Twin without balancer weights ?

[Kaptainkwak]

NOOOOOOOO 😮 😮

I believe it has been tried and the bike just hops uncontrolably like being on a pogo stick.

I personably would not attempt it because with the pistons going up together something needs to counteract the forces 😛

[Michael]

Hi KK,

there are several other twins or large singles out there that have no balancer weights 😉
Yamaha XS650 or SR/XT500, maybe some of the english twins, not sure.

Maybe the counterweight at the crankshaft must be modified as well to find the best compromise in reducing the forces in vertical direction (agains piston) and in horizontal direction, where the counterweight at the crankshaft causes forces itself.

May start with some weighing.
The piston (+0.5mm) with rings and bolt is 414 gramms.
Maybe I have to consult a “motor builder” to find out if he can calculate or measure the needed counterweight at the crankshaft.

Of course there will be more vibrations, but that is the intention, at least for a hardcore chopper 😉

Attached a graphic that shows the conditions. Especially picture C in the upper line is interesting 🙂

Cheers Michael

[Kaptainkwak]

Your educating me here Michael. I am a Design Engineer by trade but im Nuclear and know very little about engines on this angle. I am interested to see what you find out as it appears you may be onto something but that raises the question ‘Why didn’t Kawasaki do it?’

[Michael]

Hi KK,

Kawasaki wanted to run the Twin as smooth as a 4 cylinder engine and don’t want to make any compromise on that 😉

Let me see what I can find out about that!

I know already a Twin running with a balancer weight positioned “one tooth” away from planned position.
Nothing to feel against that.
Ok, it was an accident, not planned 😉

Cheers, Michael

[scavpan]

Sounds interesting Michael. I have had dealings with harley twin cranks, but they are on a common crankpin, but are similar in the fact that the pistons rise together, but dont fire together on the same stroke.They have to be statically and dynamically balanced.Scavpan

[Michael]

Hi Lonesome Twins,

for my hardcore chopper project I have to rebuild a motor.
I wonder if someone have ever tried to run the motor without balancer weights?
For sure I will need the chain, shafts and sprockets to drive the oil pump. But the balancer weights can either be removed or reduced to a minimum with a turning maschine.

Any experience or comments?
Please let me know 😉

Cheers, Michael

[Michael]

Hi Scavpan,
there is a “secret” behind all the motor and cylinder layouts.
parallel twins (our twins and the old english ones), twins with 180

[scavpan]

Hi Michael
Did you ever try the engine without the balance weights?. I have bought an engine where the camchain has snapped and took one of the balance weights with it along with the balance weight drivechain and tensioner mechanism, so I will either run without or try and aquire a set of secondhand balance weights and relative hardware.please let me know how it went
regards
scavpan

[Michael]

Hi scavpan,

no, I didn’t had the time to start that motor rebuild 🙁

But may have a spare pair of balancer weights and “axles” if you need them …

Make sure that there are no pieces broken off the crankcase, e.g. balancer chain tensioner fixing !

Cheers, Michael

[scavpan]

Hi Michael
Yes, the casings took a battering and have now had them welded just where the tensioner is mounted on the lower case.
The parts I need are
balancing weights with springs and sprockets.
balancer weight shafts.
Balance chain 06bh-sdh.
Tensiner mechanism complete

I have the spacers for the balance weights.
I have been trying to find a supplier for the balancing chain, but is very difficult to source, I am dealing with a Japanese company that deal with D.I.D. chain. The number on the chain is 06H (zero, six, H )
Please let me know what you have and how much you require for the parts.
Thanks & Regards
Mark

[Michael]

Hi Mark,

I should have the weights, sprockets and shafts.
Have to have a look into my spares department 😉

Don’t have the chain and the tensioner. These parts crack when the bad moment comes, so no such spares with me.

Will have a look and post pictures when I’ve found them.
They will not have a high price but freight costs needs to be added.

Cheers, Michael

[Michael]

Hi Mark,

have found the balancer weights 😉

One side is complete incl. washers and bearings,
other side is just the weight(and included components) and the axle, no washers, no bearings.
There are no screws included that fasten/fix the weights to the axles !

General condition is good, axles just have some coloured marks, no damage. Can be “polished” and will look like new 🙂

Attached a picture of what I can offer to you. Would that help ?

Cheers, Michael

[Author]

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