Hello, The PO that sold us a 1982 SR250 hadn’t ridden it in almost 10 yrs due to a noisy starter. When we picked up the bike the starter had been pulled and disassembled completely. We’ve cleaned it up and reassembled the starter among other things and got the bike running last night. Unfortunately once the bike is running the starter is being driven by the engine which would explain the noise the PO was hearing. The starter whine follows any change in RPM when reving the engine. The starter engages and disengages fine with the start button and we’ve disconnected any electrical power to the starter but it still continues to be driven by the engine. I’m not able to find much if any information in the service manual. Does the starter incorporate a sprag type clutch? Is this a common problem on the 80’s SR250’s? Any help would be appreciated.
Welcome. Check that you are not getting any electricity to the starter after starting the engine. I suspect that your solenoid may be staying engaged/sticking on after you release the start button.
I would say that the starter clutch is worn if the starter is still turning when the electric's are disconnected. or something related to it ? https://www.cmsnl.com/yamaha-sr250-exciter1-1982-c-usa_model8871/partslist/B-08.html#.Xv2HPnUzZ9M
Thanks for the replies so far. Upon further inspection today we’ve determined the sound isn’t actually coming from the starter. We removed power to the starter with no change in the suspect noise. Opened up the side of the crankcase and checked the starter clutch which also seems to be working properly. I took an old piece of 1/4” fuel line and began to try and trace the sound like using stethoscope. Turns out it seems to be coming from the top end. The previous owners comments about the starter making a funny noise gave us a bit of confirmation bias which took us down the wrong path. I’ve uploaded a video of the suspect “whining” noise. Is this common on the SR250? I have a couple XS650’s and neither of them sound anything similar. thanks in advance.
From what little reading I have done on this bike, they are known to starve the top end of oil due to a too large oil galley in the crankshaft. Often times the cam and rockers/cam followers suffer damage because not enough oil gets up top. In the US anyway, there was a service bulletin that included basically reducing the size of the oil galley in the crank with a reducer causing more oil to go up top. There are two bearing on the cam that may have gone bad as well from lack of oil. I would pull it and take a look. Sorry to revive this old thread, but just a suggestion. I have seen the service bulletin online and could find it again if you are interested. -Bratcop
I'm presuming the camshaft runs on actual bearings, not plain bearings. Could it have the wrong bearings fitted, i.e., fully sealed instead of open ones?
They are definitely open not sealed, they need the oil to get to them. If yours have sealed, just pry the seals out and be certain the oil mod/service bulletin is complete. New bearings are probably cheap to purchase, might consider just replacing them while in there. Bratcop
Yeah, replace the bearings anyway. There is not much else there to make such a noise and the noise does sound like bearings.
Ill take some pictures of my bearings, as I currently have everything apart. I will try to get the numbers off them if I can find them....stay tuned... Bratcop
The outside cam bearing is a KOYO brand # 6005C3. I cannot get a number off the inside bearing, but it is a roller style bearing. Hope it helps someone. Bratcop
And I was referring to an oil mod to prevent starving the top end. Here is a video link to a youtube video about it that I just ran across. I would assume it to be applicable to all Yamaha 250 singles of this era... Bratcop
