Honda Kubota MK5

[Tim]

So the weather was nasty but the excitement won the day and the MK 5 went for a very short test yesterday !
I love the sound and feel of the 3 cylinder engine but the cvt system isn't changing up correctly and the radiator is leaking for a tapping point . The front mudguard hits the exhaust when braking hard. So a bit more modification before the trials continue.

See the action on youtube. http://youtu.be/PtB_ZZWhXQ4

[gilburton]

Heavier fork springs and a less "boxy" mudguard??
The only other option might be to rework your exhaust in a similar design to your inlet manifold which would be a shame after the work you put in.
With your CVT I would go back to standard to see if that helps. Possibly your changes have made it too light ??
Otherwise nice looking bike. I wish I had the skill to turn out something similar
Just to add how does your twin compare and do you think,in retrospect, a larger bike would be better for the 3 cylinders??

[BertTrack]

Possibly it's slipping on the engine side when you put more power on it. The way it behaved when standing still and opening the throttle it didn't sound like it was putting on much load.

Any change in power into the c.v.t. should result in a feel of power on the road. If that's not synchronised you've got slip going on. I recognise it from the Track.

Is the belt pressed into the driven pulley when idle? I mean no slack and pressure on the plates and all that?

Oh and i love the way the Honda's look all dieseled up. Very nice one again!

[albertaphil]

I have the same fender clearance issue on my bike. I would imagine your Kubota is heavier than the original Honda lump. I built spacers out of pipe and stuck them in the fork tubes under the caps to preload the front suspension springs to compensate for the extra weight. It worked. My spacers are about 3 inches long. Any longer and I wouldn't have been able to get the caps on.

[Tim]

Heavier fork springs and a less "boxy" mudguard??
The only other option might be to rework your exhaust in a similar design to your inlet manifold which would be a shame after the work you put in.
With your CVT I would go back to standard to see if that helps. Possibly your changes have made it too light ??
Otherwise nice looking bike. I wish I had the skill to turn out something similar
Just to add how does your twin compare and do you think,in retrospect, a larger bike would be better for the 3 cylinders??

Hi
It seems the front mudguard is a poorly fitted aftermarket affair , I shifted it down on its mount by around 35 mm and this seem to have given sufficient clearance . If necessary I will beef up the springs as I would really like to avoid having to rework the exhausts at this stage as you pointed out . I agree the engine is tight fit however the major difference between the z482 and the d850 is a 100 mm width for the additional cylinder and the weight . In fact I fitted the 2 cylinder to it to save weight . The turbo version was more tricky and very tight on space.
Using the Super dream is an age related thing , I really really envied the superior engineering when I thrashing around on BSA star fires , c15s and it feels like cold revenge modifying then as fast as I can !
I am a bit lazy and all my templates suit the superdream making it a snip job to fit the engine as all the guess work has been done . Better the devil you know stuff .

[Tim]

Heavier fork springs and a less "boxy" mudguard??
The only other option might be to rework your exhaust in a similar design to your inlet manifold which would be a shame after the work you put in.
With your CVT I would go back to standard to see if that helps. Possibly your changes have made it too light ??
Otherwise nice looking bike. I wish I had the skill to turn out something similar
Just to add how does your twin compare and do you think,in retrospect, a larger bike would be better for the 3 cylinders??

Hi
It seems the front mudguard is a poorly fitted aftermarket affair , I shifted it down on its mount by around 35 mm and this seem to have given sufficient clearance . If necessary I will beef up the springs as I would really like to avoid having to rework the exhausts at this stage as you pointed out . I agree the engine is tight fit however the major difference between the z482 and the d850 is a 100 mm width for the additional cylinder and the weight . In fact I fitted the 2 cylinder to it to save weight . The turbo version was more tricky and very tight on space.
Using the Super dream is an age related thing , I really really envied the superior engineering when I thrashing around on BSA star fires , c15s and it feels like cold revenge modifying then as fast as I can !
I am a bit lazy and all my templates suit the superdream making it a snip job to fit the engine as all the guess work has been done . Better the devil you know stuff .

[Tim]

Possibly it's slipping on the engine side when you put more power on it. The way it behaved when standing still and opening the throttle it didn't sound like it was putting on much load.

Any change in power into the c.v.t. should result in a feel of power on the road. If that's not synchronised you've got slip going on. I recognise it from the Track.

Is the belt pressed into the driven pulley when idle? I mean no slack and pressure on the plates and all that?

Oh and i love the way the Honda's look all dieseled up. Very nice one again!

Thanks for that . I decided to swop the rear cvt unit from the turbo bike to see if the problem lies there . It is behaving just as you have detailed ie the engine maxing out rpm and the ratios not shifting up sufficiently quickly . I think I have assembled it with the spring 180 degrees out of place . Anyway before setting out for a test run I noted the electric water circulation pump had fried itself . Cheap Chinese junk, it's a magnetic drive and so it attracted oxides particles and jammed its self up . So I will hunt down a bosch pump built for the job , but till then am grounded !

[Tim]

I have the same fender clearance issue on my bike. I would imagine your Kubota is heavier than the original Honda lump. I built spacers out of pipe and stuck them in the fork tubes under the caps to preload the front suspension springs to compensate for the extra weight. It worked. My spacers are about 3 inches long. Any longer and I wouldn't have been able to get the caps on.

A ripping idea, did it stiffen the springs or lessen the fork travel ? Maybe a mix of both?

[sbrumby]

I had to do the same with the Vf750 fitted with the ruggerini 950. But not because of clearance because of the fork seals kept blowing. Just a word of warning the spacers will definately help and keep the fork seals in good health, another bonus is it will make it easier to get onto the center stand as it will sit higher, as long as the travel is restricted and it bottoms out before the mudguard hits te exhaust you are ok, but if it doesnt it is dangerous as under heavy braking you dont want the front end to lock up.

[albertaphil]

Good point about the wheel locking, Sam. I know that my fender hits the fuel pump when I push against the front brake while standing still. I haven't ridden more than 10 minutes to see what happens under moderate to heavy braking. Maybe I will have to dump the mech fuel pump after all. Everyone around here is telling me I dont need it anyway...

[gilburton]

I had to fit spacers to my already soft springs.
It worked well and was ok until I added a full fairing. Under normal braking it was fine but I had to do an emergency stop once and it left a nice dent in my nicely painted mudguard
What I did after that was, using ratchet straps and/or removing springs,compress the forks as far as they would go to see if they hit anything

[pietenpol2002]

Maybe I will have to dump the mech fuel pump after all. Everyone around here is telling me I dont need it anyway...

Might be different for the Rini, but Kubota requires either a mechanical or electric fuel pump in the interest of delivering a constant supply of pressure to the injection pump. And should you need it, I've got an electric one off the Kubota that you can have.

[albertaphil]

Thanks Ron. I actually have an electric fuel pump NIB ready for this eventuality. And I am going to have to replace the mech pump. After one pothole driveway my fender is all dented.

[alexanderfoti]

I had to fit spacers to my already soft springs.
It worked well and was ok until I added a full fairing. Under normal braking it was fine but I had to do an emergency stop once and it left a nice dent in my nicely painted mudguard
What I did after that was, using ratchet straps and/or removing springs,compress the forks as far as they would go to see if they hit anything

Funny that, we all have similar stories. My first super dream diesel grounded the metal fork out on the starter positive bolt under heavy braking. Took me a while to figure out why I was blowing 200amp fuses when braking hard.

I did the same as you on my newest build. I compressed the suspension with ratchet straps to check clearance.

[Tim]

Poncing about with the cvt cover designs

The guard fitted for the first time.

I spent some time playing with the design for the cover , 3mm expanded foam was strong and impact resistant but I couldn't get it to form any reasonable definition so I opted for thinner high impact polystyrene with a metal bracing frame underneath.

The 3 cylinder is a definite winner on performance and it doesn't seem too over bearing weight or width . Under load the engines sounds just peachy . The CVT is functioning differently to the lower powered z482 Kubota bike but not in a unpleasant way . I guess the down side will be the mpg?
So a few more test runs and the off for the MOT test

I still have doubts regrading the engine condition, once warm it runs well but on start up 1 cylinder is lazy and reluctant . Maybe swapping the injectors will prove where the issue lies?