I’ve not done any back to back testing. I thought I had the latest cylinder, apparently not. For me, motor performs more than fine, thus not spending the huge money to change. When it comes time for my rebuild, if it approaches $2,000 for rebuild + cylinder head, I may consider another motor. As much as I like the Rotax the prices for parts are out of line. Have you priced a radiator or exhaust recently? Prices for those components for other engines are typicialy about 1/3.
The letters are the production batch codes. They vary by year, and they vary in performance, sometimes by a lot. Many thousands of dollars are spent on dyno time trying to find the good ones. No one is going to just tell you what the good ones are. Once good ones are sorted out, they fetch a lot of money. The top ten in Junior at any National event are all likely on the same cylinder batch.
Hi Christian. I thought one of the reasons for change to the lettered cylinders (and evo engines) was improved production tolerances, thus levelling the playing field. I was wondering if they achieved that.
Hi Samir, like Mark wrote, lettered cylinders have been around since 2011. Prior to that they were numbered by year, so a “9” stamped on the cylinder indicated a 2009 production year. Every few years Rotax mandates that certain parts will be phased out. Last year, for Micro and Mini, 2010 cylinders and older were no longer legal. Many good 2009 cylinders were taken out of circulation, so everyone began hunting for good lettered cylinders. As far as Junior and Senior, the original plan was to ban numbered cylinders this year, but although it’s not been made official, I’ve been told that numbered cylinders are going to be allowed again for 2016 for Junior and Senior. The latest batches of cylinders from 2015 have proven to be quite even performance-wise so far, the problem is they aren’t as good as lettered cylinders from 2011 and 2012.
That’s annoying. I just took off a very nice numbered cylinder from my spare 08-bottom Jr engine to put on a lettered cylinder to prepare for this year, doing an unnecessary rebuilt ($$) at the same time. If we don’t need it, I’ll have just wasted money. And next year, we may want to be in Seniors. Guess I’ll just sell the fresh engine if it comes to that.
What letters are stamped in 2011-12? Any one have a list by production date?