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Old 06-15-2012, 08:06 PM   #31
Wirespokes
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Thanks for that data on lifters, shaft. I've replaced a few over the years, and a seen a few trashed cams. I've heard BMW just had some bad cams over the years, but it makes more sense the lifters didn't last and wore the lobes.

As for low end torque - I've always heard that boxer motors shouldn't be lugged or worked at low RPMs. I had VW bugs in my younger days and that was the instruction I got. Perhaps that's the reason the stock cam doesn't start producing power till 3K.

Also, what is the exact reason for not lugging boxers? Why is it better to make them work at higher RPMs?
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Old 06-15-2012, 08:29 PM   #32
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Quote:
Originally Posted by Wirespokes View Post
Also, what is the exact reason for not lugging boxers? Why is it better to make them work at higher RPMs?
It's not really boxer engines specifically, but any engines. Loading an engine hard at low RPMs causes huge chamber pressures and is tough on your big ends and mains. Because the engine is turning more slowly it allows the charge to fully ignite while the crank is closer to TDC where it has less mechanical advantage to turn the crank and also results in much greater pressures as the piston is still relatively high up in the cylinder. More of the charge is spent just hammering the big ends and mains rather than turning the crank in comparison with higher revs. Huge loads on the bearings coupled with lower oil pressure is a recipe for bad.
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Old 06-15-2012, 08:44 PM   #33
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I run my engine in the 2,000 range and occassionaly ask it to work from 1,500.
It will idle in first or second gear.

Sure I like the way it runs in the 3-5,500 range but there is usefull power available either side of that.

Before I mucked around with my engine the factory claim was 80% of the peak torque available at idle.
I have more ft/lbs available at idle now but it is a lesser % of the peak.

Vehicle weight is less and the gearing is the same.
Bottom end has 400,000 on it.

Do you think I should be worried about long term wear?
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Old 06-15-2012, 09:49 PM   #34
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If you've got 400,000 on it you can't be doing anything too terribly wrong.
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Old 06-15-2012, 10:07 PM   #35
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Originally Posted by Airhead Wrangler View Post
It's not really boxer engines specifically, but any engines. Loading an engine hard at low RPMs causes huge chamber pressures and is tough on your big ends and mains. Because the engine is turning more slowly it allows the charge to fully ignite while the crank is closer to TDC where it has less mechanical advantage to turn the crank and also results in much greater pressures as the piston is still relatively high up in the cylinder. More of the charge is spent just hammering the big ends and mains rather than turning the crank in comparison with higher revs. Huge loads on the bearings coupled with lower oil pressure is a recipe for bad.
Short stroke and little or no flywheel. Despite all the claims to the contrary, that is not a tractor motor. Throw in plain bearings that need some speed to ride that wave of oil and I come to realize that our engines are not made for chugging.
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Old 06-16-2012, 10:28 PM   #36
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You're probably right AW. Since I was given those instructions in my teens when I didn't know much about engines and mechanics, I thought it was something specific to boxers. And I always wondered what it was about boxers that would be different. Best I could figure was the head studs are anchored in aluminum and lugging would be tough on them - for the reasons you just mentioned.
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Old 06-16-2012, 10:31 PM   #37
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Bottom end has 400,000 on it.

Do you think I should be worried about long term wear?


Is this a joke?

What's your definition of 'long term'? A million miles?
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Old 06-17-2012, 06:15 AM   #38
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Originally Posted by Wirespokes View Post


Is this a joke?

What's your definition of 'long term'? A million miles?
No it was sarcasm!
It would have been just plain facetious to worry about premature engine failure.

I have plans for this motor beyond the 400,000 mark and I would like to think my young bloke
will have an appreciation of vintage robust & flexible when comes the time I can't ride any more.

I've owned it for 30 years and would like to get another 20 before I hand it over.
I'm slowing down in my old age and not doing the distance I previously covered.
600,000 would be good but closer to 500,000 is more likely on my watch.

If the second owner gets half what I did out of it that's and extimated 750 - 900,000 over two generations.
I've sort of figured out which parts are the wear items and have been collecting spares.
Long term is probably about the time the fosil fuel runs out.

I would like to think the fosil fuel will last a while yet.
We will find an alternate for transportation and reserve the dino juice for recreation.
Thats one of the beliefs that make me an optomist.
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Rucksta screwed with this post 06-17-2012 at 07:01 AM Reason: spelling
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Old 06-18-2012, 11:42 AM   #39
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quite a high % of BMW production goes into various bits and pieces of government service, which probablt results in lots of low speed engine operation, I'v used these bikes in lots of third world touring situations where due to road conditions etc etc you are running the engines in the 2-3K rev range, as long as the engine feels OK at those revs and will still accelerate with a bit of throttle awareness then thats fine by me. I have read on the Internet people claiming that BMWs should not be run below 4K, that just bonkers!

Charles
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Old 06-18-2012, 12:46 PM   #40
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And then some people report that they never rev their engines ABOVE 4000rpm. That's just bonkers too.

Government service bikes wear out three times as fast as normal mileage in my experience so that isn't a good example of trouble free low rpm mileage in my book.

All I know is that every airhead I have ever ridden shakes and shudders if you load the engine much in the upper gears a bit below 3000 rpm. It can't be good for them?
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Old 07-15-2012, 12:12 AM   #41
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Now that the other current camshaft thread is absorbing the general and the specific (336) discussion (intersting as it is) can this one swing back to talking about the 296?
I haven't found much information out there at all about this cam (at least in english).

Finally having the time again to get back working on my long delayed project bike, I am actually about to pull the trigger on a 296 cam but I would welcome a bit more chatter. Most of the real technical stuff in the other thread goes straight over my head.From what I have heard so far the 296 sounds like a good modification towards what I am after. Low and midrange torque beast.


it would be for my G/S
a few particulars, 1000cc siebenrock kit, 34mm mikuni's, twin plugged G/S heads, definitely putting a higher 5th in but not sure about a lower 1st- more about that below.

Being a G/S built for loaded down all-road touring, and the occasional no-load dirt-riding fun, I am not too worried about losses at 'high' RPM's. The lower it will work from all-the-better for my preferences. I do not want a race bike by any means.
To me and my calculations it seems that the 296 with a higher 5th will have plenty enough power band left for MY high speed requirements, enough to see me well and trully loosing my liscence if I felt the need.

From what has been said elswhere- higher 5th with G/S final drive sits at 70mph at around 4650 rpm (?). That is just over the 110kph that is my state maximum (only on some freeways- most roads are 100kph max).
In this thread Alibaba rekons that the 296 has the standard R80 with siebenrock kit beat up to around 5700rpm- (in this scenario) around 85mph or 136kmph. In a theoretical world where one could not get in trouble for mentioning such... that is good enough for most overtaking needs- particularly as it isn't going to stop at 5700rpm...
In short, I rarely ever push my airheads over 6000 rpm in any gear so I don't think I will feel any losses from the 296.
Peak torque around 3500 and 'pulling like a train' from just under 2000 sounds like exactly what I want.

In this scenario though, the lower 1st gear I am not sure about. My last long ride on the R90 for the first time had me wishing for a lower first on that bike (steep icy mud and a very heavy load on the bike... burned clutch a lot and general unhappiness).
The G/S though, with the 1000cc and the 37/11 final drive and the low rpm workability of a 296 might be quite a different beast, and I am worried about putting in a lower 1st and making it into to much of a useless crawling gear... I do not want to do the gearbox twice.

At this point it is not a money thing- I'm pretty set on trying the 296 cam and will soon be ordering it from Motoren-Israel. I've got the higher 5th and the updated shift kit ready to go in the box and will be sending it off soon to get rebuilt.
Aside from just trying to get some more 296 camshaft discussion- the question for me is wether to throw a lower 1st into the Motoren-Israel order and the gearbox... with all the other changes I am thinking it might be a bit superfluous.
Thus I am leaning towards not lowering 1st.

cheers,
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Old 07-15-2012, 06:24 AM   #42
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When you do the numbers on a higher 5th grear 5% less revs at 4000 plus means something.
At the other end
Minimum sustianable clutch out speed in 1st 8 or 7.6 kph is neither her nor there.


Your motor will pull better than mine down low and I rarely use 1st even from the lights.
Ist is a crawl gear anyway - up to you if you make it more so.
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Old 07-15-2012, 06:52 AM   #43
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Ontic,

Why not ask motoren Israel? If you are buying the other parts off then, you could describe your type of riding and ask which cam they would reccomend and why, then you have more info to put into the pot.


I have heard some stuff about the endurolast cam being originally designed to pass Swiss emission rules, but I'm not sure.
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Old 07-15-2012, 02:17 PM   #44
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Ontic as you probably read before I have the 296 enduro cam, re balanced crank, pistons and con rods along with gas flowed twin plug heads standard 32 bings, endurolast twin spark ignition along with the lower first and higher top gear. when this set up was tried on my standard gs with a final drive ratio of 10/32 the lower first is really low and I quickly moved out of it but when loaded up and going down steep gravel or slippy surfaces I found it ideal and it gave very good control without having to use the back brake, you feel like you can almost stop the bike on that gear in those circumstances but other than that it was very limiting in use - I now run a 37/11 rear drive on the Dakar replica and in that format the first gear feels fairly Normal but maybe I just got used to it that way, but I am going to buy a 32/10 set up to fit as its my prefered gearing except for long haul stuff. I love the 296 cam yes it revs out - at the top end but my bike is still pulling way past 6000 before feeling too strained even then it pulls fine beyond - but for everywhere in between 1000 and 6000 it works well but is happiest below 5500 for general running.The bike picks up very well from really low revs, I find on the road I hardly use the gearbox as the engine torque band deems the bike so flexible - I live and ride mainly very small twisty back roads that are potholed and or gravel (limestone which when wet is like ice) type tracks in a wet temperate zone so roads are often slippy I also tend to travel North towards and in Arctic areas more than warm climates - again the bikes ease of use on surfaces where grip is constantly limited is a huge bonus letting you get all the usable power down and through the tyre without spinning it up. I have heard and read lots of different views and theories on this site how this engine works best when revved hard - that may well be the case depending on set up - but to me I have achieved not the perfect engine but a pretty damn good one for my needs - I put my faith in Motoren Israel when they designed / developed this engine for me, my style of riding and my requirements and as much as a boxer can it works exceptionally well. Great low down, mid range power reasonable and usable top end power with good acceleration. Its a great back road bike, its usable on most surfaces but its not a road racer. Too answer your question on the lower first gear if it were me I would not bother fitting it again to be honest its a very expensive change for its limited difference and the usage it offers more so if you are going down the 296 cam way.
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Old 07-15-2012, 02:27 PM   #45
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If I can figure out how to download the printout of a dyno run on my engine when it was new built I will if that helps - but I am trying to figure that one out at the minute.
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