Bol D'Or - New Project

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Lasse
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Re: Bol D'Or - New Project

Post by Lasse » Sun Sep 04, 2016 2:40 pm

Hugo, by an afterthought, it COULD be weak magnetism in one part of the flywheel.
Have you considered to have the flywheel changed, or remagnetizized?

Must be the last straw...

Lars
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Re: Bol D'Or - New Project

Post by Lars » Sun Sep 04, 2016 5:11 pm

hugomez wrote:Hi Lars,

I thought this test would help to proof that cylinders (and re-plated) are ok, not needed to remove them of the engine. With the small area to work in this bike, removing the cylinders would be really painful. Is this completely necessary at this point?

We see there is same compression in both cylinders at BDC and at TDC. I could test also with the piston at the middle position inside the cylinder, to see how the pressure react. If there is any problem with the re-plated, I guess I would notice in the needle at the pressure machine. Would this be a solution to avoid remove them?

My main concern is not remove them, is to put it back. Even with the engine on the table is not very easy to manage the pistons rings when assembling, I can not imagine doing it with the engine on in this scooter.

I did it in the Bicarburatore and was more or less ok, because there are a lot more space to work, but in the scooter .....

Any advise is welcome regarding this.

Hugo, I did not think of the fact that the scooter is much harder to work on.
Yes, you should save the removal of the cylinders as a last resort only. But I am not sure how much the improvised leak-down test of the cylinders really prove. I agree that everything looked normal, the leak-down rate past both pistons seemed about the same. Still, I have a feeling that the sort of problem with the plating that Ian is describing would be difficult to detect through the pressure test.

But why not try Lasse's suggestion of just putting some mileage on the engine first? That will allow pistons and rings to settle in some more. You would then notice if things improve or stay the same. I don't see how it could do any harm at all.

Certainly worth trying before you go further, I think.

Ian Skinner
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Re: Bol D'Or - New Project

Post by Ian Skinner » Mon Sep 05, 2016 12:30 am

I seem to remember that this flywheel worked perfectly when Hugo put it on his SSBC. So loss of magnetism is not the problem.

I feel most embarrassed by all of this. I built this engine originally for my own use. The crankshaft I rebuilt completely within 0.001" alignment, with new seals, connecting rods, crank pins, pistons and rings. Both cylinders were refurbished by a World renowned supplier. All the gearbox internals and external selector components are as new. The carburettors are not new, however the needles and jets are. I have never encountered the problems that Hugo is experiencing with any of the many Rumi engines that I have re-worked. With all the groundless avenues that have so far been pursued, the only one left in my estimation is in establishing the relationship of the piston and it's rings with the cylinder bore in it's mid stroke. Any ideas how to do this without removing the components? Perhaps Lasse's thought to just get on and ride it, maybe be near the mark! Keeping an eye on the lubrication situation of that cylinder.

Ian

Lars
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Re: Bol D'Or - New Project

Post by Lars » Mon Sep 05, 2016 8:21 am

No need to feel embarrassed, Ian. It is clear that this engine has been built to exceptional standards.
Two of my own Rumi engines have been rebuilt by two different experienced Rumi mechanics some 10 or 15 years ago, and they are not even close to being as good as this one. Of course, the seals in my engines may have deteriorated a bit due to age only, but both engines failed the pressure/vacuum test pretty badly. I am envious of Hugo for having been able to buy this engine!

I have never heard of this type of problem, either. It is entirely possible that the cause is something ridiculously simple that we all overlooked, or that we thought had been eliminated as a possibility.

Or, could it be as simple as the new rings and pistons needing more to to seat and start providing better compression? Old fashioned break-in simply? Just running the engine some more should provide the answer to that question.

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Mon Sep 05, 2016 12:54 pm

Hi Lasse, Lars, and Ian,

Lasse, as Ian mentioned, I took the flywheel of the Bicarburatore (actually the complete ignition system) and mounted it in the Bol D'Or with the same results, so I eliminated the magnets at the flywheel as a possible source of the problem.

Your suggestion of making some kilometers to the engine is something I could try, however the bike has not documentation yet, so first I have to pass the inspection to get the number plate, to be able to freely ride it on the road.

About Ian's concern regarding a possible problem at the cylinder bore in the middle of it, I thought I could perform another test with the pressure/vacuum machine.

The idea is to measure the distance of travel of the piston from BDC to TDC, them make a chart of "for example" 10 steps. Moving the flywheel/piston one step at the time, and perform the pressure test in every step.
Doing this, if there is a problem at the middle of the cylinder, I should notice it, right?

Do you think this may work?

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

Lasse
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Re: Bol D'Or - New Project

Post by Lasse » Mon Sep 05, 2016 4:24 pm

Frankly, Hugo - a lot of hassle...
Not sure if you learn anything useable from this.

Why not drive the Scooter to the inspection, and get it registered, and get a number plate?
Because, then you will be free to get some kilometers "under your belt" - and enjoy this astonishingly perfect restoration,- before winter sets in.
Who knows, maybe the "problem" will eradicate itself, by the motor gradually "bedding in"?

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Mon Sep 05, 2016 5:37 pm

Lasse wrote:Frankly, Hugo - a lot of hassle...
Not sure if you learn anything useable from this.

Why not drive the Scooter to the inspection, and get it registered, and get a number plate?
Because, then you will be free to get some kilometers "under your belt" - and enjoy this astonishingly perfect restoration,- before winter sets in.
Who knows, maybe the "problem" will eradicate itself, by the motor gradually "bedding in"?
Hi Lasse,

Yes, I have reserved the appointment weeks ago to paste inspection in October 4th. They do classic vehicles inspection only 1 day a month, and there was the closest day possible.

Thanks
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Re: Bol D'Or - New Project

Post by hugomez » Thu Sep 08, 2016 10:02 am

hugomez wrote: .............. About Ian's concern regarding a possible problem at the cylinder bore in the middle of it, I thought I could perform another test with the pressure/vacuum machine.

The idea is to measure the distance of travel of the piston from BDC to TDC, them make a chart of "for example" 10 steps. Moving the flywheel/piston one step at the time, and perform the pressure test in every step.
Doing this, if there is a problem at the middle of the cylinder, I should notice it, right?

Do you think this may work?
.....
Hi,

These days I have been pretty busy with other things. Still I have in mind to perform the test I mention above, however I would like to know if you guys think that would be a helpful test, or maybe is a waste of time.

What do you think?, Would be possible to find an anomaly in the cylinder because of a bad re-bore doing this test?
My little Formichino here: http://www.formichino.com/pictures1.html

Lars
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Re: Bol D'Or - New Project

Post by Lars » Thu Sep 08, 2016 1:28 pm

hugomez wrote:
hugomez wrote: .............. About Ian's concern regarding a possible problem at the cylinder bore in the middle of it, I thought I could perform another test with the pressure/vacuum machine.

The idea is to measure the distance of travel of the piston from BDC to TDC, them make a chart of "for example" 10 steps. Moving the flywheel/piston one step at the time, and perform the pressure test in every step.
Doing this, if there is a problem at the middle of the cylinder, I should notice it, right?

Do you think this may work?
.....
Hi,

These days I have been pretty busy with other things. Still I have in mind to perform the test I mention above, however I would like to know if you guys think that would be a helpful test, or maybe is a waste of time.

What do you think?, Would be possible to find an anomaly in the cylinder because of a bad re-bore doing this test?
Hi Hugo,
It would not take too much time to do the test, I think. Only pressure test will be necessary, and probably only at about 5 different positions. Once you get near BDC the transfer ports will start to open, so no use to test there. Only the top 4/5 or so of the piston travel would be of interest for the leak-down test.

Perhaps you should even remove the blocking of the intake ports, since you already know that the crankcase is good. That way you only test the leak-down rate past the pistons. Might be easier to spot any difference that way.

If there is "belling" in one of the bores, I think there should be some difference in leak-down rates between the two cylinders. But it is only a guess. It is also possible that the piston rings will expand and seal enough to show about the same leak-down rate. Difficult to predict.

It wouldn't hurt to try, though.

Lars

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Thu Sep 08, 2016 3:08 pm

Hi Lars,

Thanks for your reply. I will do the test as soon as I can, probably during this weekend.

David (UHJ200) also mentioned to me by private to unblock the intake port and see how the pressure behave when the piston is in TDC. I will do it, but also at different position of the piston at the cylinder.

One question beside these tests. If I remove the cylinder heads, and I put the pistons in BDC, should I be able to see any imperfection at the cylinders?, maybe is not even necessary to take them out to inspect them?

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

Lars
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Re: Bol D'Or - New Project

Post by Lars » Thu Sep 08, 2016 4:55 pm

Hi Hugo,

You should be able to see any large imperfections in the bores, yes. But to measure the bores accurately, you would need take the cylinders to an engine shop and have them checked with a dial bore gauge.

Just taking the cylinder head off will allow you to see any obvious or major defect, though, so it may still be worth doing.

Lars

Lasse
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Re: Bol D'Or - New Project

Post by Lasse » Fri Sep 09, 2016 8:29 am

Again, Hugo - I would simply run the Scooter some hundred kilometres - in order to let the piston rings "bed into" the cylinder(s)
To bring the cylinders to a dedicated workshop, and have them measured, & compared, might be a somewhat expensive and inconclusively affair.

Why not just run the thing, and see what happens...
I believe you will be rewarded with a better, and better performance from the motor - together with a deeper knowledge about the basics of the problem.

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Sat Sep 10, 2016 6:09 pm

Thanks Lars and Lasse,

Lasse, still I am not sure if I will first try to pass the inspection and them once with the documentation follow your advise and make some kilometres to the engine to see if it "settle down".
The other option is to go for the cylinder inspection right away, but the problem is that lately I am quite busy with other things, and I do not want to see myself close to the day of the inspection, and the cylinders out of the engine.

In the last inspections I pass with my others Rumi, I never have to start the engine, was a frame, engine and general state inspection,me providing with a lot of documents to satisfy the curiosity of the inspector. Hopefully this one will be the same.

More soon.

Thanks :)
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Lars
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Re: Bol D'Or - New Project

Post by Lars » Sat Sep 10, 2016 8:24 pm

Hugo, I also think that you should just run the engine, and I have said so before. I was only responding to your question about how much you would be able to see with the cylinders on the bike (answer: Not much). I was not suggesting that you should pull the cylinders now. That should be a last resort only.

If it was my bike, I would just run it - registered or not registered! Since it is not the km that counts but the hours, you could just be puttering around the neighborhood in first or second gear. Does not matter, as long as you keep the engine running. After you have a few hours on the engine you should be able to notice if things improve or stay the same.

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Sun Sep 11, 2016 9:51 am

HI Lars,

Yes, I agreed. I will leave the cylinders out option to the last one. Today anyway I will perform the next pressure test.

Greets,
Hugo
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hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Sun Sep 11, 2016 12:50 pm

hugomez wrote: .............. About Ian's concern regarding a possible problem at the cylinder bore in the middle of it, I thought I could perform another test with the pressure/vacuum machine.

The idea is to measure the distance of travel of the piston from BDC to TDC, them make a chart of "for example" 10 steps. Moving the flywheel/piston one step at the time, and perform the pressure test in every step.
Doing this, if there is a problem at the middle of the cylinder, I should notice it, right?

Do you think this may work?
.....
Hi, I just performed this test. I did not find any strange thing applying pressure with the piston in different positions. The intake port was open, to let the air flowing. Also did the test at the cylinder that do not give problems, same result in both. However I did not find this test too accurate, maybe there is some problem with the cylinder and this test could not show it.

More soon.
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Lars
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Re: Bol D'Or - New Project

Post by Lars » Sun Sep 11, 2016 4:34 pm

Hugo, that is about what could be expected. It is consistent with your other findings. Any excessive leak-down should have shown up in your compression test, but it did not. So here we have yet another indication that everything is normal in this engine and that the two cylinders are equal. My guess is that also the very unusual problem with "belling" of a cylinder should show up in the compression test. But I do not know for sure.

It also seems extremely unlikely that you should have a) encountered such an unusual problem and b) the person inspecting the cylinder would have missed it. Someone who is measuring cylinder bores automatically measures at different heights, I would think. The whole thing seems so far-fetched to me. But we shall see what you find, eventually.

Since I mentioned the suggestion of something really simple and stupid, here is another one: What about a piece of debris from the plating process being stuck in one of the transfer channels? Or a piece of gasket material, or a blob of gasket sealant? That you may be able to check for by just removing the cylinder head and feeding a piece of wire into the transfer ports. Just a thought.

Keep going Hugo, whenever time allows you...

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Sun Sep 11, 2016 7:16 pm

Hi Lars,

Took out both cylinder heads. I do not see nothing strange inside the port from the angle I get. Nothing is covering the ports. However as I say I can not see much. I understand that a proper inspection require proper equipment and knowledges, not just me looking with the torch and touching with my fingers.

Anyway ...

More soon.
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RUMISTI
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Re: Bol D'Or - New Project

Post by RUMISTI » Sun Sep 11, 2016 10:04 pm

Hi Hugo,
I believe that the measurements in different positions, say nothing, since the piston rings have a groove which is not tight, so in any position the same result.
The Vaccum-measurement has indeed shown that the housing halves, and the sealing rings seal 100%. The ignition system, and the carburetor replaced, does not bring better results, therefore, this to 95% certainly good.
This leaves only the timing of pistons and cylinders, where something might be wrong, (edges or channels machined ??)
It is a mystery for me !!
Rudolf

Lars
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Re: Bol D'Or - New Project

Post by Lars » Mon Sep 12, 2016 7:28 am

A mystery to me too. One thing that I am not quite clear about, Hugo, is this: Once the right cylinder starts firing, does it always keep running? Also, you mentioned that the last time you rode the bike you could even get it to idle. Was that because you had then adjusted the idle mixture or did the engine improve by itself? I am of course looking for any sign that the piston/cylinders are bedding in, that the engine is improving. If there are no such signs after a couple of additional runs, I am afraid it will be cylinders-off time.

A mysterious problem, but I am convinced that you will find the the answer and the fix for it in the end. And all the members on this forum will have learned something from it.

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Mon Sep 12, 2016 8:51 am

Hi Rudolf and Lars,

Rudolf, I will try to take photos where you can see the ports. There is no much space to it because I will take them at the moment without taking the cylinders out.

Lars, answering your questions, when the right cylinder start, usually when I reduce, it stop again, but not always happened that way, once even got it to idle, but that time, when I let the bike rest at the side stand, the engine stop and them when I started again only one cylinder was working (I removed and clean the sparkplugs with break cleaner in between)

I am not sure but I think that was last time I test the bike.

Greetings
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Lars
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Re: Bol D'Or - New Project

Post by Lars » Mon Sep 12, 2016 10:45 am

OK, I had that impression too, I just wanted to be sure.

So it is not just a starting problem. That cylinder is permanently weak and is looking for any excuse to die, for example when you reduce the throttle. So something - whatever that is - is preventing that cylinder from breathing as it should. It has to be something fairly major to cause this.

If the pistons are new, it could be a manufacturing defect in one of them. The cut-out in the piston skirt could be of the wrong dimensions, or placed in the wrong position, not matching the intake port, for example. Such a problem you should be able to see by just looking down the intake ports. If you have not already done so, check to see that both pistons start opening their ports at about the same number of degrees before TDC. Also check that both ports are wide open at TDC and that the opening in the piston is matching the width of the port.

hugomez
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Re: Bol D'Or - New Project

Post by hugomez » Mon Sep 12, 2016 8:17 pm

Hi Lars,

Here the photos of the ports from both cylinders.
Attachments
LEFT-Cylinder-Moto-Rumi-ports-01.jpg
LEFT-Cylinder-Moto-Rumi-ports-01.jpg (109.91 KiB) Viewed 10457 times
LEFT-Cylinder-Moto-Rumi-ports-02.jpg
LEFT-Cylinder-Moto-Rumi-ports-02.jpg (115.16 KiB) Viewed 10457 times
LEFT-Cylinder-Moto-Rumi-ports-03.jpg
LEFT-Cylinder-Moto-Rumi-ports-03.jpg (82.37 KiB) Viewed 10457 times
LEFT-Cylinder-Moto-Rumi-ports-04.jpg
LEFT-Cylinder-Moto-Rumi-ports-04.jpg (69.03 KiB) Viewed 10457 times
RIGHT-Cylinder-Moto-Rumi-ports-01.jpg
RIGHT-Cylinder-Moto-Rumi-ports-01.jpg (104.85 KiB) Viewed 10457 times
RIGHT-Cylinder-Moto-Rumi-ports-02.jpg
RIGHT-Cylinder-Moto-Rumi-ports-02.jpg (70.6 KiB) Viewed 10457 times
RIGHT-Cylinder-Moto-Rumi-ports-03.jpg
RIGHT-Cylinder-Moto-Rumi-ports-03.jpg (94.63 KiB) Viewed 10457 times
RIGHT-Cylinder-Moto-Rumi-ports-04.jpg
RIGHT-Cylinder-Moto-Rumi-ports-04.jpg (68.68 KiB) Viewed 10457 times
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Lars
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Re: Bol D'Or - New Project

Post by Lars » Tue Sep 13, 2016 8:51 am

Superb photos, Hugo.

Everything looks absolutely perfect as far as I can see. Transfer ports and exhaust ports are completely unobstructed and precisely matching the piston profile. Clearly, no problems in this area.

The only thing left to check with cylinders still in place is what I tried to describe in my last post, but I have to correct that a bit:

Check when the pistons start opening the intake ports. They should open at the same number of degrees (or distance) from TDC in both cylinders. Also, when the pistons are at TDC, are the intake ports completely uncovered?


There are also two cut-outs at the bottom (skirts) of the pistons. They should match the transfer channels in the crankcase and cylinders. But that you will not be able to see with the cylinders seated. You would have to lift the cylinders 10 or 20 mm to see the piston cut-outs and if they match the channels. Perhaps you could try to do that. The pistons could remain in the cylinder bores, so you would not have the problem of inserting them again. Just an idea.

Lars

Lars
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Re: Bol D'Or - New Project

Post by Lars » Tue Sep 13, 2016 9:58 am

Another thought just occurred to me about this mysterious problem:
You have swapped all kinds of items on the carburetor and intake system, but...but...

WHAT ABOUT THE EXHAUST SYSTEM?

I don't remember hearing anything about the exhaust. In a two-stroke engine, of course, the exhaust system makes a world of difference.

If you have not already done so, remove and open up the muffler and look for any obstruction there. In a Formichino it is not so easy to swap the right and left exhaust, but perhaps you could just swing the pipes outwards and temporarily attach two other mufflers, just to see if it made any difference.

At least, it is one more thing to eliminate as a possibility.

Lars

RUMISTI
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Re: Bol D'Or - New Project

Post by RUMISTI » Tue Sep 13, 2016 10:04 am

Hello Hugo and Lars,
yes, I am also of the same opinion as Lars, everything looks very good on the upper side. Ian, from which manufacturer the piston? certainly not of ASSO or GOL?
Hugo, I still NOS pistons of "KS" for 42,00 bore out of production in 1954, but even with 3 piston rings, as was customary.
Good luck with the other test.
Rudolf

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