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Exhaust

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Ben Kelly20/04/2008 17:50:00
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167 forum posts
35 photos
Ok here's my problem I have aquired a very old blue bird 46 2 stroke engine but I have no exhaust for it. Does anyone know where I can get one from, or any suitable replacement. Another problem I have is with an old, os 10 2-stroke and I tried to run it but it won't suck the fuel into the carb and I have no idea why the only thing I can think of is that it has no pressure back into the tank to help push the fuel out because there is nowhere to put a fuel tube on the exhaust there is only a feed tube. Any suggestions are greatly appreciated. Thanks. Ben
Myron Beaumont20/04/2008 17:56:00
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5797 forum posts
51 photos

Ben      Hi  May I suggest contacting "JUST ENGINES" .They have an excellent reputation in all engine matters .They have an excellent web site - I personally have no connections by the way

Myron

Eric Bray20/04/2008 19:49:00
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6600 forum posts
2 photos

There are plenty of after-market exhaust systems out there. You need to know a couple of things,

a, the dimensions of the engine's exhaust port, (height and width of the inside of the port, and of the outside of the port).

b, is it a clamp-on, or a screw-on system. (like a jubilee clip, or two bolts through the manifold into the engine, or vice versa!)

c, was it an overlap type fitting, or a butt-joint and gasket type. 

d, not very important unless you want the absolute max power from the engine, how critical are you on the fit between the engine port and the exhaust manifold, a slightly larger engine than manifold will result in a step and cause a small amount of gas-flow resistance, and cost you a few rpm's. 

Simon Chaddock25/04/2008 21:28:00
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5415 forum posts
2828 photos

Ben

You say your old OS 10 "won't suck fuel". What do you mean?

All (model) two stokes use the crankcase as a pump to suck an air/fuel mixture into the engine and to then blow it into the cylinder via the transfer port. The carb provides the air/fuel mixture but at hand cranking speed there is not sufficient air flow to suck much fuel, hence the need to "prime" the engine. In the olden days this was either by turning the engine over a couple of times with a finger over the carb intake or by putting a drop of fuel in the exhaust port (no silencer!). The object of either of these methods is to get sufficient fuel into the engine for it to start so that there will then be enough airflow through the carb to provide a working air/fuel mix.

So does your AS10 draw fuel into the carb when hand cranking with your finger over the carb? If it does not then you either have a blocked fuel line or a more serious, possibly mechanical, problem.

Ben Kelly26/04/2008 11:17:00
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167 forum posts
35 photos
Ye thats it, the fuel will be sucked through when a finger is over the carb but wen we get the engine to run after priming we can watch the fuel flow back into the fuel tank instead of being sucked into the engine.
Brian Parker26/04/2008 13:34:00
538 forum posts

It's due to a loss of depression or an air leak at the carburettor.

(I assume the tank is not too low for the suction available?)

Check the carburettor 'O' ring seal and the barrel-to-body fit. Also, is the needle assembly in order? Check the fit of the fuel lines, are they air tight?

If all OK, then you need to examine for crankcase depression/compression losses ( you should be able to feel compression on both down and up strokes and hear it 'pop'). If not, is the end plate seal in good order? Or is the engine just tired/worn? (Piston/liner slack. Play in the main baring assembly).

Good Luck.

Eric Bray26/04/2008 17:03:00
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6600 forum posts
2 photos

Where in the jet is the hole? If someone has been fiddling, it could have been installed incorrectly.

If it is an open-ended pipe that the needle screws into/out of, check the fuel tank level.

 If the jet has a single hole in it, that the taper on the needle screws past, the hole should point down into the carb.

If the jet has two holes, one either side, the holes should be positioned across the carb. 

The tank should be positioned so that halfway down the tank is level with the needle-valve. 

Chris Channon02/05/2008 21:23:00
57 forum posts
1 photos

Eric, is the needle valve open at least four turns?

Do this and try running it again,

Let us know how you get on.

Chris

Chris Channon02/05/2008 21:24:00
57 forum posts
1 photos

sorry, I meant the last post for Ben, oop's

Chris

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