BOSCH IGNITION twins wire info / diagram - updated image

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BevHevSteve
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BOSCH IGNITION twins wire info / diagram - updated image

Post by BevHevSteve » Mon May 15, 2006 6:40 am

One of the big problems that needs to be addressed on ALL bevel drive twins with Bosch ignition is the pickup wires. They are always dried out and cracked due to heat from the header pipe, and inside the engine the insulation has melted. Either way you end up with ignition shorts.

Chances are, someone in the past has tried to do a repair and most likely didn;t do a complete or good job of it. The sketch below shows what wire goes to which inducer etc. so you can easily remedy this.

DO NOT REMOVE YOUR PICKUPS FROM THE CASE!!!

You should also check your pickups, the normal value for them is approx 235 ohms.
Last edited by BevHevSteve on Thu Mar 26, 2009 3:17 pm, edited 2 times in total.
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abmartin
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Post by abmartin » Mon Oct 27, 2008 1:50 pm

Does this help? Copied from a Darmah workshop manual.


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Oz Duck
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Post by Oz Duck » Thu Mar 26, 2009 4:35 am

Hi Steve

I initially wired my pickups incorrectly & couldn't get the bike started. It would splutter, backfire and kickback on the kickstarter......I ended up with a very sore foot lol.

Anyway, I swapped the wires around at the 4 pin connector, so that the lower pickup was the horizontal and the upper pickup the vertical.......no problems starting and no sore foot.

Joe

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Post by BevHevSteve » Thu Mar 26, 2009 11:02 am

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Post by Oz Duck » Sat Mar 28, 2009 5:27 pm

I also think there is an error in the 900SS wiring diagram, it is the same as the one posted by abmartin for the Darmah but there is an arrow on the ignition rotor showing anti-clockwise rotation.

It does explain in the diagram that the view of the pickups is "seen from the cover inside" so in that case the rotor would be seen to be rotating anti-clockwise.

However, if this was correct then the horizontal cylinder would be firing 90 degrees after the vertical. As I have confirmed that the upper pickup is the vertical and the crankshaft rotates clockwise of course (looking left to right), then it is the vertical cylinder that fires 90 degrees after the horizontal.

Am I missing something here guys? Or is it as Steve says that I have a different perspective on things from Down Under??? LOL

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Post by BevHevSteve » Mon Apr 13, 2009 10:39 am

bevel drive cranks rotate anti clockwise yes
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Post by JohanM » Mon Jun 22, 2009 8:36 am

Please excuse my ignorance. Having no idea about electricity on the bike. I have a 900S2, the fire on the vertical cylinder comes and goes. When u are riding full tilt the power will suddenly be gone (running on 1 cylinder), while you're at speed u can switch off the bike, turn the key further to the left and back on and suddenly you can continue on 2 cylinders???

Can the pick-up cause this? When will you know that the pick-up wiring need to be replaced, what problems will this create?

Thanks
Johan
900 S2 1983

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Post by BevHevSteve » Mon Jun 22, 2009 8:44 am

....... if you still have the original wires on your bosch pickups...........

:arrow: Then you KNOW that they MUST be replaced.

You may have a problem elsewhere, but at least you will know that THIS problem has been dealt with
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Post by Oz Duck » Mon Jun 22, 2009 10:08 am

Hi Johan

I recently bought a 1984 900S2 and had the exact same problem, the first thing I went for were the pickups.

However, in this case they had been previously repaired and weren't the source of the intermittent firing of the vertical cyclinder.

I just replaced the spark plugs and everything was fine.......easy fix!

But as Steve says, check the pickup wiring if you don't know of their previous history.

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Molex Pins for ignition subharness connecter

Post by KevinVernon » Mon Aug 03, 2009 3:11 pm

Got the darmah ignition subharness and shiny new aero cable to replace the knackered ignition cable on my GTS

having trouble finding the correct molex pins. Worked out they were 0.093 however only ones I can find are for 18-22 AWG. Molex used to make them in a number of sizes down to one suitable for AWG 30 (p/n 02-09-1143) which would be much better matched

Anyone know where I can find some of those or am I going to be forced to buy the 18-22awg ones and tinker the crimps and presumably solder them for safety

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Re: Molex Pins for ignition subharness connecter

Post by mizike77 » Wed Aug 05, 2009 11:14 am

I had the same issue. I went radio shack and found the pins. I think the are 18-22. They worked fine but I had to buy a complete connector kit just for the pins.

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Re: BOSCH IGNITION twins wire info / diagram - updated image

Post by l_aysan » Sun Mar 11, 2012 6:35 pm

Hey guys,

this is my original post on ducati.ms
http://www.ducati.ms/forums/14-vintage/ ... inder.html

basically i was running on one cylinder, my plug wires were done for so i changed to the dyna coils and new nkg wires.

I was still intermittently running on one cylinder and through swapping components and what not; it seems to be the pickups. after talking to Steve I'm now going through replacing the pickup wires with a high temp chemical resistant wire (Teflon Coated FEP)

but after taking off the case and inspecting the wires they look fairly good ... no fraying or breakage, the only little bit i can find is right up at the coil .... tiny less than 1mm square on one side of bare wire showing

Also, how do i install the new wires when i get them? where do i make the splice? i was expecting to be able to replace the whole wire. Not have to splice

pictures below ...



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Re: BOSCH IGNITION twins wire info / diagram - updated image

Post by BevHevSteve » Tue Mar 13, 2012 8:19 am

your wires are cooked. Figure out which wire goes where, take some notes and cut the wire 3/8" away from the pickup, strip the sheathing and attach your new wire. Do 1 at a time, use a straight crimp tube and hi temp shrink tube to insulate it. Repeat for ea wire. After both wires are done on a pickup use hi temp RTV or whatever and after spreading the 2 wires apart from eachother, put a dab on the exposed wires. Repeat on other pickup.
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Re: BOSCH IGNITION twins wire info / diagram - updated image

Post by Gymmy74 » Fri Dec 07, 2012 5:30 pm

I removed the pickups from the case. I should have read this a month ago.

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UPDATE: BOSCH harness kit and instructions now available

Post by BevHevSteve » Wed Jan 06, 2016 3:25 pm

I have written a complete manual on how to do a wire replacement job on your BOSCH ignition bevel drive twin.

https://store.bevelheaven.com/Install-G ... nt-Manual/

NEW: I now also have a complete wire harness kit containing a correct FEP sheathed wire harness and the misc. things you need to do the job available. When you purchase this kit you will get a complete step by step guide with lots of photos included on how to do the job correctly.

https://store.bevelheaven.com/Electrica ... SS-Darmah/

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