Sorry TT, I'm not with you there..Isn't long term durability the same as reliability? Maybe not but they are definitely related. I have been in aviation for over 35 years (Air Traffic) and have handled about 8 or 9 mayday calls from air cooled lighties, engine rough running or stopped....I have never had an engine failure in any of the cars I have had, water cooled.
It's a long story about product liability and the American trait of suing at the drop of a hat and apportioning blame. That is why the USA rarely produce new light aircraft designs, they just resurrect old product lines such as the C182 and Piper Cub because of certification issues. Basically, it's 1950's technology with a new look to it.
I didn't want to start a sh*tfight, I was just raising the issue of cooling your engine before shut down due to thermal shock and heat sink.....
Long term durability is not the same thing as reliability. Plus there are other factors involved. Aircooled aircraft engines have a specified service life, then then need to be overhauled. They spend the majority of their time at 75 to 100% throttle which is pretty hard on any engine. Compared to a car the 2000 hours or so is very short service life, so they do not have great long term durability. However in between those overhauls the majority of aircraft engines are very reliable. When you factor in human error, shoddy workmanship, defective parts, etc...it is easy to see how you can get a few mayday calls out of these engines. Let me give you some examples:
There is a condition in pilots to become hypersensitive when flying their aircraft in situations that leave them no recourse. A perfectly running engine sounds rough to them when they are flying over a large body of water with no land in sight for example. Flying into Oshkosh, WI across lake michigan a couple of years ago, I heard two calls from pilots claiming their engines were running rough...there was nothing wrong with their aircraft, they just thought there was.
I knew a guy with a cessna 172. It was a real nice airplane but at somepoint in its life the plane suffered a crack in the engine block. The plane continued to run fine and he ignored it, choosing to deal with the problem at service time. Fortunatly he was on the ground when the engine seized. A crack in the block can occur to any engine, and usually stems from a shoddy rebuild, abuse of the engine, or the blocks just get old (the plane was from the mid 1960s). They actually occur more in water cooled engines, as I have had several watercooled chevy V-8s in which I have cracked the blocks. So here is a situation where a legitimate problem devlops and instead of correcting the problem the owner chooses to ignore it frther exacerbating the situation, still no measure of the engines relaibility.
Mooney aircraft have dual magneatos to run the airplane, however they share a drive unit. Should one mag fail the other's job is to get you home, however if the drive fails then both mags are wiped out and the engine stops running. Kinda defeats the purpose of having two mags doesn't it. There are hundreds of cost saving shortcuts like this in the thousands of aircraft engine designs there are out there that have nothing to do with whether the engine is aircooled or not.
these are just a few real life examples to illustriate my point...there are an infinite number of factors that can contribute to an engine's unreliable nature and design of the cooling system is just one (anybody who has owned an old pontiac can attest to that btw). Because you see some failures doesn't automatically mean that the engine cooling system design is responsible for its unreliabile nature.
By the way: The Trinidad and Tabago, Husky, Maule, Glassair (which started as a kit plane), mooney ovation, and Beechcraft Starship are all certified airframe designs to come within the last 10 years (some coming from designs that were certified for the first time in the 1980s). The primary reasons the big three of light planes rehash old designs are: 1) it is cheaper to update than design from scratch, 2) the original aircraft are extremely durable, 3) Planes like the Cessna 172 and Piper Cherokee have a proven following and a built in market. As for engines, watercooling is starting to find its way into light aricraft as well as deisel engines, new designs are certified every year but usually where they fall flat is fudning to put them into production or lack of contracts to get them into new aircraft. But it is just easy and convinent to blame America's litigious society (which does play a role but not as big a one as you think).
now for sparty:
cb750s are noisy engines, the clutch being the biggest offender. With the bike at idle pull the clutch in and you should hear some of the chatter stop. If you are really concerned about the rebuild but don't want to tear it down, go to a bike dyno and run it. Pay close attention to the hp numbers, the power delivery, fuel curves, etc. If possible have the shop tune the bike using the dyno to get optimal performance. Your bike shoud get low 50's hp at the rear wheel (50-53hp), anything lower is indicative of a problem. the power deliver curves should be some what smooth, any major spikes or dips can also be indicative of a problem.
