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My first foray into not just one but two 1975 RD350's
- Thread starter Vincenthdfan
- Start date
Thanks.The Kawi engines had a rubber seal. It would go bad and have to be replaced.
Forgot to show the provenance items that came with the runner...owners & warranty manuals, Yamaha embossed plastic manual bag, original sales receipt, sales handlebar hang tag, previous registrations, dealership decal....love this kind of stuff.
Boy, you really did get a cherry of a buy there! Good on you
Well, got the heads, pistons & rings all de-carboned using chem dip carb cleaner, layer by layer (nothing else would touch it)....everything cleaned up really well.
Rings all measure well within specifications, as would be suspected at so few miles I suppose.
Now I sit and await parts...base/head gaskets and piston pin circlips all in the mail.
Oh well, the weather's still crap out anyway...44 degrees and two days of straight wind & rain storms. Good weather to be in the shop!
Rings all measure well within specifications, as would be suspected at so few miles I suppose.
Now I sit and await parts...base/head gaskets and piston pin circlips all in the mail.
Oh well, the weather's still crap out anyway...44 degrees and two days of straight wind & rain storms. Good weather to be in the shop!
This your first 2 stroke top end?
Got a good handle on how the rings go back in?
Not bein' an ass here, just that those that don't "get it"... do stoopid stuff like I found on my baby RD....
Got a good handle on how the rings go back in?
Not bein' an ass here, just that those that don't "get it"... do stoopid stuff like I found on my baby RD....
That ain't the half of it... they bent the hell outta the crank too...Holy cow, thats a new one....
You seen my RD200 thread?
I've got three 2 stroke threads going. Well... more not going than going... 
https://www.xs650.com/threads/one-mans-junk-72-cs5e-rd200-build.62156/
https://www.xs650.com/threads/74-rd350-yeah-i-know.62807/
https://www.xs650.com/threads/74-dt250-bitsa-the-aussie-mutt.59891/
https://www.xs650.com/threads/one-mans-junk-72-cs5e-rd200-build.62156/
https://www.xs650.com/threads/74-rd350-yeah-i-know.62807/
https://www.xs650.com/threads/74-dt250-bitsa-the-aussie-mutt.59891/
Just curious? My RD250B had solid copper head gaskets. I never replaced them just annealed them by heating to a dull red on the gas stove and they were good to go again. Are these copper gaskets still being used?
Yes, they still use them and I've heard folks do still anneal them.
I have a full top end gasket set coming so Im just going to go ahead and use the new ones from the kit this time around.
Oh the slippery slope begins... 
I tell myself, just do the minimum while awaiting parts...keep it close to being ready to go for upcoming Summer weather.
I'll just check the oil pump gap...re-shimmed it to specs.
Man, those hoses are pretty stiff, better replace them while Im in here.
Man, that injector oil is pretty stinky and off colored...I wonder what the hell it is? It aint Yamalube 2S, I better remove and drain the oil tank.
Man, that battery box and air box could use touch up paint while Im in here....and so it goes, on and on.
The cool thing though? These lil 2 strokes are so darned simply built compared to any of their 4 stroke brethren. Even my Honda CB350's have 4 times the amount of crap to remove to get to the frame like this was in just two steps. Its like going back to working on a bicycle.
I tell myself, just do the minimum while awaiting parts...keep it close to being ready to go for upcoming Summer weather.
I'll just check the oil pump gap...re-shimmed it to specs.
Man, those hoses are pretty stiff, better replace them while Im in here.
Man, that injector oil is pretty stinky and off colored...I wonder what the hell it is? It aint Yamalube 2S, I better remove and drain the oil tank.
Man, that battery box and air box could use touch up paint while Im in here....and so it goes, on and on.
The cool thing though? These lil 2 strokes are so darned simply built compared to any of their 4 stroke brethren. Even my Honda CB350's have 4 times the amount of crap to remove to get to the frame like this was in just two steps. Its like going back to working on a bicycle.
Mission creep....
Great project(s). Have a look at the heads. They crack starting at inner bolt holes. What happens is people get carried away tightening the head down. As well as annealing the gaskets for belt and braces you can give them a spray with copper gasket coat. Spray it on a short while before you intend to fit the gasket.
A lot of later RD parts fit the early models which is very handy, as an aside today I discovered that RD clutch springs fit a DT 175 basket.
I buy pistons, rods and other bits from these people, just be sure to ask them to refund any excess shipping if you don't they won't. The stuff they sell is pretty good quality.
https://www.pjme.co.uk/acatalog/Yamaha_RD350.html
A lot of later RD parts fit the early models which is very handy, as an aside today I discovered that RD clutch springs fit a DT 175 basket.
I buy pistons, rods and other bits from these people, just be sure to ask them to refund any excess shipping if you don't they won't. The stuff they sell is pretty good quality.
https://www.pjme.co.uk/acatalog/Yamaha_RD350.html
Current owner of three RDs and past owner of another. I did the crankcase seals on all of them. On the RDs it's a fairly easy one day job.
As posters noted, the crank seals have ribs, so the cases need to be split. The splitting is not hard - just follow the instructions in the Yamaha shop manual (available at2strokeworld.net). Work carefully and be sure that all the nuts are removed before carefully levering the cases apart. Then clean the case sealing surfaces with lacquer thinner, replace the seals, spread a thin layer of Yamabond and torque it up.
The enemy of the seals is not mileage, but age. Since these bikes are approaching 50 years old, replacing the seals is almost mandatory.
Bad seals will result in running lean on the points side and an oil leak on the clutch side. Neither one is good.
As posters noted, the crank seals have ribs, so the cases need to be split. The splitting is not hard - just follow the instructions in the Yamaha shop manual (available at2strokeworld.net). Work carefully and be sure that all the nuts are removed before carefully levering the cases apart. Then clean the case sealing surfaces with lacquer thinner, replace the seals, spread a thin layer of Yamabond and torque it up.
The enemy of the seals is not mileage, but age. Since these bikes are approaching 50 years old, replacing the seals is almost mandatory.
Bad seals will result in running lean on the points side and an oil leak on the clutch side. Neither one is good.
The ring was upside down.
Below: Red circle is the pin. Yellow is the half moon notch cut into the ring ends. That half moon is supposed to wrap around the pin, not butt up against it.
