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Old Sep 15, 2006, 10:53 AM
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Iraq - Baghdad
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Question
piston baffle position

Hi everybody
Actually two questions :
1.What is the position of piston baffle with respect to center line of piston (if you're looking at piston with gugeon pin hole toward you) ? ,usually the baffle is off the center line, is it closer to suction port or to exhaust port ?
2.Can I use some additives to fuel to compensate weak engine compression ?

Thank you
Yours , Majid
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Old Sep 15, 2006, 11:05 AM
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downunder's Avatar
Adelaide, South Australia
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The baffle always go to the side furthest away from the exhaust, in other words on the transfer port side because it's job is to deflect the fresh mixture up towards the cylinder head.

About the only thing you can try to help seal a worn piston is to use castor, and probably lots of it
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Old Sep 15, 2006, 10:15 PM
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Everett Wa.
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Majid,
How have you determined that you have week compression?
Konrad
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Old Sep 16, 2006, 12:59 AM
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Belgium, Lessines
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Majid,

What make & type engine is?

Daniel
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Old Sep 16, 2006, 11:35 AM
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Thank you guys
Konrad , Daniel : the engine is VECO .21 ( old , right ?!) , with piston of ring , the indication of worn engine is by my instinct ! , I can hear conpressed mixture leaking during rotation , and offers small resistance .
Installing the ring on its own inside cylender and pushed by piston head , it looks so tight when looking using magnification lense .
Please inform me further .

Thanks , Majid
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Old Sep 16, 2006, 11:36 AM
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And it's very hard to start !!
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Old Sep 16, 2006, 12:09 PM
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Everett Wa.
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Majid,
Hand rotation is a very poor way to determine compression. As I recall the Veco has a Dykes ring (an "L" shaped cross section ring). This ring relies on cylinder pressure to seal the ring against the cylinder. It is a low drag ring unlike the normal SAE "D" ring, which relies on the ring to supply the sealing pressure. The Dykes ring will appear to have low compression at hand rotation speeds.
Yes the Veco is an old engine. Is it an R/C engine? Hard starting is usually a sign of a poor glow plug (weak battery) old fuel (stale) or improper mixture (lack of priming). Poor compression usually shows up as poor power (acts like it is over heating).
Konrad
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Old Sep 17, 2006, 04:52 AM
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Konrad
I have indeed an electric starter , the fuel is good ,I used to run my OS.4 engine as well directly after preparation .
The glow plug is excellent (I checked it out), the battery is good .
The ring is indeed type L cross section , are you telling me that this type of ring offers less resistance than that of other type for the same size of engine?
I've made all adjustments that crossing the mind .
But after long and hard starting trials , it worked for 2 seconds then stopped and never worked again.
It is an rc engine , with black plastic carburator , looks very nice .

Thanks
Majid
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Old Sep 17, 2006, 12:56 PM
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Majid,
Yes, the Dykes offers a lot less resistance.
Some other points.
At some point in time 4 cycle fuels were blended with half the oil content of 2 cycle fuel. Is the fuel you have have an oil content of at least 20%?
As you started this thread with a basic question about baffle placment. I have to ask if you might have the cylinder liner in backwards? The exhaust port needs to open first as the piston is coming down.
It sound like you have a Perry carb. Is this correct?
Konrad
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Old Sep 18, 2006, 02:31 AM
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Konrad ,
Thank you for your concern and patience .
The cylinder liner was fitted correctly (Exhaust first) .
The fuel mixture I'm using is at least 25-30% castor oil , so what do you suggest ?.
I will send you pictures of the engine , and see how pretty is it .


Thanks again
Majid
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Old Sep 19, 2006, 03:32 AM
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Konrad ,
Here are 2 pictures of my engine , the issue is that there is'nt a (spring effect) when flipping propeller slowly .

Majid
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Old Sep 19, 2006, 08:35 AM
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Quote:
Originally Posted by Majid Al Khafaji
the issue is that there is'nt a (spring effect) when flipping propeller slowly
That's exactly how the dykes ring acts - you don't feel compression when turning the prop slowly. Once the engine starts running the dykes ring seals the piston and the engine runs fine.

Ivan
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Old Sep 19, 2006, 07:25 PM
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Everett Wa.
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Majid,
The engine is fitted with a Perry carb. It was a great carb in its day and it still is a good cab today. It has a problem in that the mixture slot (inside the big brass wheel) is often clogged with old oil. To clean remove the high-speed mixture needle. Remove the little E clip on the center stub that the high-speed needle threaded into. Grab the mixture disk (the big brass wheel) with your fingers and with a twisting pulling motion remove the mixture disk. On the mixture disk you should find a very thin slot cut into the part that fits into the black body of the carb. This slot will also have a small hole drilled in it. These are the fuel metering ports. To clean them I like to draw a currency note (money) through the slot. While the carb is apart check that the fuel inlet nipple on the carb body will flow fuel. Reassemble in the reverse order you took it apart. I have found that to run correctly the metering disk cannot be aligned with the index mark on the carb body. I like to set it just off the mark to the lean side (-). Reinstall the high-speed mixture needle and gently seat the needle. Back out the needle 1.5 turns. This should set the carb so that it will now flow fuel.

I recommend that you remove the muffler so that you can prime the piston directly with a few drops of fuel. Once you have the engine starting and running easily you can reinstall the muffler.

28% oil is perfect for this engine. It also likes mild nitro 15% to 25%.
Good luck,
Konrad
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Old Sep 20, 2006, 11:44 AM
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Thank you guys
Konrad ,
I've checked the mixture slot (at least by blowing air into nipple) , it was not blocked , I'll try further your advices .
Nitromethane is forbidden material to be sold !!!

Thank you
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Old Sep 20, 2006, 09:07 PM
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Majid,
Blowing into the nipple does not guarantee that the metering slot is clear of all obstructions.

Even here in the Americas Nitromethane in a controlled substance as of this August. This war on terror has lost all rational. I expect water to be band as it is made up of hydrogen. We at know what that resulted in "Oh the humanity". Just for the record the Hindenburg burned as a result of the aluminum nitrate paint (solid rocket fuel) use to protect the outside envelope from ultraviolet light.
Konrad
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