Hope you can understand this We will see how things stack up, we can adjust the top dead centre height if necessary by fitting a small spacer under the barrel, but it needs to be small otherwise push-rods and push-rod tunnel have to be lengthened along with barrel studs.
Thank you Jim from Grampian Motors, old fashioned first class service from a professional who knows his stuff It is all very well having a first class engine I can hear you say, but what are you going to use it in? Well it has got to be my favourite Foster Otter frame the one with the Triumph Mountain Cub rear end and swinging arm Its been a long time coming but we need to get this act together? Because it is getting increasingly difficult to now get parts to build an engine like this with the parts available, things are just getting more expensive daily.
I know that there are still C and B engines about with the timing side bush, and as you know I have made a conversion on the Scott Ellis bike engine, and fitted Alpha conversions into another three. But for this build we are going to set off and build the best engine we can with parts that are available, and to tune this engine to what we think would give the best power for a trials bike.
The capacity of the engine will probably be near to cc or just under, and we are going to try and build in a bit better bottom end torque. To this end, I am getting a pair of steel flywheels machined up and will probably use a Alpha big end and rod, I see no point going for the more expensive rods available, as in the end this is only a trials engine.
We could even use a B25 flywheel assembly as others have done, with good results. Well that has started the page, and I just hope someone comes up with a camera for me this Christmas? Still no camera, but it is my birthday next week! Well I thought I would publish this letter from Martin as it will give us all something to think about while I am collecting the engine parts,or making the Flywheels etc. I spent hour's yesterday trying to track down parts that I know exist, but it is not easy!
I think I have said before you think everyone is on the Net, but they are NOT, especially the backstreet engineers that turn these parts out. But that is my job isn't it? Here is what Martin sent me. Hi Charlie,. I sent a comment through the web site but it limited the number of characters I could use.
My comment was that you have given us great info on the frame and cycle parts but to do justice to the frame and the work that goes into building such a bike, we need to know how to make the engine work properly for trials. The standard engine isn't very good and I understand that although there are a number of engine builders in the Midlands, they keep their secrets close to their hearts. I assume the engine modifications are possibly different for the C15, B25, and B?
Some of the answers to recommended engine mods are already well known through Trials Central such as. PVL most popular any others? Any adjustment to PVL's recommended timing for the above engines, e. But to be honest although they both work very well and are reliable, they are still only like a unit fitted to your lawn mower, or chain saw. And is fuelled by the Lucas alternator fitted as standard, although being slightly heavier the bigger rotor may help the plonk situation, it just seems a lot more free running.
We don't really want to go down the totally electronic unit fitted to modern day trials bike with different mapping settings do we. Some people still run total discharge coil ignition and with the new lithium batteries that you now can get are tiny and keep there charge for a long time, these figure strongly on the Magic box type ignition fitted to Classic Scrambles bikes. To be honest standard or close ratio gears are just as well for today's trials on pocket sized courses.
The only real advantage that wide ratio gears had was to give you a high enough gear for the road work in trials of the past eras. Amal or even Wassell now mm. Or you could go for the New Amalminum carb more expencive but helps combat the Ethanol.
A better way to combat this is to use Aspen Fuel it may be expensive but you can then totaly forget the trouble you will have with carburation and other problems using pump fuel. A better bet and cheaper seems to be the Mikuni VM 22 carb as fitted to pit bikes. Forget you can't use them in Scotland, One trial, so who cares.
Other questions I can think of for which I haven't seen answers in TC are:. I heard of Triumph pistons in B25s, but is this as much to get the ratio right as increase engine size?
Look the only way you can know if the bike you are riding suits you is to try different things until it does. The Works BSA boys and come to that Triumph,always ran high compression pistons and said that it smoothed the motor out better. But do you know what gearing they were using? Most of the trials then were over seventy miles of road work as-well as the sections, so there had to be a compromise.
Anything is possible if you have the time to do the conversion, so yes. The B25 flywheels are actually heavier and have more inertia than the C And that is why some of the UK Midlands tuners are using these flywheels in preference to those that were fitted as standard, and even at at least one in the Cotswolds.
Same again Martin personal preference. I have fitted sleeves into Amal carbs to reduce the size of the venturi. Same with valves and proved by the BSA comp shop trying to get more traction from the B40 engines. Reducing the valve size does not always give you more torque and bottom end.
BSA S motorcycle - not complete. Frame, suspension, wheels, engine, tank, seat, oil tank and side covers in reasonable condition.
No title. Model B25 Starfire. Engine starts easily with compression release, and runs evenly and strong, as any Thumper should. Youll be pleasantly surprised when you see this show-quality cycle. Model B The motorcycle runs, drives, and shifts thru gears but leaks a bit of oil consistent with 45 plus year old bike. New battery and strap. New tires, gauge rubber, foot peg and kick start rubbers. Seat recently restored. Carb recently cleaned with new fuel filters and line.
All gauges and lights appear to work. Exhaust is solid. More News Page The Richy Vida Page Contact Me. IPaddled News Page. The News Page. A Readers Page. Another String To My Guitar. Ariel and Noriel Project. Ariel HT Factory Build Aspen Fuel. Bantam Trials Saga. DeLong Way Round. Deryk Wylde Off Road Review. Don Morley The Name Otter. Ducati Trials bikes. Foster Otter Frame Register Fraser Honda A forgotten breed. Gallery Gary Britton's Ariels..
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The Burian trials machines. The D. Motorcycles Page. The Foster Otter Triumph. We take a Look. The Original Foster Otters. The Iconic Draper Family. The Mud Plugger Build's Page. The River Otter. Then again you could just ride the Clubman route at any trial? Edited March 15, by Old trials fanatic. Join the conversation You can post now and register later. Reply to this topic Go To Topic Listing. Sign In Sign Up.
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