NZ National Secondary Schools Minibike Racing Club Inc.
NZ Mini Moto Racing Society Inc.
Q & A:
Construction Questions
Please forward your construction questions to either:
Roger Emmerson: rtemmerson@hotmail.com or Ross McDonald: rossmcdonald260@gmail.com and answers will be shown below.
Answers to your Construction Questions
Gear Ratios for Sidecar
The sidecar we are in the process of constructing this year may not have a fibreglass body.
What gear ratios can we use? Paul E at FBHS.
All sidecars have the same size motor (110cc Loncin 4stroke) and the sprocket teeth are :
driver = 14T & driven = 28T, or driver = 15T and driven = 30T, giving a 2:1 ratio.
Stronger Frame
Safety and strength of the MB frame are prime design considerations.
What recommendations should be considered to strengthening the frame headstock joint? Robbie at FHS.
Sound welds between the frame tubes and the headstock tube are vital and extra strength plus rigidity can be achieved by welding in braces or flat MS gussetts between the frame tubes. Lightening holes that do not weaken the gussetts will overall provide better strength without a massive weight increase.
Running in Oil Ratios
2 Stroke: What is the correct oil to fuel ratio for running in a new 50cc aircooled 2 stroke? Mike at FAHS.
Run 25:1 ratio for a minimum of 4 tank fulls. Do not overheat or stress the engine during this stage.
After that you can use 33:1 and race on 33:1. Ensure the petrol is straight 93 octane or 96Octane and does not contain any ethanol. Follow engine importer recommendations Newmanz R/C Direct website. Do not use full synthetic oils for running in.
25:1.ratio e.g. 10ml oil to 250ml of fuel, or 20ml to 500ml fuel, or 40ml to I litre fuel.
33:1 ratio e.g. 8ml oil to 250ml fuel, 15ml oil to 500ml fuel, or 31 ml to 1 litre of fuel.
Remember to shake the mixture well before pouring into fuel tank. Always use fresh fuel as the high volatiles evaporate over time and make starting difficult.
Oil Changes?
Four stroke engines. Should I use the engine with its oil straight out of the box? Arthur at WHS.
Drain manufacturers oil before starting the first time to remove condensation etc. Refill with good quality mineral oil i.e. 10W-40. Run engine for 10 -15 minutes. Drain while oil warm. Refill with good quality oil and drain after 5 hours use.