BMW R7 Motorcycle Engine
- Thread starter gbravo
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Help Support Home Model Engine Machinist Forum:
Rob,
I am considering making only the engine.
As I finishing this proyect, I am working in design and develop the following engine, it will be the Wright J5.
But I am thinking in a real Wrigt J5, not the design published in SIC, that have only the name of Wright J5.
I am considering making only the engine.
As I finishing this proyect, I am working in design and develop the following engine, it will be the Wright J5.
But I am thinking in a real Wrigt J5, not the design published in SIC, that have only the name of Wright J5.
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gbravo,
Excellent as ever. I see what is probably a vent on top of your crankcase. One of the issues I ran into with my V-twin was the pressure pulses in the crankcase. I had built a stubby vertical vent for mine which worked fine at slower rpm's but when I revved it up it would push oil out. I kept increasing the height of the breather until now I only get a trace of oil coming from it.
gbritnell
Excellent as ever. I see what is probably a vent on top of your crankcase. One of the issues I ran into with my V-twin was the pressure pulses in the crankcase. I had built a stubby vertical vent for mine which worked fine at slower rpm's but when I revved it up it would push oil out. I kept increasing the height of the breather until now I only get a trace of oil coming from it.
gbritnell
The boxer twin engine is the most critical configuration in terms of crankcase internal pressure, beacause both cylinders go forward and backward together.
For this problem the more common solution is a vent valve for maintain negative pressure in crankcase.
If you see the first picture with the original motor in this thread, you can see the vent valve on top of the crankcase.
German
For this problem the more common solution is a vent valve for maintain negative pressure in crankcase.
If you see the first picture with the original motor in this thread, you can see the vent valve on top of the crankcase.
German
If you compare the pictures 5 and 4 places before this post, named "Vent and cylinders" and "Hall sensor and exhaust pipes", you can see the magnet flywheel in the first picture made in aluminum and plastic material in the other. This change is due to recommendation of Roy Sholl fron CNC-engines about his CDI systems
This is copy of Roy information:
"One more thing. We have been working on hall sensor failure issues. These are very erratic and not too common just a pain in the tush. The one thing we've found is mounting the magnet/magnets in Delrin or other non electrically conductive material is best. For set ups already done we have found that gluing a .020-.025 plastic shim ( I use the fake credit cards that come in the mail ) onto the face of the hall sensor or if possible making a disk at least the same diameter as you magnet rotor will also eliminate the possibility of a sensor failure. If you glue a piece of plastic onto the face of the sensor it should be approximately 25% larger on all sides as the sensor body and I usually make it long enough to cover the leads also."
Regards,
German
This is copy of Roy information:
"One more thing. We have been working on hall sensor failure issues. These are very erratic and not too common just a pain in the tush. The one thing we've found is mounting the magnet/magnets in Delrin or other non electrically conductive material is best. For set ups already done we have found that gluing a .020-.025 plastic shim ( I use the fake credit cards that come in the mail ) onto the face of the hall sensor or if possible making a disk at least the same diameter as you magnet rotor will also eliminate the possibility of a sensor failure. If you glue a piece of plastic onto the face of the sensor it should be approximately 25% larger on all sides as the sensor body and I usually make it long enough to cover the leads also."
Regards,
German
This picture is the first complete engine assembly and I begin with the start engine intents.
After many intents, I observe that the engine is lack of compression.
I made an adapter for apply compress air and determine where the leakage is, I concluded that the problem was in the valves.
Removing the cylinders head, grinding the valves with number 600 compound and made one new valve, I assembly newly, but the engine decline start. I was many hours trying to start the engine without success.
Reading in some web pages and forums, I read that the cylinder liner finishing recommended is mirror finish and my finish was with cross hatch pattern, then I decided to build new liners with mirror finish and with some minor diameter for readjust the tolerances with pistons. But the motor continues declining to start with the new liners and pistons and rings well adjusted (in my point of view). The engine continues with lack of compression
After many intents, I observe that the engine is lack of compression.
I made an adapter for apply compress air and determine where the leakage is, I concluded that the problem was in the valves.
Removing the cylinders head, grinding the valves with number 600 compound and made one new valve, I assembly newly, but the engine decline start. I was many hours trying to start the engine without success.
Reading in some web pages and forums, I read that the cylinder liner finishing recommended is mirror finish and my finish was with cross hatch pattern, then I decided to build new liners with mirror finish and with some minor diameter for readjust the tolerances with pistons. But the motor continues declining to start with the new liners and pistons and rings well adjusted (in my point of view). The engine continues with lack of compression
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Hi German,
When getting to this point in engine building it is very frustrating to know that you have done good work but can't get the engine to work.
From what you say you have tried to fix or fixed the problem areas, although having a mirror finish on the cylinder liners is not what I would recommend. They need a slight scratch pattern to hold oil and seat the rings in.
It's strange that both cylinders have no compression. If you remove the heads and put the heel of your hand onto the cylinder and turn the engine over does it feel like it has vacuum on the downstroke and compression on the upstroke? If so then it should have enough compression to start the engine. I'm assuming that when you reground the valves they are in fact sealing.
With these elements proven out maybe you should look at something else. Are your cams timed correctly? It's possible that a small error in cam timing can prevent the engine from building enough compression to start.
With the quality of your build I would think that this wouldn't be an issue but from what you say I don't have any other place to look.
gbritnell
When getting to this point in engine building it is very frustrating to know that you have done good work but can't get the engine to work.
From what you say you have tried to fix or fixed the problem areas, although having a mirror finish on the cylinder liners is not what I would recommend. They need a slight scratch pattern to hold oil and seat the rings in.
It's strange that both cylinders have no compression. If you remove the heads and put the heel of your hand onto the cylinder and turn the engine over does it feel like it has vacuum on the downstroke and compression on the upstroke? If so then it should have enough compression to start the engine. I'm assuming that when you reground the valves they are in fact sealing.
With these elements proven out maybe you should look at something else. Are your cams timed correctly? It's possible that a small error in cam timing can prevent the engine from building enough compression to start.
With the quality of your build I would think that this wouldn't be an issue but from what you say I don't have any other place to look.
gbritnell
Lakc
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Sorry to hear about your troubles, its very excellent work so far.
Take a close look at your camshaft, and compare it to the factory one in the picture you posted. Looks like the factory cam is IIEE and you made your IEIE.
Take a close look at your camshaft, and compare it to the factory one in the picture you posted. Looks like the factory cam is IIEE and you made your IEIE.
Admiral_dk
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Your first finish with at cross hatch inside the cylinders are the correct way to do it, alternatively start with a mirror finish and use a hone to make the correct cross hatch pattern is even better when we're talking about an IC engine.
As stated, those "lines" are holding a small amount of oil in them + decreasing the friction ( a mirror finish gives the highest friction possible) and helps with bedding the rings.
It sounds like you're running into the same problems as most builders of small four stroke engines - getting the valves to seal correctly. Remember that the seat (the grey area you'll see on the valve and seat in the head) should be a tiny unbroken ring a few tenths of a millimeter in with on all the valves and seats.
As stated, those "lines" are holding a small amount of oil in them + decreasing the friction ( a mirror finish gives the highest friction possible) and helps with bedding the rings.
It sounds like you're running into the same problems as most builders of small four stroke engines - getting the valves to seal correctly. Remember that the seat (the grey area you'll see on the valve and seat in the head) should be a tiny unbroken ring a few tenths of a millimeter in with on all the valves and seats.
Lakc
Well-Known Member
Or it could be EEII but Ron is correct, I meant intake and exhaust lobes. It looks like you swapped the center two lobes in the picture of your production one versus the picture of the factory one.
willburrrr2003
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I have to say your engine is simply stunning!! I can see the care put into building it, and can't wait to see it running!!
Regards,
Will R. Everett, WA
Regards,
Will R. Everett, WA
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