center cyliner downq

T

tsquared

New member
Joined
Jan 16, 2007
Messages
12
Age
48
Location
Winnipeg, Manitoba
my buddy burnt his center cylinder down, pluged a jet. We put a new piston and rings in,with plans on a full rebuild in the summer. Now that cylinder will not pull fuel. We have cleaned the carbs but still no fuel.

I did not hone the cylinder as there were no scratches but could the rings not be seating causing insufficent vacum to pull fuel? if we dump fuel down the cylinder it fires up. If I plug the carb with my hand it will run, choking seemsto make that cylinder fire, but the other two bog. there is noticable less vaccum on that cylinder. Is there somethingin the bottom end that I need to worry about

I am just trying to confirm that skipping the honing step could be my problem. I know it has been jetted down so I am going to go back to stock size on that cylinder for the remainder of the break in.

Getting to this point we have checked
-sled is 97 sx 700
-new plugs
-changed coils
-changeplug ends
-cleaned carbs
-checked reeds
-checked compression 140 cold across the board, 135 hot.

Thank you for any input
 
I would check fuel delivery from the pump...... switch your fuel lines around and see if a different cylinder acts up.....

If your compression is equal the vaccuum should be also....
 
we swithced the fuel lines around - stayed with the center cylinder. I am wondering if the base gasket is leaking? Would that cause these systems?
 
Check the base gasket, the intake boot and gaskets.... There is an air leak to make it not pull fuel. ALL of the gasket surfaces MUST be clean and free of debris for gaskets to work correctly... Good Luck. Bandit
 
What is good to use when checking for leaks? i am thinking of spraying, starter fluid?, into an area and see if the enging responds.
 
Do a pressure test. Pull the carbs and pipes, plug the holes. pull the pulse line to the fuel pump and pressurize the motor there with NO MORE THAN 10 PSI. Close it off and see if the pressure drops. It shouldn't. If it does, find the leak with soapy water or WD 40 (soapy water works best).

The seals between cylinders will not entirely prevent the pressure from filling each cylinder / crankcase, but it will take forever unless there is an alternate path - either the y pipe or the boost bottle. Alternatively you can plug the line for the pulse to the carb and pressurize through all the carb holes (put a small fitting in your plug). If you have triple pipes and no boost bottle you will have to pressurize all 3 cylinders somehow. Stock pipe with the exhaust manifold (y pipe) plugged or a boost bottle will allow the air into all 3 cylinders.

You should always do a pressure test any time you tear down a 2 stroke. This year I found a bad base gasket on my phazer (had just bought it) and when I tore it down the piston wash told me it was way lean. Saved me a motor. On my vmaxx when I did the top end I pressure tested and found bad crank seals. May have saved me another top end.
 
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