B50/T25T and TR5T frame difference - center stand

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B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Sat Nov 16, 2019 3:46 am

I was just checking three bare frames, a 1973 TR5T, a 1971 T25T and a B50SS. All of them are bare and flipped upside down resting on the back loop and the front of the frames on the floor. Measurements with a tape measure to compare. The B50 and the T25T are the same, The TR5T has a few differences. The hole for the B50 and the T25T center stands are 26 from the floor, again remember the frames are upside down. The hole in the bracket for the TR5T (center stand?) is also 26" from the floor. The factory might have set these at that height for use on the assembly line. The brackets are very different between the B50 /T25T and the TR5T. And while some grind down the center stand lugs to fit the TR5T brackets, I think it would be better to copy the B50/T25T , trace it to the TR5T and grind to fit and of course drill out the TR5T's 3/8" hole to 1/2".
Another difference is the foot rest bolt on the B50/T25T is 3/8" and the TR5T is 7/16". I have found reference that the later B50 was also drilled out to 7/16" so this may have been a factory improvement.
The surprising difference was in the holes in the swing arm brackets. On the B50/T25T the holes are 19-20" from the floor. But on the TR5T they are 20-21" from the floor, 1" difference.So the TR5t would sit 1" higher and have 1" more ground clearance.
I have 3 of the shorter OIF center stands and 4 of the longer ones. One 1971 T25T and two 1971 B25T plus the 1974 TR5T that are together. Next will be to lift up the 250s and bolt on the different center stands to see which ones work best. The OIF center stands bolt right on to the single frames and it looks like to only mods will be to clear the side stands. The TR5T will need a additional 2.5" center section, holes drilled out and to see if the long or short stand fits best.
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by koncretekid » Sat Nov 16, 2019 2:27 pm

How much do the motor mounts differ? I have heard that the TR5T has a bump-out in the lower front left tube to clear the twin's primary cover. Would any other changes have to be made to fit a T500 motor?

Tom

P.S. Did you ever get the oil leakage problem solved on the B40? I have the same problem on my B50 Street Tracker.
life's uncertain - go fast now

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Sat Nov 16, 2019 3:31 pm

Tom
The front oil bearing down tube is shorter, the bottom frame tubes are closer together and the back mount/fender mount is different. I will post some photos this evening. Grand Daughter is coming over and we will be working on her math for up coming test today. :smile:
B40 still leaks.
That might be a worth while project this weekend to put the two frames side by side and get some photo's and measurements. I gave a friend two 1971 B25T frames so he could also build a TR5T. He picked up a TR5T frame that will needs some work and unfortunately he scrapped out the other two frames. I think he knows where there is another TR5T frame. They were rode hard here in Michigan in the woods and I think they sold a lot of them around here. I have seen a few and I actually have one with the cases split through the transmission output shaft bearing area.
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Sat Nov 16, 2019 7:06 pm

Interesting, I was just looking at the 1974 TR5T parts book and unlike the 1973 Parts book, it no longer shows a center stand.
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Sun Nov 17, 2019 2:57 am

Here are a few photos, Front down tube on the TR5T is 17", on the B50SS it is 20". Different front and bottom engine mount lugs.
Attachments
Front down tube II.jpg
TR5T front mount.jpg
B50SS front mount.jpg
Front down tubes 17%22 vs 20%22.jpg

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Sun Nov 17, 2019 3:02 am

Rear fender front mount is very different, The TR5T is beefed up here.
Attachments
T25T rear fender and motor mounts.jpg
TR5T rear fender font mount and foot rest mounts.jpg
B50SS bottom frame.jpg
TR5T bottom frame.jpg

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Sun Nov 17, 2019 3:05 am

TR5T vs B50SS/T25T rear engine areas
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TR5T in the middle.jpg
B50SS rear fender fount mount.jpg
TR5T front lower frame.jpg
IMG_1842.jpg

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Sun Nov 17, 2019 3:09 am

And finally the reason I thought the TR5T swing arm was mounted lower. B50SS is on the left, TR5T in the Middle and the T25T is on the right. The B50SS rear frame loop is lower then the other two. The TR5T seems to have a slight bend upwards in the middle. The T25T matches the TR5T 's height, but shows no sign of a bend. None of the frame seem to have any damage or bends in this area? Factory seat height adjustments?
Jeff
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B50SS - TR5T - T25T rear frame.jpg

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Re: B50/T25T and TR5T frame difference - center stand

Post by Leif » Sun Nov 17, 2019 8:54 am

Jeff, where exactly are you trying to mount a center stand? What few pix I've seen of stands mounted have been attached to the two (unique, I believe) "tabs" hanging down from the cradle just in front of the rear downtubing. Which confuses me when I see you trying to compare B50 frames with The TR5T frames.... the Tr5t stand would have to be at least 3" wider, I'd guess? Why even consider a B50?

I've read conjecture that these tabs were there for factory assembly purposes, seems pretty doubtful to me. I'd guess the only purpose they could serve would be to mount the (never produced?) center stands. Were those tabs on the 74 frames, since no centerstand is shown, maybe they were eliminated, have to look at some pix I guess?

Anyway, I haven't tried to make one for mine yet, but recommendations have been to source a T140 stand and alter from there to proper width. There has been discussion on BBF about this, search the archives. And look at the picture you posted there from BCS, particularly at where the stand mounts.

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Mon Nov 18, 2019 3:08 am

The "lugs' on the TR5T do not appear to be for a center stand, I think that they were used to hold the bike on the assembly line. The 1973 TR5T parts book's drawing of the frame looks to be a "cut and paste" frame drawing and shows the unlisted center stand in it. The 1974 TR5T parts book corrected this and omitted the center stand in the drawing. A few people have used these TR5T lugs to mount a modified OIF center stand. You will need to add a 2 1/2" section to the center to make it wide enough to fit. Be aware that there are at least two different OIF center stands out there pertaining to height.
My interest in the B50/T25T frames is simple, they have real center stand lugs on them. So I wanted to see how they did it and then use what they did and do it on the TR5T. All of the TR5T's that I have seen photos of seem to have the center stand too far forward where it contacts the ground, The B50/T25T angle is different. if you have too much angle , then to are starting to get unneeded leverage on the lugs. Most grind down the center stand to fit the TR5T frame lugs. I just thought that it would be better to copy the B50/T25T lug shape and grind the TR5T lugs to fit.
I have a couple of spare frames left and I was just using them to compare and to understand how the factory did. It is getting cold around here and I now have a Knock sensor on one daughters' H*nda CRV to replace and the thermostat just stuck open on their ford Focus. Neither job is a simple fix so it looks like the bikes are on hold again for a week. I also will be on the road at 6am tomorrow to drive one of my grand daughters 2 hours away for eye surgery.
I should have listened to my dad. He used to say " Never retire!, At least at work you get breaks and days off". :mrgreen:
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Mon Nov 18, 2019 3:26 am

I should add that for all of those who are thinking that dropping a T100 motor into a B50/T25T will be easy. It is doable, but they are several differences between the two, so give your self plenty of time. The B25 is taller then the T100, but it looks like the factory mounted the T100 motor higher up in the frame, this resulted in special cylinder head studs and head "bolt" so you could remove the head with the motor in the frame. If you need to pick up the frame, I would look around and try to find a TR5T frame to start with. They are out there and chances are if they were rode in the woods, the motor was blown years/decades ago. I have heard of and come across a few of the TR5T frames in the past. I have one TR5T motor and have seen others with a huge crack in the cases that runs from the top down through the transmission output shaft bearing. Think high rpm, huge knobby tire and a very large rear sprocket. Now add kid/younger person flogging the bike trying to keep up with the large 2 stokes of the day in the woods on on a dirt track.
Once I get caught up, 1st thing to do is to bolt on a tall OIF center stand to one of my complete T25T and to see how high it lifts it. Easy to do bolt on and it will tell me if I need the tall or short center stand to get the lift that I am looking for, I want to be able to remove the rear tire while it is on the center stand. I can then also measure the factory angle of the stand in the down position and use that to set up one for my TR5T.
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by Leif » Mon Nov 18, 2019 6:02 am

Hopefully you'll keep us posted, I'll follow your TR5T progress with interest. Especially as I still don't understand where and to what you will be mounting the centerstand... the crossbar and lugs for the B50 stand aren't there, and I don't think could be on the TR5T.

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Wed Nov 20, 2019 12:10 am

More TR5T photos. One show the factory lugs on the bottom. The next one shows where people are drilling out the 3/8" hole to 1/2" and mounting the OIF center stands. it also show why you need to cut the center stand and weld a 2 1/2" section in the middle to widen it.
Jeff
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IMG_1859.jpg
IMG_1860.jpg

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Wed Nov 20, 2019 12:12 am

These two photos are of the T25T/B50 frame. You can see the factory center stand lugs and you can see where the OIF center stand is a simple bolt on. You will have to modify the lower arm to clear the side stand.
Jeff
Attachments
IMG_1861.jpg
IMG_1862.jpg
Last edited by Jeff K on Wed Nov 20, 2019 4:22 am, edited 1 time in total.

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Re: B50/T25T and TR5T frame difference - center stand

Post by Leif » Wed Nov 20, 2019 4:22 am

I understand what you're showing, but what you posted sounds like you don't plan on using these tabs? If not, then my question would be where you would mount the stand. Maybe I'm just mis-understanding, and you do plan on using these "assembly" tabs?

The frame drawing in the 73 parts book is, as you say, a cut-n-paste, it actually shows the B50 crossbar and lugs to mount the fictional stand... big oops on someone's part.

If a different exhaust was used, I wonder if that crossmember could be welded in... but it would be a bigger headache than using the tabs.

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Wed Nov 20, 2019 4:27 am

Yes, I plan on using these tabs. But unlike most who do this and grind down the center stand to fit the frame tabs. I plan on grinding the tabs to fit the center stand. You can see the shape different if you look at the T25T/B50 frame.
And for all of the BSA single owners following these, the good news is the OIF center stand is a simple bolt on, you just have to modify the arm to clear the side stand.
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Wed Nov 20, 2019 4:36 am

Notice that on the TR5T frame the tab for the side stand is broken off at the hole and on the T25T frame the side stand itself is broken off. Seems to be a pattern of problems here. :lol:
At one time I used to see where some one was selling a repair section for where the side stand breaks off. I have not seen these repair sections in a while. If anyone knows who makes these, please post their information. I might just cut up one of the spare frames and use it's side stand tab.
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by Barry Creary » Wed Nov 20, 2019 5:34 am

Jeff I bought one from Trojen spares in Sydney Australia and it is good quality but I don't know were they get them from. I know that they will post if that helps.

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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Wed Nov 20, 2019 5:48 am

I have looked at their web site and I can not seem to find the bracket.
Jeff

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Re: B50/T25T and TR5T frame difference - center stand

Post by Barry Creary » Wed Nov 20, 2019 6:54 am

These guys seem to not put everything on there website if you want me to ring them let me know and I'll make inquiries for you.
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Re: B50/T25T and TR5T frame difference - center stand

Post by Jeff K » Thu Nov 21, 2019 3:27 pm

Barry
Thank you for the offer to contact them. I have a "extra" T25T frame that that I plan of cutting up for brackets etc. I can salvage what I need from it for now.
Jeff

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