I think i can help with your concerns.I have just done my first complete trial on my Newly rebuilt Panther.The engine is a toatl new build with all new bearings and piston.The piston was given .004"(.1mm) clearance by the rebore shop(thats what they recommend for an air cooled engine).
I managed about 250 miles of road running in before i entered my first trial and i also had concerns about it running hot on the trial.But apart from it smoking due to the oil pressure being adjusted to high(which i am gradually turning down as i use the bike) the bike never even gave any cause for concern.In fact i was amazed how well it ran.
Even though this engine is not renowned for the vast amount of finning.Due to it being pre war and the head and barrel being cast iron.It even stayed cool when covered in crap.
Your overall bottom gear ratio at the moment is 21.9:1 assuming you have a road box fitted with an internal bottom gear ratio of about 2.8:1.
Using a 17T engine sprocket instead will give an overall bottom gear ratio of 23.25:1
Assuming its a 350cc,you really need a ratio nearer 32:1- some may disagree it needs to be that low,but its certainly overgeared even with a 17T sprocket.
Calculating bottom gear ratio is quite easy- the drive train comprises 3 ratios, Primary,Gearbox internal and final drive. The overall ratio is arrived at by multiplying all 3 together.
In your case-40/18=2.22:1(primary)x 2.8 (g/box internal)x 60/17=3.53:1 (Final Drive)= 21.95:1Overall
With the above,you can substitute different teeth numbers,then re calculate to check the effect.
Thanks for all the replies guys.I will go ahead with the 17 tooth sprocket.
I had also heard about need to be close to 30:1 on the gearing but was unsure how to work this out.
I will need a bigger rear sprocket next as i don't think i can go much smaller on the gearbox.But i will try the 17 tooth at the next trial and see how i get on.
As too what bike i am riding.
Here it is. I have named it the "Ground Gripper"(i chose the name after reading about the nick name the pilots called the old trident airliner when operating it in hot climes as they were a bit marginal on the power in warm air) but it fits perfectly with my bike as its slightly too low to the ground.
Its my old 1937 350CC red panther.Which i last rode around the mid 70's when i was a lot younger and hadn't discovered beer and wimin.
I am just in the process if fitting some lifter plates to the bottom of the forks which will give me about 1 1/2 " more height at the front.But now i need a longer brake arm and cable.
I have also phoned about a new coil spring for the girder forks as the one fitted is 70 years old so sags a lot.But i can't get a lightweight spring so will order a medium weight one which is slightly longer and heavier so i may need to make some different spring mounts up but hopefully that will lift the front even more.
But all in all i enjoyed my first run out and have no illusions that i am any good at trial riding.
After starting to ride my old trial bike again after a break of about 30 odd years i have a question.At the moment its geared with an 18 tooth engine,40 tooth clutch,17 tooth gearbox and 60 tooth rear sprocket.
But due to me being rather crap and the bike seeming much to fast for my very limited skill level((but i don't know if this is in the mind or not(i managed to get round 2 sections on Sunday out of about the 30 i tried before i broke the bike)).I have a 17 tooth engine sprocket which i could use .But my question is is a drop of 1 tooth on the engine a massive drop in the ratio.
Awesome bike
in Anything goes
Posted
This is what you call a bike.
Ural vid
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