Yamaha TRX850 Enthusiasts Forum

Does anyone know which stick coils to use to convert my TRX to coil on plug? My std coils are goosed so since they need replacing I fancy ditching the OEM setup and going COP.
Cheers Ron

Researched into stick coils and most don't have the correct ohm 's to suit the Trx.
Dynatec DC-3 coils can be found for about $150-$170 a pair from the US.

Would one of your Ignitech programmable cdi boxes give me the option to use lower primary impedance stick coils?

In one word ....Yes
you can manipulate the dwell time for a preset short for a coil under 2 ohms, long or manually set your own dwell.

This gives you an explanation from the ignition manual..

Excitation (dwell time) of ignition coil can be set to short/long/manual/auto by software TCIP4.EXE. Short dwell time is for ignition coil with primary coil resistance less than 2 Ohm. Long dwell time is for ignition coil with primary coil resistance higher than 2 Ohm. If long time is used for coil with primary resistance less 2 Ohm, coil can be destroyed. If it is used short time for coil that desire long dwell time, the energy of spark could be small especially in high rpm. You can set dwell time manually also. Next option is use automatics determination of dwell time. Details are in Software section.

As for the std OEM Yamaha Trx850 ECU , it has a long dwell preset into it and coils primary ohm is rated between 3.5 to 5ohms so if you use a stick coil with a low ohm rating , it will overheat and burn .out.

Fitted the ignitech with some s/h OEM coils but still want to convert to stick coils as part of my forthcoming engine build.
Any pointers as to which stick coils are the best fit on a trx head?
Cheers Ron

(yer, I know this is an old thread, but for other people that might read it..(like I did..))

Have you looked at bikes that use the stick ignition coil?
There are quite a few later model bikes that use them.

If you match the length of the complete stick against the length of the original plug cap you should be able to find something suitable
I am posting this cos it sounds like a great thing to do to improve the spark - and to improve wet weather reliability.(no plug caps or high tension leads that can get water in them to cause problems = )
Just wires

Anyway, the coil sticks that are fitted to later model sports bikes are capable of providing sparks at way above the max TRX engine rpm, so they should work just fine
(well, they will for me cos I have the nice Ignitec ignition )

I will be looking for stick coils myself, and when I find some I will post again.

I'm not saying it right or wrong, but the guy seems to know what he is talking about:

http://www.motorcycleproject.com/text/h ... coils.html

Nowt new:

http://www.trx850.com/phpBB_forum/viewt ... tick+coils

I like the idea of stick coils because they are a neater solution with no cables that can degrade over time, and therefore more reliable.

However if they are not as good as the stock coils I dont think I will bother!

Std TRX HT lead from the coil to plug are solid core so they won't degrade in a hurry and offer the least resistance.
Power the coils via a relay and 15amp cable to lessen any voltage drop and you'll finds strong healthy spark.
I used 3mm thick 9mm I.D. silicone hose as extra insulation on copper core HT leads with success in wet weather running the dynatek 3 ohm coils but may not be needed with the Std coils. ( they already have extra insulation over most of the HT lead )

So replacing the coils is straightforward enough in so far as the tried and true solution is to buy a pair of single output dynatek dc-03 coils which are readily available on ebay and the like. I have not really had any issues with the coils but after 20 years I am inclined to replace them given I have already gone with the programmable ignition

Seems prudent to just do the leads at the same time. Where did you get the leads Cobba? If you have an online source it would be helpful

You can buy 7mm copper core by the metre online then you just need to terminate 1 end fitting into the coil as the plug cap screws onto the lead.
I was lucky enough to get a new pair of Packard 440 tinned copper core leads a fellow had laying around for his Bonneville and I just cut them back to suit.
You'll notice advantages straight away in the lower/mid range especially with the relay in place.
Plus you have the option to open up the plug gap too with a std compression TRX motor.
Cost you around $200 for the coils, leads and a relay with built in fuse.

Thanks Cobba,

I finally got around to ordering new coils and some HT lead for this job but I am in 2 minds about wiring them via a relay.

I am more inclined to use the stock wiring and just clean up all of the conectors etc

I understand that this is not optimal, as you will get a better feed direct from the battery via a relay but I use the bike in all weathers and have had a number of relays fail, due to water ingress, so I am inclined not to add a possible point of failure

I read somewhere (possibly the Haynes manual) that the stator and coils should be replaced as a set, unlesss you bypass as per the relay relay mod. But I am sceptical about this.

I am curious, has anyone replaced the coilds without runing via a relay and have they had any issues

Killer wired in a pair of DC-3 coils too but not sure if he went via a relay. Maybe send him a quick PM to find out ....

cobbadiggabuddyblooo wrote:Killer wired in a pair of DC-3 coils too but not sure if he went via a relay. Maybe send him a quick PM to find out ....

No, just changed the stock ones.