The parts break-out shows that the F800S and F800ST share the same flywheel and stator design as the F800GS and F650GS twins. The -GS bikes are experiencing an abnormally high rate of stator failures. The apparent cause of the failures is overheating. The stator runs in a very confined space with no provisions for air or oil cooling. Failures seem to start at about 35K miles.
BMW has recently released a redesigned flywheel which will likely remedy the problem.
You can read all about it here: www.advrider.com/forums/showthread.php?t=706033
Post #399 has pictures of the new and old parts ...
Unfortunately, for those of us that are out of warranty, the new "generator set" is ~$900 USD.
The purpose of this POLL thread is to see if F800S & F800ST owners are also experiencing high rates of stator failures as they put more miles on their bikes.
The POLL for the -GS twins is locate here, and you can see that from the voting so far, for bikes in the higher mileage range the failure rate is approaching 50% .... [B)]
OK, the new flywheel appears to be the key. It has new holes and chamfered edges that apparently blow enough breeze around in there to keep the stator happier.
The BMW OEM stator runs hot, much hotter than most comparable bike alternators, and tends to fail at or above 30k miles. It requires 200C rated wire and most other bikes use 185C, so re-wind jobs done by independent shops using 185C wire tend to go poof soon after they are installed. Futzing with other types of regulators or adding resistance to lower the output of the alternator may help, but BMW has come up with a new flywheel that supersedes the old one and apparently helps cool the stator.
Dan:
Yeah I think that's it .... lots of other stuff was kicked around and all that but at the end of the day...
BMW has JUST released this new ventilated flywheel and the stator looks different, likely it is beefed up,
so the new parts have not been subjected to much field testing, but my guess is that ~$900 later it will all be good.
The failures do not seem to start until 30K+ miles
There are other possible solutions for folks that do not have $900 burning a hole in their pocket, but they are not well vetted as yet.............
I'm not sure why you say that the failure rate for the higher mileage GS bikes is approaching 50%
For 20-40, 26 good, 12 fail, or a failure rate of 31%
49-60, 9 good, 4 bad, 31%
over 60, no data. under 20, 60 good, 2 fail, 3%
is 114 bikes a statistically significant sample size? I'm not sure. Any idea on how many GS bikes were sold?
Nonetheless, an approximate 1/3 failure rate above 20K miles isn't pretty. Then again I'm almost to 60K and no failure (fingers crossed).
You are indeed correct 100 or even 200 bikes isn't a statistically significant sample size.
The numbers are morphing as more votes come in....
Based on the mode of failure it would almost seem fair to discard bikes with less than about 25K or 30K miles from the sample set,
I don't think anyone is going to see a failure ... of the type we're concerned about ... with less mileage than that...
I'd like to see at least a handful of votes from the 60K+ crowd ... but I guess that's a real small "crowd".
I don't know what I was thinking in the beginning, likely the only thing this survey can do is "heighten awareness" of this potential weakness in the bike.
My 07 800S went 93,000 miles and no stator problem; my wife has 55,000 miles on her 09 F650GS and no problems yet; my 08 800ST has 23,000 miles on no problems yet
If the stator burned out this is very unusual at 6000 miles. As for luck, well, you are under warranty and will presumably (worth checking) get the new style flywheel, which is ventilated to help prevent this. So not paying and getting the improved part is lucky, compared to those who paid out of pocket when their stators failed and did not get the new flywheel. Somewhat slim consolation, I admit, but...
It's not so much that the one on the right is a piece of crap -- it's a perfectly decent flywheel as far as flywheels go -- but that the piece of crap stuffed inside it (stator) needs a bunch of extra ventilation because it is a poor design, and may remain one even with the new flywheel. So fingers crossed that those fancy beveled holes will blow enough air in there to offset the weakness of the stator. [}]
This is very good for you, If at all possible I would try to get a look at either the parts, or the bike before they button it back up,
just to insure that you did get the new design ... []
I'm a curious is the failure could depends of climat (UK, US Texas, North-South, humidity, etc.) also if you're riding alone or with companion (2 pers. on one bike)? My voltage regulator died on 9.5K miles (~15000 km) cuz last 0.5K i was ride with my girlfriend, and after that the R/R was fried. Most of my riding is stop-ride-stop (commuting in capital of PL) - meybe this is some clue?!
Hi Lléo, I live and ride in London England where it hasn't stopped raining since April! Bike is kept under cover overnight though. I've never carried a passanger.
The first time one was seen in the spare parts channel was early May 2012... so just guessing ... they probably started going into production bikes in 1st quarter 2012?
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
BMW F800 Forum
935.3K posts
59.4K members
Since 2005
A forum community dedicated to BMW F800 owners and enthusiasts. Come join the discussion about performance, gear, riding, modifications, classifieds, troubleshooting, maintenance, and more!