Parilla Mag 95 - Help needed

[Robin Ovens]

Hi,

First post here and im after help. We have a Mag 95 that we just cannot get to run right, we rebuilt it again this evening and tried to run it up, not under load just to see if it would run and it seized within about 15 seconds. Prevoulsy we had run it on track and it siezed within about 10 minutes. We are trying to eliminate problems one by one but now we are stuck.

a.. I ran a mix ratio of 312ml shell racing M to 5L of 97 octane Total Excellium.

b.. Tillotson HL360A, rebuilt but Dartford Karting and set to 1 turn on the low jet and 1.5 turns on the high jet

c.. Seized within about 10 seconds of running

d.. fuel lines checked and free flowing

e.. had a new piston and bore hone, all running freely with good compression

f.. We are using an NGK B11EGV, to being with but we have a 10 and 9 available

g.. that the kart was stood for two years previous to this

We cannot see what is causing this, the kart is new to us and we are determined to get it running properly

We haven't touched the bottom end of the engine, so things like the crank seals and the reed valves have not been touched yet.

What oil to fuel ratio should we be using? we ran 16:1

Why when the plug is out and its turned over quickly would it not suck up much fuel despite the carb rebuild and with a correctly bled fuel system?
What effect would degraded reed valves have?

what effect would degraded crank seals have?

what effect would a blocked exhaust have?

Thanks in advance for any help.

[Jim McMahon]

Where did it sieze exactly? What areas of the piston? How does the bottom end look?

Blocked exhaust could cause excess heat to stay in the motor but it would run pretty poor and im not sure if it would stick as quick as it did.

Air leaking past crank seals (or reed/carb) can cause it to stick yes. But not usually that quickly and you will find you need to choke it a lot to keep the motor running. ALWAYS vacuum and or pressure test your motor after a rebuild. Check youtube for a guide.

Other possible causes of a stick...
-Incorrect skirt \bore clearance
-Incorrect ring gap
-Bore out of square
-Cylinder/crankcase not square relative to each other
-Insufficient squish
-contamination, something left over from the rebuild or something else breaking up in the motor.
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[Jim Russell, Jr.]

If you are seizing withing 10-15 seconds of start up then there has to be a bore and/ or piston problem.
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[Robin Ovens]

Definitely, its simple to us now somebody has pointed it out, we were running completely the wrong clearance, due to me completely mis understanding how the piston and bore size were related.

[James McRobert]

if it has seized a couple of times you really should pull the bottom end apart to make sure it is clean and there is no bearing damage. i would at the very least change the seals once you get your new piston and ring fitted to the right spec.

[Walt Gifford]

I should hope he got the engine fixed inside of 4 months.