. #2
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    Tony -

    I don't have experience with the big bore kit. I just recently put a stock 1000cc kit from Siebenrock on my /7 top end overhaul. I bought the kit through Ted Porter and got advice from him. My concern was the bump in compression ratio, from a nominal 9.0 to 9.5. I think that would have meant that I needed to consider dual plugging. I chose not to go down that path and opted for the base gasket which knocked it back to 8.8...close to stock. So, far I like it.

    The R100R should have a compression ratio of 8.5...I don't know if that means you could go to say 9.0 without any consideration for pinging, etc....I guess that would be a function of the head design, cam design...not sure...that's a little outside my wheelhouse. I think you might have to fool with carbs, maybe as simple as raising the needle or changing the needle jet. Virtually most of the time, you'll be running on mid throttle or the needle, so that would be the area of checking out the idle circuit as well. Exhausts bring a whole new aspect into tuning...I'd be inclined to remain stock and try and change things a little at a time to see what the effect is going to be.

    Who will you be buying it from? I'd suggest getting input from them, too.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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