My RD125 Special

Twintuned · February 03, 2020, 02:10:21 PM

I havent been on this forum in 4 years, so i decided to share one of my builds since then.

The engine is a Ls2 100 bottom end, with RD125 top end. Its heavily ported and has durations similar to a TA125. Crank currently being built to TA specs by Gary Braun. Power is from 9k-12.5k. The pipes ive built to match my porting, silencers are made entirely of aluminum. Vm26 carbs, rd350 boots, stock cages opened up with fiber reeds, little boost bottle. Spark provided by an Electrexworld CDI.

The frame is actually a RD200, because i had a donor roller in my shed. The modifications to make it like a TA frame are as follows. De-lug, bronze bush swingarm pivot from 15mm to 12mm, use RD125 swingarm, add rearset foot brackets, cut out and make upper shock mounts narrower (never fun). Weld in spacers for engine mounts, inner fender tabs, rear cable holders, coil mounts, and tach/fairing mounts if you choose. Vapor honed hubs, laced up with Akront 1.60 rims.

Gas tank and seat i made fron .063" 3003 aluminum, tig welded (next tank i will learn oxy/acy on 1001 alum). The gas cap is a repop, but the mounting base and breather cap i made by hand. The yamaha decals are TA125 replicas. I read about a guy waiting 15 years to get a chance to buy a real TA tank, so i just had to make my own.

I spent 3 years of parts gathering and researching before i built anything. It was one year of consistent building on nights and weekends. I have done some testing on rural roads, first time out i was having trouble pulling in 5th with 15/35 sprockets. I went to 13/35 and it screamed. Gary has pressed on a shorter 5th i found, but im currently in the early stages of modifying a YFS200 six speed into it to get my top speed back. I plan to cast my own 100cc cylinders for Ahrma racing, so that is whats next. I will probably make a new frame, Van Tech style for once its a race machine. The TA seating position is extremely aft.
Dont see a lot of people messing with the little twins, so information is typically direct to anyone who has a TA, or the RDX racers in the UK, if you have any questions regarding them im happy to help.
Cheers, Sean from Detroit.

Twintuned · February 03, 2020, 02:16:24 PM

Gas tank stuff

Greaser Greg · February 03, 2020, 02:21:25 PM

Very cool. That's a real "build"!

SoCal250 · February 03, 2020, 08:13:16 PM

That is awesome! Beautiful work, especially on the tank, pipes, and gas cap base

85RZwade · February 03, 2020, 09:02:37 PM

Magnificent!
Wade

mnein · February 04, 2020, 07:52:34 AM

Beautiful work.

27 Cycles · February 04, 2020, 08:42:06 AM

Very cool bike/project. Small displacement bikes are the best!!!

m in sc · February 04, 2020, 01:47:22 PM

so good.

EE · February 04, 2020, 09:46:57 PM

Really nice work!!!!!

motodreams · February 05, 2020, 02:03:54 AM

Looks awesome. Some good work on those rearset mounts as well. Have any spare upper rearset bars made? I need a couple bent for a similar rep. This is fairly close to the TA which I am guessing you modelled off! Very nice work.

RD7 · February 05, 2020, 04:30:54 AM

Love it !

Twintuned · February 05, 2020, 04:08:12 PM

Quote from: motodreams on February 05, 2020, 02:03:54 AM
Looks awesome. Some good work on those rearset mounts as well. Have any spare upper rearset bars made? I need a couple bent for a similar rep. This is fairly close to the TA which I am guessing you modelled off! Very nice work.

Thank you. Yes its a direct TA knockoff. Unfortunately i dont have any other spare tubes made, I borrowed a friends tool to do them. Although im sure you could get away making them with an oxy/acy torch, the bend isnt that tight.

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My RD125 Special