Triumph tr5mx Build

johnu

Active Member
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It's been a while since my last build on here (T500) but it's time for something different.
My dad (Ken) passed away a year ago and he was a motorcycle nut. He restored many bikes mostly BSA's and Velocettes. Unfortunately I had to sell all of his bikes excecpt one as I'm in SoCal and he was in England. I kept his 1959 BSA Road Rocket (RGS replica). I followed in his footsteps with the love of bikes and racing. He taught me so much about bikes and restoration and I am passing that knowledge on to my son also who will be helping me with this project. I'm going to dedicate this build to my dad.
So I picked up this 1974 TR5MX (wish I could have found an actual beezer but this is close enough) which I am told is actually 570cc. Supposedly only ran a couple of times after a rebuild but that was about 1985 so it will be a full engine strip down. I got two sets of wheels with it the road going wheels that are on it with the shouldered alloys and an another set that I was told and I believe to be true are the offroad hubs. The bike has a California road title
<200


I have always wanted a vintage 4stroke mx bike so this is the perect base or that. I will be changing the geometry a bit to take some of the slackness out of the rake and increase rear wheel travel. I'll be making my own tank, seat and exhaust. The engine will just get reliability upgrades most notably a Carrillo con rod and improved lubrication.

So here is what I am starting out with.
 

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teazer

Well-Known Member
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That is way cool. Comical hubs and all. It's hard to believe that a B50 looks so good when its great grandfather the C15 was so bland and uninspiring.

Can't wait to see what you do with it. Your builds are always so clean.
 

johnu

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Ok so I've actually been working on this one for about a momth so I have moved forward a bit. First think I wanted to address was the geometry. BSA specs say the bike has 27* rake with 6.5" travel on the front and 4" on the rear. I got hold of original BSA drawings and comapred that to my bike and not all adds up! I think the draftsmen and the frame builders must have gone down the pub at lunchtime on the day they made the frame fixture:p My bike with the suspension all the way extended (have to have a baseline) ended up with 30* of rake, it was like a chopper!!! So I set about gettting back to 27* rake which is not too bad for a dirt bike. I had to relocate the shock mounts and build a slightly longer swingarm. These two things increased the swing arm angle to 11* which is not too bad. I am also using adjustable length shocks so I can fine tune if needed. Now I will have 6" of rear wheel travel.
 

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johnu

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We also fired the beast up just too hear it run:cool: It is a bear to kick over plus no choke. You have to flood the heck out of it then get it just past tdc and give it a big kick, plus you have to set the idle up high before kicking. If you touch the throttle you are doomed!
 

Rider52

Active Member
I bet you find a lot of variation. Both BSA and Triumph were on the down hill slide in 73-74. They started combining bits between the two brands to make "Triumphs". In 86 I found a 1974 Triumph 650 still in the crate at a mega dealer in Ohio. The dealer went bankrupt and auctioned off the inventory. I bought several Honda/Kawasaki bikes/parts lots and this one Triumph. It was one of 900 built before the Triumph workers went on strike in late 73. I had no idea and promptly pulled it from the crate! It looked more BSA than Triumph and several things didn't match the factory pictures/descriptions. My bike had the BSA type tank but I saw another 74 that had the Triumph style tank. I believe they were throwing parts until they had a motorcycle. I do believe you have a great project so push on! Big single joke - easier to push start than kick start!
 

johnu

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Yeah I have a jacked up right knee too so starting is no fun. I will have to have my boy at the track to fire the thing up or roll down a hill;)
We got the swingarm mostly finished aside from the chain guide bracket and the wearstrip. Also modified the rear of the frame for the new upper shock mount location.
 

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johnu

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Well I got my exhaust done this week. Had to brush up on the old brazing skills, still a bit rusty
;-)
Next will be a new rear brake pedal then the seat and tank. Never made a seat like this from scratch before.
 

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johnu

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Small progress rear brake pedal made. Next job is the aluminum side panels. I have had the color scheme for this project worked out from day one. Unfortunately I cannot find a gold dimpled aluminum 40 hole 21"wm1 rim, I'm not even sure about the rear as its a 40 hole 18" wm3. This will be disapointing if I can't get these rims. I have a 36 hole front hub from a 1980 Yamaha 465 that would work perfectly but then it would not be eligable for pre 74 racing.
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doc_rot

Oh the usual... I bowl, I drive around...
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if your dead set on the color of the rims you could powder coat or if you want to really get into it you could have the anodization stripped (or strip it yourself) and reanodzed for a couple hundred bucks
 

johnu

Active Member
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Got side panels mostly finished. Also built and engine work stand, my boy did the welding.... he is getting better!
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johnu

Active Member
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Well I have got some stuff done but stil moving at snail pace. Swing arm is done with lower chain guide and the upper wear strip mounted. Also repaired the damaged front hub using my new tig welder. It looked like a pigeon crapped on it from a great height until I machined it up:D Also decided to go with Sun gold non dimpled rims and stainless spokes from Buchanans, shoud be arriving soon.
 

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johnu

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Sun rims and spoke kits showed up from Buchanans today
:thumb
I was wary about ordering them as it was a $900 purchase but this is top shelf kit. Just need to do a proper job of building them up, don't want any trouble when I'm landing the 80ft triple:cool:
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Popeye SXM

Also used for MX
Wow $900, Sometimes I manage to get my money's worth on a purchase, I hope this the case for you. They look great
 

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