no airbus?

Discussion in 'General VFR Discussions' started by Phil Clark, Oct 12, 2018.

  1. Phil Clark

    Phil Clark New Member

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    Can anyone help? I have fitted an RC36 engine in an RC30 frame. There's absolutely no room for an airbox as the carb bell-mouths are about 2" from the bottom of the fuel tank. The carbs are standard RC36 34mm flat slides. I know this is far from ideal. My question is: will the carbs function OK? I know my early Honda RS1000 carbs (off a CB1100R) won't close the throttle without extreme modification because they need the airbox. Are the RC36 carbs different? Any advice extremely welcome.

    Incidentally - my RC30 tank is a special HRC one which has two huge air tubes welded through (like the RC45) so I don't think my carbs will suffer from lack of fresh air.
     
  2. popkat

    popkat New Member

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    I guess this is a track bike yes ?, It should run fine with no airbox but you will need much bigger main jets, possibly bigger idle (slow) jets too but it will run on stock idle's, you will need to adjust the mixture screws to allow more fuel.. On my RC24 with no airbox i'm running around 150/152 main Jets (keihin jets) I think standard jets were 118/122 so quite a big jump, your idle jets will most probably be 38, so you could be looking at something like 42 if you want decent low speed running. A dyno set up will help perfect the jetting, find someone who is good with carbs.
    Try to modify the airbox base to fit so you can use the mesh to cover the carbs and protect them a bit from dirt and stones, also would be worth putting a mesh in the air tubes.
    Lastly it will be very loud inside your crash helmet, a bit like a motogp bike, 4 open carbs below your chin, lovely :)
    Hope that's of some help.

    .
     
  3. Phil Clark

    Phil Clark New Member

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    Thanks - this is very helpful and gives me a starting point - cheers
     
  4. John carnahan

    John carnahan New Member

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    I also found my 91 VFR750 needed the airbox/filter the hard way. I was like a dog chasing it's tail couldn't figure out what was wrong. Wouldn't rev. over 4K. Then my mechanic friend(he and I had gone over/cleaned the carbs)asked if I had put the airbox on? No. He told me to put it all back together and go ride. I did and it worked fine.

    He explained. These bike are closely tuned. They run on a 14-1 air/fuel ratio. W/O air cleaner/airbox it will run (or try to run) closer to 16 to 17-1. Too much air, therefore needs more fuel.

    I guess,

    Jack
     
  5. Phil Clark

    Phil Clark New Member

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    Thanks Jack. I have so little clearance under the RC30 fuel tank - so little chance of any air box. Does anyone happen to know if RC30 carbs will fit on the RC36 engine? Race RC30s ran without air boxes.

    I guess I'll find out when I get it running!
     
  6. popkat

    popkat New Member

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    you won't fit RC30 carbs in the V, it's been tried and they won't go, also they would be very expensive.. As I said it will work with no airbox but you need to jet it correctly, my jets I listed earlier will work initially and well enough to get it running but you then need to get on to a rolling road/dyno to get it perfect.
    Keep us posted on how you get on, and some pictures would be good, i'd like to see what your building :thumbs:


    .
     
  7. Phil Clark

    Phil Clark New Member

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    Thanks once again. I will post photos if you're interested when I have something to show. I bought an ex-Suzuka 8-hour race RC30 frame, swinging-arm, tank, forks and other stuff. I don't have an RC30 engine and not prepared to pay the going rate for one (I have other Honda race bikes including an RS1000 rep., P&M, Dresda and Joey Dunlop's CB1100R). My plan is to build a bike that I can ride without scaring/killing myself - 100 bhp is enough if the bike is not too heavy - I am 65 y/o now. I have standard RC30 wheels now and have got discs, footrests, bodywork and other stuff. I picked up a fairly low milage RC36 engine for the price of an RC30 gasket set. I've now taken the frame to a top guy in Holland to remove some dents - he races in Moto 2 and tunes engines, makes some brilliant exhaust systems (in titanium or s/s), has a good dyno and fully understands carbs. He will be making the exhaust and sorting out the carburation. I shall be using an Ignichech racing ignition system which matey from Holland will set up. The grand plan is to build a "Suzuka 8-hour" replica thing. Incidentally, I'm British but live in Germany!
     
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  8. popkat

    popkat New Member

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    Wow some cool bikes you've got Phil, would love to see some pictures of them. the RC30/36 project sounds like it could be a good road bike. I don't have anything like the exotic bikes you have, wish I did. I have my VFR750 race bike, and a Katana tucked away in my garage (long term project) I also raced a Suzuki Katana 1100sxz (very rare bathhurst model) for a sponsor and friend back in 2013/14 and won a couple of championships with CRMC. You may know some people I know or know of here in the UK ?

    .
     
  9. Phil Clark

    Phil Clark New Member

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    I do have some interesting bikes - sadly, they just sit and gather dust. I enjoy putting them together but lack the ability to ride them. I used to go to a lot of CRMC meetings but bot bored with all the new Manx Nortons, Rob North Tridents and such. The grid was packed with Hondas, Kawasakis and Suzukis when I used to watch races back in the days. Alan Cathcart always asks if he can race-test some of my bikes but as CRMC are not interested in letting them race, I keep them here under dust sheets. Always seems to me that CRMC is run by Manx/ G50 fans and isn't interested in proper classic racers at all. I'm friends with John Neate (Classic Endurance champion) and Ian Lucas (the chap who looks after the Howard Lees/ Team Bike/ That's Racing RC30s). They both help me a lot - that's why I ended up building the RS1000 rep. that is way too fast for me! Email me (philipclark2@mac.com) and I'll send some photos. I really rate the RC36 engines and think they would make excellent race bikes. RC30s are not so much more powerful, too fragile and way too expensive to race, in my view. John Neate now has some of the ex-Honda Britain RC30 stuff and is building them up to race. Interestingly, at the Spa Biker's Classic at Spa this summer, John's Honda CB1100 Harris was much faster than any of the RC30s and there were some top bikes and top riders there. I'm impressed with your racing history - I always loved Katanas.
     
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  10. popkat

    popkat New Member

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    Small world, I raced the Katana for Ian Lucas.. I'll send an email over.

    .
     
  11. popkat

    popkat New Member

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    CRMC is evolving, (a little) they now have a superstock class for VFR's, GSXR750's, FZ750's etc, there 2 superbike classes, a few big Kawasaki Z's. and some XR69 repilica's. They allow anything to parade and it would be good for your bikes to get an airing to blow some of those cobwebs away, I'd love to parade something for you, but as you don't know me I guess that's unlikely. Also you'd need to transport them from Germany which i would imagine would be a bit of a nightmare.
     
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