billbofagends Posted May 19, 2013 Report Share Posted May 19, 2013 Hi folks, Been having a few overheating issues with my Txt 280 (non pro); I'm hoping someone can give me some further guidance. Already replaced the fan motor once but has failed again quite quickly. I've been looking at the voltages being produced and I suspect I have a failed voltage regulator. Measuring the AC voltage supplied to the fan motor rectifier (the Leonelli box screwed to rad cowl) I get 17~18v on idle and up to 60v with the bike rev'd up. The DC voltage out of the rectifier is hovering around 25~28v at idle. This to me suggests the regulator isn't working as I should always be getting a fairly stable 16~17v AC (guessing here) supplied to rectifier what from I have read in other posts. I have had the regulator out ("Transval 415 box" hidden up in top of the frame behind the coil and CDI) to clean the contacts etc but this doesn't seem to have have helped. - If the regulator has gone, can it damage the fan motor / fan motor rectifier, or anything else for that matter (bike still runs fine, apart from fan motor)? - Using the wiring diagram linked below, where it indicates a resistance, is this between what the resistance label is pointing at and earth? http://www.trialspar...ams/Kok2001.jpg Any advice would be welcomed on the above. A tip for anyone looking to replace the fan motor who has the "Mitsuba PM-3" motor. This motor is common to a lot of other bikes it is just difficult to find which ones. With a bit of eBay research I've found that Honda fit this fan to the CBR125, VT125 (Shadow) and XL125 (Varadero) from around 2004 onward. There are plenty of CBR125 fans listed and all relatively cheap. I've just picked up a 2010 one for £10 delivered. I will confirm it does the job when it arrives! Cheers Sam Quote Link to comment Share on other sites More sharing options...
sting32 Posted May 21, 2013 Report Share Posted May 21, 2013 (edited) Bil, there was a post about troubleshooting, there are 3 problems to double check, before you have to replace anything including the fan motors. first thing to do is see if your fan works, take a 12v battery and hook some leads to it so you can touch to fan, if fan runs still, then you know it is one of 2 things left. Check your ground wires for corrosion & continuity, then you have to put fan back like it should and short the lead that hook to the "thermo-Switch" (many call it a thermostat) all that switch does is make the leads "magically" touch when water gets to the right temp. if the switch is bad, no fan. that switch interupts the lead from fan to ground, until it gets within the range of 170-180 degrees water temps. if shorting the wires together (I use a paperclip to touch both terminals on the thermo, while engine is running. fan fails to turn on, then you might have rectifier problem (again assuming you proved your fan will run on a 12v battery somehow. there is more advice I believe, on gasgas.com "tech" pages... or find mr JSE, he knows more details like multimeter readings you can check, I think. Edited May 21, 2013 by sting32 Quote Link to comment Share on other sites More sharing options...
copemech Posted May 22, 2013 Report Share Posted May 22, 2013 Seems as though you know what you are doing, so I will try to help. First , try your motor off a 12V battery to see if it runs. Second, The AC input off the mag must be rectified to DC and regulated to 12 -14 V. Both functions are done by shunting excess to earth by the boxes. If rectifier is out, one would fing excess AC to motor, may effect regulator operation. If reguletor is out DC too high, eventually taking out motor. Third- Thermo switch in circuit easily by-passed for testing if needed. I think it entirely possible to burn out one the little motors n short order with overvoltage. Quote Link to comment Share on other sites More sharing options...
billbofagends Posted May 22, 2013 Author Report Share Posted May 22, 2013 Thanks for your help both :-) Tried the motor on a batt when I first got hold of it, was all good, now it wont spin up without a shove and causes a load of interference to the radio in my workshop so pretty sure it is a knackered. Good news is that my cheap CBR125 fan motor looks to be the right motor but will need the fan swapping over :-) I have the thermo switch bypassed so I can rule that out. The fact the AC voltage was getting up to 60v with revs out the back of the regulator says to me it has gone. My mate has kindly got hold of a spare regulator and rectifier unit, albeit from an older bike with the Ducati electrics fitted. Regulator is listed as same part number in the diagrams online though so should do the same job. Going to have another look at it tomorrow to see if I can get it sorted for some weekend riding. Thanks again for the pointers so far. Sam Quote Link to comment Share on other sites More sharing options...
billbofagends Posted May 24, 2013 Author Report Share Posted May 24, 2013 Think I've sorted it. I've replaced the regulator with an older ducati type unit which has brought the AC voltage down to around a stable 10v. Weirdly, the DC from the rectifier without the fan connected still showed over 24v but dropped to around 13v with the fan connected and running. I've yet to run it properly though... Regarding the cbr125 fan motor, yes it does do the job but despite having the same part number, there is a lip on the back which means you can't fit it through the plastic holder. You have to file the motor hole out quite a bit to get it in. It's 10 quid though so the bit of modifying is worth it. Quote Link to comment Share on other sites More sharing options...
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