Runout (800R E-TEC example)
The runout measurements of high mileage large bore 2S sleds is the holy grail in my opinion. It would be easy to compare notes if runout was a common measurement, but it is not. The measurement is especially uncommon on high mileage sleds. There is no apparent reason to bother if the sled works, hence ignorance is bliss. The thing is, out of 100 owners of these large bores 2S, maybe one 1/4 will say they are only good for say 5,000 miles, yet that 1/4 is the loudest and drives 3/4 of the populous opinion. The worst part is, there is no data to support anything.
What we lived through from the beginning of 2021 to the end of 2022, so two full years plus, we were not privied to any data. So a high mileage 2S owner can say they are good for 10,000+ miles, and a low mileage 2S owner can say it only good until 3,000 miles with no data to help understand the reason(s) for survival or failure. In that respect I have attempted to learn what measurements appear to matter the most.
What I have been able to measure over the years is sparse, so a little here and there to at least gain a reasonable understanding. The following is an example of the measurements I have taken and some things that I could draw from. I did this in Dec of 2021 because I could finally cross the CAN/USA border.....
Below are the picture of Mike's (RX7MachZ) 800RE clutch that I drew the twelve hourly clock positions on the movable sheave with the 12 O'clock relating to the PTO Top Dead Center. I did use the degree symbol as shorthand, so I apologize for the confusion. The added numbers on the movable sheave represent the fixed sheave runout, and the numbers on the fixed sheave represent the runout on the outer perimeter of the fixed sheave which I take as a reference prior to removing the clutch.
In the first picture below, note the highest runout on the fixed sheave perimeter is somewhere between the 5 and 6 O'clock position. This is a huge tell. In the second picture, note the large circle on the movable sheave that I drew an arrow to point to it. This circle is expected to be at or near BDC as shown. The crankshaft PTO stub has a large circle for the alignment mark which is near in line with the 6 O'clock position. Sorry that I do not remember how close it was to 6 O'clock, but it was close enough. Note the highest runout on the fixed sheave perimeter did closely match this position.
At near 5,000 miles I had done an extensive runout measurement on the same sled which has around 0.0035" runout on the crankshaft in the 4 to 5 O'clock position. Over 5,000 miles later (10,000+ miles total) the high spot was still near to the same position and closer to 6 O'clock.
Did BRP figure out the most likely HIGH spot on the crankshaft?
This new offset came about in 2012 for the 800RE, so 8 years after the first 1000 SDI production in 2005. How often do you see this stuff even mentioned??? It does happen, but it is rare. I recently found one that I had never seen and dated years ago, so it did happen, but again it is rare. I meant to add it here, but I need to find it again which will hopefully be less than the five years it took to find that Bill Cudney post on clutching which was brilliant. On a side note, the best way to keep a secret is to share it in the open. A secret only has its worth if it deemed top secret, so revealing anything in the open forum suggests that it is not all that relevant. In a way, that is actually a good thing.
Assume the end of the clutch shaft is five inches away from the end of the pto crankshaft end, a crankshaft runout of 0.001" will be multiplied five inches away. Now assume the taper on the clutch shaft is not perfect and has its own runout of 0.001" . Once the final clutch assembly is balanced, the heavy point shown by this balance mark will likely relate to the highest runout of the clutch shaft. So if the runout is independently measured on the clutch shaft, then the heavy spot on the final clutch assembly will likely match to the highest runout. Did you get all that? Probably not because of my poor explanation. A visual aid would make so much easier to see, but I don't have one so you will need to try and figure it out on your own.
All that I am trying to do here is to show pictures of measurement taken by me to give an idea of what I have been doing over the years.
What BRP appears to have done after marking the heavy spot on the clutch, is to index it with the lowest runout on the crankshaft. In taking the runout measurements is how I came to assume
the relationship. BRP has provided an explanation that I have posted on DooTalk, but I would only find it years later after having done my own work. Ironically I have posted BRP's explanation on DooTalk, but I do not have it handy. I do remember that it did not go into the detail that I am suggesting, but it did go a long way in suggesting a balance offset. Another thing that BRP has provided, is that we are allowed to clock parts when there is a question of unbalance, or better yet we may have to if the vibrations are too high.
By the way, don't expect to find this stuff in shop manuals. BRP provides a lot of insights in their Tech Manuals and Bulletins.
The next picture shows the Sheave Runout being the highest @ 0.011" between 11 and 12 O'Clock. I like to see 0.005" of less, so a 0.011" sheave runout is getting high! I was looking at this measurement prior to BRP explaining the designed 0.024" runout on the 2017 850, but I did not yet understand the impact on the belt until BRP explained it. Until then, I was trying to find a happy medium between clutch shaft and sheave runout.
Pull&Release relationship of the belt
When I first read BRP's explanation in late Feb or beginning of March of 2017, my jaw literally dropped. Within 15 min I has read it three times, and within an hour I had realized that I had been way over my head. Now that I was beginning to understand the effects of sheave runout, what was I supposed to do about it??? I still do not have a clear answer, but I know to continue measuring. I should mention that prior to BRP's explanation, I had already figured out that a high sheave runout on the Secondary fixed sheave was a source of abnormally high vibration. But again I had yet to understand the source from the Pull&Release relationship of the belt until BRP explained it.
All of these measurements were predicated by the understanding that there was much to be learned with runout by those who had done it before me, which I mean what I learned from joining DooTalk. These guys are few and far in between, but they do exist and have posted on DooTalk. Considering that I was able to absorb their experience to push my own interest further, it is reasonable to expect you can take it much further.
Where to go from here?
Start by measuring and worry about fixing things later. DooTalk may have only one related post in 100,000, but it does exist. For example, DOOREV800 showed the possibility in correcting the sheave runout on his Secondary/QRS fixed sheave. I don't know if this is a long term solution nor if it can be applied to the Primary clutch fixed sheave, but it is a beginning.
If you are focused on only the 1000 SDI, my hope is to provide insights that were learned from over a decade ahead that is backwards compatible. What I am posting is over
5 years old!