vfr750r

You are correct about running the engine first. It does make a difference to the balance due to all the metal having to go through temperature shock and for the bearings in the shaft tunnel to settle etc. But this is usually only needed when you change bearings or from a brand new turbine. Simjet do the same thing at the factory. Once the engine is assembled from new it is balanced then test run then balanced again. From new the engine balance does change after the first run. There doesnt seem to be a lot of difference when doing this on a engine that has had a bit of running and you do a bearing change. But I can assure you that there is a big difference when you do a dumb bell balance and you take the compressor off to reassemble the engine. I would say 9 times out of 10 that you will have at least a 10 to 20 gram per mm difference from the original. There is no way you can get that compressor and nut in the exact same spot as it was when you did the dumbell balance. We can prove it and have done so many times. The only real way to get a good running balance is to core balance. Remember that before I got the Schenck we used to only do dumbell balancing. I can do both with the Schenck and also test and quantify the results between both methods. I am not trying to be a smarta*se at all and I might seem to be pontificating but I am not....as I have said previuosly after getting this balancer I found out a lot of misconceptions about balancing and I was surprised by the results, the difference is now we can actually see and measure the difference between both methods.

Regards

Mark Kyle