Basket Cases

[Kombivan]

While most two-stroke kickstarts rotate the motor somewhere between one and one-and-a-half revolutions per kick, the manages a bit over three revolutions in 90 degrees of rotation of the kickstart shaft
The first photo shows the point at which my kickstart engages, and the second photo shows where three revolutions is achieved. Yes it does feel pretty weird to use. Why is it made like that?

They are made like this because they a 3 times harder to start.

[Kombivan]

While most two-stroke kickstarts rotate the motor somewhere between one and one-and-a-half revolutions per kick, the manages a bit over three revolutions in 90 degrees of rotation of the kickstart shaft
The first photo shows the point at which my kickstart engages, and the second photo shows where three revolutions is achieved. Yes it does feel pretty weird to use. Why is it made like that?

This is also to save you the embaracement of clutch starting your bike in public.

[BOGWHEEL]

David, are you certain that it's not a side stand as well?

[Kombivan]

Possibly its a kick stand only as there not worth starting.

[Kombivan]

If the kick start was 2 foot long would you try starting it with 2 feet?

[Guy53]

For a shorter rider, I can see the benefit of a kick starter that engage '' late '' it give more leverage.
Guy

[Greg Harding]

The OSSA MAR 250 design presents quite a few opportunities for head-scratching if you look closely. I reckon if you wanted to write an amusing book for people who like old dirt bikes, showing the weird and oddball design ideas seen on 1970s bikes would be a great subject.
The MK1 MAR has a couple of weird, unhelpful things that were fixed by the time the MAR Mk 2 came out. Can anyone suggest what they were?

Hi Everyone,

David, the more that I look at the , the more weird things that I find, for example behind the front sprocket which is on the Right Hand Side tucked away just above the bashplate is a different location for a gear lever So to answer your question, my guess is the MAR Mk 1 had the brakes ON THE WRONG SIDE

re the brakes having excessive spring return, I took off the return spring that was on the brake camshaft (on the outside surface of the brake plate) and it lightened it up. Your idea had me thinking that maybe you could fit a spring to the chain tensioner that went to the swingarm rather than the brake shaft, and remove the spring that twists the brake shaft upwards

My thoughts were similar, but the rear brake cable drags a little and needs the brake cam return spring. Also thought removing the main (dual purpose) spring and starting again, however the chain tensioner pivots on the brake pedal arm and not on the swingarm, so the extra helper spring for the rear brake was an easier solution.

I did some more work on the MAR today and thought that it might be fun to see if anyone can come up with logical (or not-so-logical) reasons for some of the the bizarre design features they used.

There are quite a few things that are a bit weird, but I thought I might start with the finning on the crankcase. I took this photo with the bashplate removed to show the fins better

Any ideas?

Fantic use a similar design and I think the fins are all about surface area for cooling. Volkswagon drivers understand this really well.

images[2].jpg (42.24 KiB) Viewed 5314 times

Having those fins there would keep the fuel cool prior to entering the combustion chamber thus when the fuel is ignited it would expand at a more rapid rate than if hotter. bit of a comparison would be driving at night compared with driving in the day at night the vehicle always goes faster and performs better.

For a shorter rider, I can see the benefit of a kick starter that engage '' late '' it give more leverage.
Guy

Guy, If you have not started an before, the load starts at a lower than some other bikes level, which also happens to give more force. Because the kickstart drives through the clutch and therefore the primary drive (which seems quite a low ratio) means more revolutions of the crank per kick. It also means the clutch has to be out for starting.

[Kombivan]

That Kombi turns up everywhere on the net I notice it has a raidator, so no cooling fins there.

[Guy53]

I don't remember having started one like that, but on my Bultaco I wolud have liked to have more leverage ( maybe that means I am a .... )

Guy

[David Lahey]

I don't remember having started one like that, but on my Bultaco I wolud have liked to have more leverage ( maybe that means I am a .... )

Guy

No you are not a ....., I reckon that for Bultacos up to 250cc, the kickstart works a treat, but the big ones (360cc) can be a bit of a challenge to kick over. I have a 360cc Alpina that I have to treat like a 4 stroke to start it