RUN IN - TUNING - MAINTENANCE - GLOW PLUGS
RUN IN PERIOD
Correct break-in procedure is vitally important if you wish to get the best performance from your new motor.
Over the last two years we have developed the following “best practice” for running in the GO motors we race and sell.
We strongly suggest you follow the steps below to get the utmost performance and long life from your new motor.
The following break in and tuning procedures are aimed at people new to nitro motors. As such, it is very descriptive, and some things will seem obvious to the more experianced racer.
Please take time to read through the full procedure, as there is information pertaining to your new motor that will be of interest to all racers.
Before mounting your new motor in your buggy or truggy, remove the back plate and apply some after run oil (Dextron ATF is ideal) to the main bearing race, crank pin and rod bottom end. Put a few drops of after run into the exhaust port and move the piston up and down to coat the sleeve liner and piston sides. This will prevent a “dry” start. Replace the back plate.
Mount your new motor in your buggy or truggy so it’s completely ready to go (clutch, pipe etc fitted), and fill the fuel tank. We believe you should break the motor in using the same fuel you will be running when racing (up to 25%), so no lower percentage nitro, or higher oil content break in fuel is required. We feel 30% nitro is a little strong on a new motor, so if you want to run 30% for racing, wait until you have a couple of litres of up to 25% through first.
If you have access to a Competition Heat engine pre heater, put this on the motor and pre heat for 9 - 10 min. We strongly recommend the use of the Competition Heat pre heater units, as they are by far the most effective way to thoroughly saturate your new engine with heat for easy and motor friendly run-in tanks. If a Competition Heat unit is not available to you, use the following method to heat your motor -
Wrap the cooling head with tin foil. We want to keep the temperatures as close to normal operating temperatures as possible during break in, while running the motor slightly rich. The foiled cooling head will assist us with this.
Obtain a hot air gun (paint stripping gun) or powerful hair dryer and pre heat the motor.
You want to concentrate the heating on the cylinder area (both sides) and some on the crankcase area beneath the cylinder. Heating the cooling head using this method will not heat the motor sufficiently (unlike the Competition heat unit). You want to heat the cylinder and crankcase so they are too hot to touch (around normal operating temps for the motor if possible). As a guide, 30 - 40 secs with a paint stripping gun is sufficient. A hair dryer may require a little more time.
Set the needles as follows -
GXII-5RHO MkII 3 needle carburettor:
HSN 1.25 - 1.5 turns OUT from flush. LSN 1.5 turns OUT from flush.
DO NOT ADJUST THE MID RANGE NEEDLE. It is factory set for peak performance.
GXII-5RHO 2 needle carburettor (silver lsn screw):
HSN - Flush. LSN Flush
G5T 2 needle carburettor (black lsn screw):
HSN - Flush. LSN - 1.0 turns in from flush
The motors will start and run at these initial settings.
Once you have the motor warm, get fuel to the motor by blowing into the exhaust stinger to push fuel through the fuel lines and into the motor. As soon as you see the fuel in the fuel line enter the carb, stop blowing or you may flood the motor.
NB: If you are using the Competition Heat unit, you can unplug the unit from it´s power source once the motor has reached temperature, and leave the heater unit wrapped on the head in place of the tin foil. Just be careful the lead coming from the heater unit does not get tangled or damaged.
As soon as you have fuel to the motor, place the car on the starter box, apply the glow starter and start in the usual manner. The motor should start easily after the pre heating.
GXII-5RHO 3 needle carburettor:
Lean the Low Speed Needle and the High Speed Needle together an hour at a time
if required until the motor is running quite rich, but is still able to be throttled up freely without it stalling.
All 2 needle carburettors:
Lean the Low Speed Needle only an hour at a time if required until the motor is running quite rich, but is still able to be throttled up freely without it stalling.
DO NOT IDLE THE MOTOR ON THE STARTER BOX ANY LONGER THEN NECESSARY.
As soon as you have the needles set as above, place the car on the ground, on a flat surface and start driving it in large figure of eights, gently raising the throttle to 1/4 in nice even pulses.You may need to raise the idle a little to keep the motor going during the first few tanks. Try and keep the temperature at around 95 C to 110 C (the foiled or heater unit covered head will assist us with this).
What we are looking for is a nice warm motor, with lots of fuel going through it.
Do this until the fuel tank is nearly empty.
Stop the motor just before the fuel tank is empty.
ENSURE THE MOTOR IS PLACED AT BDC, WITH THE PISTON MOVING FREELY IN THE BOTTOM OF THE SLEEVE.
This is very important, and should be done every time you stop a hot motor.
Let the motor sit until it is back to ambient temperature (remove tin foil or heater unit for the best cooling effect). Refill with fuel and go through the same head covering, heating and starting procedure as before.
You now want to run another 7 tanks through your motor using this procedure in the following manner, keeping the temperature around 95 C to 110 C, letting the motor cool to ambient temperature between each tank, then tin foiling the head (or leaving the heater unit on the head) and heating the motor before re-starting each time.
If the temps get up to around115 - 120 deg C that is ok.
Tank 2
Figure 8’s up to 1/4 throttle (same as first tank)
Tanks 3 - 5
Figure 8’s up to 1/2 throttle
After tank number 5 take time to check the tightness of the 4 x head bolts, and the bolt securing the carburettor setting pin assembly. The initial heating and cooling of the motor during it's first few tanks can see these fittings "bed in" and sometimes become slightly loose. Tighten the head bolts firmly, and make sure the setting pin assembly bolt is "nipped up". Overtightening of the setting pin bolt can result in damage to the carburettor throat, resulting in a loose fitting or "wobbly" carburettor assembly at a later time, so don't over tighten, just make sure it is not loose.
Tanks 6 - 10
GXII-5RHO 3 needle carburettor:
Lean the Low Speed Needle and the High Speed Needle by 1/8 of a turn.
All 2 needle carburettors:
Lean the LSN only by 1/8 of a turn.
Now do Figure 8’s over a wider area, with the occasional 3/4 throttle run for a few seconds at a time, raising the revs up and down evenly.
If you raised the idle speed initially on the first few tanks, you may now find after the motor has had a few tanks of fuel through, and you have leaned the needles a little, that the idle may now need to be lowered back down to an acceptable level.
After tank 10, you can remove the tin foil or Competition Heat unit from the cooling head and tune for nearly normal running (but still just a little on the rich side) by -
GXII-5RHO 3 needle carburettor:
Leaning both needles a further 1/8 of a turn.
All 2 needle carburettors:
Leaning LSN by a further 1/8 of a turn. Leaning HSN by 1 or 2 hours only
Run another 5 tanks at the track with this slightly rich tune at a steady pace, but not a race pace.
At tank 15 you can now start to put a pretty good race tune on the motor by -
GXII-5RHO 3 needle carburettor:
Leaning both needles somewhere between a further 1/8 to 1/4 of a turn.
Exact needle settings are hard to predict due to differing fuel brands, so tune by sight and sound for peak performance from this point on to suit your individual set up.
All 2 needle carburettors:
Leaning the LSN by a further 1/8 to 1/4 of a turn.
If the motor is still a little rich at the very top end, then lean the HSN by a further 1 - 2 hours only.
If you start to get lean bog - richen the HSN back up by 1 hour at a time until lean bog ceases.
The motor will still be tight with considerable pinch left, but will perform nicely.
The remaining pinch will slowly go over the first 7 - 9 litres of fuel you put through the motor, with the performance improving as the pinch reduces.
Whenever possible, pre heat the motor before starting - right throughout it´s racing life.
This will greatly reduce engine wear and help to maintain good compression.
We strongly recommend fitting a new con rod after the first 9 - 11 litres of fuel have been put through the motor. This is common practice, and usually recommended by most race engine manufactures.
The reason for this is very simple - During the running in period when the engine is very tight, the con rod is under tremendous strain due to the piston coming up against the very tight fitting sleeve (metal pinch). It is possible that the stresses and strains placed on the con rod during this period may weaken it, resulting in rod failure later in the engines life. The con rod may well be fine, but as a precaution against such failure, it is recommended that the rod be replaced after the majority of the metal pinch has gone from the motor.
When replacing the con rod we recommend fitting new wrist pin retaining clips. These items should not be re-used once taken out.
GO Racing NZ offers a post run-in con rod replacement kit for $30
This includes:
1 x 21-0600 connecting rod (normally $35.20)
1 x Packet of two "G" clip wrist pin retaining clips (normally $3.50)
If you don't have the tools or expertise to replace the con rod and wrist pin clips
GO Racing NZ can do the work for you - free fitting, just return postage fees will apply.
If you have any questions about this run-in procedure, or anything else regarding the GO range of motors, please don't hesitate to call or email GO Racing NZ Ltd at:
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TUNING GUIDE
GXII-5RHO motors fitted with 2 needle carbutettor (silver lsn screw)
GXII-5RHO motors post Nov 2011 fitted with the 3 needle Gen 6 carburettor
G5T motors fitted with the GX Series 2 needle carburettors (black lsn screw)
BASE SETTINGS
If you have completely "lost" the tune on your motor, or are tuning from scratch after re assembly of the carburettor etc, return the needles and idle air gap to the following base settings:
2 needle carb (silver lsn screw)
HSN (High Speed Needle) – Flush
LSN (Low Speed Needle) – Flush
IDLE AIR GAP - .5mm to .7mm
3 needle carb
HSN (High Speed Needle) 0.5 of a turn out from flush
LSN (Low Speed Needle) 1.0 turn out from flush
IDLE AIR GAP - .5mm - .7mm
DO NOT ADJUST THE MID RANGE NEEDLE. It is factory set for peak performance.
2 needle carb (black lsn screw)
HSN (High Speed Needle) – Flush
LSN (Low Speed Needle) – 1.0 turns in from flush
IDLE AIR GAP - .5mm to .7mm
Unfortunately due to some copyright complications, the remainder of our tuning guide information has had to be removed from this website for the time being.
If you require some assistance with tuning any of the carburettors listed above, please contact us by phone or email for help or more information.
Some tuning tips
Remember that changing the HSN settings will have a direct effect on the LSN settings.
If you lean or richen the HSN to any extent, you will lean or richen the LSN too.
This is because the HSN (along with setting the amount of fuel delivered for top end running), also directly determines how much fuel the LSN receives overall.
Think of your engines carburettor as a garden hose. The HSN is the tap, and the LSN is the nozzle on the end of the hose. The tap (HSN) controls how much water gets through the hose to the nozzle (LSN).
Changing the idle speed also changes the LSN settings, because the LSN is part of the throttle slide assembly. If you increase the idle speed, you are also richening the LSN. Conversly if you lower the idle speed, you are also leaning the LSN. This appies to all slide carburettors.
If you get lost with the tuning – just return everything to the factory settings (including the idle gap) and follow the above tuning procedure. Remember, once you have the idle gap and basic LSN settings done, always run at least one tank through to ensure the motor is close to normal operating temperature. Always tune your motor when it is hot - this is very important.
Some common faullts
Once you have your motor tuned and running sweetly it should not change it's tune dramatically.
If your motor suddenly looses performance or appears to start running lean or rich - don't automatically start tweaking the needles. If the motor is in good condition, the tune will not change that much, so start looking for external faults. Here are some culprits to check for, starting with the most common faults first -
Glow plug - make sure it is in good condition and done up tight.
Fuel and pressure lines - check for splits around the connections to fuel nipple and exhaust pressure nipple. Fuel and pressure lines can also melt on mufflers or get cut by the flywheel.
Exhaust pipe seals - these can wear out and and let exhaust gases escape (particularly the header to pipe connection which can see some movement during racing).
This will drop the pressure supplied to the fuel tank and make your motor run lean.
Check the chassis under the pipe connection for a puddle of fuel and oil. If the chassis is wet, replace the seal.
Head bolts - make sure these are nipped up tight.
Pinch bolt - make sure the pinch bolt is secure. Do not overtighten though.
Front engine bearing - the front bearing seals can wear out causing air to be entrained into the motor through the front bearing. This is normally a big air leak causing very lean running, high motor temps, and a very erratic high idle.
This requires replacement of the front engine bearing.
Fuel tank lid - check the spring on the tank lid is working properly and closing the lid tightly. Also check the O Ring inside the lid is in good condition and sealing properly.
Fuel tanks can also develop cracks around the seams. Look for this if your motor performs well to the half tank mark, then starts to do funny things when the fuel gets below the seam line and allows air into the tank if there is a leak.
Carburettor needle O Rings - these can become worn and leak air past, or become loose enough to let the needles vibrate around and change the tune.
Check for a broken clutch spring causing early engagement (can feel like lean bog).
Check that the clutch nut is done up tight. If slightly loose the flywheel can slip and spin initially on the collett and cause the engine to sound flat off the mark or out of corners.
Also check that you haven’t left your fuel in the sun. This can change the fuels properties and lead to slight changes in performance.
Try to keep your fuel at an even temp by storing it in a shady and well ventilated area.
If you have any questions about tuning, or anything else regarding the GO range of motors, please don't hesitate to call or email GO Racing NZ Ltd at:
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MAINTENANCE
Nitro powered Micro Engines, because of the harsh environments they operate in and the extreme stresses and strains placed on them by constant loading and high revs, require very good care and maintenance.
Any single cylinder engine this size, producing nearly 3 hp and revving at close to 40,000 rpm will eventually fail if not regularly serviced, with high wear components being replaced as required.
AFTER RUN OIL
We strongly recommend the use of an after run oil such as NitroNinja ARO everytime you have run your motor. It only takes a few minutes to carry out this procedure, and it can add gallons onto the life of your motor. When you have finished running your motor for the day, run it out of fuel.
Disconnect the fuel line from the motor. Apply the glow starter to the motor and turn it over on the starter box until it will not fire anymore. This burns most of the fuel out of the crankcase.
Now remove the glow plug and put 3 drops of after run oil down the plug hole. Now remove the air cleaner, open the throttle fully and place 5 drops of after run oil down the carburettor throat.
Spin the motor over on the starter box for two bursts of 4 seconds to atomise and disperse the after run oil throughtout the entire crankcase and bearings etc.
Make sure motor is at BDC, then replace air cleaner and glow plug.
The after run oil gives a protective coating to all the internals to help prevent rust forming internally, plus it also stops your motor getting a "dry start" next time you use it.
Rust will form inside the engine because of traces of fuel left on the internal components, even after we have run the motor out of fuel. The methanol in fuel is hygroscopic, meaning that it attracts moisture from out of the surrounding air.
The moisture it attracts reacts with the nitromethane to form surface rust, which can penetrate bearings etc, and cause premature engine wear and ultimately engine failure.
BEARING REPLACEMENT
Everyone has differing views on bearing life and when your engines bearings should be replaced.
Obviously, if you are checking your motor and find any sloppyness, stiffness or notchy rotation, the bearings should be replaced immediatly. However, the best policy in our opinion is to replace major components like bearings etc before this happens, as stress and strain on other components resulting from the faulty bearings has most likely already happened by this stage.
As a guidline we recommend changing front and rear bearings every 13.5 litres (3 gal) of fuel through the motor. This equates to approx 105 tanks of fuel in a buggy, and 90 tanks of fuel in a truggy. Some will say this is over-kill, but we think it's better to be safe rather than sorry.
105 tanks of fuel in a buggy equates to 15 club meetings of racing, which is a lot of wear and tear on a motor, especially in summer with the dusty conditions.
The cost of front and rear bearings for your GO motor is $52, so it's not a massive outlay once or twice a year depending on how much you use your motor to keep it in good condition.
CON ROD REPLACEMENT
Once again, everyone has differing views on con rod wear and replacement.
Of all the components in your motor, the con rod does the most work. As you may have read in the run in section, most manufacturers suggest replacing the con rod at around 9 litres (2 gal) after the initial break-in period and some racing. This alleviates any possibity of rod failure due to the rod being strained because of the initial tightness of the motor.
Once you have replaced the initial con rod at 9 litres, it is just a matter of inspecting the con rod at regular intervals and replacing it if you suspect any undue wear. Most con rod wear is found in the big end bushing, where the con rod attaches to the crank pin. Remove the back plate from your motor and rotate the motor to TDC where the piston locks at the top of the stroke. Now see if you can wiggle the flywheel and notice any slop in the bushing around the crank pin. If there is noticible movement, you should replace the con rod. Remember - this motor is spinning at up to 40,000 rpm, so any slop can result in excess wear and possible component failure.
In older or well used motors, this slop can sometimes be caused by a worn crank pin. This requires the crank to be replaced as well as the con rod.
Also, if you have an over-rev situation, caused by faulty radio gear etc, it is a good idea to replace the con rod (due to possible stretching of the rod) and give the rest of the motor a thorough check over.
GLOW PLUG TIPS
In a well tuned motor, your glow plug should look like the following -
Bottom of the plug should be a light brown colour and slightly damp.
The filament should be a silvery grey colour with no obvious distrotion.
If the bottom of the plug is very dry and dark in colour, you are running too lean.
If the filament is distorted or damaged you are either running way too lean, you do not have sufficient head shimming for the nitro % you are running, or you are running a plug that is too hot for the % of nitro you are running.
The GXII-5RHO motors come factory shimmed at .5mm (1 x .3mm alloy shim and 1 x .2mm copper shim). We strongly recommend you do not run with reduced shimming unless you are running only 20% nitro.
If you are running 25% fuel you can run a medium to medium hot plug with no problems.
If you are running 30% fuel we recommend running nothing more than a med temp plug to avoid the following if you start running too lean - detonation / plug damage / flame outs.
Higher nitro content fuels raise the compression ratio of your motor. If you are running a hot or ultra hot plug with a leanish race tune, this raised compression ratio can combine with the hotter plug to cause detonation.
Slight detonation can cause shock waves that will damage plug coils causing plug failure. In some cases the coils will be broken off and can fall into the cylinder and pass through the motor causing serious damage to piston and sleeve.
Major detonation can cause extreme piston damage or a broken con rod resulting in a destroyed engine.
If you have any questions regarding any of the above information, please don't hesitate to call or email GO Racing NZ Ltd at:
