JLSP305 – 300cc 5 cylinder Honda by Jean-Luc Borgetto

JLSP305 by Jean-Luc Borgetto - Honda 300cc 5 cylinder

JLSP305 by Jean-Luc Borgetto - Honda 300cc 5 cylinder

JLSP305 Honda 5 cylinder rear view - 5th exhaust is high on the right next to the rider's leg

JLSP305 Honda 5 cylinder rear view - 5th exhaust is high on the right next to the rider's leg

How many of you know of the 125cc Honda 5 cylinder racer ridden by Luigi Taveri in 1966? It's a truly fascinating bit of engineering. Jean-Luc Borgetto, who we last wrote about way back when he built the JLS503, a 500cc 3 cylinder racer, inspired by the MV Agusta 500 GP bike, has built another beauty.

His new bike, the JLSP305, takes inspiration from the 125cc 5 cylinder, looking like the original in every way, though the JLSP305, a 300cc 5 cylinder brings more displacement to the table. Of course, to build this bike, he needed an engine and since there are no 300cc 5 cylinder engines anywhere, Jean-Luc had to build one himself.

JLSP305 cylinder head

JLSP305 cylinder head - click to enlarge

It took eighteen months to build the bike and it looks absolutely superb. He says the DOHC engine should rev to about 20,000 rpm. The exhaust is split for cylinders 1 and 2 on one side, 4 and 5 on the other with the number 3 exhaust wrapping around the engine and exiting high and next to the rider's leg on the right, the same as on the original racer.

JLSP305 bottom end and transmission

JLSP305 bottom end and transmission - click to enlarge

Jean-Luc neglected to tell me exactly what engines he started with when he sent me the note about his new bike. I'm a bit curious and I'll let you know as soon as I find out.

UPDATE: As Todd guessed in the comments below, Jean-Luc confirms the engine is a Honda 250 CBRR (1980 to 1987 only available in Japan, NZ and Autralia, a few in England and USA but nothing in France). Welding on one more cylinder, he made a new 120 degree crankshaft, cylinders 1 and 5 together, 2 and 4, and then 3. He also made two new cams. He built the frame following a photo from the Motegi Honda Museum. The brakes are Honda replicas from Hungary. Carburetors are Keihin CR.

Link: Jean-Luc Borgetto

Be sure to check out the video below.

Comments

  1. says

    i say, “just spectacular.
    Wy building such a thing ? Becaus it can.

    My project is,
    Building a Yamaha racer like “yes, here we are again” the 500 cc 4 stroke MV Agusta.

    The build has to be exactly as Yamaha would have done herself, back in the days of
    the “roaring sixty’s / seventy’s”.

    So, i’m gonna take a XS 750 ( triple) engine, bring it back to 500 cc and waist the cardan drive to change it to chain drive.
    Further the revs need to improve to ‘let’s say about 12 to 16 K. (if possible)
    The engine as a hole needs to be tuned.

    Then the frame, gastank seat, and so on need to be like the Yamaha racers from that era.
    Such a bike never excisted, and that my friends is enough to take on this project.
    Imagine that sound, intake and exhaust, yeah, like a MV.

    Mind you, this project can take a while before it’s finished.
    The planning counts years instead of months, so to speak.

    Floris Fleddérus.

  2. B50 Jim says

    Stunning! It sounds like the Mountain Lion from Hell! I love jewel-like, complex engines that are built to top standards… and the odd number of cylinders makes it even better. Can’t wait for the video of it on the track!

    • Steve says

      On the track? YES!!
      I anxiously await video updates of that banshee going up through the gears.
      Paul… are you listening?

  3. Jim Kunselman says

    Wow! What a snarl! B50 Jim is right about it being the ‘Mountiain Lion from Hell’.
    Good job, Jean-Luc.

  4. Rich says

    Okay – now I understand. At first I was imagining he developed this thing from scratch – just some CAD software or drawing table and lots of ambition. I was picturing an air-cooled successor to the sixties engines. Mind you, I am not downplaying what Jean-Luc has done. It is stunning. But a bit more fathomable as something the dedicated, fanatical enthusiast could actually accomplish. It is a great feat and I salute Mr. Borgetto for this incredible accomplishment.

  5. joe says

    Great project ,and superb finish ! I saw the original multi cylinder Honda factory bikes racing and they sounded totally awsome.great work Jean-Luc.

  6. Paulinator says

    Damn!!! The vid makes my little computer speakers pump out 3D sound.

    Is there extra material added to the #3 reciprocating/rotating masses? Or maybe to all the other running mates? If the engine can make 20 000 rpm with the longer crank it must be very well tuned against harmonics…or naturally immune.

    Beautiful craft…

  7. GuitarSlinger says

    I’m not usually much of a fan for the Classic RepliRacer genre but this bike is stunning .

  8. Dano says

    Thus one sounds as though it has a ton of torque for a 300. The only other multi-cylinder that produces a sound sweeter than this one is the 250 / 6 cylinder that Honda made. It didn’t have the torque, it appears this one has…but it certainly had the RPM’s.
    Wonderful work of art…beautiful!

  9. frogy6 says

    If it was made from a cbr 250 that had a 20k rev limit so if his work is good it should still have a 20k limit.

    To the above comment. No it wouldn’t have torque. The original 250 engine was a revy bastard and made its power high. Adding cc’s with a extra cylinder won’t make it a torquey engine.

    Nice work though

  10. says

    That is one heck of a wild and fun looking bike. Gives me those old butterflies in the belly feeling. Building the power plant took lots of thinking.

  11. Sick Cylinder says

    I beleive the rev limit on the original CBRR 250 four was 22,000 revs so 20,000 revs for this example sounds possible.

    Guy Coulon used the same engine to make a six cylinder 300cc bike which has previously been featured on the knee slider.

    I would be interested to know why the builder used 120 degree cranks – wouldn’t five cranks spaced at 144 degrees be the norm for an inline five – or did he get the crank from Guy Coulon?

    Great work and thankyou knee slider for another stunning and technically interesting project.

    To the guy considering using an XS750 engine for a GP replica project – good luck !

    • identiti_crisis says

      I’d always read that Honda made their 5 cylinder motor from a triple and twin, sort of stuck together (that’s the best info I’ve been able to come across, anyway.)

      Since a triple has 240° firing intervals, you end up with a 120° crank; similarly, a 5 cylinder engine has 144° intervals, but you end up with a 72° crank, because of the overlap into 720° (four strokes). Prior to seeing this, I would have expected the “twin” part of the engine to be one of Honda’s 180° jobs.

      But this is clearly not a triple and a twin, it’s more like a six-cylinder crank with one of the middle cylinders removed. The straight six crank is just a triple mirrored about one end, with three pairs of throws offset at 120°. The missing cylinder here means it’s uneven firing, like a six with a blown plug. It was probably a bit rougher running than an even five or six, but it sounds great, so it’s well made up for!

      Perhaps the effort required to find a safe even-firing (144°) crankshaft was too much for hand-calculations at that time, or maybe even impossible given the materials, required engine speed and rider vision. So instead they stuck to a known quantity to avoid the hell of trying to find the crank that least wanted to shear itself lengthways at 20k rpm…
      That said, the missing central cylinder will have introduced an up-and-down shake to the engine, although only of the same order as a 25cc single (or 60cc in this particular case).