For the love of a tractor engine: The life and times of the 18R-G

[Sam_Q]

anyone have any suggestions on how I can find anything in this thread without reading 3800 posts? I am trying the site search on google and I am still finding it hard to get the right information. I don't think there should be a single thread for one type of engine, there is just too much to cover

[SilverRA23]

search has worked well for me when i have been looking... and when i couldn't find it i asked... no one has jumped down my throat about asking a question again, I am sure no one will beat you up sam if you do accidentally ask about something that has been covered.

[leso]

Hi All, I need some starter advise. I have a 10.5:1 compression 18RG that I'm having trouble turning over. Engine has been off the road for few cold damp months and will only crank slowly. I'm about to go over all the earth connections and positive on the starter to ensure all connections are clean but is there anything else I can check while I'm poking around? Couold there be an issue with the starter motor itself? Seems to be pulling a lot of current while cranking and the battery worked alright on my 3TGTEU although this has pretty low compression.

Glen

Glen dont think the compression should be a factor my rg turns fast with same pistons as you... what you could try is to get a set of GOOD jumper leads put them onto your battery and then to your starter...bypass the existing cables...
they are only as thick as they need to be . i put big cables on mine it turns fine with a pissy little battery...try it.... if it helps take one off and try again etc and see what happens.

[o_man_ra23]

How much current is it drawing?? I mean you must have measured it to be saying that it is pulling a lot of current right??

Firstly - how freely does the crank rotate by hand with the box in neutral and the plugs removed? You should be able to turn it by hand without too much drama. If not, there could be a clearance issue internally.

Second, have you tried jamming a wire straight from the battery to the starter signal? That's the spade connector on the starter solenoid. If it turns better this way than with your key, I would suggest putting a relay in for the starter circuit.

Third, what are your starter earths like? Try a separate large cross sectional area earth direct to one of the starter mounting bolts (clean the starter's contact surface with sandpaper/a file first)

Fourth, what voltage is the battery at?? It should be about 12.5V stationary.

Leso is right in that the cables can be a restriction, since the stock starter is a 0.8kW unit, at 12V, it draws ~67 Amps - which in DC terms is quite a lot. Locked rotor current is a lot more. Clean every electrical connection, both power and earth, and don't forget the battery terminals. 240 grit wet/dry is a good one for this.

[2004lowlux]

got carbies this arvo "yay!!!" test fitted them and the trumpets and now im very glad i ordered the short ones it looks like a tight fit those ramflo filters wouldnt clear the booster so it was a bit of win.
now is a question of do i need the balance tube or do i block the ports.

[o_man_ra23]

Depends how well you can tune the carbs. Technically it isn't required, however it helps to remove slight variations in the butterfly positions/idle mix screws. The carbs have an internal balance between the two barrels, so it is really just the slight differences between the two carbs which it is to smooth out. I would guess that at full throttle it would have minimal effect, and would have the most effect at idle and light throttle/cruise.

[2004lowlux]

just looking at where that alloy balance tube is meant to bolt on top of the manifold it looks like the ports have been blocked off anyway so thats all good

[The Witzl]

Regarding cranking speed.....

.... upgrading the solenoid wire only helps to ENGAGE the starter motor, it doesnt help with cranking speed. It is worthwhile fitting a starter relay, as this does help with engaging the starter.
The biggest impact you can have for cranking speed is the main power wire to the starter, and your engine and battery earthing.
Make sure your battery earth is SOLID, with a decent 4GA cable at minimum (i would personally go 2GA or 0GA).
Engine block earth should be 4ga or 2ga to the chassis.
Dont forget to earth the cylinder head too - 8ga is generally enough.

.... then make sure you have a niec big FAT power wire to the starter. If the battery is in the front, go for at least a 2GA.

Remember, a starter motor pulls a couple of hundred amps.

[o_man_ra23]

If your starter is pulling a couple of hundred amps for more than a few milliseconds constant, you have a problem. There is a contact within the starter which closes when the solenoid engages. You have to pull the starter apart to service this contact (will probably be tarnished and pitted), but it isn't too difficult.

Stock 18R starter is 0.8kW, which at 12V works out about 67A. As the starter motor is not a constant power device, the current will go down as the battery voltage does, however it will draw between 4 and 8 times the nominal current during the first couple of milliseconds. It is this very high torque, high current period where you will draw the most current (CCA rating is exactly that, cold cranking, or locked rotor amps which the battery can supply for a very short period to get your flywheel moving initially). Once the engine gets to cranking speed (couple of hundred RPM at best), which doesn't take too long, the current drops back down. If your battery voltage is low, and your engine slows right down at each compression (ie every half revolution), then you will draw more current than normal and what is left of your battery power will fade extremely quick, not to mention the damage you will do to the isulation on the starter motor windings due to overheating them, which will lead quickly to starter motor failure. It is a bit of a snowball effect, and I have killed at least 1 starter trying to develop a base starting tune.

You can get a 1.0kW reduction gear starter to suit which will help you crank. These are usually lifted from 22R's.

Sorry for the repeat of information, and the possible over-detailed response, however just thought I would provide that information for those who are able to understand but didn't know.

[2004lowlux]

been trying to crank mine over found the starter with the engine was dead so i swapped the 18rc starter in and bingo! its cranking and ran for a second but cut out once i released the key making me think its a balast resistor issue but its got 22r electronic ignition.

[The Witzl]

there are reduction gear starters we can get for 18Rs?????
motherfucker i need to get me one of those!!!

Owen.... under startup load, the surge on a starter motor will be a couple of hundred amp, and will last longer than a couple of milliseconds. Would be more like tenths of a second, or more. This surge load will also apply when each cylinder hits TDC compression, but not quite to the same degree as startup load.
Your figure of 62A is the continual draw should the load on the motor be consistent, which it is not.

Ever chucked it on a scope??

[o_man_ra23]

The current draw will drop sharply after the motor starts rotating, which is very quick, especially if there is backlash in the mesh between the starter gear and ring gear.

Yes, there will be a surging load, however it won't be anywhere near a couple of hundred amps. I have found a 4ga cable from a boot mounted battery to be quite sufficient when starting a slightly higher than normal compression 18R-G.

[Nevakikamukau]

Guys,

I am fitting a Scorcher electronic distributor to an 18RG using a HEI coil. What I am thinking of doing rather than chase the ballast resistor wire back is to use a relay at the coil with the ballast resistor wire as the signal trigger and a direct 12volt feed to the relay. This will give a constant direct 12v supply to the coil. Any problems with this set-up?

Cheers,

Pete

[o_man_ra23]

There are 2 power feeds to the ballast resistor. One is from the ign circuit, the other is from the start circuit. Make sure you use the one from the ign circuit (the other won't be active unless the key is in the start position)

[Nevakikamukau]

Thanks Owen,

What I was intending to do was to just use the existing +ve wire to the existing coil as the signal input to the relay, with a direct feed from the battery to the other relay input. Then when the ign is switched on the ballast resistor supply should trigger the relay to supply the direct 12v supply to the new HEI coil. Yes??

Pete