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I have a problem and I hope its something stupid because I think I tried everything logical.

Twin cylinder cat D&D 757 motor with an older set of CPC 48mm carbs and a Wahl Bros. high volume fuel pump.  I used this motor for the past two years with very little problems.  I rebuilt the top end and the only thing different from last year is the carbs and fuel pump and 1 more additional degree of timing.  I purchased a new Avenger 1 because the EGT's never worked on the old one. 

 I had a problem with the idle circuit during initial break-in and was sucking in an excessive amount of fuel and kept fouling plugs.  After several calls to Dale Cutler I think I got the carbs figured out or at least I understand whats wrong with the older ones.  The problem is the EGT's on the Mag side only climb to about 250-275 degrees during idle (2500 RPM's) while the PTO side gets up to 375-400.  I have been figuring that I either have a problem with left over fuel in the case from the original carb problem our a problem with the mag cylinder.  This is what I have done so far.

1. Checked Spark in both cylinders.
2. Checked Compression both cylinders are the same a little low at 120 psi but still haven't broken in.
3. Switched carbs to opposite cylinders mag cylinder remained unchanged.
4. Ran it several time to try and clean it out but I am trying to be careful not to raise the RPM's to high because of fresh top end.
5. Swapped EGT Probes to verify probes and gauge is working same result
6. I cheched the carbs, wiring, probe routing, fuel, compression again and everything seams to check out.  The engine doesn't sound terrible maybe a little rough.

Just before I was getting ready to tear it down I decided to try one more thing and this is the part that stumps me.  I pulled the plug wire off the PTO side and the EGT on the Mag side climbed to 375-400 degrees.  Then I pulled the plug wire on the MAG side and the PTO climbed to 375-400 degrees.  When I go back to running both cylinders again I get the same result as originally 400 on the PTO side and 275 on the MAG side.  When I try and throttle it up a little the MAG temp doesn't climb and sometimes seems to drop while the PTO goes up as expected.

 Any Ideas before I pull the cylinders and tear it down.

What oil are you using?

Actually that is another thing that I am doing different.  I used to use Spectro Synthetic but are now using Arctic Cat APV Synthetic.

 

electricity will go to the least point of resistance if you have a weak stator that will only produce enough electrical power to partially fire the coil it will favor the cylinder that is easiest to fire.by pulling off a plug wire on one cylinder you have given it no choice but to go to the remaining cylinder.this is only a suggestion but stator problems are the toughest to diagnose when the machine still is running,ask anyone who has experineced stator problems with any machine,there are ways to keep stators alive longer for summertime when the heat is double in the ignition housing ,you also didnt mention what cylinder your fuel pump was powerd off of? todd 1-260-316-2839.

The pulse line for the fuel pump is on the MAG side.  I was worried about the stator but anytime i have had them go bad, they go bad all at once but I guess it makes sense.  As far as the easiest cylinder firing wouldn't it be the shortest plug wire, that is the MAG side.  I put a 4 degree timing key in could that have an affect on the spark at idle.  I Also needed to install the Cutler TPS Block but could only set it for full throttle, Dale said not to worry about the idle setting because I was only drag racing.  I think I'll check all the wires going to the stator because I did have the Mag off to replace the timing key.  I also have another coil I could try.  I am thinking of putting everything back to the way it was last year starting with the carbs and fuel pump.  Thanks for the help!

if the coil has resistor caps installed on the coil wires then you may have a cap going bad ,even if it is on the shortest wire it would still be easier to fire the other cylinder ,that is why i said stator troubles are tough electricity is hard to predict and sometimes control,like guessing the location of a lightning strike.you just have to go from start to finish on basic diagnosis,. compression-spark-timing-induction-expulsion.good luck

you stated you rebuilt the top end and are using synthetic oil. If you did not break the motor in on a petroleum based oil, that is your problem. We did that one time and it took a little more than a season to get the cylinders up to proper compression. You probably have glazed that cylinder and the rings are not seating properly. That is why your compression is down and you have one cylinder that is not coming up to temp.

^^  +1