RD350 Cafe Racer / Brat Project

[jamiebridge]

Hi Guys,

I am UK based and this is my first build, I managed to pick up a Yamaha RD350 from ebay that was badly advertised, it was just described as 'yamaha rd350' with one picture:

From the original picture it seemed it may need a lot of work but also looked like it could be a promising basis for a great two stroke cafe project, i decided to place a few bids and won the bike for £600, the next day my dad and i set off with a rental van to go and pick it up. We got there and to our surprise the bike was in very good condition for its age, it was obvious to us that it needed some work however it was in a much better state than we anticipated, and the reason for the sale was that the previous owner bought it thinking it was a 350lc.

We got it home and into the garage where it sat for a few weeks until we started to strip it down.

Incredibly everything went very smoothly (not to jinx the rest of the build or anything) but parts came off like butter. It was apparent that somewhere down the line someone had previously started this build and had either run out of money to fund the project or had encountered some serious engine problems.

A week later pretty much the whole bike was stripped down, we decided to crack open the engine and to our surprise it had been converted from a 350 to a 250, we are guessing this, as the gearbox is 6 speed but the top end is a 250. So the plan is to re-instate it back to its original 350cc engine.

Aesthetically i am wanting to go down the brat route, one because i think the style looks awesome, and two because this style is very rare on a rd350, is there a reason for this? For example rear tyre clearance?

So plans are as follows (I am open to all kinds of suggestions from you guys).

Convert engine back to 350cc
Electronic ignition
Remove oil tank and run on premix for slicker look
Expansion pipes (possibly DG, maybe handmade depending on money)
Rear sets (these are hard to find in the UK and I don't want to import due to costs, so suggestions would be great, i also wear a size UK11 shoe so i need plenty of room)
Cutting the rear frame and installing a rear loop (not sure on rear tyre clearance for this?)
Removing frame seat tabs and other tabs i will no longer need
Powder coat frame black
Powder coat wheels fully black
Brat style seat, brown leather
Get the forks re chromed
Clip on bars with brown leather grips
single tachometer (possibly just rev tachometer for a sleeker look)
New front headlight
Rear light (small round type)
New rear shocks (simple black style)
Need new air filters
Front brake calliper and braided hose
New tyres possibly bridgestone (wanting to go as wide as possible on these but retaining the best possible ride and performance.)
Tank repainted either cream white or matte blue

This thread will be updated with more images throughout the build.

Thanks for your interest and any help / advice you may give.

Jamie

 

[bradj]

Measure the cylinder studs the 350 and the 250 run different lenght studs so if you put 350jugs on a 250 bottom end you could strip the head bolts i can get you the differemt measurememts so you know if you need longer studs o and replace the crank seals first and for most. side note my rd is just about as hot as you would want a street motor to be and...i run points so dont think they are gonna keep you from having a fast bike. i had my tuner run the numbers on a set of dg pipes and he told me and i quote "these pipes are perfect for a stock to mild street motor"
the rd nerds hold there nose up at them becouse they dont cost 1100 dollars.
There cheap and they work

 

[teazer]

RD250 and 350 are more or less the same and later ones came with cast wheels and 6 speed trans. That bike has cast wheels and an earlier shaped tank, so it's probably a bitsa. The key to the mystery are frame and engine numbers. They tell most of the story.

The 350 makes more power and to save transmissions Yamaha changed the primary drive ratio and along with that they also changed the tacho drive gears and oil pump and gear. Count teeth on primary drive gears and then check those against the manual and it will tell you if the bottom end is 250 or 350.

Then count gear teeth on each shaft to see if the transmission is RD250/350 or 250/400.

Brad mentioned stud length already, so measure them first and let us know what you find. 350 barrels are taller than 250 which is why the studs are a different length. Somewhere here I have the stud lengths in a spreadsheet for years of doing mix and match Yamaha race bikes. Some combos work and some don't.

DG pipes are good but check pricing on them compared to say Swarbricks which are way more sexy and maybe not too much more in the UK than DGs. Or go for some Rizla pipes (roll your own).

Don't go wide on those stock skinny rims if you want to go round corners and you'll need a speedo to get an MOT and even if you got away with that, the cops will no doubt throw the book at you for not having one.

 

[jamiebridge]

Thanks for all the help guys, i will check it all out this weekend and hopefully get an answer! Im starting to think it could be a 250.

 

[jamiebridge]

This is a very quick mockup, ignore the pipes, i didn't have time to photoshop anything in place, and also the wheels are spoked, i will be keeping the alloy ones currently on the bike: