G'day race fans. Was going to call this post !just for shits and giggles!. 3 years ago i aquired a as3/rd125cc engine for free, then 2 years ago i bought a Yl3 bike as spares for my yl3 100. For a while now i have been sorting through the engine and bike and buying parts for a build. At one stage i was going to build the bike as a yl1 100cc factory race replica complete with clip on's and bathtub fairing.
I've decided to create a regerstered cafe racer that will have some performance, all be it mainly in the engine not the frame or brakes.
Engine will be a Rd125 reed valve engine. It will run 24mm Mikuni's with larger Ct1 reed blocks with carbon reeds. The crank has just been rebuilt the cylinders ported and bored for new pistons. Sorting some chambers to run of the factory headers, although i would like to build a set from cylinder to stinders. Stock the rd125 had 16hp at 8500 rpm using 18mm tekei carbs. I'm hoping for 23-25hp at 10500rpm.
This is all going into a pressed metal utility 1968 yamaha frame. The engine mounts and aligns the the drive sprocket the same as the original 10.5hp 100cc engine. I've aquired new alloy rims, some trick home made alloy rear sprockets and i have an as3 tls font hub that may be used.
Unlike the restoration of my yl3 this bike will be open to the cafe treatment and also the ever dwindling budget.
Going to paint the bike black and silver (alloy) and remove some of the rear mud gaurd to improve the line of the frame with the cafe seat. There will be no side covers or auto lube. Need to source some high output coils. Looking at LED cafe syle blinkers and rear tail light. Best thing about this whole bike for my shits and giggles will be it will have a tacho. Bought a vintage tz tacho 2 years ago with this projest in mind.
Anway for the past few weeks i have been spending an hour and a half every afternoon, working on parts and buying parts. Here's a few photo's of what i had in the start. more photo's and update to come.
yamaha yl3 125 racer build
Re: yamaha yl3 125 racer build
photo of quick mock up.
Re: yamaha yl3 125 racer build
stock yl3 100 
Inspiration 
factory gyt Yl1 race replica
Inspiration 
factory gyt Yl1 race replica
Re: yamaha yl3 125 racer build
Excellent project gman!
You did such a great job on the first YL3, you've really set your self a high bar. Look forward to seeing your progress.
You did such a great job on the first YL3, you've really set your self a high bar. Look forward to seeing your progress.
Re: yamaha yl3 125 racer build
G'day race fans. Today i fianaly got lucky with some usable crank cases. I've got two other sets that either have chain or water damage. Finally found another engine that i've been able to salvage the cases from, added bonus is 2 more side covers. 
The pistons where seized in the bore from the bike sitting out in the elements for the last 10 years. Had to drill a dozen holes around the edge of the piston then take to it with a cold chisel to brake up the piston to release one cylinder. I was able to then rotate the crank which lifted the other cylinder away from the case to enable dissasemble. Into the oven, 20 minutes on 180deg 
Then with my home made case seperator i had the cases apart. 
The pistons where seized in the bore from the bike sitting out in the elements for the last 10 years. Had to drill a dozen holes around the edge of the piston then take to it with a cold chisel to brake up the piston to release one cylinder. I was able to then rotate the crank which lifted the other cylinder away from the case to enable dissasemble. Into the oven, 20 minutes on 180deg 
Then with my home made case seperator i had the cases apart. 
Last edited by gman on Sat Oct 03, 2015 11:35 pm, edited 3 times in total.
Re: yamaha yl3 125 racer build
some photo's the sprockets from an old yl1 racer and new alloy rim.
a few tanks to choose from. would love another chrome one but at the moment the bugat won't allow, i will save the best one for chrome later and paint the one of the others. 
a few tanks to choose from. would love another chrome one but at the moment the bugat won't allow, i will save the best one for chrome later and paint the one of the others. 
Re: yamaha yl3 125 racer build
I bet Mrs.Gman was impressed with the Yamaha pie!
What year is this thing Gman? Horizontally split cases from later models certainly makes it easier to strip a siezed motor. I like your puller though. Nice work.
Where did you get your rims?
What year is this thing Gman? Horizontally split cases from later models certainly makes it easier to strip a siezed motor. I like your puller though. Nice work.
Where did you get your rims?
Re: yamaha yl3 125 racer build
mr's gman lives in her own house and i'm only aloud 1 bike in her garage. Rims i found on ebay from a seller in the states who abandoned a project he was going to use them on. can buy them out of thailand for more money. The engine is 1972/75 the frame 1968. A piece from here a piece from there. What bike do you ride ged?
Re: yamaha yl3 125 racer build
Ahh Racing Boy rims. I sold a set for gold 36 hole units on ebay a while bak, bought em for my XL500R project years ago but decided not to use em. The rims werent too bad, dunno what quality the alloy was tho, but the anodising was done over a not too well prep'd surface and showed some marks and light spots, but otherwise for the money they were ok, not DID or Excel perhaps but they dont cost like those do. Would I use them again? Probably not, I do like the better brands quality, but they are a good price point for a project.
Re: yamaha yl3 125 racer build
yer racer boy. $75us plus postage. 17inch for the tiddler. cheaper then buying chrome steel to replace the rusted ones i have.
Re: yamaha yl3 125 racer build
This forum has the most annoying habit of swallowing replies..... 3 times now.
Your domestic arrangements sound similar to mine whereby I have a fantastic shed but signed away all rights and interest in house other than sleeping, eating and watching telly.
I didn't sign away the carport though, which is currently occupied by a 1983 Ducati Pantah I built about 5 years ago and a 1954 BSA M21 I've restored over the past 22 years. I'm also working on an RD/TR3 replica on another thread here.
I asked about the rims because I ordered up a Chinese set this week for an SR250 project I'm working on but I'm looking for a flanged set for the RD/TR replica but there proving elusive at the right price.....
Your domestic arrangements sound similar to mine whereby I have a fantastic shed but signed away all rights and interest in house other than sleeping, eating and watching telly.
I didn't sign away the carport though, which is currently occupied by a 1983 Ducati Pantah I built about 5 years ago and a 1954 BSA M21 I've restored over the past 22 years. I'm also working on an RD/TR3 replica on another thread here.
I asked about the rims because I ordered up a Chinese set this week for an SR250 project I'm working on but I'm looking for a flanged set for the RD/TR replica but there proving elusive at the right price.....
Re: yamaha yl3 125 racer build
Interesting youre having issues with replies, LB is too from what he posted, maybe you guys have the same issue?
Re: yamaha yl3 125 racer build
g'day race fans. Keeping with the tight budget i thought i'd give an idea a go as far as header pipes for some chambers. I have 3 sets of header so i picked the worsed set and cut them with with grinder up the guts.
Then with some help from sockets and some hammers i've been reasonable succesfull to flandge the pipe from inlet diameter of 32mm to outtlet diameter of 52mm , 250mm total lenght. the original bends are still there and i hope to use some old curved header steel to weld 2 wedges into the expansion gap and form the pipe. Crude it may be but i'm not versed in the art of cones and i had the idea and i think i will get the result for no dollars. ol mate that ported the cylinders will run the number's on his chamber software and build me tuned lenght chambers to attach to the headers. need to find 24mm mikuni round slide carbs with bolt on mount, to suit ct2 manifolds. anyone have some or know of any? Early (pre 1975) dt's had them.
Then with some help from sockets and some hammers i've been reasonable succesfull to flandge the pipe from inlet diameter of 32mm to outtlet diameter of 52mm , 250mm total lenght. the original bends are still there and i hope to use some old curved header steel to weld 2 wedges into the expansion gap and form the pipe. Crude it may be but i'm not versed in the art of cones and i had the idea and i think i will get the result for no dollars. ol mate that ported the cylinders will run the number's on his chamber software and build me tuned lenght chambers to attach to the headers. need to find 24mm mikuni round slide carbs with bolt on mount, to suit ct2 manifolds. anyone have some or know of any? Early (pre 1975) dt's had them.
Re: yamaha yl3 125 racer build
Good idea Gman. If you're able to stitch that back together ok, you should have a crack at the chambers. Your doing the hardest part of the pipe right there. The compound curve between the header and the start of the chamber.
Re: yamaha yl3 125 racer build
G'day race fans. Today i did a quick mock up to check the line of the seat and check carb clearence. Removed the old seat mounts, will need to fabricate new ones. Placed some tape on rear fender to take a photo to study how much i'll remove from the rear fender.
This week i bought 2k paint to try through a gravity fed gun. Finally have all the set up to paint myself. Going to make a booth between the house and the neighbours fence using drop sheets.
I have 2 thoughts to which way i go with the bike.
(1 )All black with a silver stripe from headstock to tail with chrome front fender, black engine covers or (2) black frame , white tank with tz tuning fork logo, red fiberglass front gaurd, polished side covers.
This week i bought 2k paint to try through a gravity fed gun. Finally have all the set up to paint myself. Going to make a booth between the house and the neighbours fence using drop sheets.
I have 2 thoughts to which way i go with the bike.
(1 )All black with a silver stripe from headstock to tail with chrome front fender, black engine covers or (2) black frame , white tank with tz tuning fork logo, red fiberglass front gaurd, polished side covers.
