Bad crank seals '74 rd350 What else should I do while in there?

[rmcdougal]

 

Just got the bike together and then pressure checked it. So it looks like I'm going inside the engine.
Is there anything I should do while it out of the frame?

[Organicjedi]

inspect the pistons, rings, bores, rebuild the crank and replace all seals and gaskets

[m in sc]

trans bearings.

[Yamaha 179]

From the little bit I could see in the picture it is a very nice looking bike for something 45 years old.  Depends on what your level of involvement can be.  You can easily spend $2K on the engine alone and end up with a bike worth a bit more on the market but a bunch more in fun.  (And that amount is you doing a lot of the assembly work.)  Quality parts, not from India or China, cost money and a good
two stroke technician, capable of boring and honing cylinders properly, takes a little effort.  (Like looking here on the forum.) 

So, decide on what you want out of your project.  If it is a first class motorcycle be prepared to spend some money and some time.  You CAN manage both, if you are careful.  If you want to do it as affordable as possible that is possible also; just be prepared to be disappointed.
Lyn Garland

[motodreams]

seals all around and bearings if they are needed.  Countershaft seal should get done while in there otherwise inspect and replace as required.  Check the ring end gap and replace those while in there.  Most of the consumable parts, seals, bearings, rings etc. are low cost to replace and the cost of replacement is largely labor which you are already doing to get to the crank seals.  Measure clutch plates, springs and such for wear and inspect everything else.

These are hardy engines and given the shape of the bike you are mostly doing preventative maintenance beyond the crank seals and any other obviously damaged parts.

[rmcdougal]

Thanks guys, I am new to these and not really familiar with the tweaks they need. I don't have the money to go all out but I am going to be doing the labor myself with the assistance of a more experienced friend. I'd love horsepower but it needs a big return rate for the money. Is there any easy polishing that I can do and get results?
I am going to try to get this thing on the road so I can enjoy it. I am not even going to have aftermarket pipes on the thing unless I am given some, so I don't expect any huge gains. 

Reliability>Horsepower

[Organicjedi]

Basic performance upgrades-

You can do a 520 chain conversion. Lighter chain=more ponies to the rear. TDR125 replica reed petals are a nice addition. A higher flow air filter might help. RZ/ Banshee intakes with a crossover tube.

[quocle603]

Just clean it up. Check bearings, crank, clutch, piston, rings, cylinders. Double check everything and seal it up.

[SUPERTUNE]

Basic performance upgrades-

You can do a 520 chain conversion. Lighter chain=more ponies to the rear. TDR125 replica reed petals are a nice addition. A higher flow air filter might help. RZ/ Banshee intakes with a crossover tube.

520 Chain conversion a great upgrade...
He was referring to change stock original steel reed petals to the Tony Doukas Racing fiberglass reeds that Tony makes for the RD's known as the YZ125 reed upgrade replacement reed to fit the RD's.
Polishing, No.
Fresh cylinder bore work is a major good thing... if still stock and a lot of miles on topend.
Most don't understand the performance, good jetting and running of a 2 stroke depends on proper piston clearances, round and perfect bore and ring sealing...
Inspect crank tolerances and if within spec's go ahead and put on some new outer main bearings while your there and is a cheap to do to prolong crankshaft life longer until a rebuild is necessary. 
Hang on now... don't tell him about doing the RZ/banshee intake manifolds with a crossover just yet... NOT needed for him at this point! (your putting the cart before the horse)
Yes, take the transmission gears completely off the shafts (lay out all the gears in order very careful) and inspect for any seizure on the gear to shafts, very common as these bike are over 40 years old and if ever run low on transmission oil the chances for seized gears are very high.
Looks like that you have a '74 model, so check to see if you have a late '74 that has a 7 plate clutch or and early '74 that has a 6 plate clutch.

If an early model you may think about using some new YZ250/fz1000 fiber plates, as the 6 plate are borderline at not slipping. Most RD do have rubber cushion rings that do need to be taken out and thrown in the garbage as being 40 years old they're hard and junk to reuse today, just better without them!   

Chuck

[oldguyRD1964]

Wondering if you can explain more about the yz250 clutch plates, I'm thinking about replacing the clutch plates on my rd250 would you replace the springs too? 10k miles on my bike 73.

Thank you, David

[plastictrip]

Replacing all the gaskets and seals with quality parts is almost a given as mentioned above. Measure everything and use the factory limits as gospel, especially with the crank. It's worth it to have a trained eye look your crank over as they often look fine, but it's what you can't see that can bite you later (big end bearings, mains past their prime, out of true, etc.). Clean ring lands and new piston pin clips are also often overlooked but important.

[SUPERTUNE]

Wondering if you can explain more about the yz250 clutch plates, I'm thinking about replacing the clutch plates on my rd250 would you replace the springs too? 10k miles on my bike 73.

Thank you, David

Sorry I missed your question, mad busy this summer...

The YZ250 clutch fiber plates are wider than stock RD fiber plates. In RD stock clutch pack they come with rubber cushion rings that are placed in at the same time as the fiber and sit right inside of the fiber.
They were supposed to help the clutch have smooth engagement and dampen clutch rattle. Worked just ok when they were new stock powered bikes, now they're 40 +years old and the rubber are rock hard and with a good running engine and not new... the old clutch plates don't have a chance of not slipping.
By using the YZ250 or Yamaha FZR 1000 plates you throw the old rubbers in the trash and these plate take up the space where the rubbers were and now you have much more friction surface x 7 plates is so much better and you don't have to go as crazy with real stiff racing Barrnett springs.
Just a set of aftermarket 10%-20% springs do very well and won't kill your hand pulling in the clutch lever!

Chuck

Stock plates.



YZ250-FZR 1000 plates.

[tony27]

That's quite a large increase in surface area with a fair amount of clearance to the hub still, very easy upgrade