change connecting rods?

mmeadows · Post by **mmeadows** » Fri May 31, 2013 12:33 pm

can it be done? i remember someone asking this along time ago and everyone said its not worth the hassle as used assembled cranks are easy to find

but.....

im trying to build a worthwhile 83-84 aero engine and use the stock 7.?? gears it comes with.

what do we think about changing the connecting rod to accept the af05e pistons / bbk? do we think the cranks are similar enough that it wont effect the stroke too much?

mmeadows · Post by **mmeadows** » Fri May 31, 2013 12:33 pm

can it be done? i remember someone asking this along time ago and everyone said its not worth the hassle as used assembled cranks are easy to find

but.....

im trying to build a worthwhile 83-84 aero engine and use the stock 7.?? gears it comes with.

what do we think about changing the connecting rod to accept the af05e pistons / bbk? do we think the cranks are similar enough that it wont effect the stroke too much?

ottoman · Post by **ottoman** » Fri May 31, 2013 1:43 pm

Changing out a rod isnt too hard if you have the equipment and the skill to true it back up. Changing the rod length doesnt affect the stroke.

mmeadows · Post by **mmeadows** » Fri May 31, 2013 4:57 pm

so i would need to have a shop do it.

ottoman if you don't mind skooling me for a second.....why would rod length not change stroke?

If displacement is pie / 4 (bore2) (stroke) (number of cylinders) then wouldn't the stroke, which is measured in length, which is affected by the length of the connecting rod, change the stroke, and thus change the displacement? if i remember correctly the 83-84 nb50m has a much longer piston so im guessing it has a shorter connecting rod. i mean there are a few ways to get to 49cc's

I'm confused

swimmingfree · Post by **swimmingfree** » Fri May 31, 2013 5:02 pm

it not the rod that make its were strock of it that counts..
swimmingfree

mmeadows · Post by **mmeadows** » Fri May 31, 2013 5:04 pm

swimmingfree wrote:it not the rod that make its were strock of it that counts..
swimmingfree

lol but still confused

swimmingfree · Post by **swimmingfree** » Fri May 31, 2013 5:23 pm

41mm bore 37.4 stroke i think is my se50 ==49cc
39mm bore 41 stroke is a dio i think ==49
not at home to look at the book ...
swimming

Wheelman-111 · Post by **Wheelman-111** » Fri May 31, 2013 9:59 pm

Greetings:

Stroke is determined by the distance between the centerlines of the crank and the con-rod big end axes. The piston travel is twice that distance, between top and bottom dead center, regardless of the con rod length.

Honda has the resources to set up a production line with high-precision extremely powerful presses that line the flywheels up with the crankpins accurately in 3 planes. Toothless tattooed guys named Gus in dimly lit greasy shop backrooms have the ability to be almost as precise if they practice for ~40 years or so.

Duke · Post by **Duke** » Sat Jun 01, 2013 9:31 am

There is a shop in Oregon I believe that rebuilds cranks. I inquired about having some scooter cranks rebuilt and they quoted me at $40 per crank with my supplied parts + shipping. Seems like a pretty good deal considering the rarity of a good AF05E crank

check em out! RB-designs.com

ottoman · Post by **ottoman** » Tue Jun 04, 2013 11:51 pm

Doing cranks isnt really that hard... you need a press and some fixtures (u can make em) a couple of V blocks and a pair of dial indicators, feeler guages and a soft hammer... copper is material of choice.
Im sure there are videos out there of it being done. I used to do dirt bike cranks all the time when I worked for the Kawasaki dealer.

Wheelman-111 · Post by **Wheelman-111** » Wed Jun 05, 2013 10:08 am

Greetings:

So Ottoman has the Skills of the Few.
Not everyone has had the good fortune to work with Pros.
Maybe you could market those skills to the Forum?
We need your dental records and a tattoo shematic first though.

Post by **noiseguy** » Wed Jun 05, 2013 10:18 am

ottoman wrote:Im sure there are videos out there of it being done. I used to do dirt bike cranks all the time when I worked for the Kawasaki dealer.

I looked a few years ago and couldn't find anything. I found 1 PDF that described the procedure conceptually, for H-D cranks (I believe.)

For $40 labor, I wouldn't bother learning how unless I had all the tools already.

ottoman · Post by **ottoman** » Sat Jun 08, 2013 2:35 am

http://www.youtube.com/watch?v=SnCCml93a40

http://www.youtube.com/watch?v=Egs2zcknN74

http://www.youtube.com/watch?v=aGuURCbqBOo

http://www.youtube.com/watch?v=-kErQcpfg4k

http://www.youtube.com/watch?v=bs1yCpomCKM

mousewheels · Post by **mousewheels** » Sat Jun 08, 2013 7:55 am

Thanks for the links ottoman

wiki crankshaft topic is updated to include videos

JJ Joseph · Post by **JJ Joseph** » Sun Jun 09, 2013 2:14 am

You have to ask yourself if it's worth all the fuss to rebuild. Last time I needed to major my Dio crank, I went on to ebay and found a brand new crank with rod & bearings all in one finished package for $29. It arrived in a few days, and then another day to check and install. It was from Taiwan, and 2 years later it still runs like a top.

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