Monty race ignition

[Fitz]

Hi guys, just some observations if you are going to fit an aftermarket ignition to a Montjuic

My race engine is completely new, lightened balanced crank, Carrillo rods, Ross ceramic coated pistons, very high compression ratio, S1 cams, running standard carbs at the moment. After some discussion I bought a backing plate to fit a Boyer Bransden ignition system with a dual output Dynatek high performance coil (3 ohm after discussions with BB)

I started a lively discussion about this when I started my engine, the UK opinion suggested it was a common enough set up, the buys at Redax were convinced that it could never work. If you think about it its a 180 degree engine, using a BB set up with dual pickups but only one output to the coil, so every four strokes the ignition was firing both cylinders every time each of the two magnets passed each of the two pickups, multiply this by the motor running at say 9000rpm and you can imagine the work load for the ignition and coil

My engine started but I had a misfire that I could not get on top of, I tried all of the usual suspects, fuelling, timing etc, the alarming part was that my lovely new SS exhaust system glowed red and is now blue, I dont mean it got a bit warm, it GLOWED RED

The plan from my engine builder was to run the motor a few times prior to removing the cam box cover to re-torque the head, I did not get this far, during a short run on my bench the head gasket blew apart that badly, it was protruding between the head and barrel joint - see the picture

I took the advice from Red and scrapped the BB combination and bought a Sachse unit designed specifically for the Monty and Atlas engines and a pair of 3 ohm single output Dynatek high performance coils and rewired the ignition system while my engine man rebuilt the motor

We reinstalled the engine over the weekend and fitted the Sachse unit, after trying for three hours, we could not get the engine to start so abandoned the work. I revisited the instructions and talked to Red and Sachse to see if there was any advice and to check the Sachse instructions, I  read them over and over and they made little sense to me

In the Sachse instructions, there is a section that tells you to set the left cylinder to TDC, rotate the magnet to just before the South pole marked on the plate triggers the top pick-up which will illuminate the LED (make sure you have the right rotation side for anti-clockwise direction) turn the ignition on, rotate the magnet plate until the North (N) mark  passes the pick-up which will cause the LED to go out (although it does retain a little glow - this is correct) you then lock the magnet plate using the three grub screws

I also took Red's advice and drilled two small holes through the magnet plate to enable a pair of circlip pliers to be used to rotate the plate on the boss, Redax's version has a modified rotor that avoids having to do this

I thought that this was incorrect and perhaps a translation error, how could moving the magnet plate from S to N do anything, the instructions ARE correct and so was RED, the bike started perfectly and runs that well I had ticking over on the bench, the exhaust is now running cooler too

So if anyone needs a virtually new BB ignition system for a twin cylinder engine and a single dual output Dynatek coil you know where to come

Thanks to Red for the advice and I can recommend using either their version or the full Sachse version of this ignition, I have the technical stuff downloaded but you can get it from the Sachse website anyway

Now to finish the project and get it racing  Cheers Red

 

[redax5]

glad you got it all sorted in the end Dave
now your next issues will be fuel related 

when you first posted the details of your ignition system I just could not see how it would work
in fact, I was seriously impressed when you posted that the engine was running, never even thought it would start
expected the engine to backfire through the carbs and blow them off their inlet stubs

would have loved to see the glowing red hot exhaust headers, that would have been impressive
I used to trawl U-Tube searching for engine dyno runs to watch and listen to, some of those big horsepower V8's can light up their headers under load

should have installed an Ignitech black box though being a race bike, being able to program the ignition map to suit your own engine is the way to go

good luck

 

[Dellortoman]

... expected the engine to backfire through the carbs and blow them off their inlet stubs

Me too. Plugs would have been firing on the inlet stroke. Piston somewhere a few degrees before BDC, inlet valve open and a fresh charge of fuel on the way in. I'd have expected the carbs to be glowing red hot, not the exhausts!

 

[LaverdaIan]

Hi Dave, glad you got it going too.. another Monty racer to turn the crowds on.. good luck on the track.
I've got Ignitech in mine, very simple and reliable, and as Red advises, programmable to the bike's performance. Still running 32 Dells, and it is flying.
Interested in your comment that you took #1 (LHS) piston to TDC, as the 500 Laverda is timed at the TDC of #2 (RHS)
But hey, it's running, you're into it, so must be OK..
Good Job and good racing to you mate.

8)

 

[phil37]

so every four strokes the ignition was firing both cylinders every time each of the two magnets passed each of the two pickups, multiply this by the motor running at say 9000rpm and you can imagine the work load for the ignition and coil
 

Think I may have confused the issue on t'other forum when I put up a photo of the magnet holder off a 750 - that runs at half engine speed. The one I supplied to Fitz is (should be ??) like the one in this photo that only has one magnet.!! - so I can't see why it wouldn't work as my own Atlas ran this set-up, along with Bob Dixon's Barcelona 600. I'm not familiar with the Bb box that fritz is using - maybe it or the Pk are faulty. - Regards - Phil

 

[redax5]

the issue as I see it is with using a single dual coil to try and run a 180 degree phased engine

by default you have to supply a spark every time either of the pistons reach TDC thus Spark Plugs are also firing at BDC
this causes two issues

coil saturation time is crippled, for the above engine working at say 9,000 rpm down Donnington front straight, the coil is being tasked with working at 18,000 rpm as it has to fire 4 times in a 720 degree four stroke cycle instead of twice for a "normal" wasted spark ignition set up
does not sound like an ideal racing ignition system to me

second issue is what is happening when you fire the Spark Plug at BDC on the Induction stroke, and this is what I posted on the "other" forum
your piston has been travelling down and sucking in a fresh fuel charge and just before it gets to BDC (ignition advance map is in play here) the system throws a spark into an uncompressed fuel/air mixture, it has to ignite, it has no choice

and that is why I am impressed that Dave even got the engine to run at all, I thought that the carbs would be blown off

Dave's BB Ignition system with 1 x dual coil would work fine on a 750 engine being 360 degree crank phase
on the 500 Monty 180 engine you need to run two x single pole coils and fire them independently

 

[LaverdaIan]

I've got two dyna coils.. pretty sure each one leads to one cylinder or the other.. works fine for me..

8)

 

[Fitz]

Me again, just to clear things up, Phil was correct about the number of magnets, my mistake, one rotor magnet - two pickups. The BB box has two inputs, one from each pick-up but only ONE output which I had going to a dual output Dynatek coil - It still didnt work, the head gasket picture is attached

You can see the difference and before I put my new exhaust system on (thanks Phil) have a look this you tube clip https://youtu.be/2USpuHcA6Tw

This my bike, sat ticking over on the bench, no glowing exhausts and picks up really well on the throttle and sounds (hate this Americanism) AWSOME

Just for information, the Sachse box of tricks has 9 pre programmed advance curves and another setting for continuous firing to help wit the set up all at the twist of a small selector switch

The only bad bit of the design is the three grub screw fixing the rotor to the crank, the lads in Oz tell that if they vibrate out they are going to trash the trigger plate, I have used thread lock as advised but Red has a modified rotor that overcomes this issue

I just need one more fairing bracket making then it is finished, off to Oulton or Donnington to bed the motor in and see how we get on, off to the Dyno man then all being well racing soon 

If anyone needs more info let me know