Tech Tips

Ural - Diabolical Ignition Module Diodes

 

 

This problem is experienced in the type 1 ignition systems. They are the type which have the ignition module mounted under the rider’s seat. It’s a small aluminum & plastic rectangular box with cooling fins on the top. If you have noticed that your bike has been idling fine and running at high speed nicely, but coughs & sputters when pulling away from a stoplight, your ignition module may have the diode problem. Most people think that the problem is caused by the carbs and spend their time cleaning, tuning and synchronizing the carbs only to have the problem persist. When all else fails try replacing the ignition module diodes.

Step 1 Remove the ignition module from under the rider’s seat.

(see photo)

Step 2 Open the box.

Step 3 Locate the diodes.

(see photo)

Step 4 Unsolder the diodes and replace them with either 1N4005 diodes or Radio Shack p/n 276-1114

(see photo)

Step 5 When you replace the old diodes with the new ones make sure that the lines on the diodes are facing the same direction as the old ones were!

(see photo)

Step 6 After the new parts are soldered onto the board reassemble the module & enjoy the smooth ride!

p/n 276-1114

---

In your diode fix text on the NARMA page you specify using 1N4005 diodes in  the text but the pic is of 1N4001 diodes. Which are the correct ones? I used the 1N4001, is the amperage rating high enough? The diodes that came out of my box were totally different than the ones in yours, they were  metal "tophat" looking cans rather than silicone. Now I'm wondering if I replaced the right ones heheheh.   --  Gonad

As for the diodes either type will do. The 4005 is a really good general purpose but the Radio Shack 4001 will do nicely. The diodes that you took out are an ancient type. The fact that they don't look quite like the ones I took out tell me that they use whatever is at hand when they build the boxes.  --  Derek

October 31, 1998 --  Hay, what's up with the diodes?
Are some of you haveing problems with the low power ones, ie; 1N4001.  I have used this and the bike runs great, but am I looking at trouble down the road?  Is it necessary that I up grade?  My bike was running good when I performed the mod and I think it is running better now. The 1N4001 DIODES cost ~  $ 0.49,piv~50v,max current~30a. EURO RETRO = URAL / DNEPR  --  Sidney

October 31, 1998  --  Sydney, it was suggested that the diode mod should use the absolutely highest rated diode that Radio Shack has to offer. That's probably pretty good advice to follow. Especially since the price isn't much more. Although I haven't heard of any difficulties with the one that you used, I'm going to change the procedure to use the latest part number. I always like to make things as strong as possible. Sort of like my Dad who built a sailboat that weighed twenty-two tons!   --  Derek

November 1, 1998  --  Here's a part number for a super duty, overkill to the max, take no prisoners diode for the ignition module repair. Radioshack 276-1114  2.5 amps (80 amps surge) at 1,000 volts Peak Inverse Voltage rating.
If this puppy doesn't last, not much will! --  Derek