My Waiex is undergoing major surgery due to the axle bolt failure incident, and I am using this downtime to make some improvements as follows:
-Switching to the Rotax ring mount
-Matco toe brakes (I already have toe brakes but more braking power could have saved the day). The Matco rims I got are suitable for tubeless tyres so I have gone with tubeless.
-New gearbox with the oil spray nozzle
-Zero timing the engine for everything outside the crankcase (Rotax is too precious to allow us mortals to purchase parts or obtain info in their crankcases). Their loss, as there are plenty of living examples of Rotax engines exceeding 2 x TBO.
-Increasing horsepower with the larger Edge cylinders.
-4 blade E-Prop as the extra horsepower require a much larger prop than I have ground clearance for. Hoping the extra blade doesn’t impede on speed. E-Props were adimant that speed wouldn’t suffer but I think there must be some sort of speed loss.
-Thinking of making a ram air plenum to feed the carbs cold ram air.
James aircraft wheel pants because I am too lazy to make new ones. I will be making new gear leg fairings as per info I have studied from Mike Arnold. His video on moldless wheel pants is excellent and I probably should have made a set of those.
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Rotax has a good system for determining life remaining on criticle components based on remaining time before TBO.
They list minimums and maximums for new parts, and mins and max for both 50% and 100% worn limits. For example, if the engine is at 50% TBO and the parts are 50% worn, that is considered good to go, as it is expected the engine will still make it to TBO with those parts.
For my engine that has 2100 hours on it (100 past TBO) I wanted to replace all parts that were beyond new specs so I could consider the engine as new.
I was surprsed that most of the parts were still within new specs. The carbon build up was quite a lot and very hard to remove. One of the exhaust valves had erosion at the weld joint that I believe could have been a manufacturing fault in the joint but Rotax thinks it is from the carbon build up. I remain open about the cause.
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I decided to replace all exhaust valves with the new to Rotax sodium filled valves. The intake valves were all as new but one of them hadn’t been rotating so I decided to replace all 4 of those as well. All the new valves lapped in well to the seats. The springs were all in new specs. The only parts that were outside new specs were the rocker shafts and bushes so I replaced those too.
I lapped in the new cylinders to the heads as they don’t have a gasket. Took some time to ensure no paste got into the nickasil cylinders.
Incidentally, the old nickasil cylinders still had the hone marks showing quite well. I will eventually clean all the old cylinders and piston assemblies and determine their remaining life left in them. Not that I will ever put them back on this engine.
The valve guides were still within new specs so I just replaced the intake stem seals.
I also refurbished the accessory case and relaced the water pump shaft, oil seal and impeller seal and also all the associated O-rings and rear main oil seal. The starter sprag clutch was good so I didn’t replace that.
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I think the question was asked some time ago about the dimensions of the Rotax Sodium filled exhaust valves and wether or not they would fit the Aerovee heads. The stem is 7mm and they are 32mm face. I am pretty sure the VW ones are larger than that which makes sense as the VW is a much larger engine, just slower reving to make less HP
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8mm stems, 35.5mm exhaust, 40mm intake.
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Are you planning to do true ram air (e.g. positive pressure) to the carbs or just route cold air near the intakes? I caution against positive pressure. You would also need to somehow direct that same pressure to the float bowl or your engine will run increasingly more lean at higher airspeeds.
Kawasaki toyed with ram air in the early 90s and learned that lesson quickly.
Yes Dan, I am planning on positive air pressure and will run the Atmospheric float bowl tubes to the same ram air pressure
OK, cool. Looking forward to seeing some details when you get there!
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