How do I test a reed cage?

[thefox]

OK, I am still working on my brother's YT125. After some assembly MY bro put some starter fluid in it and it fired up and ran for 2 seconds, then when he went to pull it again it didn’t get any compression. So I think it might be the reed cage. The reeds are new and the cage was replaced with a used one that looks good. I can't see any gap in between the reeds and cage but I took a flash light and put it into the manifold and could see some light coming from around the reeds. I also tried sucking in fro the intake (that looked weird) and it blocked most of the air but not all of it.

So does it sound like my cage is bad? How else would I test it? Any thing else it could be?

[Unclediezel]

If you have a manual---they give you a "GAP" spec----
If you think 4stroke for a second---the valves seal the cylinder during compression stroke---your reed is asked to do the same thing---any leakage at all, is lost compression. Comp pressures -----upwards of 100 psi---can in no way be duplicated by "Blowing " thru it----so if it leaks by your mouth--it will definitely leak under normal operating environments.If you need the specs, Holler back --I can scan the pages for ya.

[thefox]

Yeah if you can send the specs. I can't find them in my book. I can't see any gap with it just sitting on the workbench but when I put a light behind it I can see just a little getting around the reeds.

[TeamGeek6]

Enough starting fluid to run 2 seconds, with no 2 stroke oil, is a recipie to finish off an already worn set of rings. Reeds arent causing this problem.

in a 2 stroke, the cylinder cant get compression until the piston rises above the exhaust port, and since the intake port is almost at the same level, the reeds even being taken out wont make a large difference. Ive measured pressure at the reeds on my 250R, its nowhere near the compression pressure - it would blow out the crank seals if it was.

[thefox]

Enough starting fluid to run 2 seconds, with no 2 stroke oil, is a recipie to finish off an already worn set of rings. Reeds arent causing this problem.

in a 2 stroke, the cylinder cant get compression until the piston rises above the exhaust port, and since the intake port is almost at the same level, the reeds even being taken out wont make a large difference. Ive measured pressure at the reeds on my 250R, its nowhere near the compression pressure - it would blow out the crank seals if it was.

It has a new piston and rings, well 2 seconds run time on them at least. And when I say no compression I mean my gage reads about 3 psi, if I hold my hand over the plug whole I can fell air come out but then when I put my thumb covering the hole I don't feel much compression.

[Howdy]

It has a new piston and rings, well 2 seconds run time on them at least. And when I say no compression I mean my gage reads about 3 psi, if I hold my hand over the plug whole I can fell air come out but then when I put my thumb covering the hole I don't feel much compression.

Put your hand over the carb and see if it is blowing back at all ( with the spark plug in it ). If it's not blowing back then there is a good chance the reeds are good. If it is blowing back then pull and inspect them. Every 2 stroke I worked on does allow a little blow back, but not to much.
Howdy

[thefox]

Put your hand over the carb and see if it is blowing back at all ( with the spark plug in it ). If it's not blowing back then there is a good chance the reeds are good. If it is blowing back then pull and inspect them. Every 2 stroke I worked on does allow a little blow back, but not to much.
Howdy

OK, I just tried that but since the engine is out of the frame it wasn't very easy. It didn't feel like there was much air blowing out of the intake but there wasn't much getting sucked in either. I will try again tomorrow when I can have someone pull it over while I hold the engine and put my hand over the intake.

[hrc85250r]

dude, to check your reeds just look at them, if they look worn or like they are cracking get new ones, since this thing is air cooled make sure you have the top end together right with the gaskets on it correctly....sounds like you have a big time leaky head gasket....

[Howdy]

OK, I just tried that but since the engine is out of the frame it wasn't very easy. It didn't feel like there was much air blowing out of the intake but there wasn't much getting sucked in either. I will try again tomorrow when I can have someone pull it over while I hold the engine and put my hand over the intake.

If your not sucking much in, then you need to find out why. As hrc85250r mentioned it could be a bad head gasket. Other things it could be: Bad base gasket, broken ring ( I have broke my share of them ), and more.

The more you describe the symtoms, the more I am leaning away from it being bad reeds. You may try putting the piston at TDC and hold it there. Then blow a little air into the cylinder via the spark plug hole. Look and feel for any air leaks and you should find your problem.
With the piston at TDC and air blowing in:
If it comes out between the head and cylinder: Bad head gasket
If you get a major air flow out of the exhaust: Bad Rings or piston to cylinder clearance

I hope this helps.
Howdy

[slow200s]

well sounds to me like you have a weak piston, and that your wrist pin is bad, and that your head is warped but thats just me.

[Huffa]

As far as I know the reed has zip to do with compression and your motor should run with out ANY reeds in.

All the reeds do is control the flow of fuel at slower rpms

If you put a teaspoon of oil in SP hole and it perks right up that's telling you the rings are bad. If it doesn't you may have a combo of bad head gasket and rings or just rings.

Maybe the bore is shot also?

A blown head gasket can sound like a bird chirping too when the air is being forced out. Tweet-Tweet!

Like said too, it could be the base gasket.

[TimSr]

Put a few drops of oil in the lug hole. You need the rings wet to seal. Starting fluid dries everything up. If you still have no comprerssion, you need to take the top end back off. Something isnt right. Reeds affect compression in a very minor way. They will not cause you to drop to 3psi. Basically, they are a one way valve for air flow BEFORE it begins being compressed. If you tear down an early 70's two stoke you will notice they dont have any!

When you go back in, the problem should be visible. If nothing with piston and rings stares at you, inspect the head very closely for a crack. Cracks are not easy to see.

[Mosh]

your crank seals could be bad too.this will let air out the seals and dramatically affect your compression.

[Huffa]

your crank seals could be bad too.this will let air out the seals and dramatically affect your compression.

Yep, and to test them am I correct to say it needs a leak down test then?

[Unclediezel]

soapy water around the cylinder and pull the cord----look for the foam --just like you would on a bicycle tire-----
By the way---GUYS-----If the trike would run without reeds-----then what keeps the intake charge in the crancase and not puffed back out thru the carb??????
2-stroke guys---2 stroke--think!!!