Fouling Plugs

[Speedy]

quote:Originally posted by Lloyd Boland

Okay, let us consider this.  If we accept the fact that a specific volume of fuel (gas plus oil) is metered as it goes through the carb by the jetting, it mixes with air and goes into the engine.  A very simplified version of what happens.  If we have a certain mixture, lets say 20:1, and we reduce the oil concentration to lets say 32:1, we have decreased the amount of oil that enters the engine per the same metered volume.  If the total volume of fluid enters, then we have incleased amount of gas that mixes with the air and decreased the amount of oil.  Because the jetting hasn't change, the total volume (gas plus oil) remains unchanged.  If this is correct, by putting less oil in the pre-mix, you untimately increase the gas and therefore the gas to air ratio mixture increase, it becomes richer.  If you change your gas to oil ratio, you may have to change your jetting (you may have to lean it out slightly).  I was given this lecture many years ago.  It seems logical to me but it is counter-intuitive.  I previously thought that if you put in less oil you leaned the bike out, but if my logic above is correct, you actually make the bike richer with less oil (because of more gas enters the engine).

Anyone else heard of this?

Lloyd Boland

Sorry for the circle logic.

Yes you are right.
Gas reacher-Oil leaner,and often you have to rejet accordingly to the change.


Helmut"Speedy"Clasen
 Ontario Canada
http://speedy_c.tripod.com
http://picasaweb.google.com/vindurospeedy
2 x Sachs MC-GS 250-7A
1 x Hercules 350-7A 77
2 x Hercules 250-7A 76
2 x Hercules 250-7A 77
Zuendapp 125 GS 72-73

[Speedy]

quote:Originally posted by Big Mac

Excess fuel or "flooding" into the crankcase, as WFOPete points out, will cause this symptom. Usually, it will start and blubber at closed throttle, but die as soon as you open it up at all. Sometimes it won't start at all, with plug showing nice blue spark and coming out wet w/ fuel. A 250 Harescrambler I had did this if I left the fuel taps on while parked for an hour+, as the floats weren't closing the needle valve off all the way and carb was overflowing a tiny bit down through the intake. Didn't cause the plug to foul, but plugs will wet-foul at times.

If you're not aware, the KTM motors (like CZ motors) have an allen head screw up between the fins, right below the crank, just for the purpose of draining excess fuel. Just a teaspoon-full of excess will cause it--once drained, my 250 would start first kick, run perfect. Not sure if the Sachs have a drain screw...if not, turning off fuel and laying it over on the side will sometimes clean it out sufficiently. I'd try this easy fix first.


Jon McLean
Lake Grove, OR

Not the KTM engines but the CAN-AM engines have that drain (and crankshaft locking)screw under the engine.

Helmut"Speedy"Clasen
 Ontario Canada
http://speedy_c.tripod.com
http://picasaweb.google.com/vindurospeedy
2 x Sachs MC-GS 250-7A
1 x Hercules 350-7A 77
2 x Hercules 250-7A 76
2 x Hercules 250-7A 77
Zuendapp 125 GS 72-73

[Rain Man]

Speedy, my 73 175 JackPiners have the drain screw on them.  You got to make sure all the glass beads outta the hole when rebuilding the motor also.

Raymond
 Down East Pentons

[454MRW]

All of my KTM 175-250-400 engines have that drain screw beneath the crankcase. I always leave the plug in when glass beading the cases, just to make sure not to weaken or eat away at the threads. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[Speedy]

quote:Originally posted by 454MRW

All of my KTM 175-250-400 engines have that drain screw beneath the crankcase. I always leave the plug in when glass beading the cases, just to make sure not to weaken or eat away at the threads. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

I stand errected....[8D][B)]

Helmut"Speedy"Clasen
 Ontario Canada
http://speedy_c.tripod.com
http://picasaweb.google.com/vindurospeedy
2 x Sachs MC-GS 250-7A
1 x Hercules 350-7A 77
2 x Hercules 250-7A 76
2 x Hercules 250-7A 77
Zuendapp 125 GS 72-73

[MattyQ]

Dane,

Appreciate your thoughts about the ignition.  I was told my motoplat was damaged due to it freezing one winter by the previous owner , so I am not sure if it is even worth testing .  I would love a PVL unit however , low on funds right now.

Matthew Quinlan