750 vs 850 balance

Ken,
Your absolutely right.

But every time I have weighed the amount of oil in a stock crankshaft it has been between 98 and 100 grams. Jim

DaveK said:

[
Yes, it isn't anything to do with worn isolastics or carbs just he is sensitive to vibration and most bikes are prone. (I don't have a problem on his bike)
Just wondering what others thought about the conclusion we came up with.

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If his 850 vibrates, then a lot of folks would say that the isolastics need work, or the carbs are out of synch.
Tell us that these have actually been attended to, rather than try to redesign the bike first ??
Has he actually tried loosening or tightening the iso shims ?
A time back, I had a 1000cc BM, and could tell it needed the carbs synching when the handlebars got the tingles.
(solid mounted engine of course).
To this end, it had quik-remove float bowls, so you could tip out any water dust rust in the fuel that might be interfering with smooth running.
Research folks at BM must ride their bikes to know this is common....

Anyone ?

Edit.
Mk111 , no way ?

part-numbers-mkiii-con-rods-t5078.html

Time Warp said:

Why would the con-rods be different between two 1971 crankshafts.
The flywheels are the same, the balance holes differ and notice the ones out of the fastback have a different model number R3R1R and no oil jet holes.
Pre Commando perhaps ?

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This needs to be a different thread ?

The oil squirt holes were dispensed with somewhere in the Atlas era. ?
It was found it wasn't a lube problem that required them = they solved the piston problem...

I would have thought crankshafts and con rods were more to the thread subject than how much oil is in the sludge trap which will obviously be full or you would get cavitation and loss of oil wedge.
That thread suggested Atlas in the last post, I will use the 1972 rods as they are close to new.

I've ridden off more than once w/o one plug lead on and didn't know it till at hwy speed air resistance a mile or so not getting the expected Combat throttle response to then notice the thumper like sound but not enough horzontal imbalance to get through the isolastics to notice that way. If anything is in a bind by diagonal mis alignments or too tight gap it can be rather miserable to dangerous to ride in rpm its tolerable. If tires too low air that can raise isolastic onset and lessen its deepness of isolation. I'd had 1000 miles days that I didn't want to end the trace in the twisties as sun set close to getting home. I doubt there is another cycle that can be made so invisible low effort comfortable. Keep striving for a fully fettered Commando til unforgettable smooth sailing.

The JPN race Nortons reportedly decided that at race speeds the oil was just sluicing through the crank,
and not holding pressure at all.

Its important to note that oil pressure in the big ends is a fairly recent invention.
Engines used oil SPLASH FEED for decades and decades, and no one noticed the 'loss of oil wedge'.
i.e. it happens whether there is pressure or not.

The extra oil with an oil pump/pressure just provides more cooling....

??

You need a different thread for varieties of conrods.

hobot said:

I've ridden off more than once w/o one plug lead on and didn't know it

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Well hillbilly, you must have the sensitivity of a sleeping rhinocerous.
I'd keep that quiet if I were you....

Its OK to sledge him, its hobot we are talking to here folks.

Not worried about his bike. If anything my iso's aren't setup proper think last time I checked they were worn so I shimmed them and then it was too tight. So went back to how it was. Prolly pretty loose for most peoples comfort.

In my defense of one plug wire off I was switching out plugs with my buddy failing boyah charging so on windy busy hwy and road blasted and only using ordinary easy throttling. Other times have left one off checking for fire but noticed one lung sound and lack of power to catch it right off.

hobot said:

I've ridden off more than once w/o one plug lead on and didn't know it till at hwy speed air resistance a mile or so not getting the expected Combat throttle response to then notice the thumper like sound but not enough horzontal imbalance to get through the isolastics to notice that way. If anything is in a bind by diagonal mis alignments or too tight gap it can be rather miserable to dangerous to ride in rpm its tolerable. If tires too low air that can raise isolastic onset and lessen its deepness of isolation. I'd had 1000 miles days that I didn't want to end the trace in the twisties as sun set close to getting home. I doubt there is another cycle that can be made so invisible low effort comfortable. Keep striving for a fully fettered Commando til unforgettable smooth sailing.

Click to expand...

How on earth could you ride off on one cylinder and not realize it????

comnoz said:

Ken,
Your absolutely right.

But every time I have weighed the amount of oil in a stock crankshaft it has been between 98 and 100 grams. Jim

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You're quite right, Jim. I went back and looked at my balance sheets, and that was 50 grams per side, for a total of 100 grams. That means the calcs I did for percentage change with and without oil need to be corrected. For the example I gave, the difference would be 13.8%, not 5.9%.

Seems to be my week for posting mistakes. I clearly need some new meds.

Ken

I've started up in shed and got a little ways out to realize something missing but also a few times on very giusty hot hwys helmeted after switching plugs with Wes to try to get a few more miles to civilization to tediously investigate so all focus on his starting and seeing him actually get going I'd step on start then try to catch up at norma-lish brisk Cdo acceleration which even on Peel's worse sluggish limited rpm power curve combo was still adequate to do so w/o WOT in lower gears with half again more luggage needed for just one fella's week long camping, so didn't notice lack of power till 4th after 60 mph. I've left with a wire off on Trixie too and didn't get vibed enough more to notice it that way just the exhuast note and lack of response. D/t crashes and Rough paths Wes and I get electrical grimlins so time to time pull plugs to check spark with less resistance. Can an isolastic Commando pilot feel a change in BF? If so how so?

Ken Left Coast Racing maniac made big threaded holes in Peel flywheel to mess with BF from almost best stock crank load averaging BF to over 100% if using depleted uranium like steam rollers and boat ballast. Peel BF investigation concerns power pulse patch hook up not vibe transmission. Hard to beat making tire noises over engine and wind roar while leaned to fouling when sonic range of engine pulses through the secondary dual isolatic line of drive suspension system definitely matters enough I have nil respect for anything else's turning forces.

Its perhaps important to mention here that the official Balance Factor for these isolastic Commando engines is listed as
52 % DRY,
as listed in the Factory Workshop Manual specs printed circa 1973.

This has never been a secret, nor is it a recent discovery or revelation...