RXX factory carb settings

[1MACGYVER]

Ok great, maybe I am safe at the 1100ish range- ill do some more plug colour checks as I go

 

[Sportster-2001-951C-Stock]

Ok great, maybe I am safe at the 1100ish range- ill do some more plug colour checks as I go

Yes perhaps. They're measuring 100mm from the piston skirt, which is supposedly the optimum location to catch peak exhaust temperature according to BRP for the aircraft engines, and then judge by plug color. The probe is simply used from there to monitor in flight temp anomalies and probably their gauge has some preset warning limit, that's what I'd want.

Have you torn one of these motors down, did you find a puddle of oil in the crankcase and was everything nice and oil covered? I dunno why I'm asking, perhaps in curious preparation for that day, when it arrives.

 

[1MACGYVER]

Its been a busy week, after starting to run in the big bore motor it didnt seem right so we started checking things. It turns out the 1050cc pistons I bought were slightly shorter from the top of the rod to the top of the piston, long story short I had only 85psi compression in both cylinders. Consequently I have learned a lot about 2 stroked this week.

Initially we checked the squish and found it was over 3mm, pulled the engine and swapped the base gasket to the smallest quickly available (0.6mm) and re-assembled it and re tested, we had 2.6mm.

Pulled the engine apart and took the cylinders up to the machinist and got 1.2mm taken off the top and reassembled it, now with a squish of 1.35mm we were looking good, put the jump pack on the starter and it only hit 115psi.

Very disappointed with what i thought was a hi comp setup we started looking at the dome volume, originally it was going to take too long for the heads to get machined from Mel Miller so I bought the kit from someone locally who never installed the kit on their ski and told me it was the same as what I was going to buy. Included were 55cc domes and it turns out I needed 50-51cc.

Out of desperation as the first race is Sunday- I got the domes welded and machined out to approx 50cc and today we re-assembled it, jump pack on the starter it hit 160psi exactly on both cylinders- exactly what I wanted.

I had it out today for a test and after some tuning it is holeshotting quite well but only hitting 6500rpm, I just need to lean out the high speed adjustment and hopefully ill be at full power.
The EGT gauge has been scaring me into richening up the mix essentially sending me in circles as the readings are showing as hot but the plug colour was perfect, im fairy certain that is down to the probe location being too close to the skirt as discussed earlier so ill relocate them to the right position and should get more accurate readings.

 

[Matt Braley]

Sorry about your troubles and thank you for the great data and pics. What do you mean by moving the sensors? Are you going to cap the 1/8" holes and re-drill and tap? I would not unless you port match it or have another 951 mani to try again with.

Good luck at the races! Please post about it.

 

[1MACGYVER]

Yeh I was going to cap/plug the holes and install them in the pipes 2" down from the gasket. Do you think the 1/8 holes where the sensors went in will affect the exhaust flow or something?

 

[vanderli barbosa]

This leakage can be installed on the GSX Limited? increases as the power and the final speed?

 

[1MACGYVER]

if you mean 'linkage' its the link rod between the carbs that opens the butterflies as you pull the throttle, your carbs should have it
it will only help if your carbs arnt balanced