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Old 11-26-2011, 08:25 PM   #91
danedg
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Bullshit



I want a rear disc as well...
....damn thing runs like a raped ape.......
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Old 11-26-2011, 08:28 PM   #92
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Originally Posted by danedg View Post
I want a rear disc as well...
....damn thing runs like a raped ape.......
I guess coming off a /2 just about anything firing on all cylinders is going to feel like that. But there's a whole other world of "raped apes" out there you owe it to yourself to try.


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Old 11-26-2011, 08:34 PM   #93
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I never knew that?

I thought all the post '81 liter boxers sold in the US had 8.2:1 pistons?


Well, youre right about that. I guess what I was thinking was you could still buy R100S (Not R) pistons that were pre-'80, but they'd fit.

Also, R100RT from '79 till '84.


Only on the US models does the CR suck. :( Sorry Dan, I led you wrong.
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Old 11-26-2011, 08:39 PM   #94
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Also, R100RT from '79 till '84.
US spec on the RT's was 9.5:1 on the '79 model and 8.2:1 from '80 on.

In fact, there may have been a change to 8.2:1 in the middle of '79 model year production.

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Old 11-26-2011, 08:39 PM   #95
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I guess coming off a /2 just about anything firing on all cylinders is going to feel like that. But there's a whole other world of "raped apes" out there you owe it to yourself to try.


But...why?
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Old 11-26-2011, 08:42 PM   #96
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US spec on the RT's was 9.5:1 on the '79 model and 8.2:1 from '80 on.

In fact, there may have been a change to 8.2:1 in the middle of '79 model year production.

Maybe, but they (the pistons) are still available from Max's. SO they didnt come standard, but you could/can get them. They used to be cheap, but now you can get the whole Siebenrock kit for the price of two BMW pistons.

Sorry for the drift.
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Old 11-26-2011, 08:43 PM   #97
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Old 11-26-2011, 08:54 PM   #98
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Maybe, but they (the pistons) are still available from Max's. SO they didnt come standard, but you could/can get them. They used to be cheap, but now you can get the whole Siebenrock kit for the price of two BMW pistons.

Sorry for the drift.
I believe they're the Euro spec 9.5:1 pistons that where used through all years of airhead produciton after '79.

I want a 1070cc Siebenrock kit for my GSPD.

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Old 11-26-2011, 08:55 PM   #99
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But...why?
Do it for science.


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Old 11-26-2011, 08:55 PM   #100
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Sorry to continue the thread drift, Ontic, but I've been running 87 and 89 octane in my single plugged PD with the 9.5 pistons, and no pinging at all. Runs great. I dont think 9.5 is too great a CR to run regular or even sub-regular gas in.
Thanks, good to know.
Ok, well I'm still officially on the fence about this...

It is quite tricky trying to figure out what octane fuel will be available especially with my vague and rather open-ended plans. If I really didn't have to think about twin plugging then the power up and higher 5th is still very appealing to me.

Chances are really sub-regular fuel would be a rarity- so if I was going to do the power-up I'd want to have a strategy in place to deal with it in the few times it was unavoidable (preferably without relying on carrying some sort of 'octane booster' which I know I would never have when needed).
Downshifting and keeping the rpm up (and just not pushing it so hard) seems to help avoid pinging when it occurs on my 90/6, though I'm not sure how much of a serious strategy this could be.
Any tricks to quickly, easily, safely and reversibly lower compression?

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Sorry for the drift.
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Old 11-26-2011, 09:05 PM   #101
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techincally, carrying a thicker head gasket would get you a lower CR, but you dont want to be swapping that around for a tank of fuel

Easier to retard the timing if there was a problem, I think.

Like you say though, it really depends on where you think youre headed. I've never had to buy gas out from a hand pump in a barrel, or a soft-drink bottle, yet, but they are out there, deep in Mexico and Cambodia. I would think fuel contaminants would be a way more frequent thing, like water or just crap, and not the octane rating. Hell, its almost impossible to find Leaded fuel anymore, and I've never heard of anything below say, 85 or so.
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Old 11-26-2011, 09:34 PM   #102
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techincally, carrying a thicker head gasket would get you a lower CR, but you dont want to be swapping that around for a tank of fuel

Easier to retard the timing if there was a problem, I think.

Like you say though, it really depends on where you think youre headed. I've never had to buy gas out from a hand pump in a barrel, or a soft-drink bottle, yet, but they are out there, deep in Mexico and Cambodia. I would think fuel contaminants would be a way more frequent thing, like water or just crap, and not the octane rating. Hell, its almost impossible to find Leaded fuel anymore, and I've never heard of anything below say, 85 or so.
Thicker head gasket is one option I had read of and could be a solution, but yeah, this certainly wouldn't be done for a tank of fuel- more like done for a ride through a region of expected poor fuel- if the fuel was proving a problem.
Timing retarding might be a better way. Nice if it could be done at the press of a button...

I've done a fair bit of riding in Vietnam and Laos and a little in Cambodia and Thailand. Aside from the major cities in Laos, when off the main tracks where I tend to gravitate to, most of the fuel I bought was out of soft drink bottles and a fair bit of it in vietnam was the same, and if it wasn't that then it was hand pumped out of a barrel. Actual bowsers were very uncommon where I rode. Didn't seem like bad fuel as such, but on rented bikes I really didn't pay much attention nor care so long as it ran.

I'll definitely be doing a lot of riding through those regions, not to mention Timor, Indonesia and Malaysia in order to get there. I hate to imagine filling up my 45 liter tank out of soft drink bottles but it will probably happen

If there is a definite path then that is it.
After that if the ride continues then probably overland to India and then the rest is just speculation depending on how my personal and carreer life works out... (inbetween 'holiday' tours I'll be trying to do slabs of work in different countries).

Anyway, food for thought,
thanks.
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Old 11-26-2011, 09:41 PM   #103
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Sorry to continue the thread drift, Ontic, but I've been running 87 and 89 octane in my single plugged PD with the 9.5 pistons, and no pinging at all. Runs great. I dont think 9.5 is too great a CR to run regular or even sub-regular gas in..
very useful information ... been worried about taking my 74 R90S to places with low octane fuels. sure is good to know your PD with 9.5 piston do well on 87 fuel.

have you taken a compression reading yet? R90S measures 185 psi with a known to be correct Snap-on gauge.
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Old 11-26-2011, 09:52 PM   #104
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One of the regulars here, and I think he's Canadian, ran a simple water injection system that eliminated pinging.
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Old 11-26-2011, 09:54 PM   #105
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Nope. It'd be cool to find out, for grins.


I guess i should say I havent heard any pinging over the sound of the valves
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