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Offline Roel1964

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Tiger 800 strange noise coming from alternator
« on: July 17, 2018, 10:23:08 PM »

I shot this video after i found the reason for the strange sound that my Tiger 800 was making at a cold start. The noise seemed to disappear once the bike was warmed up. So first i thought it was the cam chain rubbing against the cam chain guide. But i didn't find anything during inspecting the cam chain, resetting the cam chain tensioner and checking the cam chain guides. The noise seemed to come from the left side of the engine. So checked the alternator and found that 2 out of 3 screws that hold the stator were not tight to 12Nm. But after tightening up the screws, the noise was still there and still seemed to come from the alternator. Then i started checking the battery voltage and found that it was a little on the low side, but still OK. I checked the alternator coil resistances which were all OK. Then i checked the rectifier/regulator statically i.e. checking all the diode-junctions. All seemed OK. But when i disconnected the alternator and started the bike, the strange noise was completely gone. The starter motor also ran faster and the engine sounded a lot better. So the rectifier/regulator was not working properly. I only noticed that the battery voltage was about 12,8V and that the headlights were sometimes "flickering", so the voltage was not constant.
In the video i first start the bike with the alternator connected to the malfunctioning rectifier/regulator, causing the strange noise and after that i disconnect the alternator from the rectifier/regulator and start the bike so it runs from the battery. When you compare the sound, you can hear the difference. In reality the difference was even more audible than in the recording.
The 2 loosened up screws of the stator were probably the result of the high drag force between the rotor and the stator, since the malfunctioning rectifier/regulator was causing an unbalance in the stator currents.
The noise was loudest at a cold start and seemed to get less when the bike was warmed up. In fact it was not because the bike warmed up, but because the battery was charged up to a higher voltage and this seemed to make the rectifier/regulator more stable.

Offline chuckxc

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Re: Tiger 800 strange noise coming from alternator
« Reply #1 on: July 17, 2018, 11:50:21 PM »
Good find, thanks for the posting.
I've had a similar problem on another bike, but same failure mode. The typical Rec/Reg units tend to fail with a shorted diode or mosfet so they then present  an excessive  resistive load to either the alternator stator coil or else the battery, depending on which component fails.

Replacement is the only option, but before you do,  suggest you test the coils, wiring and battery to make sure they were not the cause of the r/r failure.


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Offline Roel1964

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Re: Tiger 800 strange noise coming from alternator
« Reply #2 on: July 18, 2018, 11:20:36 AM »
*Originally Posted by chuckxc [+]
Replacement is the only option, but before you do,  suggest you test the coils, wiring and battery to make sure they were not the cause of the r/r failure.
Exactly, in my case the rectifier/regulator probably died because i was letting the bike idle a lot standing still in the garage, while testing for another problem. So there was no air flow to cool the rectifier/regulator. With the Tiger 800 the rectifier/regulator gets quite a lot of heat from the radiator and exhaust pipes. On the other hand, the battery was near the end of it's life, so the rectifier/regulator had to work harder to keep the battery charged.

I tested the rectifier/regulator on the bench while disconnected from the bike. I used an adjustable power supply connected to one of the coil inputs of the rectifier/regulator. With the adjustable power supply i could increase the voltage from 0 up to 30V. I had set the current limit of the power supply to about 1A and connected a multimeter to the regulator output, that would normally go to the battery. I tested each of the 3 coil combinations using forward and reversed current, to check if the rectifier and the regulator both work. When increasing the voltage of the power supply the regulator will start short circuiting the power supply at the moment that the voltage at the output is around 14,4V.
Because the current limit is set to 1A, the power supply voltage will drop as soon as the regulator rise to draw more than 1A. This way you can safely test the rectifier/regulator.
The bad regulator was tested this way and it was clear that the regulator was not working at all. I could increase the voltage up to about 20V at each coil combination and the regulator started oscillating wildly.
I also tested the new regulator this way to see if my test was working properly. It worked just fine and regulated the output voltage to 14,4V while i increased the power supply voltage from 0 to 30V. The regulator starts drawing more and more current from the power supply when continuing increasing the input voltage above 14,4V. That is what a good regulator should do.

Offline chuckxc

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Re: Tiger 800 strange noise coming from alternator
« Reply #3 on: July 19, 2018, 12:16:04 PM »
Yes, what you are describing is a Shunt type regulator. (SCR's) Pretty crude really, just shorts the excessive input current to ground and so into heat. Newer Mosfet designs increase input resistance so as to limit input current when over 14.4v. More efficient, and less load on the alternator.
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Offline skidmark66

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Re: Tiger 800 strange noise coming from alternator
« Reply #4 on: July 20, 2018, 06:56:06 AM »
Interesting this have wondered if my bike has this increased noise as well.
Will check it out great bit of info good post.
I can remember reading sometime ago a guy had similar problems on his bike and just moved the reg rec away from a similar area and the problem went away. Think the bike was a track bike so got hot very quick on off all day long and was cooking them regularly.

Offline crispey

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Re: Tiger 800 strange noise coming from alternator
« Reply #5 on: July 20, 2018, 10:44:44 AM »
 @Roel1964 Thanks, Ive got this noise, funnily enough I had it months ago but it went away and has just recently come back, so I checked the cam chain and tensioner and the stator screws but all were fine, noticed the stator was getting discoloured so am thinking a new stator. Put it back together and didnt seat the seal that the cables run through properly and that popped out so I had a major oil loss issue, luckily noticed it before anything disastrous happened. Havent had a chance to do your reculator check yet, but could it be the cause of the stator discolouration?  Heres a pic



Not to savvy on this stuff but does the stator look on its way out and if so is there a cheaper option than the Triumph 350 one, obviously good quality.

Offline chuckxc

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Re: Tiger 800 strange noise coming from alternator
« Reply #6 on: July 20, 2018, 01:57:15 PM »
That stator coil in the pic has overheated in the darkened area. It could likely be a short to ground because the copper insulation enamel has failed. Alternatively, you may have lost so much oil that the alternator ran with no oil....it is supposed to be cooled by oil splash.
To test, all 3 coil contacts should be electrically isolated from ground. An ohmeter will quickly show the fault. Or, two or more coils are in contact with each other. Also a failure.
If your battery doesn't see 14.4 V charge from the regulator, you know for sure you have either a failed R/R or shorted alternator coil(s).
« Last Edit: July 20, 2018, 02:00:05 PM by chuckxc »
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Offline crispey

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Re: Tiger 800 strange noise coming from alternator
« Reply #7 on: July 20, 2018, 02:41:43 PM »
Thanks chuckxck, this photo was taken before the oil issue. So judging by Roel1964 post and video it could by the RandR thats at fault.
Again any clues as to where to get cheaper than Triumph but good stators?

Offline tauzero

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Re: Tiger 800 strange noise coming from alternator
« Reply #8 on: July 20, 2018, 10:10:44 PM »
Google "motorcycle stator rewind". These might be within striking distance of you: http://www.rexs-speedshop.com/Workshop-services
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Offline Captain Crazy

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Re: Tiger 800 strange noise coming from alternator
« Reply #9 on: July 21, 2018, 12:21:50 AM »
RE: Stator ....  check/repair

Years ago when I had a similar issue with one of our off road bikes, I used these guys .....  :027:

http://www.westcountrywindings.co.uk/index.htm

They can Test and Rewind if necessary ... as well as selling other bits like R/R ... so a possible second avenue to check out if you need?

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TIGER 800XCR - ''BLACK on BLACK''

 


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