Rk café racer build thread. All of your tips, pointers & advice are welcome

This is the start of my build so ill try and put pictures up of the build as I go but can't guarantee anything.
We start with the bike, an RK, unlikely contender for the café build but I got it for $300aud and its dohc but it was a basket case and was missing a few things... Like pistons, and the timing chain and a few other things but we will prosper. Let's keep moving on shall we. So the first thing we did was looked at the bike.


Then I reduced the weight so I could start from the ground up. Removed everything I didn't need like the chunky seat, stock exhaust pipes, everything stock, cut the frame and trimmed off all the tabs and excess frame, fuel tank and finally the engine and all its parts. Ended up like this.
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Also if anyone has tips for carbs, cams and a rebore I'd be greatful. I'm looking at tm34 flatslides, a 75mm bore oversizing the valves porting n polishing the head, lightening the engine and all heavy parts and a rear brake conversion, I want to build something like this.

Ok so doing some math trying to figure out potential hp so as follows is what I got-
Atmospheric
pressure: 99Kpa, temperature 25°c, standard density @ 1.156kg/m^3
4 stroke, 0.5 revs per stroke, 2 revs per cycle
2 cylinder, 75mm bore, 53.4 stroke, 36cc combustion chamber, bore/stroke 1.404
Displacement per rev 235.9cc, total capacity 472cc

Final number and most important, the horses- should be 49.67hp hopefully. Now go with some custom pipes, 2 into 1 @ 1.5" port side and 1.75" exhaust side going into 16" slash cut shorty. Tm34-2 mikunis on ram tubes and micro mesh screen filters. This thing should fly. I'm looking for specs on 50/50 or lumpy cams and if anyone has tips on getting more power and making it applicable.

megacycle cams did a shaft for the SOHC I would have a looksey at their web site

Had a look n downloaded the catalogue, will see if they have one's that fit or if it's gonna be a custom job. Hoping they have something, just sucks that this model isn't popular enough for performance parts

Just wondering and i read the big bore thread, will the stock conrod wrist pin size up to 17mm? If so I'm looking at the kz1000 75mm pistons, 39mm intake and 33mm exhaust valves. Just curious if it'd all mesh with minimal work. Also that thread said xs400s aren't built for speed, a ducati monster 600 hits just under 200kph and is only 5kw more powerful and weighs about 7kg more when wet so is it me or does 200kph seem doable?

Ok more math and a picture I had to find the brightest fuel line i could and took some style tips from Drewpy. Starting to get there but won't be finished for a while yet.
I found a formula to measure the intake runner for optimum length at a desired rpm range.
Ok please follow with me and let me know if I'm missing anything or if you have tips.
So to start out we need the intake velocity frequency, who's is calculated as follows-
Take the intake valve duration, 109°, and subtract it from the cycle duration, 720°, to find the valve closed duration. 720°—109°=611°. Now we need openings per second at target rpm, so devide 60 by rpm, 60/9500= 0.063 openings per second. Times that by 2 for length of cycle 0.0063x2= 0.0126.
Now the home stretch, calculating the velocity stack length- ok times the length of cycle by the closed duration, 0.0126x 611°= 7.72. Divide 2 full revolutions by that number, 7.72/720= 0.0107, this is the valve reopening time. Speed of sound is 13536" per second. Take 0.0107 multiply it by 13536" to give velocity stack length. 0.0107x13536"= 145.13569". now take this number and divide it by 2, 145.13569/2= 72.567". That's one long fucking tube. Seeing as the pulse needs to go back up the tube, then down again we can divide it by 2 over and over again to find the correct length tube from the back of the valve to the tangent of the velocity stack. About 9.07" or 230mm, seems right but if not I'll round it down or double it for super long stacks... All the for about 2.2hp

can you post bigger pic? Clutch window is always cool...

Can't help with math...

Is that bigger? I tried but photobucket only goes so big

much bettter... Thanks. Do you already know what kind of tank you want to fit on this frame? I am looking forward to see final bike!

Yeah I have a good idea for a tank, similar to the tank on this bike, www.returnofthecaferacers.com/2013/02/gull-craft-yamaha-sr400-cafe-racer.html?m=1 but I'll be making it outta 2 layers of carbon 1 layer of carbon kevlar hybrid and 1 of Kevlar on the inside. Seat and tank will be one unit. Also changed my mind on ram intakes to velocity stacks performance gains and tuning would similar from a far simpler system

Wow...I'm impressed...

I see heaps of bikes and I'm like "I would love that bike". This bikes something to bring me and my dad together, he had a h1 and a 600b, hoping to impress him alot and try n start over. It's gonna be more money then what it's worth to some but if it works and kicks something off id be glad to spend as much as I am on it

Good progress so far! I'll be following this thread.

This isn't the adds place but I'm selling a 85% complete set of bs34 carbs from the bike, I've got my tm34s so I won't need these ones anymore. $50aud ono you pay postage and I'll pack it as small as possible to cut postal fees

Who loves maths? I do!!! Ok so did some more, measured the bore and such to make sure custom barrels will fit. If we got to the upper parts of the cylinders we can see a very flimsy edge on the oil ports, easy fixed, we remove them and increase the top external diameter of the sleeves to 87mm. Correct me if I'm wrong but I should be able to get away with a retainer edge, the lip at the top of the sleeve cuz I don't know it's actual name, of about 3mm cuz stock is 4mm. Now 87mm—6mm=81mm, 81mm—10mm is 71mm, gives wall thickness of 5mm for the sleeve, shave that n save weight make it 3mm gives a savy 75mm bore. So from there we stroke the engine 9mm and that gives an awesome number, I don't know the compresion ratio yet cuz I don't know what size rods but I'll am for about 10.1:1. Anyway 62.3mm stroke and 75mm bore and 36mm combustion chambers gives 586cc, almost 600cc. This with custom cams, bigger carbs, lighter crank and other rotating parts and velocity stacks should put the hp up higher. Hopefully close to 55hp~60hp if not higher. Now for money. This is gonna slow my build down alot so please be patient and I'll keep you updated as I go.

The crank won't last long, just throwing that out there. Trust me, I wanted to do the same but logical engineering shot me down. Will end up being a grenade with a short fuse. Unless you are having a billet crank made, then in that case I salute you.

Then salute away my friend. Custom crank shaft is gonna get built and fitted. So far I'm looking at $550 for custom 110° cams, $320 for 2 kz1100 pistons rings and pins, crank cost I don't have yet and neither for the rods. If I can do it I wanna take the 50hp original goal, smash it, grab the new 60hp goal and pass it and get as close to 70hp as the stock head can take with some porting and polishing..