Poor mans RC30 - hunting for advice please?

Hi there,
I will be coming to the end of a bike mod project in the next couple of months and I have started thinking about what I will start with for the next money drain.

I'm sure the question has been asked before and also attempted but I would love an RC30, but there is no way I can afford the £15-16000 asking price, also I like working in the machine shop anyway.



So I have a cunning plan. Create a modern take on the RC30 that has terrific handling and enough power for a track day, with the classic style looks and sweet sound of the VFour.

-Get a 96-97 VFR 750 (frame most like the original RC30).

-Tune and big bore the engine with 837cc kit, gas flowed head, K&N's etc. Aim for 120bhp.

-replace rear shock with newer race setup

-replace front end with machined yokes, new GSXR K6 forks brakes etc.

-Use original style wheels, or perhaps something lighter.

- RC30 fairing (or maybe something more modern.

- Custom endurance style tank

- Custom exhaust seperate front and rear systems Rear exiting from the seat, front cylinders Motogp style by right foot peg.



Further consideration regarding using a newer pre Vtec 800 engine bored out with Fireblade pistons making it 900cc, will the 800 engine fit into the 750 frame?

Can the engine use forced induction? (dont really want to dabble with this to be honest).

Now I know that the engine internals are different with a 360 crank etc but is there anything else that will cause me major issues or head scatching moments?

Thank you very much in advance for any advice.

Here is the Bike that I am soon to finish, a 73 CB750 race style. My other bike is a round eye 92 blade and I have a GSXR750 K6 for racing which may donate it's front end for the project if I part it on ebay.
But I guess I just like Honda 4's

 

nice build......... sounds like a good project

 

Great idea!

Looking forward to your build.

I know a big bore kit was made for the 94-97, but are they still available?

BZ

 

man that cb750 looks like one of my nighthawk's wet dreams lol.
as for forced induction, the 800s definitely can take it(ask toro) im sure the 750's can too, but carboration will be an issue.
i am interested in the possibility of dropping fireblade pistons in a bored out vfr engine. id like to see what the various cbr's ( 900 919 929 954 1000) piston diameters would add up to in a vfr (if they fit)
and how they would affect the compression ratio...

 

Nice bike. Who made the pipes?

 

Awesome pipes!!!!

 

That Cafe CB is just AWESOME! love it

 

Thank you for the comments guys

The exhausts are by Swarbrick Racing. They are 4 into 4 and have no baffles or any sound proofing, just straight through pipes, so I think they could end up being a bit loud. They have been a nightmare to sort out as they are expensive and come 1/2 finished, you need to cut and weld the bends in the 4 x mega's and then weld on the brackets. Then get the damn things ceramic coated.

I think that the VFR/poor RC30 will be easier than the CB to build as the CB has a modified and re welded frame to allow head removal, complete bead blast and engine / frame respray, bits machining, seat remolding and a heck of a lot of polishing etc. It was a full restore, whereas the parts for the VFR should be in far better condition with just the replacement of most bearings etc.

The hard bits on the VFR will be things that I cannot do, like cylinder re boring and yoke machining (doubt I can do the yokes although I do have access to a good mill and lathe).

For that I know a firm that are pretty spot on as they have done engine work some pretty good race teams.

 

im planning a similar project with an 86 model, just procured a spare engine to do the work to, ive been looking at other pistons that could be used, not sure of crown heights but i think that the cbr range is possibly the way to go, just using the figures i can find on the net ive got the 929 pistons giving 836cc and right up to the cbr1100 giving 952cc's on standard stroke so i think its a case of how much do we want to spend and can we physically get the pistons into the engines before they burst into a waterway/oilway? i think liners are defo the way to go, then its a case of head work and improvements on fueling and exhausts. im thinking of adopting the twin outlets like a motogp bike, and doing away with the airbox in favour of cone filters, then setup and tune to get the best output. im also putting my fat girl on a diet, i want weight down to 180kg which i think is possible, but all this will have to be done on a budget and i will be doing suzzy and brake mods first cos i think thats where this bike falls down most.

keep me posted as to any info you find out and if i find any i'll pass it on to you.

 

TTS used to have a drive in/drive out big bore deal in the late 90's when I lived in the UK, from memory it was like £850 or so

TTS Performance Parts Ltd

word was about 120HP and rumours of cooling issues

that said, you can get RC30 fairings from Motorcycle fairings, bodywork, fairing, seat, lower, fender, race tail, race body, rear hugger, fuel tank, air box, custom fairing and cafe racer;. but without the RC30 paint job, it will just be a boring custom VFR - go all in!

 

tts dont do the bits anymore as the bike is so old, they are onto gixxers and busa's now

 

i'm eyeing up a set of pistons from a cbr1100 blackbird, would take it out to 952cc's if i remember right, just need to find out crown height and pin size to see if they are comparable to the standard ones, wont hurt if i have to have the gudgeon pins either rebushed or the rods rebushed or if i have to have a bit of meat taken off the top of the crowns but if its too much then its no good so if anyone knows can they let me know please as i might be on to a winner here

 

are you planning on getting the bike down to 180kb wet or dry? because 180kg=396lbs and thats redicufuckinglously light.

your specs are:

Dry weight 199 kg 439lbs
Wet weight 230 kg 507lbs
Frame weight 14 kg 31lbs
Engine weight (dry) 77.3 kg 170.5lbs
Fuel Tank 20 litres

so 31kg or 68lbs for the wet
plus 14kg or 31lbs for the frame
plus 77.3 or 170lbs for the engine

equals 122.3kg or 270lbs
that leaves you with 57.7kg or 127lbs

for wheels, tires, shock&forks, swingarm, plastics, radiator etc...
i dunno, i guess its possible if thats your dry target.

all these numbers are giving me a headache....

 

well i was going for wet, but with those figures i think i might struggle, dunno though i'll give it a damn good go and see what happens, as is im getting rid of the subframe clocks lights massive exhaust massive seat and anything else that won't let me fit the cbr stuff, then its front end upgrade, rear end upgrade (might be onto some magnesium wheels) so i think it will be close but ive bout a pair of scales to be sure anyway

 

cool keep us posted

 

I cant find the post, but I hear the CBR 929 pistons will work as a big bore kit on the 800's

 

lol i havent been able to find any post since the site was revamped...
anyways i think its possible, but at the least its deffinetely going to need cylinder liners and an upgraded cooling system.

 

yeah ive heard that the 929 pistons have been used and checking the figures i can find on the net, it would take the 750 to 839cc which isnt bad but i cant find any info on crown heights or pin diameters so im a little reluctant to try it just yet. i was looking into the whole moto gp look and im seriously considering upgrading the rad to a much bigger unit, something along the lines of filling the whole of the v piece of my fairings, options so far are to use a ducati v shaped oil cooler at the bottom and something like an r6 rad or maybe a zx10, but as im unemployed and building this on a budget (which means learning to do carbon fibre and fabricating everything myself, which is ok as i used to be a fabricator) but i have made a few budget buys that may just help the project along like front bodywork from a cbr1000rr 05 (race so no holes for lights, they will come later) for £50 and a 5.5" rear wheel (i know its going to be tight but i recon i can make it fit, i have a big hammer and an angle grinder!) which came with tyre for £35 delivered. ive also just bought a full ss bolt kit for the engine for £13.
so as details come together i will post them up, might even start my own thread!

 

wait... this isnt your thread? lol