Yamaha TRX850 Enthusiasts Forum

Hi all.
I am looking at swapping out my original coils to try and get a running issue sorted.
The old coils test within spec but I am wanting to get everything spot on for the future.
(It is a new bike for me and it barely ran when I got it.)
The new coils and leads/ caps have a lower resistance than the old ones.
Old 25 kohm new 15.3 kohm
My question is can I swap to these new ones without damaging anything?
Or do I just renew my old leads and keep the old setup?

Cheers .

1 metre of 7mm Copper core is only a few $$$ and easy to replace . The HT leads simply unscrew from both the cool and the cap.
Inside the cap you can unscrew the brass bung with a flat blade screwdriver and inside the cap you remove the spring and 10k resistor. ( 5k resistor one the spark plug will deal with unwanted RF )
Cut a small (M4 from memory) brass bolt the same size as the resistor and put that and the spring back in place inside the cap. It helped boost the spark once again but I found a little lacking on 1 coil.
I’ve just replaced my coils with Ignitech 3 ohm coils and gained a good bright spark on both coils once again. ( but I did use the new 7mm copper core and plug cap mod from my old coils... )
I had previously ran ( larger green ) Dynatek 3 ohm coils which where even better again than std but couldn’t be bothered modding things on this TRX to suit.

The spec for the coil secondary resistance is 10.4 to 15.6 kOhm, so I'd say your old coil is on the way out and the new coil is OK.
Either way, higher or lower secondary coil resistance won't blow anything up, just affect how much spark you get.
Check that the primary coil resistance is correct, spec is 3.4 to 4.6 Ohm, as this can blow the ignition unit if it gets too far out of spec.

If you are spending money on the bike, get an Ignitech ignition unit from the guys in Czech republic. Its worth every cent.

So what your saying is I can mod my old ones with new leads and remove the 10k resistor and that would lower the resistance 10kohms which puts them down to the new ones spec.
I think I will try my new forseti ones and see what they do.
If they don't work well I will mod the old ones because they test in spec at the primaries.
But I don't know whether they will break down once hot.
Cheers.