Johnson 250 help

[MickeyMoo]

Hey...

I have an Odd Lotts 757. It has 2 johnson 250 brushed motors. I fly it and a pusher jet with these motors since I have a bunch sitting around. I was flying the 757 with a weak 3s and the motors in parallel. Last year I smoked the motors on the 757 with a 20c 3s pack
(too much, I know :rolleyes: . I put a good 2S pack in it today and it ran fine at first. After several minutes the motors began to squeal very bad and loose power. They didn't seem to get hot during the flight (I brought it down to check). The motors felt ok turning by hand. The j250s seem to hold up much better in my pusher jet (one will last all season). I'm wondering if its because its a pusher and the 757 is setup in a tractor configuration. I think the prop adaptor pushes up against the motor housing in the pusher config taking the stress off the shaft. I'm using a GWS 4025 prop in both cases. Should these motors hold up on a 2s in a tractor config?

[kit]

Put some oil on the bushings.

[MickeyMoo]

I put some on the front at the field but couldn't get to the back of the motor. Didn't help. I'll get to the back today. Never had one sqeal like this on the pusher jet. May have to pull one out and take it apart. I'd like to get more than one flight between changing motors on this plane :o

[MickeyMoo]

Well... I put some Triflow on the front and back of the shaft yesterday and then ran the motors at low throttle in the garage to seat the brushes. At first I thought it helped but after awhile again it began to screech. Not squeal but screech so loud you want to take a bat to it :eek: Moving the throttle up will stop it screeching momentarily but then it will start again. The motors feel fine turning by hand. Just thought some one may have some experience with this :confused: Never happened with my pusher setup. I thought maybe I had a bad motor but both are doing it and they can't have more the 30 minutes run time. may just have to tear one apart and check it out :rolleyes:

[rick.benjamin]

If the motor bushings were unlubricated before initial use,
then they were damaged by friction on your first flight.
http://www.rcgroups.com/forums/showthread.php?t=235961&highlight=johnson+250+bearings
Some folks have replaced bushings with bearings.

[MickeyMoo]

Thanks Rick...

Thats what I was looking for. Now I have an idea of the problem is when I change them. With the GWS 4025 I'm pulling almost 20 amps (combined) and have about 8oz thrust WOT. This must cause a lot of friction on the bushings. This isn't a problem with the pusher setup because the prop adapter pushing against the motor housing taking the load off the shaft. Not sure what the original purpose of these motors (got mine form All Electronics) was but I'm guessing it wasn't designed to handle 70+ watts and an 8oz load on the shaft :rolleyes:

[MickeyMoo]

Update...

Put some triflow on the front and rear bushings. This helped but didn't eliminate the screeching. Put the tube form the WD40 in one of the front holes of the motor and gave it a few shots :D This did the trick. Must have hit whatever was dry. The motors work fine now. I'll give them a shot every few flight to keep'em lubed :p