Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Moto Rumi technical problems or solutions
Lars
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by Lars » Fri May 22, 2020 2:21 pm

greasy-fingers wrote:
Fri May 22, 2020 12:38 pm
always good when you find the definite cause to a problem :wink: . reading this reminds me to ask - I do not like the idea of the split pin on the flywheel nut, if you cannot reach the position to match the slots in the nut with the hole in the crankshaft without overtightening it requires you to back the nut off !!. I have always tightened the nut to around 50ft lbs and not fitted the split pin, I would be interested to hear what others do ?
I don't like it either.
The solution, I believe, is to do what Parmakit did on their crankshaft assemblies: Replace the castle nut with a regular 19 mm hex nut! Properly torqued down with a serrated lock washer underneath, it will never come loose by itself. And so much easier to work on.
That is how it is done on my Junior, and that is what I plan to do on the SS. That split pin is a nuisance.

hugomez
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by hugomez » Fri May 22, 2020 10:51 pm

greasy-fingers wrote:
Fri May 22, 2020 12:38 pm
Always good when you find the definite cause to a problem :wink: . Reading this reminds me to ask - I do not like the idea of the split pin on the flywheel nut, if you cannot reach the position to match the slots in the nut with the hole in the crankshaft without overtightening it requires you to back the nut off !!. I have always tightened the nut to around 50ft lbs and not fitted the split pin, I would be interested to hear what others do ?
Hi Graham, yes, it is nice to find and solve the problem, thanks that we have here each other to help when is needed.

About the pin, I am not sure if you mention that because me previous comment at the beginning of the tread, in my case I was talking about the little metal piece that goes in the groove of the crankshaft axle. Sometimes I use the wrong words because I don't know the right English word.

Moto-Rumi-Formichino-Big-surprise-ignition-12.jpg
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About the split pin, to secure the nut, I actually like it, it give me more confident that whatever has it is not going to get loose. My Bicarburatore (not the Sport) has a modern crankshaft and the axle don't have the small hole for that split pin, and honestly I don't like it.

I understand what You and Lars say, but in my case remove that split pin and add a new one take just a few extra minutos. Not too annoying but a lot of peace of mind.

Just my opinion.
My little Formichino here: http://www.formichino.com/pictures1.html

Lars
Posts: 291
Joined: Fri Nov 02, 2012 3:09 pm
Location: Sweden

Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by Lars » Sat May 23, 2020 8:31 am

I understood what you meant, Hugo. You were talking about the key for the shaft.
But that does not change my dislike for the castle nut, requiring a special tool (which I do not have!) and split pin - for no good reason.

Only my opinion, too.
I am just glad my Junior engine has the better solution, and that the nut can be tightened and torqued with a standard socket.

hugomez
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by hugomez » Sat May 23, 2020 12:09 pm

Lars wrote:
Sat May 23, 2020 8:31 am
I understood what you meant, Hugo. You were talking about the key for the shaft.
But that does not change my dislike for the castle nut, requiring a special tool (which I do not have!) and split pin - for no good reason.
Only my opinion, too.
I am just glad my Junior engine has the better solution, and that the nut can be tightened and torqued with a standard socket.
Hi Lars,
I understand what you mean. Certainly the special tool is annoying. I made it myself with the Dremel some years ago. Not very pretty, but works fine so far. (See photo)

I wonder what tool you are using to keep the flywheel not rotating while you are tightening or loosing the nut. In my case I also made one but not very strong. It can break at anytime, then I will have to find another way. I wish I would have one original tool for that (I have seen them and is perfect), but unfortunately I don't have it. Very curious about how you manage.


Special-tool-flywheel-nut-Moto-Rumi.jpg
Special-tool-flywheel-nut-Moto-Rumi.jpg (53.38 KiB) Viewed 125 times
My little Formichino here: http://www.formichino.com/pictures1.html

UHJ200
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by UHJ200 » Sat May 23, 2020 1:55 pm

Earlier in this topic I noted that the flywheel was positioned without the aid of a woodruff key in an effort to get the timing correct.

Assuming that no battery is fitted and that the electronic ignition relies solely on the AC current supplied by the flywheel then NOT using a woodruff key is a rather bad idea.

This because the magnet in the flywheel has to be in the correct angular position relative to the coil in the stator to make best use of the magnetic flux to power the rest of the ignition system. It matters not be it electronic or original, weak output weak spark, strong output strong spark!

The castellated nut I have no problem with but then I made myself a simple tool to deal with it. (I think there may be a drawing of it somewhere in the manuals section.)

As smooth as the Rumi engine is the crankshaft is subjected to a lot of nasty acceleration forces. The flywheel has a good deal of mass that really does not want to be accelerated and will do its best to wring itself off the crankshaft. This is where the taper comes in and is why it needs to be a smooth and accurate fit in the flywheel. The castellated nut is there merely to hold the flywheel in intimate contact with the crankshaft taper. Once the nut is "snug" then further tightening sufficient to expose the split-pin hole should be sufficient. Remember that at best 90% of the applied torque is borne by the first 21/2 threads, the end of a thread, as on the crankshaft, is a stress raiser, therefore over exuberant application of the torque wrench is not recommended.

hugomez
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by hugomez » Sat May 23, 2020 3:26 pm

Hi David,

Yes, this crankshaft axle don't have the woodruff key, the reason is that this electronic ignition need the flywheel in a certain position, and happen to be different than the original position that the flywheel has when using brake points. So the only way to "turn" the flywheel is not using the woodruff key.

Greets,
Hugo
My little Formichino here: http://www.formichino.com/pictures1.html

Lars
Posts: 291
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Location: Sweden

Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by Lars » Sat May 23, 2020 4:28 pm

hugomez wrote:
Sat May 23, 2020 12:09 pm
Lars wrote:
Sat May 23, 2020 8:31 am
I understood what you meant, Hugo. You were talking about the key for the shaft.
But that does not change my dislike for the castle nut, requiring a special tool (which I do not have!) and split pin - for no good reason.
Only my opinion, too.
I am just glad my Junior engine has the better solution, and that the nut can be tightened and torqued with a standard socket.
Hi Lars,
I understand what you mean. Certainly the special tool is annoying. I made it myself with the Dremel some years ago. Not very pretty, but works fine so far. (See photo)

I wonder what tool you are using to keep the flywheel not rotating while you are tightening or loosing the nut. In my case I also made one but not very strong. It can break at anytime, then I will have to find another way. I wish I would have one original tool for that (I have seen them and is perfect), but unfortunately I don't have it. Very curious about how you manage.



Special-tool-flywheel-nut-Moto-Rumi.jpg
Hugo, your tool for the castle nut is nice. I am not as good with the Dremel tool as you are, but I might try to do something similar.

For holding the flywheel, i usually improvise some device to hold it. I have considered making a tool for that purpose too, but I normally don't have any difficulties loosening the nut. That nut is not supposed to be all that tight for the reasons UHJ200 explains above: It is the conical taper that locks the flywheel to the shaft, so the nut should not need any heroic forces to undo.

But a special tool to hold the flwheel should not be too difficult to make. I envision a steel bar with two bolts threaded into it, placed in such a way that the heads fit inside the openings in the flywheel. Perhaps someone on this forum has made such a tool that he can post a picture of.

Lars
Posts: 291
Joined: Fri Nov 02, 2012 3:09 pm
Location: Sweden

Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by Lars » Sat May 23, 2020 4:50 pm

Hi again, Hugo.
This tool looks nice for about 22 Euros. 10 mm too tight for the Rumi flywheel, though. Should be possible to modify, or find a larger version.
https://www.rinab.nu/moped-klass-2-a/Ho ... gIXefD_BwE

Here is another one, more along the lines I described. I might get one of these.
https://se.grandado.com/products/1-pc-j ... gJdRPD_BwE

greasy-fingers
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by greasy-fingers » Sat May 23, 2020 5:44 pm

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greasy-fingers
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by greasy-fingers » Sat May 23, 2020 5:45 pm

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greasy-fingers
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by greasy-fingers » Sat May 23, 2020 5:47 pm

uk ebay item 401044755977 typically Chinese "crap quality" so buy two as one will break, but they are only about £9 each

hugomez
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Re: Engine doesn't sound as it should ... (BIG SURPRISE INSIDE)

Post by hugomez » Sat May 23, 2020 5:49 pm

Thank you very much Lars and Graham for the links and photos of this tools.

The one I made and using successfully many times is this one, but as you can see, it is made with thin aluminium and reinforced with two tube bars, to avoid it to bend. If I remember correctly that was a piece of aluminum that came from a window. :lol:
Now that I know it is not necessary to apply too much torque to the nut, I will probably be able to continue using it, but in case eventually it break, I know what replacement tool I must search for.


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My little Formichino here: http://www.formichino.com/pictures1.html

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