Streetfighter build in progress - pics

gentlemanjim

gentlemanjim

More Wrenchin than Ridin
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I just acquired a 1983 XS400RK (Seca). Yamaha was on 400 cc twin spree back then. XS360/400 SOCH, XJ400 Maxim DOCH and my baby Seca This is the DOCH, 6 speed, counter balanced, mono shocked version. Fairly high tech for the time, but still has the charm of an aircooled twin. Similar power of the XS650 with a 10,000 RPM redline. I plan to re-build it with a minor Streetfighter look. Sadly there is not much support out there with parts or information. Hopefully we wil change all that here.

Here is where it all starts: Pretty Fugly now
IMG00071-20101108-1527.jpg
 
I guess the power/weight ratio is about the same, if not slightly in the 400's favor. I stand corrected!
 
Are these apples to apples comparisons? How much hp is lost due to the transmission, chain, and rear wheel on a motorcycle? 20 percent? Are the XS400 numbers measured from the crank and XS650 numbers from the rear wheel on a dyno? I find it hard to believe that an extra cam would make up for almost 40% less displacement. I'm not sure how many people have ever put an XS400 on a dyno to see what it'll do. Plenty of people have with the XS650 though. Anyone have any XS400 DOHC dyno charts?
 
It does sound a little extreme. But the dohc models received a pretty good bump in power over the sohc, 38 to 45. Throw a cam in there, get one or two more hp?

Then you have the 650 only making 52hp stock.

What I'm curious about is the torque. You can achieve similar hp, but I would imagine the 650 has a good deal more torque. And I bet it would show, side by side.
 
I know we have been duped for ever by manufactures withh false power claims and dry weight. All I want from this bike is a light, nimble, high revving - fun ride that looks way cool. It's not a 650, but they weren't paarticularly quick anyway. If Yamaha used the same crystal ball for publishing HP figures (400/650) it shlould my needs quite well.
 
I think it'll suit your needs just fine. A buddy that I ride with has an xs1100 cafe, and while he blows my doors off on the straights, he can't even get close to me in the twisties.
 
Moving along here's how she looks now - still stripping, cleaning and polishing. I did the brake hub and one engine side cover - came out awesome I'll post pics tomorrow. Stripped the clear coat with paint stripper, washed in muratic acid and buffed. Bobbed the front fender too, I like.

Big big dilema the fuel tank rusted to hell and back even rotted through in one spot. This is really going to crimp my plans. Plently of parts for the XS400R, but not ta ank in sight. Any suggestions for an atlernate? I'm going for the Cafe/Streetfigher look.

IMG_2012.jpg
 
The choice of tank on any custom build and its size, shape and placement makes or breaks a bike for me. I've managed to buy 5 different tanks so far and have gone full circle and like the one that came with it best, lol.

The Seca has a complicated shaped tank as stock to hide that large backbone arrangement that looks pretty street fighter style already. It's hard to imagine something else on there, something with a deep tunnel with an angular shape, hmm...

Cafe/streetfighter made me think of that Jesse Rooke KTM, maybe some early KTM tanks might fit.

Jesse%20Rooke%20KTM.jpg
 
Weld up that massive backbone cavity and use that as a tank! Seriously though, if you could adapt a Honda CB500t tank to fit on there, I think it would look awesome. I believe it is perhaps one of the most cafe-esque tanks ever manufactured. I have one I have been saving, and it will be used on either a CB450 dohc, a TX650, or an SR500.
 
Got the spark ignitor today form a vendor on EBay. With heart palpatations (electrics especially 27 year old and from an unsecure source - scare me) I plugged it into the harnes plulled a plug, cranked and SPARK YEAH! Reinstalled the plug hooked a temporay fuel tank and instant start - running great. Now I'm real inspired to get her done so I can terrorize the neighborhood.

As far as the fuel tank I'm going to braze a metal patch over the hole clean out the rust by electrolisys and coat with RED-KOTE Fuel Tank Sealer - See attahced
 

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Good to hear that it's running. Be careful brazing that tank.... if it still smells of gas take the proper precautionary measures.
 
Ome updates from yesterday.

Chopped the Pixie tail - next bob the rear fender.
IMG_2015.jpg


Strippped the tank - messy job. but better than creating and eating a pound of paint dust.

IMG_2016.jpg


And Now for the Challenge weld in a patch to this disaster and a few pin ole elsewere.

IMG_2017.jpg


In the mean time I've been derusting parts in a platic bucket and using the electrolisys process - Amazing! All in all I'm very pleased with this scooter
 
Travis said:
Good to hear that it's running. Be careful brazing that tank.... if it still smells of gas take the proper precautionary measures.
Click to expand...
Yes of course. I rinsed it out with muriatic acid and then flushed with running water for what seemedlike forever. No gas smell just ugly inside.
 
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