Before I get going on the MK5 I need to tell you about the MK4 , which is hot off the production line!, It ran for the first time on 1st Feb
It's a superdream 250 fitted with a kubota z482 500 cc twin cylinder . It's fitted with an RHB 31 turbocharger and intercooler. Transmission via CVT made by comet extracted for an Axiam micro car. Rear drive via tooth belt and pulley.
I have only driven it around the playground so far and its too early to report on performance . I have a non turbo version to compare it with. More news to follow.
I successfully failed to report the development of MK 4 so I will try harder on the next build MK5 which will start in the next few weeks , to be ready for the big knock event.
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MK 5 Engine kubota d850 850cc 3 cylinder
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MK 5 Engine kubota d850 850cc 3 cylinder
Kubota Honda MK 5
MK5 will be a Superdream fitted with a cvt transmission , toothed belt rear drive. The engine is a Kubota 3 cylinder 850cc engine. I have a concern if the total lager overall weight will still make it a good ride ?
I will try and plot its development as it unfolds ......... More to follow........
True but even with twin discs, there is still less stopping power than a good twin piston sliding caliper. I ended up making a bracket and fitting yzfr125 Nissan calipers, even with half the pad area they where twice as powerful
Tim wrote:... I have a concern if the total lager overall weight will still make it a good ride ? I will try and plot its development as it unfolds ......... More to follow........
This is why I gambled by going with the D722. It is nearly 50lb lighter (83kg range vs 63kg range for D722). With the IP fuel turned up on the D722 output should be just less than a stock 850 to 900cc. Add Turbo and and should be equal to these larger engines but still significantly lighter. All in theory of course. Very much look forward to reading about your progress and experiments with your bike.
PS- are you sure the Axiam CVT you have is Comet? I thought they were CVTech Products out of Canada ?
alexanderfoti wrote:Ibthink the 850 might make the super dream too heavy. The brakes aren't great in the first place
Hi Alex , luckily I am an oldie and grew up with British bikes and their poor brakes , more speed retarders than brakes . I recon it will cope but the MOT requirements may force a reengineering of the brakes!
Cheers Tim
alexanderfoti wrote:Ibthink the 850 might make the super dream too heavy. The brakes aren't great in the first place
Hi Alex , luckily I am an oldie and grew up with British bikes and their poor brakes , more speed retarders than brakes . I recon it will cope but the MOT requirements may force a reengineering of the brakes!
Cheers Tim
heh true, that was my experience with the superdream as well
Tim wrote:... I have a concern if the total lager overall weight will still make it a good ride ? I will try and plot its development as it unfolds ......... More to follow........
This is why I gambled by going with the D722. It is nearly 50lb lighter (83kg range vs 63kg range for D722). With the IP fuel turned up on the D722 output should be just less than a stock 850 to 900cc. Add Turbo and and should be equal to these larger engines but still significantly lighter. All in theory of course. Very much look forward to reading about your progress and experiments with your bike.
PS- are you sure the Axiam CVT you have is Comet? I thought they were CVTech Products out of Canada ?
Hi your spot on its CV Tech and not comet, thanks for pointing that out . On the MK3 bikes CVT I wanted to improve mpg and have changed the front spring for a much lighter version and now it holds the engine at round 2000 rpm . You loose on power but hay if it was about speed I wouldn't do diesels !
Eddy Wane wrote:Hi Tim.
Lovely looking bike. Do you have any build info (measurements etc) especially CVT / swinging arm area.
Hi
The rear drive is the starting point and I have used a preferred size rear belt and pulleys therefore their is no modification to the swing arm and in indeed the only frame modification is shortening the front down tube by 35 mm to clear the starter .
The CVT centres I think is 345mm but I would need to check on my jig first. I have made simple gauging jigs to help line things up and this one will prove if they are any good!
As yet I haven't proven the design ie ratios, balance , Mot etc and It wouldn't be wise to copy this until its clocked some miles!
Cheers Tim
The MkIV looks very organic to me, perhaps even more so because of the exposed CVT. A shame you can't leave it like that or it will wrap your left trouser leg (and you'll be lucky if it's just the leg of your trousers) around itself.
Is there any way for you to design a CVT cover mimicking the optic of the naked CVT as closely as possible? If not from tin, then maybe a cover made from some sturdy yet transparent plastic, acryl, silicon? (All of this, of course, assuming you are building MkV from another Superdream and not from the MkIV.)
Another thing to be aware of if the weight has increased a lot you will probably be replaceing the front fork seals on a regular basis. This can be solved quite easily by removeing the top nuts and fitting a spacer or making new longer spacers in my case. I had fitted 3 sets before someone put me right.
Blunt Eversmoke wrote:The MkIV looks very organic to me, perhaps even more so because of the exposed CVT. A shame you can't leave it like that or it will wrap your left trouser leg (and you'll be lucky if it's just the leg of your trousers) around itself.
Is there any way for you to design a CVT cover mimicking the optic of the naked CVT as closely as possible? If not from tin, then maybe a cover made from some sturdy yet transparent plastic, acryl, silicon? (All of this, of course, assuming you are building MkV from another Superdream and not from the MkIV.)
Hi
I think your views are spot on, I aim to fabricate something along your lines of thinking tomorrow and will post up the results.
MK5 will made from another Superdream as I would like to make comparisons between a range of version!
Cheers Tim
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Close up of the CVT guard .
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As mentioned keep it organic! Belt guard made from Cedar.
Looking good, both right (love the wood lol) and left side. Now for a cover for the front CVT pulley, you really should think about forming one from transparent acryl, and keep it as form-tight to the pulley as possible, so that will keep the puristic style.
Thanks both for the feedback I really appreciate it , and if you hadn't mentioned " an organic look" I wouldn't have thought of using of wood . I could investigate forming a acrylic transparent cover but I'm not a big fan of plastics. I guess if other persons want one it might be worth it . Also I am not sure if it would fit in the vacuum forming machine!
Cheers Tim
Disclaimer
Please note the bling blue lights on the radiator coollng fans are not by design, I forgot to remove them from the fans before fitting them and now I have to drain and remove the radiator to get to them.
Thanks for the thumbs up ! hopefully I will be there with 3 diesel bikes!
I have not yet had the MK 4 turbo on the road as I haven't be able sort sensible insurance . I have fitted a boost pressure gauge and at idle the needle fluctuates into the vacuum or negative pressure , understandable as the turbo is really not working at idle. At max speed the pressure rises to a max 8 psi but holds steady at 6 psi no load . I am unsure as yet what pressure the waste gate springs in action as I can't find any specs for the car it came from ,Suzuki cappuccino ? Any ideas other than pressurising it to test it?
The boost is around 4 psi at approx 3000 rpm no load
Last edited by Tim on Wed Feb 19, 2014 6:34 pm, edited 1 time in total.
Great, Tim, I will be there with my contraption hopefully. Fingers crossed, I lost 4th gear recently, and going down from 3rd went straight back to first...
I thought the shifter pawl had cracked on the end, but dismantling the box shows no damage at all... No idea, hoping its grit, got a new gasket on the way and I will re-build it. Just to go re-weld a mount and I will will be ready for the next big nock.
Any chance I can test out a couple of your new builds there? When is the new big knock?
Hi Alex
Try a CVT , no more gearbox issues and outstanding in traffic or city driving! Be sure to try it out at the Big Knock you may even become a convert!
Cheers Tim
Tim wrote:Hi Alex
Try a CVT , no more gearbox issues and outstanding in traffic or city driving! Be sure to try it out at the Big Knock you may even become a convert!
Cheers Tim
My understanding is (which may be flawed understanding lol) By the time you take into account efficiency in keeping engine in the power band your overall efficiency of the vehicle is higher with CVT tranny even though you have a small margin of less efficiency in the CVT compared to a geared one. Also much easier to maintain.
Last edited by coachgeo on Mon Feb 17, 2014 7:07 pm, edited 2 times in total.
The engine is always operating in the correct powerband with a CVT and is less strain on an engine which was designed for constant revs.
Where it loses out is you can't trickle along at low revs in a high gear to save fuel.
They are also useful as they don't take up much room if that is a problem.
The use of a CV Tech/microcar type CVT means the belt/components will last a long time especially on a lower powered single cyl engine but I believe even on a Kubota Z482 Aixam car the belt life is 11000 mls so a lighter bike should be longer.
Tim, if you keep this up, yours might be the first entry in the "YOUR DIESEL MOTORCYCLE BUILD PLANS" thread here on the board. Not to trivialize your fine work in any way, but you've come about as close as anyone to plug-and-play.
gilburton wrote:The engine is always operating in the correct powerband with a CVT and is less strain on an engine which was designed for constant revs.
Where it loses out is you can't trickle along at low revs in a high gear to save fuel.
They are also useful as they don't take up much room if that is a problem.
The use of a CV Tech/microcar type CVT means the belt/components will last a long time especially on a lower powered single cyl engine but I believe even on a Kubota Z482 Aixam car the belt life is 11000 mls so a lighter bike should be longer.
Hi
I agree with your reasoning and think the CVT system is reasonably efficient. The lack of mpg is due to the engine running outside its fuel efficient rpm . I can verify that if the CVT was inefficient say loosing 1bhp for instance this lost energy would endup as 750 watts of heat . Most of the time the CVT is running as cool as a cucumber , just Luke warm .
I have found that by reducing the spring force on the front pulley allows it to keep the engine rpm around 2000 rpm , of course you lose performance but it's about the mpg for me .
Unfortunately the CVT also holds the engine speed constant on the overrun giving excessive engine braking and if you jump to the Primary and secondary drive thread you can see I am pouncing about with a one way drive or ratchet like a bicycle to see if it ramps up the mpg!
Last edited by Tim on Tue Feb 18, 2014 7:11 pm, edited 1 time in total.
pietenpol2002 wrote:Tim, if you keep this up, yours might be the first entry in the "YOUR DIESEL MOTORCYCLE BUILD PLANS" thread here on the board. Not to trivialize your fine work in any way, but you've come about as close as anyone to plug-and-play.
Hi Ron
Yeah but you have to like Honda superdreams, CVTs transmissions and kubota engines all mashed up together !
Cheers Tim
