Simplex engien

[Franz Rongen]

Hello,I would like to intoduce myself briefly: my name is Franz and i live in germany  near Aachen.

I have owned a 1925 Neracar MK B since 2014. I also have aquestion about the simplex engien: do the 2 storke engiens vibrate very strongly ?  

when you accelerate it shakes the whole machine, the front fende has already cracked.

greetings frongen9

[andy pugh]

On Tue, 6 Apr 2021 at 22:01, Franz Rongen <fron...@gmail.com> wrote:

> I have owned a 1925 Neracar MK B since 2014. I also have aquestion about the simplex engien: do the 2 storke engiens vibrate very strongly ?
> when you accelerate it shakes the whole machine, the front fende has already cracked.

Mine vibrates a bit, but not to the extent that you describe.

Do you know if it has the original piston? Someone here a few years
ago calculated that the engine is over-balanced, in that the crank
weights are a bit bigger than necessary for the piston.
So if, for example, your bike has an aluminium replacement piston that
is lighter than it should be you would get vibration.

It is also possible that the crank-pin / big end is worn or that there
is a problem with the engine bearings.

I have had a problem with mine where the rivets holding the flywheel
to the keyed hub became loose. That created a noise, but not really
the vibration that you describe.

--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912

[Franz Rongen]

Thank you for your prompt replay.

We have re-stored the crankshaft. Yesterday I removed the cylinder to check the piston ,wich is made of cast iron and very heavy . 

However , the piston pin has som play. Likely that will be the culprit.  You don`t happen to know the weight distributon from the piston to the crankshaft of the 285cc engien ?

[andy pugh]

On Tue, 6 Apr 2021 at 23:38, Franz Rongen <fron...@gmail.com> wrote:
>
> Thank you for your prompt replay.
> We have re-stored the crankshaft. Yesterday I removed the cylinder to check the piston ,wich is made of cast iron and very heavy .
> However , the piston pin has som play. Likely that will be the culprit. You don`t happen to know the weight distributon from the piston to the crankshaft of the 285cc engien ?

I don't.

I have several Model A engines that I could weigh, but that wouldn't help.

[Ben]

Hello Franz, I encountered the same problem and secured all bolts and nuts with Loctite medium strong. Later found that the engine was overbalanced. I made a new piston which is hevier than the old one.  By increasing the weight of the piston with piston rings from 423.3 to 533.9 g, the balance factor was reduced from 70% to 58% .  This reduced the vibration, which we could measure with sensors. But, the vibration was certainly not over. See atachment for details. More details upon request. Good luck. Ben.

Op woensdag 7 april 2021 om 01:03:31 UTC+2 schreef bodg...@gmail.com:

[Franz Rongen]

Hello  Ben, thank you for your very detailed.

We set the ignition to 8,2 and 10,5 mm befor TDC , but we couldn`t get a good runout. 

How many mm have you set your ignition to ?

Have a nice weekend .

Franz