forestroke

I think I like the whole concept of the new CD engines from RCV. I was thinking, wouldn't it be great for RCV to make a twin of their CD series? It just seems to make sense to me.

It would simply be putting the entire top assembly on the bottom as well. The gearing for the valve timing is simple to put in phase and there you have it, a twin without any real effort. Of course, the only minor changes will be in the crank where you would have to thin the con rods and make the crank a little longer to accomodate two con rods... But other than that, bingo... you have a twin... do I get some money for this? :-)

forestroke

And... you can use a standard motor mount as well!

Another issue is the placement of the carb and exhaust. Since the valves will be turning in opposite directions, the exhaust/carb sequence will be flipped. My suggestion is to put the inlets both in the back so that you can use a single carb/throttle setup and create headers for the exhaust of which one will come out on the top (flat twin) and one will be from the bottom leading to a single chamber or pipe before exiting.

Then you can chrome the top caps and the exhaust and make it a peice of art instead of its less than exciting appearance today.

The price point 189 for one... say US$400 for 1.7hp with 28oz without silencer (attribute 7oz to shared components) for the 116t and you have a twin that will take on saito and O.S. (if they made one in that size). It's the same weight as the 100t Saito with a little more power (1.7est vs 1.6) and less moving parts, no valve timing/lift/clearance to contend with AND still much smaller than the saito

Saito 169mm
RCV 134mm-138mm (est)

forestroke

I guess there isn't much interest in this product!

Hobbsy

My Feedback: (102)

Actually there is interest in this idea, it has been presented to RCV and they're looking at it with interest. And, you're correct, it would be very easy to do.

ZAGNUT

My Feedback: (1)

nope! if it's going to be worth anything it needs to be a boxer and that means two crank throws an a rear bearing...still doable but a little more complicated

the single crankpin could be still be used if they made a radial....ASSuming they could keep the proper gear ratios with the larger case needed


dave

forestroke

Actually, I looked at the Saito twins and they seem to just have one pin on the crank, not two. If it were two cranks with a rear bearing, it would be much more difficult since it would require a lot more investment in designing new castings, gears (the original sleave/valve drive gear would not be the in the right place anymore) and add substantial weight. As I doubt it would be a high volume product, added investment would likely take it out of contention. I understand that two pins would make it run very smooth but the added complexity is enormous. But the whole idea was to create something very easy to execute.

I'd love to see this in the marketplace.

forestroke

I meant one crank throw, not one "pin"

Hobbsy

My Feedback: (102)

Both the Saito .90T and the .60T have double throw cranks which necessitates split big ends on the rods.

Matt Kirsch

My Feedback: (21)

A single throw crank would make it run and sound like a Harley Davidson.

Flyboy Dave

My Feedback: (21)

....and vibrate like one....

....the boxer crank is obviously preferable....[sm=thumbup.gif]

Dave.

William Robison

My Feedback: (3)

With an odd fire twin you not only bave bad vibration problems, the intake pulse irregularity prevents using a single carb to feed both cylinders. Saito learned this lesson, that's why their odd fire twins all have two carbs.

An odd fire horizontal twin? As far as I am concerned they needn't bother. That's regression of design, doesn't approach anything of quality.

Bill.

spuck5644

Bill, I'm pretty sure I've seen the Saito 300 twin in both single and dual carb versions. Am I missing something here?

William Robison

My Feedback: (3)

Steve:

You have missed nothing.

The Saito 300 twins are even fire (two crankpin) engines, but Saito sells two versions of it. The FA-300TL is a single carb engine, while the FA-300T-TDP is a little bit heavier, the rpm red line is a little higher, and it's $110 more expensive. It also has twin plug heads.

My opinion? 2 1/2 ounces more weight, 400 rpm more, and one tenth more hp isn't worth the added $110 cost.

Repeating: No, you didn't miss anything.

Bill.

forestroke

Well... I guess RCV can still make the twin but it wouldn't nearly be as easy as I had imagined. Unless the con rods can be offset and thinned massively, it's not going to be easy. Double throw would make offsetting one cylinder and create a whole lot more effort. A new casting would be necessary to offset the cylinder. There would need to be room for an gear to compensate for the offset. The gear on the second pistons valve/sleeve would need to accommodate the extra gear in order to keep the 45 degree. Of course a new crank would need to be designed.

The good thing about all of this would be that with the extra gear, the carbs can both be in the back and the exhaust can now both exit from the bottom of the pistons making the exhaust much prettier.

It's still easier than a cam driven twin but it is not quite as easy as I had hoped and imagined. Unless of course, RCV would like it to sound and vibrate like a Harley, which, IMHO, wouldn't be all that bad... wouldn't be as bad as a similar displacement single, right?

forestroke

i have just bought a 90T from ebay and now i'm wondering if i'm going to be displeased with the single crank arrangement. i only thought of this thread after winning the bid :-) no matter. i'm very happy with the purchase and if it likes to shake rattle and roll, so be it. it'll be in a big cub that will not be put through too many Gs. i still think RCV should consider a twin... just like the 90T. it might be a "regression" in design but it also might be quite desirable. built it RCV and i promise i'll be one of the first to buy!!!

Hobbsy

My Feedback: (102)

The single crankthrow Saitos barely vibrate at all. I don't know where you guys get that, obviously not from practical experience. Their tortional impulses are heavier than any vibration.

hanoiboi

I have a Saito 130 which has a very unique sound (close to a Harley), but not that much vibration. It's kinda kool! It's also a very reliable engine, IMA.

donkey doctor

Hello; After looking at their design, it looks like a fellow could just take the bottom cover off two of them and cut down the lower big end down so that both rods would fit on the crank side by side, then bolt the two top ends together, after taking the crank out of one of them. I understand the offset problems so if a side by side deal can't be made to work, how about a knife and fork style big end, like Harley has? If I had two of those engines I would buy a few connecting rods, and try it.

forestroke

DD - that's EXACTLY what i thought... should be simple. but i don't see RCV taking any action. i also don't believe that it's bad to have harley sound and additional vibration. the only problem is in the carb. with single crank, it necessitates two carbs. would be better if it was just one. but then again, i just bought a 90T and wouldn't mind a 100T or 130T so i'm definitely not scared of twin carbs!

RCV? what do you say?