I'm mulling over the upcoming rebuild of the RD250 I bought over the holidays. It's cosmetically rough, so the tank and side panels will need a repaint. I'll either do it in rattle cans or take it to a body shop for a spray. Either way, the colors will not be stock, but I'm OK with that.
I already have an RD250 (and a bone stock 350), so it's a question of doing something new and enhancing the resale value. I've been mulling converting it to a 350. I know that I would need new cylinders, pistons and heads and am looking at my options.
I'd have to get a set of used 350 heads. New jugs and slugs are available from India and I'm curious if anyone has used them and what their opinion was. As I recall there used to be an option using Vito's cylinders and pistons, but those seem to be NLA.
So are the kits from India junk or are they worth a try?
Cant enhance resale value by putting junk parts on.
You may get lucky with a set of cylinders that are not oval or have holes in the liners from porosity or liners that twist. But you would need to get then ported as they will have Indian market port timing.
The NZ guy who built the 700cc RD sidecar used them for his motor, but he put a huge amount of work into them to make them reliable.
You will be better off looking for some used parts
id keep it a 250 if possible
I agree that if the parts are junk, they should not be used. Just trying to find out if they are junk - and it appears that they are. I'll keep a weather eye out for used jugs that I can have rebored.
Mark, why keep it a 250? I have a disc front end to put on it. Thought I might as well go all the way.
Hi Gene!
A name from way way back in time...we're all old now! :vroom:
Chuck
P.S. If you find good topend I can help with the machine work. (bore and glass beading and of course piston kits and parts)
Realistically you are looking at sinking more money into the bike than it would be worth if you are converting to a 350, if you are looking to sell in the near future. If you will keep for some time then the entertainment value may make up for the added cost. It likely has a *bit* more value (as it will already not be original) as a 350. If you're going rattle can paint job you are already targeting the bottom of the market though and the 350 top end will be an investment making up a large fraction of the bikes value. Just saying!
It's a lottery with those cylinders, one I bought was not useable, the liners are pressed up from the bottom and can move down, and the porting is for the Indian market.
If you use them without fixing the porting the bike would be a complete slug and unreliable to boot.
They were a good option for us but I would not recommend them to anyone as an upgrade.
Thanks for all the replies and ideas. My current two-stroke stable is this:
RD350 - bone stock original - mechanics and motor rebuilt
RD250 - generally stock with what I think is a good rattle can paint job - mechanics and motor rebuilt
RD250 - came to me as a basket case - on the last stages of reassembly into a café racer - many non-stock parts to replace missing expensive ones
RD250 - purchased in December - pretty much complete and looks like a good candidate for a full restoration
I must say that I find that the 250 has nearly as much pep as the 350 (likely because of the gearing). With the TLS front brake it stops well. Of course, the handling is the same. I think the ~$1000 difference in price between the 250 and 350 comes more from cachet than performance.
With the new RD250 I got a complete RD350 front end. That's what started me thinking about making the latest purchase into a RD350. But it would cost me about $500 for the heads, slugs, jugs and machine work. And, as was pointed out, I end up with a bitsa that is worth only little more than a stock RD250.
It might be that a better idea is to put the RD350 front end on the café. Then I can make the new 250 a restoration project.
Really just thinking out loud here, but comments and suggestions are always welcome.
^ yup. this. :vroom:
Some photos:
My bone stock RD350
The "mostly stock" RD250
The RD250 basket case turned café racer. It's nearly finished.
The newest RD250. And it came with a bunch of extra parts including the RD350 front end.
Sorry for the multiple posts. The photos bumped up against the posting limit.
Internet claims 30hp vs. 39hp and as you have identified otherwise a very similar bike. 30% more hp is significant. If you gross that up into car terms you are looking at 300 vs. 400hp. Definitely material difference.
Otherwise I think you are being realistic in your costs.
its closer than you might think. just fyi, look at the transfer port duct area 250 vs 350. You can squeeze a lot of power out of a 250.
I did a 250 years ago, it would run dead even with a stock 81 LC. It was ported to death but it was definitely NOT slow. A stock 250 is really good. I wouldn't count it out.
I just checked and the stock gearing appears to be the same on the 250 and 350. Both 16/40.
But, my 250 feels nearly as strong as the 350. Both engines are fresh and the jetting is good. They both have strong urge off the line. The 350 is a bit more wheelie prone in first gear, but the 250 is not far behind.
I do remember taking a brief ride on a friend's new RD250 in '73. That bike MOVED.
primary gearing, crank to clutch is different. the 250 is more aggressive.
Ahhh, that explains it! Thanks, Mark.
That's a good reason not to "upgrade" to RD350 cylinders. You would still have the short internal gearing.
ive actually used 250 primary gearing on a 350, then made it up on the sprocket and chain. this slows the clutch down a bit. its nth degree stuff but it helps the motor wind up faster. just .02
I run 250 primary gearing on my RD.
I do too. Its fast. Just really screams on the highway at 75mph. Like 6600rpm.
Quote from: Gene Ungar on March 05, 2020, 10:40:24 AM
I just checked and the stock gearing appears to be the same on the 250 and 350. Both 16/40.
But, my 250 feels nearly as strong as the 350. Both engines are fresh and the jetting is good. They both have strong urge off the line. The 350 is a bit more wheelie prone in first gear, but the 250 is not far behind.
I do remember taking a brief ride on a friend's new RD250 in '73. That bike MOVED.
Are you sure you counted right?
The stock RD fronts are a 15T sprocket, maybe has been changed from stock?
Chuck
I looked it up on the partzilla site, Chuck. It showed the same 16 tooth front sprocket for both. The website might have been wrong, of course.
Must be...because stock is a 15T.
C
yup. stock is 15.
Quote from: m in sc on March 05, 2020, 10:30:26 AM
its closer than you might think. just fyi, look at the transfer port duct area 250 vs 350. You can squeeze a lot of power out of a 250.
I did a 250 years ago, it would run dead even with a stock 81 LC. It was ported to death but it was definitely NOT slow. A stock 250 is really good. I wouldn't count it out.
Mark, the BMEP potential of the 250 is far greater than the 350 making them a sweetheart to modify. The 2R8 top end has the outside dimensions of a 400 so cooling is better too.
Quote from: Gene Ungar on March 06, 2020, 08:40:33 AM
I looked it up on the partzilla site, Chuck. It showed the same 16 tooth front sprocket for both. The website might have been wrong, of course.
Partzilla (and other vendor sites) will usually show only the current available or most recent available part, not the original installed part from the factory. To confirm original specs you should look at Service Data from Yamaha or a vintage Yamaha Parts List
THE TECH LIBRARY »Yamaha Factory Specs and Info »Yamaha Service Data (http://www.2strokeworld.net/forum/index.php?topic=40.0)
THE TECH LIBRARY »Yamaha Factory Specs and Info »Yamaha Parts Manuals (http://www.2strokeworld.net/forum/index.php?topic=41.0)
And yes, 40/15 is stock for the RD250 & RD350
Quote from: John Ritter on March 06, 2020, 10:26:37 AM
Quote from: m in sc on March 05, 2020, 10:30:26 AM
its closer than you might think. just fyi, look at the transfer port duct area 250 vs 350. You can squeeze a lot of power out of a 250.
I did a 250 years ago, it would run dead even with a stock 81 LC. It was ported to death but it was definitely NOT slow. A stock 250 is really good. I wouldn't count it out.
Mark, the BMEP potential of the 250 is far greater than the 350 making them a sweetheart to modify. The 2R8 top end has the outside dimensions of a 400 so cooling is better too.
exactly, the possibilities IMHO are really (outside racing) sort of overcast by displacement desire.