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EuroIron
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what various methods have been employed in the pursuit of speed and/or more displacement

what known weaknesses or strengths frown upon or favor the various methods

and have any of you run heads having an exhaust valve guide saving vane welded inside the port?

anyone even running 600 or so cc's at a CR of 10:1 or more?

EuroIron
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and does anyone know of a taller geared final drive, bmw or otherwise

taller than 1:2.91?

1:2 would be better even if Italian or Japanese but don't want to have to suffer comstar or similarly ugly heavy wheels

Allan.Atherton
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Re: a bigger boxer engine hop up discussion

"EuroIron" wrote:

what various methods have been employed in the pursuit of speed and/or more displacement... what known weaknesses or strengths frown upon or favor the various methods... and have any of you run heads having an exhaust valve guide saving vane welded inside the port?... anyone even running 600 or so cc's at a CR of 10:1 or more?

I saved this from the /2 Group which may be of interest:
=====================================
From: Brian C.
Sent: Monday, February 17, 2003
To: Herb T.
Subject: RE: R69S Performance Tips

Herb, Upgrading engine performance beyond manufacturers design requires engineering and trial and error too. I did do this with my engine, using a limit which was that the engine could have no outward signs of the modifications. If you have set no such limit, you have more options. I determined that the engine could not derive much more horsepower from more RPM, the crank design just cannot tolerate much more, so I went with torque modifications. I made extensive use of a Dynojet Dynamometer to verify results of each mod. I would list modifications basically in order of practicality: 1..Lighten the flywheel... faster acceleration, easier shifting, faster deceleration, harder starting 2..balance the engine... smoother, will tolerate higher horsepower without shaking apart 3..Increase the compression/hotter cam... I went to a 328 cam and 10-1 compression. Do it together or the engine will ping all the time. As you know, a milder cam increases compression due to less valve overlap, a hotter cam decreases compression...valves are open longer in the cycle. One must engineer this change or it will be a very costly trial and error experiment. 4..Go to Mikuni flat slide carbs...this also must be engineered, bigger is not necessarily better, but the adjustability and flow design is much better than the stock carbs.. 5..Go to dual plug ignition...higher compression...helps control flame front and will allow higher compression before pinging sets in. The domed piston of the R69S create a squish problem and shrouded flame front that limits the efficiency of the combustion chamber, dual plugging starts the fire from both sides at once, doubling flame speed and decreasing pinging. This mod will substantially weaken the head, not good for reliability.

Experiment with plugs to get the coolest plug that will not soot up. Remember...the coolest plug is used in the hottest engines. I use a racing plug that has no recess in it at all! I also have to use 110 octane leaded CAM2 racing fuel in the engine! Keep this in mind when engineering...this fuel costs about $5 per gallon. Plugs last about 1000 miles in this environment before they foul out from lead.

6..lighten the reciprocating mass...use custom pistons with lightened skirts, titanium valves, special springs, cast titanium rocker arms, moly push rods, custom lifters, etc. Bad for longevity, very expensive, probably gives little horsepower but will increase acceleration and top end a little. It is neat to know that technology is in there! I did make custom titanium roller rockers and push rods, cost... about $2000.

7..Add-on systems such as turbos, superchargers and nitrous injection. These things will probably crush the crank but sound good at the biker bar!

These are about it unless you want to go full race, which would be better done starting with a sleeve bearing, pressure lubed engine. My engine cost about $10,000 to date(I modify the engine continuously, it is currently only generating about 55 rear wheel horsepower form the original 35 or so at the rear wheel) which is an esoteric exercise, not good value for the horsepower, just fun as a toy. This discussion needs to be much more technical to be of any use as a guide. This is more just a discussion of the pros and cons and issues involved in performance tuning a /2 engine.
=====================================

Allan.Atherton
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a bigger boxer engine hop up discussion

"EuroIron" wrote:

and does anyone know of a taller geared final drive, bmw or otherwise, taller than 1:2.91?...

Here's all the BMW ratios I have heard of. The 2.909 is your 2.91, and that's the tallest BMW drive made.
26/6 4.333 R50/2 & R69S sidecar
27/7 3.857 R60/2 sidecar
25/7 3.571 R50S
27/8 3.375 1968-on 4.00 tire
25/8 3.125 Pre-1968 3.50 tire
32/11 2.909 R60 pre-1960
32/9 3.556 R67-R67/3
35/9 3.889 R51/2, R51/3, R68
25/6 4.167 R26-R27
27/6 4.500 R27
32/7 4.571 R51/2, R51/3, R67/3 sidecar
35/8 4.375 R67-R67/2 sidecar
24/5 4.800 R25/3 sidecar
26/5 5.200 R26-R27 side car

EuroIron
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thank you on the ratio chart

that will be very helpful and save me from some boring copy and paste doc stuff since I need to clear out all the pesky /2 /3 stuff here I won't ever use

guessing I'll poke about and see what Guzzi and the Japs have since I really didn't want to run two different tires on each end and even 3:1 or so ain't quite gonna cut it even with a 27" tall 18 on the rear

I was kinda thinking along the lines of a welded up stroker crank and bores large enough to require sleeving

interesting would be to see cam specs for the /2 /3 engines......... I'm looking for something very short duration with wide lobe centers and I am thinking some of the milder tuned ones should have something that might just work

I am guessing that to spin one of these to 7 grand and hold it there, is going to require welding the crank pins even with stock stroke since it seems doing a flat crank in one of these would make a real jackhammer

the stock rods look strong enough and it appears I have them in more than one length and forging

anyone know? grenaded one of these in spectacular fashion before, for some reason other than slingers?

I know it's much easier just to do a /5 or later but I've already had and tweaked a fast one of those and really I wish I had a flatty BMW to bring to life

comet
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a bigger boxer engine hop up discussion

During the 1960s dealers sold and installed a 750CC cylinder kit. This may be a good place to start............Comet

EuroIron
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I think that would be enough and I'd guess such a set up is about unobtainium? I'll look at some 600 cylinders and see if they will hold such a sleeve or do you know if that has been done already?

you ever use any hard machinable plastic shaft couplers instead of the rubber ones?

I have a small stack of them but have never noticed them on any bikes, most are green and some are white

I haven't decided transmission yet but I am leaning towards the earls type trans due to gearing but I like the exposed drive shaft and almost enough to convert the later trans to an exposed setup

seems like if the plunger trans and shaft will tug a heavy hack they should hold up fine with smooth application of 40-50% more ponies pushing a very light load

not looking to go drag racing so slick shifting, that would be nice, isn't a must have

niall4473
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Euro,
I think the plastic shaft couplings are for 250 singles, my old R26 had a white one. Whether they're man enough for your project I doubt, they'd probably split the first time you changed down.
There are still 700 car motors about, they used to be a popular conversion into the plunger frame (not the Earles fork type one though), and being based on the R75 would stand some tuning I would think. Theres one for sale in the UK now, new for GBP1200, but a secondhand one would be cheaper, theres also a 51/3 frame up on ebay.de that has the special sump with it, but that would not be difficult to make. One added bonus would be the electric start!
Here's a conversion, incomplete, unfinished, that came up a couple of years ago.[img][/img]

Presumably if it was feasible to take the bike motor of the time out any further BMW would have done it, as they used bike derived engines in the Isetta 250/300 and 600 and they would not have developed another motor without good reason, being bankrupt at the time.
[img][/img]
(apologies for any copyright infringement)

I can't see why anyone would go to this much trouble if the standard motor would just bore out to 750.

Quote:

I haven't decided transmission yet but I am leaning towards the earls type trans due to gearing but I like the exposed drive shaft and almost enough to convert the later trans to an exposed setup

seems like if the plunger trans and shaft will tug a heavy hack they should hold up fine with smooth application of 40-50% more ponies pushing a very light load

I don't think you can mate an Earles type gearbox with a plunger rear drive, wouldn't your bike go backwards?

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EuroIron
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I don't think without sleeving........ and I haven't measured to see if it appears as though it can be done and not cut thru.....

that boring to 45 inches is possible

there appears to be plenty of meat to take them a couple mm over but probably not stellar for slow speed use during summertime

however, I don't think I'll be using a BMW final drive since they don't seem to have tall enough cogs readily available

I do know where one of those engines is sitting right now, buried under a work bench

and I've seen they were used in some of the smallish race cars instead of the motorcycle engines

flip side is, a poked over 600 cc engine, with the crank pins welded up, and two slightly over driven 22 inch screw blowers with recircing throttle valves, would probably be a handful of fun and a large enough challenge

be nice to get the displacement up enough so that a flat top could be used at 7.5:1 CR

whadday reckon this is?

inserted a pic of it after a bath

and do you think I should shine these up and ditch the Koni's?

niall4473
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Difficult to get any perspective on the gearbox but I would guess 250/300 Isetta, and as for the AMC candlesticks, should you ditch the Konis' for them, er.... no.

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Yeah looks like it, 250 Isetta gearbox.
[img][/img]

drawing lifted from www.isetta-online.de

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EuroIron
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yeah........... those Koni's work very well

the candlesticks do have a certain minimalistic bit of charm to them though

what do you have hiding under those BMW shrouds on your Velo?

now, where is the good point to measure for the 1/4" offset difference on the pre and post 68 final drives to make certain that is what they are?

I am looking at a pile of them with one must be post 68 and two 32/11 pre-60's

and right off the bat, I'm not seeing it

going to get some measuring equipment and will take a stab at it

going to liquefy them all so if anyone is looking for some really nice low miles units

speak now before I turbo-list them

aiming to have them on this evening but for sure before prime time tomorrow

also going to let some "non-S" and "S" transmissions go and all are very nice

615-478-4175

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Quote:

what do you have hiding under those BMW shrouds on your Velo?

just the same as in your pic with the candlesticks, regular Konis I put on in about 1985.

Quote:

now, where is the good point to measure for the 1/4" offset difference on the pre and post 68 final drives to make certain that is what they are?

Sorry, cannot help at all there, don't know anything at all about such modern stuff, by post '68 do you mean /5?.
I would start by measuring from the shoulder of the splined shaft that mates with the hub and the input shaft c/l. then the input bell housing face and the spindle c/l, and the input shaft c/l and the face of the brake actuator spindle boss in the drum and look for any differences there to known units, like you have, thats just a suggestion.

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EuroIron
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somehow I kinda figured you'd pull such a stunt and hide some Koni's under there......... nice

I agree that is what that gearbox is, thanks

it cleaned up really nice

post 68 I mean 68 and 69 /2 and US versions, I think anyhow

they had a half inch wider tire and not sure if the swing arm is also different to clear up front

niall4473
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Doubt if the swinging arm is different, you'd need a shaft with two Hardy-Spicers, unless its just a slimmer tube, therefore the difference would have to be in the rear drive case between the input c/l and the output shaft shoulder, thinking about it, you'd need a different spindle too, surely, and the rim would have to be offset by 1/8", like on a bendy Norton.
You live and learn, I'd never heard of this modification, but then, living on this side of the water, I've never seen a US fork bike either.

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comet
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EuroIron, The 750CC kit used a new cylinder that required a larger opening in the crankcase. Dealers used a boring tool supplied by the company. The base of the cylinders covered the four mounting studs. Long internally threaded tubes attached the cylinders to the housing. If you would like to see the setup send me your E-mail address and I will send you a picture of mine. I actually know of two others in the USA. The 400 X 18 rear tire used on the US models fit the standard swing arm but had to be deflated to remove or install..............Comet

EuroIron
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that rocks, like to see it and a bit of machine work is only a step

ironpimpofpain @ yahoo.com

EuroIron
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geeze......... the more I look at that Isetta box

the more the notion of a BMW sidehack or trike, with reverse, appeals to me

de dion off a tiny euro sports car and 3 wheel indy suspension

EuroIron
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yeah the 600 or 700 trans-axle would be the way to go for a trike

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