OzVMX Forum
Clubroom => Bike Talk => Topic started by: Marc.com on May 02, 2009, 10:32:15 pm
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what is it
(http://i245.photobucket.com/albums/gg71/marcFX_photo/Afbeelding476.jpg)
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something odd like cr125/250m in a 77 78 yz frame perhaps thanks Michael. :)
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VERY DIFFERENT, NICE.
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Converted using all Honda bits, I reckon. Swingarm is more Honda than Yamaha, once you look beyond the obvious.
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Nice conversion, interesting 8). Where did you pick up the pixie Marc. It a backyard or shop conversion isn't it?
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looks kind of like the Kramer monoshock setup from way back when. Have seen the setup on Maico's and also most famously on the Marty Moates XL350 based KS1 Powrell 450 racer. ???
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The Dual shock is remeniscent of the Kramer Maicos. Swingarm does look a bit home made but not a bad job at all. probably works well.
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looks like th yz125 c or x i just bought same donk and frame swingarm but honda tank and seat
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Its all Honda except for the swingarm. Maybe a clever back yard job. Looks quite good.
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looks like th yz125 c or x i just bought same donk and frame swingarm but honda tank and seat
is the YZ running twin shocks, looks like someone had been there before KSI.....apart from Vincent
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So do you know the history Mark? As i am interested.
looks like th yz125 c or x i just bought same donk and frame swingarm but honda tank and seat
Hmmm. I think you need to put them glasses on mate. Its basically a cr with a back end mod. :)
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It seems all Honda like Nathan said and appears to be a pretty good backyard conversion. I doubt it'd be much of an improvement over the original as the front end seems to be untouched. It's a cool unit though
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Maybe that's a Franks honda??? ???
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Maybe that's a Franks honda??? ???
I think that sounds close, it is definitely not backyard job. I would like it.
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If it was a Franks honda or similar wouldn't you think they'd make a whole new frame? That appears to be the original honda frame.
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could be replica of Franks replica, wow makes you wonder why Honda didn't do that in the first place
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wonder why Honda didn't do that in the first place
my guess would be patent/royalty questions. Didn't Yamaha hold the patent (ex Tilkens) at the time?
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could ask Suzuki the same question Luke but either way they all went on to built world championship winning bikes ;)
(http://www.mxworksbike.com/Suzuki_Cantilever.jpg)
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If it was a replica or special monoshock frame it wouldn't have the top shock mounts on it would it...
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Japanese are funny with patents, the Yamaha monoshock looks exactly the same as what's on a old Phil Irving designed VINCENT (http://www.thevincent.com/vinmodel.htm) . I wouldn't have paid Tilkens 1 cent as he didn't invent the cantilever monoshock but only reinvented it. Like Honda and the single sided swing arm that they paid fortunes for, when the Ducati 916 emerged with a single sided arm, Honda's patent lawyers couldn't get to Ducati HQ fast enough.Claudio Castellegoni invites them down to talk about it, ushers them in, coffee and amoretto's, half way through the lawyers 'we're going to take you to the cleaners' speil, he jumps up opens the blinds and says "Look at the beautiful view from my office", just so happened there was an old 50's Guzzi with a single sided arm spoiling the view. ;D Single sided arms appeared on lots of bikes after that.
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Tilkens offered the monoshock system to Suzuki which they tested before rejecting it. He then offered it to Yamaha and the rest is history. The photo probably comes from Suzukis test period with the system.
Lozza, Tilkens did indeed copy the triangulated swingarm idea from Vincent but that was only part of the deal. Tilkens single gas shock was a radical departure from the Vincent twin shock concept and is the meat of Tilkens invention. Kramer, Cheney and KSI are more like the Vincent idea than the Yamaha monoshock system.
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Hey Firko,
From memory Tilkens actually built his prototypes around the CZ platform and he used a Citroen car shock absorber.
The entire monoshock thing really wasn't that radical [much more of an evolutionary adaptation of previous systems] and required more compromises than really necessary in a great design. It took Yamaha years to really make it work, but by then it was obsolete. But it certainly gave the bikes a unique look and gave the marketing men something to talk about.
That should get the Yamaha guys typing.
VMX42
P.S. just for the record [before they string me up] my favorite Works Bike is Hannahs 0W40. Does that get me off the hook??
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Absolutely right Jeff. I've got a photo of one of the CZ prototypes here somewhere in my disorganised "other shit" photo file. I'll try and dig it out.
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Tilkens single gas shock was a radical departure from the Vincent twin shock concept and is the meat of Tilkens invention. Kramer, Cheney and KSI are more like the Vincent idea than the Yamaha monoshock system.
hardly call switching it up to one shock a radical departure. Tilkens didn't invent shit that hadn't been tried before. BTW if Honda were that worried about intellectual property issues they might like to compensate Triumph for the oval piston twin conrod design in the NR750.
welcome back Firko, nice to have your rather extensive knowledge back in the house.
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Marc..It's not so much a radical departure but different enough to be seperated from the twin shock Vincent design. I agree that the monoshock wasn't any better than any of the more advanced twin shock designs but it was a step into the future (using technology from the past). Thanks, it's nice being back.
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Nobody paid much attention to Yamaha's patent,I can only find Hakan Andersen's 73 YZ 250 as the first monoshock , HERE (http://www.getphpbb.com/phpbb/viewtopic.php?t=1429&mforum=2stroker) Nico Bakker is making cantilever/damper in spine frames. Maybe tzeggy can post some pics of aftermarket monoshock TR/TD/TZ frames(Exactweld??) which all seemed to have monoshocks.
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Rather than posting the photo of Lucien Tilkens CZ prototype here's the link to it on........
www.mxworksbike.com/Tilkens_mono.htm (http://www.mxworksbike.com/Tilkens_mono.htm)
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Monoshock wins because of the larger valve piston area (to put it into really simple terms). Not sure if the seperated oil/gas set-up was at all common in the pre-Yamaha-monoshock days either - but it is also another win.
We can discuss the merits and originality of the original Monoshock's execution (particularly the placement in the frame), but it was a step foward purely because it used superior technology in the shock absorber itself.
(As an aside, the geometry of KTM's PDS is broadly similar to that of most twin shock Evo bikes - despite the torsional loads it puts on the swing arm, meaning that extra weight that has to be built into the swing arm, they still chose to use one shock with a 46mm piston - just like Yamaha/Tilkeins did 25 years earlier.)
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In my opinion Horst Leitner, the developer of the KTM single sided linkless suspension was an even greater inovater than Tilkins. His ATK bikes used an almost identical suspension setup to that of the KTM back in 1985. He's a pretty smart cookie as the following shows.
http://www.motocrossactionmag.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=DEECF290064245968723324C25A0976A
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In my opinion Horst Leitner, the developer of the KTM single sided linkless suspension was an even greater innovator than Tilkins.
hmm so Horst forgot to bolt on one shock and invented counter shaft mounted front brake that work like hell, not to mention using 4 sprockets where 2 were doing the job, having been near a 406 the parts that didn't work were the rear brake and A Trak. America has a Hall of Fame for everything. BTW I think the later single sided chassis wrapped around the 604 was much under rated and a really good thing.
Sorry Firko i am not convinced about a major hall of fame worthy leap forward happening at ATK.... however it did happen.... at Hamamatsu cho when the 'Full Floater' rolled out the door and made everything that had gone before it look like a joke. Old Tanaka san in Suzuki's chassis department probably got and extra 10 000 Yen in his bonus and will never be a Hall of Famer, but Honda are still borrowing the floater for their GP bikes to this day. true rising rate and the shock being compressed from both ends....whiskers that's radical.
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Fair enough Marc but my point is that he developed the suspension that KTM called such a radical innovation 16 years earlier on the ATK. I own an ATK and admit the countershaft rear brake is a wank but they're a much better bike than you give them credit for. I agree the Full Floater was a pretty good step forward and did make all of the other linkaged suspensions look a tad underdone at the time. Kawasakis similar Uni Trak wasn't bad either.
Sorry for wandering off on a thread tangent. That Honda at the beginning of the thread may indeed be one of Kelvin Franks experiments. Can somebody check with him? He's home with some crook knees from being run over by a hit run driver.
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There should be an article on a Franks Honda 125 in Issue 39 of VMX and I've been liaising with Kelvin on and off the last few months. I'll ask him about this one as well. He has already mentioned that the first couple of Franks Hondas he did utilised the majority of the existing Honda frame while later versions had a whole new frame.
However, of all the pics I've seen of his versions, none of the swingarms look like the one in the photo at the start of this thread.
Ken
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Good call Firko - Horst Leitner will be remembered as one of the few great innovators of the late 20th century.
Fans of Douglas Adams (Hitchhikers Guide to the Galaxy, Dirk Gently) will probably remember his cat door allegory. The simple version is that we can all look at a cat door and say "Yep, that's really simple and really obvious" - but its only obvious after someone else has invented it. That 'someone' must actually possess an exceptional brain, even if its easy for Joe Average to dismiss their inventions as obvious.
Virtually every step foward in the world of dirt bikes is the same.
I mean, how easy is it to sit back and look at our pre-75 bikes and wonder why the hell it took so many years for someone to 'invent' long travel suspensions?
Or wonder why we finally adopted disc brakes, decades after cars had proven that they were a zillion times better?
Etc.
Stuff like the old Suzuki Full Floater were obviously big steps foward, but - like the Tilkeins monoshock - weren't completely new, and used existing ideas adapted from elsewhere and modified/added to them.
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Suzuki just straight out nicked the floater from Nico Bakker and Bimota(Bimota made frame for the TR500) who had rocker arm rear suspension, in about 76 ;D Yamaha seemed to have copied that big bulb on the end of the mono shock also ???
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I own an ATK and admit the countershaft rear brake is a wank but they're a much better bike than you give them credit for.
Hey Firko don't get me wrong I have owned one, also I am fan, looking for 604 at the moment. As I mentioned I think their take on the single sided shock and frame was really something, and you got the best parts, suspension, hubs etc into the deal. Like getting a KTM 520 5 years early ;D
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Back to the original post - it looks all 73-74 honda to me too (except for obvious swingarm mods). A couple of things make me wonder if its actually based on modified MT frame w all excess brackets removed. The backbone extends further down towards swingarm pivot (like MT frame) to allow room for top of shocks & top mounts. Rear frame/mudguard loop is CR style but looks longer than std CR so could be cut-down MT loop. Most likely its modified CR frame tho.
I actually did a very similar mod to my brothers CR125 in 75, & built an up-pipe to go w it. It was a relatively straight forward mod on the std CR125 frame & it worked quite well. But I wondered if the frame would have cracked & kept cracking if we kept it that way since the original frame wasn't built to take forces in those directions. No doubt, swingarm was more rigid (a boost for an Elsie) but it was heavier & w the weight up hi (the bane of that whole system) it was no better than other LTR mods we'd tried, so we reverted back to lay-down shocks & lived happily ever after.
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But I wondered if the frame would have cracked & kept cracking if we kept it that way since the original frame wasn't built to take forces in those directions.
I think when you consider how half assed welded, thrown together motorcycle chassis were in the day then actually your margin for them not cracking must be pretty high, with the KSI replica I decided to tackle this by placing the shocks very close together and making the top mount a double shear, that way you spread the load across as much of the frame as possible, guess we will see.
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Marc,
I wasn't referring to yr 'KSI'-XL. The XL-S frame is much more robust than a flimsy 73 CR125 frame.
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Hi,
Most of that bike seem to be a M1 or M2 CR250 ,'75 '76
M2's had exhaust out left hand side of barrel and an up pipe,
and a lower engine cradle.
interesting anyway
cheers
Noel
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Noel an M1/M2 had moved forward top shock mounts, this bike has the mounts the same as the M and they all had a lower engine cradle.
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You could be right,I'm not positive
the top mounts were moved a bit but I thought most of the movement was along the swing arm,
the M1 and 2 had the lower engine cradle, lowered and the engine moved forward as well, was what
I was trying to say
cheers
Noel