Yamaha RD350 meanderings.

I posted a few odds and ends from cobbling my little RD together in the Motorcycles thread but seditiously, kept a full record on a local bike forum out this way. Long story short, bought it for 500 bucks and wanted to make it faster and more fun to ride on an extreme budget. Learnt loads along the way and it ended up working pretty well.

Check it out here if you're bored...

https://www.bayarearidersforum.com/forums/showthread.php?t=557276

After a few upgrades to the shed, I'm thinking about carrying on with the tweaking.

First on the list, is a set of 350 cylinders, which I will port more aggressively than I did the 250s. I've a spare set of heads, which need a recut on my new lathe to optimise the squish band and chamber size for the 350 barrels, and I might make up another new set of pipes, to my own specs and in 22 rather than 20 gauge this time for diet purposes.

Speaking of which, there are several other components that are notably portly. Rims, which I'd like to re-lace with aluminum, yokes, which are boat anchor-esque and swingarm, which is bendy and too short as stock. Both yokes and swingarm are more involved than stuff I've done to date, but hopefully now that I'm tooled up to do them, should be fun projects.

Anyways, still got to finish fixing the lathe first so likely no updates for a little while....

Pic after the first rebuild - it made it 850 hard miles in 3 days, with only about 20 miles of 'running in.' Good for a genuine 100+ now but it's all above 7k and peakier than I'd like. Will be bringing the RPM down and the power up with the 350 barrels, hopefully make it a little less hard work and have the crank live longer.

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Nice one, got a few RD’s and LC’s. One is an RD 400 which would be a similar vintage to this. Great fun.

Cool! My first fast bike experience was a 350LC, yeeeeeeeeeeears ago. Love them.

I got around to fixing the back gear on the lathe. Now I just have to take the headstock apart and put the repaired one in. The back gears in it at the moment are trashed, so rather than undertake a monster repair, I got another one from eBay. It was missing most of a tooth, which probably would have still worked ok, but it would have bugged me to use it as is. Seems there are a variety of methods for gear repair, from filling with braze and filing, to drilling and tapping a couple of grub screws. I milled a little slot, and filed up a steel tooth to go in. Cut some grooves in it for capillaries and silver soldered it in. I played the torch over the gear for the length of ‘don’t fear the reaper’ to burn off any carbon in the cast iron, and let it cool slowly. Seems Ok.

Also fixed the shift problem. I found a Grom shift arm that fit the splines and offset and made a little extension piece for more leverage. Works great and I can finally shift 1-2 and find neutral without grinding my toe to pieces.

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Looking forward to reading more on this project. Subscribed.

Vicious power band ?

Not sure anything with sub-40 Hp can be described as having a vicious power band but it’s very pronounced. :)

In common with most non-PV two strokes with top end pipes, there’s a big hole in the curve just before it starts working.

Excellent and what a bargain it was. You would never find anything like this around that price in the UK. America just has loads of cool stuff lying around in barns and the like. All of our Yam MX bikes came from the states, mainly Cali.

Not sure how I missed this thread. Seems like the quite the bargain, which always helps with a project. Looking forward to more updates.

After something of a saga, I now have a operational lathe, with working back gears. Made a T nut this morning to mount a quick change tool post and it works a treat. Just need to borrow a level and I should be in business.

I think first order will be swingarm - Was thinking about a fixture for one last night. I reckon 1.5” 16ga, 4130 Chromoly, should be nice and light, whilst still being much stiffer than stock.

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Need to make a little table for tool holders and other tchotchkes to sit behind it first. I fucking hate woodwork, so that will be quick and filthy dirty.

For anyone geeky like me, the lathe is a Logan 9 series from the early 50s. 11” swing and about 24” centre to centre. Now that I’ve fixed the gears and fitted new cross slide and compound nuts it works a treat. Originally came out of the Jet Propulsion Laboratory in Altadena!

Table done. Just waiting for some DIN strips to arrive to screw to the back for tool holders. After that I can borrow a machinists level from my mate and get after making the swingarm jig.

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Ah a nice shelf to collect chips 😁

True! Somewhat easier to Hoover them up from there than the floor behind. Not that they don’t end up everywhere anyway.

Unsurprisingly love this!!!

Saddened that I’ll never get to see or smell it (2stroke the smell of my teenage years).

Same here mate. You know you’ve a berth and a set of wheels if you ever make it out my way!

You’re a gent.

Would love to at some point

DIN strips work a treat for toolholders. I should have got 3. Picked up a cheap Chinese 50mm shell mill to help squaring up the box section for the jig - most impressed so far. I’ve asked the local metal place to quote me on the raw materials for the jig and swingarm so hopefully will be able to get the metal next week.

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Oof - the materials quote came in hot. Nearly $500 bucks for everything to make the jig and a couple of swingarms (seems a good idea to make two.)
I've had a quick look on ebay and I can save a bunch of $ buying the 12L14 steel for the axles and fixtures but the aluminum, the 4130 and rectangular tubing for the swingarm and jig frame are much of muchness. The credit line of marital goodwill is a little stretched, seems I might be a bit longer getting started.....

Might take a trip up to the metal store and see if I can score the Ally from the remnants pile as the sizing is not so specific.

Impressed with this project

After seemingly endless pissing around with the lathe to get it to work right (or get me to work right….) I picked up some metal for the swingarm. Ended up with an assortment of remnants that should do the job for a fraction of the price. Not much actual work done yet, but I did cut and square the arms, then mill the slots for the axle.

Because I’m paranoid, also made a test piece and welded it to see how the bend would work. Ended up doing a second pass as I always go too fast if I’ve not welded for a while but it passed the hammer test with flying colours. Mild steel is a lot more forgiving than Chromoly but will likely do a couple more to get my eye back in.

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That looks like it's going to be a very long swing arm!

Humbug. Got a filthy cold and confess turning dials and sweeping up while feverish is no fun. Got the end caps finished and the axle inserts nearly done. After that I’ve got to make some inserts to hold the needle rollers for the pivot end, then I can get cutting and pasting.

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Despite being ill looks like you're cooking on gas to me. The milled slots look good too, no doubt a lot cleaner than if I tried with the pillar drill and files.

I think you could do them just as easily on a pillar drill, with the right set up. Quite convenient to just plunge an end mill through and cut them out though.

Mine is a version of this - you should treat yourself!

https://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Milling-Machines/SIEG-SX27-Mill/SIEG-SX27-HiTorque-Mill

I will cave and buy a DRO at some point because it's painful counting turns without one. Don't really need it for this though.