1972 6hp reed question

hi. i have rebuilt the carb twice now, replaced head gasket, base gasket, coils, plugs, wires, points, condensors. it has hot blue spark from both plugs. ive seen it...still wont start...the reeds were gummy and sticky, i removed them, took apart and cleened in my "gunk" carb parts cleaning solution.. replaced back on, still wont start.. compression is 90lbs in both cylinders...but no start...<br /><br />if i put fuel directly into cylinders via plug hole, it runs for 1 second...<br /><br />if i squirt fuel directly into carb and close choke, nothing...<br /><br />i am gonna order "boysen power reeds" right after this....<br /><br />heres my questions.. could it be the ignition timing.. how can i check it without the engine running...<br /><br />what could i have missed..... im at my witts end here<br /><br />mikey

Re: 1972 6hp reed question

Mike,<br /><br />I think you are thinking correctly about timing. You have everything necessary for combustion. But, do we have spark at the right time?<br /><br />Check to see if the plug(s) fire when the piston(s)are at, or near, top dead center.

Re: 1972 6hp reed question

Sounds like a good case of an air leak to me. Reeds seldom just go bad, unless they just break a petal.

Re: 1972 6hp reed question

air leak from where? i have 90lbs of compression on each cylinder....or do you mean onthe carb side of it, please be more specific, im losing my mind on this thing....<br />and as for the reeds, they were gooey and covered in thick varnish, so i cleened them, not to mention being 32 years old.

Re: 1972 6hp reed question

How many cylinders ? <br />Plug wires on right plugs ? <br />Carbs tight on head (that may be the air leak) <br />allowing the vaccum to be somewhere besides through the carb throat(s)

Re: 1972 6hp reed question

FYI - the front coil always fires the top cylinder on magneto fired OMC 2-cylinders...<br />- Scott

Re: 1972 6hp reed question

The timing can never be very far out on these magneto systems, since the magnet must be just over the ignition coil in the right place for you to get a strong spark. Unless the armature plate was put in sideways or something.<br />Of course, they can be 180° out, as Chinewalker pointed out. <br />I've got to say, this one is giving me fits. It sure sounds like a primary compression problem, but what would affect both cylinders? Plugged exhaust mabey? I don't think a leaking oil recirc hose would do it? How did things look in the crankcase when you pulled the reeds?<br />Just throwing some stuff out there...

Re: 1972 6hp reed question

I agree with paul. This sounds like a text book case of a leaking crank case. Areas to check, top and bottom main seals, case halve joint, intake manifold/carb area. Could possibly have a crack some where. Try soapy water or oil as a way to find presure or vacuume leaks.

Re: 1972 6hp reed question

i got motor to start today, fuel pump is shot so i must keep pumping bulb about every 30 secs.. water pump is shot... sounds like a knock, can a 2 cycle have a knock?<br /><br />im bummed now, as you can tell... still extreamly hard to start... i still think the reeds may be leaking air, i.e, not sealing all the way....<br /><br />both cylinders are firing...revs and idles down nicely ONCE IT STARTS.... im going mad here... any thoughts?<br />as for looking for leaks, i have replaced the lower crank seal, maybe i did it wrong.. could this really leak air/pressure... it mounts on th driveshaft and is pushed upwards against block with pressure from a lil spring... not a good design....<br /><br />my NISSAN runs like a dream.....omc can bight my but<br /><br />mikey

Re: 1972 6hp reed question

Hi Mike <br />It sounds like you my have found your crank case leak. I forgot to mention the fuel pump. As you know the fuel pump works off pluses from the crank case. If you have a bad diaphram or mounting gasket, this could cause the simtoms you describe. Sure 2-strokes can knock. They can puke rods with the best of them. Before getting all too excited about the knock, try a new fuel pump and water pump. Get the the proper adjustments made. Then see if that doesn't help the noise some. These are the most basic, simple little motors. Don't try and over complecate it. I'll bet this motor is just a bit older than your Nissan. It was probably run hard and put up wet. I wonder how the Nissan will do after 40 years of that kind of treatment. As far as I am concerned the design of the lower main seal is fine. OMC used this for years, since the early fifties as far as I know. Yes the main seals can and once in a while fail and leak. In order for a 2-stroke to function you must have compression in the cylenders as well as in the crank case. When the piston is on the up stroke it creates a vacuume on the crank case, this draws in air/fuel past the reeds or other type valve. The when the piston is on the down stroke it presurizes the crank case, forcing the air/fuel into the cylender. So with your motor having a bad fuel pump it is like it is trying to run with a hole in it's side. Does this make sence? Now with all that extra air and the fuel not being really sure with way to go (because the leak) you will not likely get the correct mix to the cylenders. This may be the cause of a lot of knocking.

Re: 1972 6hp reed question

thank you soooooo much!! that makes a ton of sense now. i know the pump is bad, and i know the diaprham is bad as well...<br /><br />the motor had been stored for years, unkown, but whoever had it before me didnt know what the word"maintanence"was...... <br />i have black oilly crud dripping down and out the lower unit.. and i traced it back to the lower crank seal....<br />this is why i use this board... <br /><br /> i hope this thread can be used for somebody elses knowedge and education at another time. thanks