MK III starter motor 4 field coil, 4 brush upgrade

I am in the process of trying to do the 4 field coil, 4 brush Prestolite starter motor upgrade on my MK III. I am using the original housing rather than a Harley/Prestolite housing and have installed 4 field coils and 4 brushes as well as a needle roller bearing to replace the drive end armature bush. The problem that I have is that I cannot get the motor to run in the correct direction. It runs very well but only in the opposite direction. I need very specific directions on where the brush wires should be connected to the field coils and what holders all 4 of the brushes should be placed in. I have the field coils connected to the original connecting spot on the housing, so if this needs to be moved, please let me know this also. Thanks.

The instructions that came with the four brush kit I fitted to my own MkIII shows the brush adjacent to the terminal post and the one opposite connecting to the terminal post. The other two connecting to the field coil connection. Although I do not know if there is a difference if four field coils are used?

While i have not completed this mod to my bike as of yet it is my understanding that if you use the original case, you have to rotate the brushes 90 degrees which will mean slotting the case for the post. I believe that is why they use the Harley case as it is already orientated correctly.

Good luck and lets us know how you make out.

L.A.B. said:

The instructions that came with the four brush kit I fitted to my own MkIII shows the brush adjacent to the terminal post and the one opposite connecting to the terminal post. The other two connecting to the field coil connection. Although I do not know if there is a difference if four field coils are used?

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Ron ,thank you for your message. When you talk about the brush adjacent to the terminal post are you referring to the brush holder that is directly in line with the post(going towards the center) and then the holder that is directly, 180 degrees, across from it ?

If that question was intended for me (L.A.B.) then, yes.

Jack,
It's been several years since I last did one of these, but I believe that if the motor spins backwards you need to move each brush one position clockwise and it will reverse the rotation. This can be a stretch for some of the brush leads, at least with the Harley field coils that I used.

Jack Moffett said:

I am in the process of trying to do the 4 field coil, 4 brush Prestolite starter motor upgrade on my MK III. I am using the original housing rather than a Harley/Prestolite housing and have installed 4 field coils and 4 brushes as well as a needle roller bearing to replace the drive end armature bush. The problem that I have is that I cannot get the motor to run in the correct direction. It runs very well but only in the opposite direction. I need very specific directions on where the brush wires should be connected to the field coils and what holders all 4 of the brushes should be placed in. I have the field coils connected to the original connecting spot on the housing, so if this needs to be moved, please let me know this also. Thanks.

Click to expand...

12/9/05, I got everything figured out today. The difference in performance, over the stock set up, is very impressive and well worth the time and money. The total cost was about $100. If anyone wants the directions let me know.

Jack,
How did you attach the brush wires to housing? Spot weld? Silver solder? I tried to do this mod using two Norton starters, intending to make one four-pole, but found it nearly impossible to remove the screws securing the field coils to the housing. It was much less trouble to pick up a good used Harley field coil at a swap meet.

The biggest improvement on this is to use welding cable to make some decent size starter cables. The stock wires just won't carry enough amperage/voltage to spin the motor effectively. With the four pole modification and large cables, I can start my 10:1 compression cafe racer!

However, I believe the final answer is DynoDaves replacement starter.

Ron L said:

Jack,
How did you attach the brush wires to housing? Spot weld? Silver solder? I tried to do this mod using two Norton starters, intending to make one four-pole, but found it nearly impossible to remove the screws securing the field coils to the housing. It was much less trouble to pick up a good used Harley field coil at a swap meet.

The biggest improvement on this is to use welding cable to make some decent size starter cables. The stock wires just won't carry enough amperage/voltage to spin the motor effectively. With the four pole modification and large cables, I can start my 10:1 compression cafe racer!

However, I believe the final answer is DynoDaves replacement starter.

Click to expand...

I'm sure that DynoDave's Hitachi starter does a very good job. I have exchanged a few emails with him and he seems like a very nice guy. I almost bought his Japanese starter motor but when I thought about it I decide that, if I could improve the original motor enough to to a good job, I'd rather have that on my MK III than a Japanese motor, so I just decided to take on the challange of improving the original Prestolite starter motor. I sent a lot of time on the internet trying to find the specific information I needed and couldn't find any very specific information that explained it all clearly so I just decided to see if I could figure it out for myself. Fortunately, after a lot of trial and error I did. To answer your question about the field coils; on my starter housing there was a fixing loop for the original field coils attached to my housing, on the inside just a little counter clockwise of the negative feed fixing slot. I solder all 4 of the field coils (I used Accell High Torque field coils) together and then fit the open end into the loop, crimped it and soldered it using a high output soldering gun. I used the same soldering gun to solder the field coils together. I tried a regular soldering gun for awhile but it just wouldn't generate enough heat. Once I got the high power gun it was easy. I'm working on a diagram that shows how everything goes together and it should be ready in a day or too. I don't know how to put it on the website (maybe someone else can) so if you want to see it send me an email, zekemoff@wmconnect.com, and I will send it to as an attachment that you can download and print.
The improvement in performace over the orginal motor is very impressive so I'm very happy with it and am glad that I didn't buy the Hitachi motor. I also replaced the brass bush on he drive end with a Torrington B118 needle roller bearing.

After 8 dismal years i finally have a starter that works great and would just like to take a minute to thank Jack Moffett for his help and patience. Jack was kind enough to supply me with all the information i needed and with help from the local starter rebuilder here in town this starter is now a thing of beauty. My cost was $60 for the Accell High Torque field coils , $30 for the 4 brush plate and $60 for putting it together for a total of $150 Cdn. I was contemplating putting it together myself but after a day of messing around i decided it was not worth the frustration. The guy at the rebuild shop spent the best part of a saturday doing the job so well worth the $60. As i was in need of a new battery i decided to go a step higher and installed a Deka AGM EXT15L. It is rated at 190 CCA but the test at the shop showed over 400 CCA and fits in the original battery tray without any modification.

Jack , once again , thanks.

Hi Jack,

Can you send me the modification sceme for the Prestolite starter?

Thanks,

Wim

wim@vbeurden.eu

Does anyone have an OEM number for the oil seal that fits in the end cover of the Norton starter? It carries a Norton part number of 066310, but the only place that I can find that has it is Norvil. I don't want to send across the pond just for an oil seal.

I haven't had to mess with these for several years, now I have three to do. Even the aftermarket field coils, brushes, and brush holders are getting hard to find.

Thanks in advance.

Starter for MKIII

I purchased an 850 electric start. Not to much electric starting is going on since the startermotor is missing! I realise that one could buy a new one from Colorado Motorworks for $495 but does anyone know of a source that I actually could afford? Prestolite starters are used by evinrude outboard motors but there are many different kinds. No idea which one would fit the Commando. I know the "electric assist" is considered a "sissy" thing but I buggered up my knee and have sometimes a hard time kick starting especially in the slightly cooler Canadian winters... Besides, it would be nice to have it on the bike since it is an empty space now. Any advice is appreciated

Various Harley Prestolite starter parts (field coils/4 brush plate etc.) can be used in the Commando starter, however, the starter end plate that connects it to the primary case and the armature are specific to the Commando, so is not just a 'bolt-on' job I believe.

As L.A.B. points out, the armature and end cap are specific to Norton. If you don't have those, a Harley or Evinrude starter will not fit. This leaves CNW's Prestolite copy (if you like chrome) or Dyno Dave Comeau's Hitachi based version. Dave's website seems to be down at the moment, but I believe his starter retails for around $385 and is somewhat more powerful than the 4-brush Prestolite.

I have some spare end caps and field coils, and could build you a Prestolite starter if you could find an armature, but you would still have over $200 invested. PM me if you wish to pursue this.

If you have just a "hole" in in the primary, are you missing the idler gear and the rest of the gear train?