Yamaha TRX850 Enthusiasts Forum

Time to rebuild my wiring loom and re terminate the mods I have done with better connectors.
I'm also changing the power feed to the coils to work directly from the battery via a relay.
Simple test is to meter the voltage at your battery and then meter the voltage at your coils.
There will be odds on you have a voltage drop and under 12v so your not getting the full potential out of your coils.

There are 4 wires
What I'm doing here is using the original coil feed from cylinder1 as the power to trigger the relay when the ignition is turned on. (green wire and black earth wire attached to relay complete this circuit.)
Cylinder 2 original coil feed I will use as the trigger on a 2nd relay for my O2 sensor set up.
( you don't need it just tape it up or you can use it as I have for an accessory feed)

So when triggered this opens the circuit to draw power directly from the battery through the relay to the coils (shorter heavier red cable and the longer heavier red cable coiled up with the Y split to feed both coils attached to relay)
The result being a stronger spark simple performance modification and at no detriment to the std coils.
The relay I have chosen to use has added protection with a built in fuse from the battery feed and the original cylinder 1 ignition feed used to trigger the relay already runs through the original TRX ignition fuse in the fusebox so there is protection for both feeds to the relay. .

Heavier 15amp cable is used on the battery/coil feeds and all connectors are crimped,soldered and then heat shrink for insulation.
I will be mounting mine under the front section of the R/H side cover beside the battery tray.

I'll be making up another 3 so if anyone wants one ($30 shipped in Oz) send me a PM.
I've used ring terminals not spade terminals on my coil feeds due to the Dynatek coils and the others I make will have insulated spades to suit the std TRX coils.
The green wire will have a blade terminal to connect to the original wiring harness so everything plugs straight inplace on the std TRX loom and coils.
Ring terminals are used for the battery feed and earth.
I will be taking my battery feed straight from the battery side of the starter relay.

You can easily remove the fuse from the relay as an added anti theft device too.
So if they know how to Hotwire the std ignition switch, this will slow them down why they trace why they still have no spark.

best to check the earths as well.

What's the difference in volt drop between the original and modified systems Cobba?

dandywarhol wrote:What's the difference in volt drop between the original and modified systems Cobba?

Yes, interested to know. Interested in a harness too if the drop is significant.

What I'm acheiving by this is bypassing a few extra connectors, switches and cable length & thinner gauge cabling.
The power to the coils runs from the ignition key through the neutral & side stand switches, the LHS handlebar clutch switch and ECU , back up to the handlebars on the RHS and through the kill switch and then to the coils. The headlight power is drawn along this feed too .
So I have effectively bypassed any extra load, all these switches and connectors and all these 0.1-0.2v losses start to add up.

Any voltage loss or extra load now is not an issue as the original coil feed is only used to trigger the relay which needs 2/10th of bugger all.
Voltage to the coils now runs down a 4mm /15amp cable about 500mm long straight from the battery with only the relay inline.


Cleaning all the connectors and switches will help but you can't stop wear n tear after 20 yrs.
I had cleaned all these point during the rebuild and I was suprised how much grime had built up even on the std connectors still in use on the harness.

I never bothered to meter the coils before the mod as I knew I would gain from previous experience.
As someone mentioned before, a good earth is a must too.

Australian model TRX's have the headlight hard wired and on as soon as you turn the key and this is drawing power along the same chain to that feeds the coils so a simple test is take a voltage reading from the battery, then one from the coil feed black/red lead.
Take a reading under load too when you hit the starter and motor idling.
Don't forget to meter the battery while idling too.

common mod for old Kwak z900/1000, maybe worth putting a doide on the relay coil as well.

Finished the harness rebuild last nite and had the chance to fire it up this morning.
Ignition on, the battery and the coils meter 13.6v and with the motor running they both come at 14.3v .
Motor response is beautiful as I was expecting, sounds clean and crisp and revs with no hesitation right from idle.

cobbadiggabuddyblooo wrote:Finished the harness rebuild last nite and had the chance to fire it up this morning.
Ignition on, the battery and the coils meter 13.6v and with the motor running they both come at 14.3v .
Motor response is beautiful as I was expecting, sounds clean and crisp and revs with no hesitation right from idle.

Those coils are good for that voltage and where you have them positioned will keep any extra heat generated at bay well done.

You running a stock battery cobba?I wouldn't expect to see any more than 12.6 from a fully charged battery after the surface discharge has been removed by the coils

Shorai Lithium ion


LFX18L1-BS12
SHORAI LFX Lithium-Iron Powersports battery, 18Ah PbEq 12V eq, “L” polarity, Case Type 1
Sku: 4897034420135
Part Number: LFX18L1-BS12

Specifications

Weight (grams): 1048
Cranking CCA (A): 270
Weight (lbs.): 2.31

Took the bike for a bit of a ride to book in on a dyno run and have definately found gains with this mod.

Finding more low down torque and overall running with pick up through the rev range in top gear roll ons with no hesitation and just asks for more. ( as the Ducati and r6 rider found out over the bridge )
Didn't take long to find the limiter in 2nd out of a corner and can easily start to lift the front wheel and bounce along the Tarmac if I roll on more than half throttle if over 3,000rpm.
I've still to set the mixtures as its hunting from idle and still a little untidy till 2500rpm.
I'll get around to checking float level too.
Hand on the coils after spirited riding and cool as a cucumber.

17-41 gearing ( soft limit set so far at 9000rpm)

For Dynas improperly matching to the ignition will be the major factor in making them run hot and ultimately crack. Better primary voltage should lead to increased secondary and a better bang as you have found

Are the stock coils not man enough for the job?

Hello everyone,
Im happy to find this small cool mod.Im not a Trx owner i have a Tdm 850 2000 so this will
work for me just fine also.
I found this video with a guy doing a relay mode

https://www.youtube.com/watch?v=mqUdxWzZkog

Anybody knows if i modify the relay like the guy in the video will have as a result on stronger spark on the excisting mode with
the ignition coil relay?
Are there any dangers involved,meaning causing damage to a part on the bike?
Excuse my ignorance,electrics aren't my strongest thing.

Replace the HT leads while at it.
7mm copper core lead is easily sourced and you can pick up 1m online easily for a couple of $$$
Remove the resistor from the plug caps too and replace with a small piece of brass rod or cut a brass bolt.
Resistor spark plugs are all you need for noise suppression and are standard anyhow on the trx.