SOO *

diosoljah · Post by **diosoljah** » Fri Apr 29, 2005 2:38 am

check the reed valve, it may be faulty and rebuild and clean out the carb

ferchja · Post by **ferchja** » Fri Apr 29, 2005 8:52 am

With my experience in engine repair and rebuilding, I would not suspect the lower jug gasket, as that is just there to seal the jug to compress the intake charge to move it into the combustion chamber. The compression reading you are getting is north of the lower gasket (between the piston and head).

I would look at the reed valve (& gasket between the reed valve and cylinder). If you honed the cylinder you may have oversized it enough that the rings worked well, but after they seated themselves, they are not wide enough to hold the compression. Doesn't take long to remove .005" from a cylinder (i.e. .0025" from the wall). Did you mic the cylinder to see the before and after diameter to make sure you were within spec?

To test for your leak, do a leak down test, get a leak down guage and turn the cylinder to TDC, within 10 degrees, load it up with air and listen to where it comes out.

Jeremy

BTW - I assume the clean the carb comment above is a sarcastic comment. Pretty funny!

vette76 · Post by **vette76** » Fri Apr 29, 2005 10:23 am

u said something about the reed valve gasket,would the reed valve really cause loss of compression?

ferchja · Post by **ferchja** » Fri Apr 29, 2005 2:34 pm

Yes, since it allows air/gas into the cylinder, but not let it escape during compression. The gasket may allow a loss of compression but not a near zero compression. The reed valve may not be opening to allow air in at all causing no air to move into the cylinder - No compression (no air to compress). The majority of the compression stroke is above the reed valve, so that would not indicate a zero compression. If you have already checked for air intake blockage work downstream from the air intake. If no blockage then check the reed valve by removing the intake and turn it over watching for the reed valve to open and close. It should make a sucking sound (obviosly)

The jug has openings at the bottom for exhaust and intake, but the top 2/3 is nothing but cylinder, piston and head/gasket. The cylinder is solid, so no issue there, that leaves piston and head. If the gasket is new and you got the right torque readings on the bolts that limits your compression to two things (if the reed vavle moves freely)

1) Head is warped and/or the jug deck is not level.

2) The piston rings/cylinder walls are not sealing properly. Could be bad honing, oversized cylinder wall with stock rings, broken rings.

With nearly a zero compression I would say the headgasket is not the issue cause you would hear that much air coming out the top. I would bet on the air going past the rings. You may be lucky and it is just a broken ring. Did you put the rings on in the proper order? Upside down? (not sure there is on the Spree, there is in normal 4 cycle engines)

Last but not least, it could be a broken/bent rod.

You just had it apart, I would take it off and recheck measurements on the cylinder and head to make sure all is well.

Jeremy

diosoljah · Post by **diosoljah** » Fri Apr 29, 2005 3:34 pm

if your using the original reed valve since the beginning life of the ped, you should definately get a new replacement and about the carb cleaning thing

a clean carb looks and performs better than a dirty one, and about the low compression, if its not the cylinder, piston, head, head gasket, crankcase gasket, it has got to be the reed valve, just rule each one out. hope your back on the road soon...have a good day man

ferchja · Post by **ferchja** » Fri Apr 29, 2005 5:57 pm

On a 2-cycle engine the reed valve allows intake air/gas mix behind the piston, when the piston is moving up on the compression stroke. The reed valve does not hold back the compression. If you look inside the engine the reed valve inlet goes down behind the piston. On the power stroke the piston forces the air/gas mix from behind the piston, through the inlets at the bottom of the jug, then as the piston passes those inlets, it compresses the air/gas mix to fire. The reed valve only keeps the air/fuel mixture from returning to the carb when the piston is coming down on the power stroke. Unlike a 4-cycle engine where the intake valve is part of the compression because it is inside the compression part of the engine (i.e. above the piston on the head - OHV, or next to it like a flathead or L head)

Carb has nothing to do with compression.....nothing....

Reed valve/gasket would only cause a near 0 compression problem (which is what we are talking about) if it was not opening up. It would cause a low compression situation (i.e. less than spec) if it allowed part of the air/gas charge to return to the carb or out through the gasket.

Jeremy

vette76 · Post by **vette76** » Fri Apr 29, 2005 9:07 pm

i checked the reed valve and it looks pretty good.(moves free). again, i dont think its the rings because i checked and there is no damage,the rings have only been run a short time, and it just died with no warning or anything like powerloss,exc.

ferchja · Post by **ferchja** » Fri Apr 29, 2005 10:32 pm

A sudden loss, with no warning is a usually a fatal failure. If you truly have only 5lbs of compression, and it happened like a light switch, one second ok, next second dead, then it seems you have a damaged ring, bent or broken rod. It's tough to hear the failure if you were driving with the sound of the muffler going. The ring/parts may be at the bottom of the crankcase.

When you crank the engine do you feel/hear air coming out of the head? Put a kleenex or light tissue around the head with the spark plug in and crank the engine to see if air is blowing by the gasket. If no, then you are left with the rings/piston/rod and jug (out of round, out of tolerence to current rings). Can't be anything else for zero compression if the reed valve is opening to allow air in. If the reed valve is allowing air in (when you crank it) then you know the cylinder is at least partially sealing when it moves up the cylinder to provide vacuum to pull the air/fuel mixture. This would point to the head gasket, as the vacuum to pull the air from the carb is not reliant on the head gasket sealing. You could literally have the head off the jug and if the piston rings are sealing properly air would still be pulled into the engine crankcase.

As a general point when dealing with engine rebuilds. I rarely just slap parts together without checking what the condition of the parts are. Measuring the cylinder for tolerance (spec) and checking for round within spec are critical when replacing rings or installing a piston. Engines are precise to within a .001" a human hair is .002-.004" Honing a cylinder without knowing what you have for meat on the cylinder wall to take off before you go to an oversize piston and rings is suicide for the engine.

Not saying someone can blindly do it without having success, you are just playing the odds that you are precise and still within tolerance.

Like I said you may have lucked out and it is just a blown ring or bad head gasket seal. But if you take it apart have it measured and check with a honda dealer for the specs of the jug.

Jeremy

burnt_toast · Post by **burnt_toast** » Fri Apr 29, 2005 10:56 pm

i had a complete engine failure when my engine overheated going down a steep hill. it broke a ring and scratched up the whole cylinder... not pretty. thats when i had to do a second rebuild. go ahead and take your cylinder off and see what it looks like, best to find out now if its ok or not.

vette76 · Post by **vette76** » Fri Apr 29, 2005 11:16 pm

the CYLINDER AND RINGS ARE FINE. the reed valve works, i didnt know that would effect compression. if that effects compression then does the cylinder base gasket?(in between the jug+engine)i didnt get a base gasket so i used the gasket maker stuff in the tube. when i removed the jug, there was none left. the point i am trying to make is the jug to crankcase not being sealed, would this have anything to do with compression loss?

ferchja · Post by **ferchja** » Sat Apr 30, 2005 8:44 am

If you have confirmed that there is no gasket material left on the bottom of the jug, then that is not faulty compression. It is no air getting into the cylinder. Simaliar to the reed valve sticking (vacuum). If the gasket is gone then air is not being forced into the cylinder but out the botttom of the jug on the power stroke.

Great news! With the $7 part you will be back up and running. The lesson learned is that engines run too hot for gasket making material on the block to hold. Mostly gasket material is used on valve covers and differential covers, etc. where pressure and high heat are absent.

Jeremy

vette76 · Post by **vette76** » Sat Apr 30, 2005 11:54 am

ok, thanks for all the help.it said heat resistant but not that much heat i guess.i ordered extras this time.

ferchja · Post by **ferchja** » Sat Apr 30, 2005 7:39 pm

What probably happened is the gasket melted/oozed out and then you lost your torque on your head bolts and the combination of air leaving the bottom, and the head gasket not completely sealed.

Hope it works.

Jeremy

vette76 · Post by **vette76** » Sat Apr 30, 2005 7:43 pm

thats exactly what i thought.even loosing a little tourque would cause it to blow because the head wasnt exactly even.but i evened it out with some very fine sandpaper,you could see where the gasket blew out from oil stains.