Full Brew Seca.

Browsing through the XJ cd got me thinking. As there is little interest in buying my turbo, I am beginning to think I should perhaps just keep it and turn it into something special. I want to find a decent 900 motor I could rebuild and stick in it, then turbocharge that. Everything should slot in without too much hassle. The fairing would be tossed if it got in the way, but by all accounts, it needs just a bit of modification to accomodate the cylinder head. So far, so good. So then I think, how could I make the engine bigger. I guess finding oversize pistons and rings from the aftermarket is probably difficult, if impossible, so what could I pull from the Yamaha parts bin? Well, since all the other Maxim/Seca motors are smaller, it would seem to be hopeless, unless you consider the smallest of them all, the XS400 Seca/Maxim. Seeing as how it has about 2/3 the displacement with only half the cylinders, it naturally follows that it must have a bigger bore. Bingo! 69mm, bigger than even the 900 at 67mm. So, using the stock Maxim 400 size piston, we can calculate the displacement as (69 X 69) X .7854 X 60.5 (900 stroke) / 1000, which gives us 226cc, X 4 cylinders = 904cc (versus 853cc for the stock motor).

There are several questions. Can a 900 cylinder be taken out 2mm? Is the wrist pin height and bore size correct for use in the engine? Is a 4th oversize Maxim 400 piston still available, which would give us 958cc, assuming 0.5mm for each oversize? Could a Seca engine live with a 10.8:1 compression ratio (before lowering for turbocharging)? If the 900 liners could not be taken out 2mm, would the 400 liners be long enough to give proper support to the pistons at the bottom of the stroke (7.1mm shorter stroke)? Of course, fitting the xs parts to the 650 block would net 783cc displacement, which would probably be enough for a considerable increase in performance as it stands. The 650 stroke is actually 1mm shorter than the 400, so the pistons would be well supported.

Anybody have access to 400 and 900 parts at the same time? It would be kind of a neat project.

 

You could just buy a Seca 900 they are quick, would you really need the turbo on a 900?

Seems like a lot of work and money with the chance of it not working as planned.

Why do you want to get rid of the 650, not fast enough for you?
watch this vid....makes anything else seem slow!

YAMAHA R1 TURBO
http://www.youtube.com/watch?v=S-ppGiwc0wQ

 

I think this is a very interesting idea. You will need to do a lot of research and asking around of engine builders to see if this is possible.

 

That R1 seems a bit useless to me, it doesn't seem you can ride it on two wheels!

 

yeah he couldnt seem to keep that front wheel down

 

Mac, Just thinkin outloud here, but if you turboed the 900 you'd have quite a rocket on your hands, Would all the extra work/money/uncertainty in adding an extra 101cc actually be worth it. I would reckon that the gain would be negligible. At least when considered with the cost and work required assuming it even can be done. But that just my 2 cents, I really have no idea whether it could be done. Good luck to you though!

 

There's a guy in here that has a 900 Turbo. The lower end and head is a fairly easy swap-over. I don.t know the particular ... but you could PM him and look at his web site. The web site shows everything he did during the build.

He also has a complete 900 Engine that I have been storing for him in my shop. He might have lost interest in it and you could negotiate a price with him.

He bought it privately, from a 900 Guy, around here. I'd like to have it moved-out of here!

 

Hey Rick, I didn't see anyone else with a 900 turbo, could you send me a link? Do you have any first hand experience watching it run, or know any of the pitfalls he experienced building it? I'd love to have that motor, but freight from Billerica to Ottawa might be a bit steep.

 

Look-up member "injuneer"

Check his profile and visit his website.

 

:lol: That's a unicycle with front wheel "landing gear"

 

They eliminate the front wheel to save weight on that R1, then just keep it at 8000 rpms.

 

I'm so slow ...
"Unicycle with Langing Gear"
Now I get it!!!

LOL!!!