My recent purchase RD250B

[grcamna3]

I don't know exactly what the composition is. They're used in a bunch of Yamahas from the era. They are black or grey and some kind of plastic far as I can tell- maybe graphite based or something as I think it was too early for nylon, Delron etc. in widespread use back then.

I'm sure Mark would know and probably chime in when he sees this thread.

I hope to find a quality needle bearing swing-arm kit from someone.

[RDnuTZ]

just enlarged your picture and noticed there is no beauty trim on the seat and looks like you got a new cover there? Overall in really nice shape!

[SoCal250]

Welcome and congrats on the new ride! Looks pretty nice and appears to be all original. I have one just like it sitting in my garage waiting for restoration attention.

The '75 model has frame/engine numbers ranging from 352-300101 to 352-311250 so yours is from the early part of the model year. (#1964)

So for the 75' model year there was 11,149 RD's produced? Now is that just the 75' RD250B or is that all inclusive of 250's and 350's made in the year 1975?

Based on serial number ranges released by Yamaha, they built 11,150 RD250s for the '75 model year. That range above is only for the "B" model. All '75 models have a frame/engine number starting with 352-3xxxxx
A '73 has a 1 after the dash and '74 has a 2.

[SoCal250]

I don't know exactly what the composition is. They're used in a bunch of Yamahas from the era. They are black or grey and some kind of plastic far as I can tell- maybe graphite based or something as I think it was too early for nylon, Delron etc. in widespread use back then.

I'm sure Mark would know and probably chime in when he sees this thread.

I hope to find a quality needle bearing swing-arm kit from someone.

Bronze bushing upgrade: https://www.economycycle.com/product/bronze-swingarm-bushings-rd250350400r5ds6ds7xs/
or
Needle bearing kit: https://www.economycycle.com/product/swing-arm-bearing-kit-needle-bearing-type/

[grcamna3]

just enlarged your picture and noticed there is no beauty trim on the seat and looks like you got a new cover there? Overall in really nice shape!

Yes,the seller deleted the special seat beauty trim. 

I want to find a stock RD350 top-end and turn it into a 350.
I want to locate unmolested jugs and heads.

[grcamna3]

I don't know exactly what the composition is. They're used in a bunch of Yamahas from the era. They are black or grey and some kind of plastic far as I can tell- maybe graphite based or something as I think it was too early for nylon, Delron etc. in widespread use back then.

I'm sure Mark would know and probably chime in when he sees this thread.

I hope to find a quality needle bearing swing-arm kit from someone.

Bronze bushing upgrade: https://www.economycycle.com/product/bronze-swingarm-bushings-rd250350400r5ds6ds7xs/
or
Needle bearing kit: https://www.economycycle.com/product/swing-arm-bearing-kit-needle-bearing-type/

Which swing arm bearing kit is the best:needle bearings or bronze bushings ?

[RDnuTZ]

just enlarged your picture and noticed there is no beauty trim on the seat and looks like you got a new cover there? Overall in really nice shape!

Yes,the seller deleted the special seat beauty trim. 

I want to find a stock RD350 top-end and turn it into a 350.
I want to locate unmolested jugs and heads.

Okay, here's everything you want to know about the 350 conversion in 1 thread started by the Master  You'll only need to come up with a set of heads to go with the top end kit. enjoy!

https://www.2strokeworld.net/forum/index.php?topic=5650.0

[grcamna3]

just enlarged your picture and noticed there is no beauty trim on the seat and looks like you got a new cover there? Overall in really nice shape!

Yes,the seller deleted the special seat beauty trim. 

I want to find a stock RD350 top-end and turn it into a 350.
I want to locate unmolested jugs and heads.

Okay, here's everything you want to know about the 350 conversion in 1 thread started by the Master  You'll only need to come up with a set of heads to go with the top end kit. enjoy!

https://www.2strokeworld.net/forum/index.php?topic=5650.0

I'm checking-out that thread:thanks.

I was looking at those cylinder/piston kits a week ago on Ebay.
I spoke to an 'old school' powersports machinist who I have dealt with for a few years and he said the china cylinders can not be 'relinered' when the cast iron wears;something about the process they were manufactured with,where the outer aluminum was poured around the sleeve and the sleeves can't be pressed back out.
 
I know it will take a while for the cylinders to get to final bore-job;plus I am very gentle on my engines w/ plenty of warm-up,etc.
I may never get to max-bore for years.

I'm considering finding a pair of stock Yamaha cylinders in good shape;but if they need to be bored bigger than max-bore,maybe I could find if LA Sleeve,or somebody might have a good sleeve to replace them and get them resleeved.
I think my independent powersports machinist does re-sleeve the stock Yamaha cylinders,when needed.
I know,I know.. it'll be much more $ and searching for a pair of sleeves,but it's an option I want to pursue.
I may get lucky and find a low-miles set of cylinders that haven't been ported yet    'keep dreaming,right?   

[RDnuTZ]

so no hurry to convert it to 350 then 

In my case I have several RD projects started 20+ years ago and then mothballed. My immediate priority is just get the 74 350 and 77 400 back together running and on the road before I'm too old + rebuild a couple spare 350 motors I have on the shelf. Luckily there's more affordable options for cranks, top ends, updated electricals, etc. come available over last 20 years to meet my needs 

[grcamna3]

so no hurry to convert it to 350 then 

In my case I have several RD projects started 20+ years ago and then mothballed. My immediate priority is just get the 74 350 and 77 400 back together running and on the road before I'm too old + rebuild a couple spare 350 motors I have on the shelf. Luckily there's more affordable options for cranks, top ends, updated electricals, etc. come available over last 20 years to meet my needs 

I understand. 

[m in sc]

ther is absolutely no reason to waste time re-sleeving stock RD cyls TBH. the repros are so cheap its not worth it, and port rubbing to port rubbing, the porting is the same. i know, i've done it.

[2 Smoker]

Nice find, gorgeous machine

[Brad-Man]

As far as needle bearings vs bronze bushings for the swingarm goes, here's my 2¢:

Needle bearing will react faster for ultimate in handling.

It has been said that they need to be taken out and rotated to avoid wearing in the top needle rollers, but if you don't ride much...

If you weigh more than the 185 I was when I was twenty then you may not notice much difference in terms of reaction between the two...

Bronze won't rust.

YMMV.

[m in sc]

bronze bushings will actually handle a load better. (from an engineering stand point)... so, does it matter on an rd? not really

[grcamna3]

bronze bushings will actually handle a load better. (from an engineering stand point)... so, does it matter on an rd? not really

I like to get a set of bronze bushings w/ a sleeve that will have a nice,tight fit.
Do bronze bushing typically use special grease,or just standard graphite auto chassis grease ?

I have enjoyed a pair of Hagon(low-end)rear shocks on my little lightweight 81' Honda CB125S w/ an XR200 engine for 5 years;I'm not sure there's still a dealer for them here in the USA(UK manufactured)but I'm looking,because these are very good quality,for the price.

Which decent(low-profile look.. theft deterrent)stock-height rear shocks do all of you RD guys like to run ?