Dyna III with 3 ohm coils

[kfz]

Evening all,

As is well know  Dynatek changed the spec on the coils from 3 to 5 ohms.  Simple question can I install a 1- 2 ohm Resistor of suitable wattage (what amps?) and continue to run 3 ohms coils.

Not that this a problem on the LM1000 as its blown a coil land fried the RH circuit in the box so that needs a complete new kit.   

I guess I'm asking is what current is safe?

Kev

[redrider90]

I'ver burned through  three 3 ohm coils in 30-40K miles. I do not remember how many miles I had on it when I installed the DYN III system. I also had to replace one module. So DYNA sucks for me.

[Antietam Classic Cycle]

I'd just go with their (black) 5 ohm coils and be done with it. 

[PeteS]

I am still running 3 ohm coils on my LeMans but added 1 ohm 50 watt resistors to each coil. This after a sending unit died. So far with about 20k miles no failures.
The ones I am using look like this.

[Rough Edge racing]

  I bought a 950 Guzzi that came with a Dyna and 3 ohm coils.I have no idea how old the ignition was..On the first longer trip with the bike I had to ride home 50 miles on one cylinder when the ignition crapped out..Coil and ignition issue...Can't say it was from the 3 ohm coils, but just saying..
  I suspect the Dyna is primitive with no dwell control to keep prevent overcurrent to the coils ..?

[kfz]

I'd just go with their (black) 5 ohm coils and be done with it.

Which is what I need to do with LM but the other bikes it becomes prohibitively expensive. Dynatek stuff is 50% more in the UK.


Kev

[kfz]

I am still running 3 ohm coils on my LeMans but added 1 ohm 50 watt resistors to each coil. This after a sending unit died. So far with about 20k miles no failures.
The ones I am using look like this.

Thanks Pete I think I will do the same.  Why not a 2ohm,  50 watt seems ample i guess.

Kev

[kfz]

Think its worth putting a fuse in to protect the unit?

Kev

[mtiberio]

funny... last year I bought back my old Guzzi race bike that I raced in 1992 and 1993. I sold it to a collector in 1994, and he didn't use it. When I got it back, I noticed it had a Dyna III and 3 ohm coils. I ran it all last year doing land speed racing. I just sold it again, still with the 3 ohm coils. One thing I did learn from Manfred Hecht at Raceco was that you can never turn on the ignition, and not start the motor or the coils will overheat and crack. Just one data point, YMMV.

[Chuck in Indiana]

I've been running 3 ohm coils on Mouser's secondary ignition for over 20 years..



I'm also running them on the AeroLario. I tried putting a resistor on it, and started fouling plugs. <shrug> Took it off and it's been fine since.
As Mike says, don't leave the ignition on without it running, or it will lose it's ju ju. Other than that, I've never had a problem.

[Moto]

I've been running the Guzzi original 3A coils with a Dyna for many years without a problem. Don't forget to flip the kill switch if you want to turn on the other circuits without starting the engine. This will save the coils from overheating.

Moto

[kfz]

yes, yes, and mines done 90k and 20 years on 3 ohm coils but today I need a new box at £260 GB and new coils at £160 GB.

400 quid bill, nice. I'd rather the other bikes didnt do this.

Kev

[Moto]

yes, yes, and mines done 90k and 20 years on 3 ohm coils but today I need a new box at �260 GB and new coils at �160 GB.

400 quid bill, nice. I'd rather the other bikes didnt do this.

Kev

Well, well, you got your answer above, from Pete S.

Whether something that takes 20 years to develop as a problem is going to be cured by adding a resistor, nobody knows.  Perhaps you are wasting your time by adding a resistor, and maybe the resistor will crack its terminals, as mine have. Good luck.

Moto

[PeteS]

Thanks Pete I think I will do the same.  Why not a 2ohm,  50 watt seems ample i guess.

Kev

Kev, The resistor I used was actually a 10 watt version of above. Same package. I was guessing. Higher wattage won't hurt, it just takes up more room. I used a 1 ohm as a compromise. Each ohm reduces output voltage by some amount.
A resistor also reduces dv/dt (change in voltage with respect to time) which is how fast the spike rises and falls. Its the peak voltage coming back at the sending unit that can cause it to overheat and fail.
The Lemans spends a lot of time at redline when doing track days and adding the resistor hasn't seem to affect performance one bit.

Pete

[mtiberio]

Which is what I need to do with LM but the other bikes it becomes prohibitively expensive. Dynatek stuff is 50% more in the UK.


Kev

dont buy from UK distributor

[kidneb]

I had a dyna III failing far away from home once, after I had been running the stock 3ohm coils for years without problems.
But for some reason I had mounted a set of the aftermarket 3ohm coils that many dealers are pushing, saying they are a direct replacement for the original ones.
But seemingly not so if you are running a Dyna III, as they have a smaller diameter/smaller cooling surface than the stock ones and get overheated.

What to think about all the discussions throughout the years about the Dyna III and what ohm coils it is designed for ? And Dynatek obviously having (had) a hard time to find out themselves ?

Anyway,- I`ll post a couple of links here that may be of interest, I`m finding Morizzis (RIP) posts interesting, as he had a lifelong experience running his LM3s in everyday life,- and he knew his stuff.

http://www.guzzitech.com/forums/threads/explanation-of-the-working-of-ignition-coils-please.9827/

https://www.euromotoelectrics.com/12v-Ignition-Coil-Moto-Guzzi-BO-Coil12V-p/bo-coil12v.htm

     Ben

[rodekyll]

Which is what I need to do with LM but the other bikes it becomes prohibitively expensive. Dynatek stuff is 50% more in the UK.


Kev

Any 5-ohm coils would do it.  You aren't married to dynatek coils just because you've got the ignition portion of their kit.  I use Bosch blue coils whenever possible.  Generic, cheap, and good.

[mtiberio]

Any 5-ohm coils would do it.  You aren't married to dynatek coils just because you've got the ignition portion of their kit.  I use Bosch blue coils whenever possible.  Generic, cheap, and good.

and huge

[PeteS]

One mistake I see a lot of folks make with Dyna coils is mounting them with a hose clamp similar to the stock coil. You have to mount them using pole piece in the center to a good heat sink. Never had a Dyna coil failure only an ignition unit.

Pete

[rodekyll]

and huge

That's the "whenever possible" part.

[kfz]

That's the "whenever possible" part.

Yea agreed Pete.  The LM has a alloy H bracket  bolted to the fame and the Mille has a two little brackets welded to the frame.

Kev

[Chuck in Indiana]

One mistake I see a lot of folks make with Dyna coils is mounting them with a hose clamp similar to the stock coil. You have to mount them using pole piece in the center to a good heat sink. Never had a Dyna coil failure only an ignition unit.

Pete

I have Dynas properly mounted on Mouser.. but a prospective builder hit the master switch with his knee when he was getting out, and it was left on for days. That killed a coil.. and the battery.

[Testarossa]

My T is still running the 3.3ohm bosch blue coils installed at the factory in 1974. The last 15 years on a Dyna iii. When I convert the Mille to Dyna, next week, I will keep the original coils.
Bear in mind that 3ohm coils are labelled 3.3, and 5ohm coils are 4.7. So there's really only 1.4 ohm difference. Not worth worrying about.

[kfz]

My T is still running the 3.3ohm bosch blue coils installed at the factory in 1974. The last 15 years on a Dyna iii. When I convert the Mille to Dyna, next week, I will keep the original coils.
Bear in mind that 3ohm coils are labelled 3.3, and 5ohm coils are 4.7. So there's really only 1.4 ohm difference. Not worth worrying about.

Not worrying, just getting tired of breaking down, melting coils and frying Dyna units.  Lovely day today spent at chester services waiting for HGV driver tow truck Tacho hours.  Prefer to ride the bike than the tow truck.

Kev

[kfz]

Teach me not to take the points plate...




map geojson

[moto-uno]

 FWIW , if you contact Dyna they still recommend 5 ohm coils with their Dyna ignitions !  Peter

[lucian]

Pete nailed it , the big old round oil filled coils can take the heat and work great but. Many times they will not fit in the desired mounting location. The black 5 ohm dyna coils will, but require a more  substantial heat sink when mounting.   They need to be mounted with a heavy enough connection to the frame to conduct the and dissipate the heat. The main reason any coil fails is over heating.