1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

1973 Commando 850 in Seattle

Discussion in 'Norton Commando Motorcycles (Classic)' started by walt_mink, Sep 14, 2017.

  1. walt_mink

    walt_mink VIP MEMBER

    Feb 10, 2013
    Hi all,

    After years of thinking about it, I've finally gone ahead and gotten myself a Commando! Wow, does that ever scratch an itch. I've been wanting one since I was a kid. I have a long history with British cars from the 60's and with brass and nickle cars, so I don't come into this blind, but I'm certainly not up to speed on classic bikes. This is going to be fun!

    So, some background: When I went to look at it, the gentleman couldn't get her to fire up, which I was sure was attributed to bad gas clogging the carbs and petcocks. I could tell it had been sitting longer than he wanted to admit. It's a '73 850 with a 75 (I believe) front end on it. Not sure how (or why) that happened but I suspect the originals were damaged at some point. The numbers don't match, and the paint isn't great, but I'm not looking for a concours correct original - I just want to ride it. For other mods (as far as I can see) it's got a Mikuni and a Boyer ignition. I got a great deal on the bike because of the lack of seeing it chooch, dragged her home, and set about getting everything cleaned up.

    I broke the carb down and cleaned it out with the ultrasonic cleaner and a bucket of elbow grease. It was in need, for sure, but wasn't too terrible. The petcocks, on the other hand, were disgusting. Once those were clean, I filled the tank with some tumbler media and detergent from my vibratory polisher, and shook the tar out of it for about an hour. After a thorough rinse, I used the POR fuel tank kit to seal everything up. Once it cured for five days, I popped in a new battery, new gas, and started kicking. I got her running on the third or forth, which I take as a victory for a kick-start newb. I got the idle set at about 1000 rpm and it ticks over pretty steady. Brakes, clutch, trans, lights, and charging all seem to work okay, so I took her out for her maiden-to-me voyage.

    Overall, it seems to run pretty well. The brakes are certainly nothing to write home about, but I think they can be improved with some tinkering. The clutch is a tough one, but again, I think a new cable will go a long way towards helping that out. I believe I overfilled the oil tank and, as a result, I have a very well lubricated right shoe, but that's no biggie. The only real issue I have is that when the bike is nice and hot it starts to miss really badly. At first, it was just low down in the revs (~1/4 throttle), so I was tinkering with the air screw trying to find a happy spot but then it started acting very poorly no matter what RPM I was at.

    I'm leaning towards it being an ignition problem since it gets much worse with heat, but logic says I should look at the last thing I worked on, which was the fuel system. I'm relatively sure I did a good job rebuilding it, but again, I always doubt my last job. Maybe the experts here can point out something obvious with the setup on the Mikuni.

    Needle - 6DH3 on the middle ring
    Slide - 2.5
    Main Jet - 250
    Pilot - 35
    Cutaway - 2.5
    Needle Jet - 159
    Air screw - I started with it at two revolutions out and tinkered from there.

    Anyway, I'm extremely happy to add this to my stable of misfit vehicles and look forwards to many many years of tinkering with it.


    Cheers all!
  2. Mr. Rick

    Mr. Rick VIP MEMBER

    Feb 6, 2009
    Nice lookin machine! Congratulations!
    Did you tell us what size the Mikuni is? Others on this forum know the proper setups for these...
  3. triumph2


    Aug 13, 2008
    159 is the type of needle jet not the size, which will be something like P-4. What size is the carb?
  4. Fast Eddie

    Fast Eddie VIP MEMBER

    Oct 4, 2013
    Boyers often suffer a failure where the wires are soldered to the back plate in the points housing. This can (and did with me) cause strange intermittent misfire symptoms. It's very easy to look at this and assume all is well. Give the wires a good looking at a good tug. If they're sound, you've nothing to fear - if they're not, you've nothing to lose!
  5. laurentdom


    Nov 30, 2012
    She looks really superb! Congratulations.

    Re: the stiffness of your clutch, in addition to changing the current cable for a new one (Venhill Featherlight as an example) you may find interesting info about the disks stack height either on this site (sorry, don't remember which keywords to search...) or on the Old Brits one where Fred explains very clearly how to set it up (in his technical pages I think). Dynodave knows also a lot about it.

  6. frankdamp


    Oct 7, 2005
    The Commando clutch should be a fairly light pull. For a heavy clutch, check out an Atlas! Since the bike has been unused for some time, the cable could have rusted up. The original cables were just steel wire in a steel tube with no lubrication. I don't think any of it was CRES. A new, modern-style cable with Teflon impregnation would resolve the problem. There may also be some corrosion issues with the plates and cage.

    I'd love to see the bike - they're pretty rare in the Northwest. Maybe you could get it ready for next year's Oyster Run. This year's Run is next Sunday, 9/24. We've lived in Anacortes for 18 years and I've gone into town every year to look around. I haven't seen a Commando there yet and maybe only one or two Dominator/Atlas bikes. Last year the weather wasn't very good and there were "only" about 20,000 attendees. There have been more than 40,000 some years.
  7. rvich

    rvich VIP MEMBER

    Jul 25, 2009
    Some easy things to overlook that shouldn't be:

    Clean the kill switch.
    Clean the ignition switch.
    Still have the molded electrical block under the tank? Throw it away and work out another way to connect those wires whether traditional bullets or something else. Make sure the ignition is getting full voltage. Then go back to the carb. The time spent cleaning the electrical won't be wasted even if it doesn't solve the problem.

    Is the ignition points or electronic? (Edit: Now is see the Boyer listed. Double up on cleaning the electrical contacts!)

    Regarding clutch pull, the stack height does make a big difference. So does lubing the cable and making sure the lever arm in the transmission is properly aligned with the cable. Different camps on how to properly set up a clutch are about as varied as what kind of wine to serve with Chinook salmon.

  8. Nater_Potater

    Nater_Potater VIP MEMBER

    Apr 7, 2013
    Nice looking bike! I'd love to find one that doesn't carry the significance (to my family and me) that mine does, only so I'd be more at ease to perform some "better" mods/upgrades.
    Is that an aftermarket horn up by the coils?

    I'd say "yes", unless someone merely swapped the stock legs side-to-side, a la MkIII. There's much conjecture about why that was done on the '75.

    Pay attention to Fast Eddie's comments about the Boyer pickup coil wires.

    The only change I can see from my 34mm is the slide cutaway. Mine's a 3.5, but it's also running a 35 idle jet at 2400 feet above seal level. As for the idle mixture, it should end-up somewhere around 1 turn out. At sea level where you are, you may need to be closer to a 45 on the idle jet to get that 1 turn out. That may then cause you to be too rich just off idle, which would then necessitate the 3.5 slide. Such a can of worms...

    Have fun!
  9. 1up3down


    Jan 12, 2011
    your setting are all ok except the standard air screw setting is about 1 and one quarter to one and a half turns out from seated, but that should be with a 40 pilot
    for example I am at around 6000 feet altitude and use a 35 pilot and air screw 1 1/2 turns out so you are close but I would order a 40 and set air screw 1 1/2 sea level

    in addition, you are going to need to get intimate with your primary and how to self service/clean the clutch plates and learn how to set the clutch inside the primary
    and so you should order a tool you will need, a commando clutch spring tool, also get a shop service manual, a haynes or whatever

    on to wiring, yours is now some 45 years old, you could have poorly grounded wires or fractured wires, causing the engine to miss at various speeds
    you can try to live with it and hope it does not leave you stranded, or you can at some point get fed up and decide to re wire the bike, lots of help on the forum!
  10. walt_mink

    walt_mink VIP MEMBER

    Feb 10, 2013
    Hi all,

    My apologies for not responding sooner - I got called out of town a bit unexpectedly. I'm writing this from 32,000 feet over the East China Sea. Isn't technology grand? Anyway, let me respond to your great questions:

    I think it's a VM32, but I'll have to verify.

    Well, crud. I'm not sure. I see some chicken scratch on my notes that looks like P-4, but I'll have to verify next time I'm back in there, which might very well be soon.

    This was excellent advice - thank you. I pulled off the plate and found a few problems.

    * First, there was a ton of oil floating around in there, so everything needed a good cleaning. I believe the oil came from my ham-fisted oil tank overfill, but I'll monitor to be sure.
    *Second, the bullet connectors were not assembled well at all, which could have easily resulted in poor connections and possibly even a short to ground. I sorted that out with new connectors, solder, and heat shrink.
    *Third, the solder joints on the unit were, indeed, quite poor. I reflowed everything and am a bit happier, but am unimpressed with the build quality.

    Thanks very much for the pointer. I think I'll make this one of my first projects this winter. You also got me to look up Old Brits, which is just a few miles away from Seattle, so I really appreciate that! I like knowing they're so close.

    Thanks, I'll be taking care of replacing all the cables this winter. They're all a bit worse for wear, so it's a worth upgrade.

    Yeah, I'll try for next year. I've done the Oyster run before on my modern bikes, but trying it on the Norton sounds like more of an adventure. :)

    This, I think, was the key to a big part of this. I noticed the next time that I tried (and failed) to start the bike that when I tickled the kill switch the bike would give me a puff, which lead me to look closer. I was expecting a normally open switch, not normally closed, so the importance of cleaning and protecting this connection became a lot more apparent once I was in there.

    There has also been a lot of hodgepodge work in that switch housing. There were extremely poorly soldered connections, odd chunks of electrical tape, and very weak sections of wire that have suffered hack jobs over the years. I cleaned up everything to the best of my ability, but I think it'll take more work to get me happy with it. It did, however, seem to alleviate some of my issues.

    I dunno - is it an aftermarket horn? It's pathetic - I know that much. Ha ha. Thanks for the pointers on the idle screw. I think I have a (self inflicted) timing issue now, but once I have that fixed I'll start from one turn out.


    Good advice - I've got the parts ordered. I'll get into the primary this winter for some exploratory surgery. You're also right on the wiring, but I know myself, and if I rewired the bike then I'd probably end up doing a full restoration because I can't control myself. I really need to finish restoring my car before I do that. That said, if it gets to be too much of a problem I'll have to give in.
  11. walt_mink

    walt_mink VIP MEMBER

    Feb 10, 2013
    Okay, so with all of that good advice taken into account, I made a little progress. As I mentioned above, I cleaned up the kill switch and associated wiring which made a big difference and I cleaned up the distributor and wiring too.

    While that improved things, doing the work knocked the bike out of time (duh) so I'm not sure if the issue is fixed. I tried to get it re-timed, but my old strobe died in the toolbox, so I'll have to wait for the new one to arrive before I can knock out that project.

    I also decided that I wasn't happy with the quality of the Boyer setup. The wiring, the assembly, and the general condition of it makes me nervous, so I did what I do best: I ordered a ton of expensive parts. :) I bought a tri-spark ignition, single coil conversion, and the high output charging system. I ride in the city a lot with the lights on, so I thought that would be a good bit of prevention for future problems.

    So, I hope to get some time this weekend (once the jet lag wears off) to dig into it and get it installed and timed up. I'll let you know how it works out.

    Thanks again for the great advice.
  12. gortnipper

    gortnipper VIP MEMBER

    Nov 11, 2013
    You should look at installing a horn relay switch and an aftermarket horn if you dont have one. The stock horn IS pathetic. I have a Fiamm that was better, but improved hugely with a relay switch.


    If you ride a lot at night, you should also look at a LED bulb, either as a Trucklite lens replacement or even just a replacement BPF P36d bulb like one of these -

    http://www.dynamoregulatorconversions.c ... s-shop.php
  13. lazyeye6

    lazyeye6 VIP MEMBER

    Feb 28, 2014
    "I bought a tri-spark ignition, single coil conversion, and the high output charging system."

    +. +. +. All that's left is to install a Podtronics or Tympanium regulator and then rid yourself of the archaic Lucas Zener Diode and Rectifier. :D

    You noted that your points cavity was full of oil when you replaced your electronic ignition. That sounds like the oil seal behind it has failed,
    and/or you need a reed breather to reduce the pressure within your crankcase. This was happening with my bike. I replaced the oil seal and it
    still leaked there. It went away when I installed a Comstock Sump Breather.
  14. walt_mink

    walt_mink VIP MEMBER

    Feb 10, 2013
    Yeah, agreed - I'm going to need more '"Hey - quit trying to kill me!" power from my horn. I'll take your advice on the relay and will start shopping for a horn. I dig the Trucklite, but will probably start with the LED replacement. Thanks for the pointer.

    The Tri-Spark alternator upgrade comes with a Podtronics regulator, so I should be covered there. Box shows up tomorrow, so I'll hopefully get some time this weekend to get it all installed.

    Thanks for the warning on the breather. I'll look at modifying the breather along with some attempts to slow the pace of wetsumping this winter. On the oil seal, I'm hoping (and thinking) it was just from the oil being sprayed everywhere along with a missing screw on the cover. I'll keep an eye on it for sure.
  15. walt_mink

    walt_mink VIP MEMBER

    Feb 10, 2013
    I snuck out to the shop this afternoon to do a little preparation for the parts to arrive tomorrow. I guess I'm a bit eager to get some play time before the winter sets in. :D

    Anyway, up on the stand and tank off to make life a little bit easier. It soon became pretty apparent that the PO wasn't much of an electrician.

    Wire nuts for the horn:

    Twisted and taped wires for the blinkers:

    And just generally a LOT of electrical tape and wire taps. I'm considering just replacing the harness before I set to soldering the connections in. Any advice on who makes/sells the best quality harness?

    While I'm on the topic of wiring, I went to clean the grounds, but can only find the one on the head steady. Are there more that I'm missing?
  16. cjandme


    Feb 5, 2011
    Add some more ground wires for sure.
  17. rx7171

    rx7171 VIP MEMBER

    Oct 8, 2007
    For wiring harness I'm happy with the one I got from Commando Specialties. I've been told they also have one that doesn't have all the unneeded wires that were used for the police bike version.
    OldBrits a great supplier also. Great tutorial's on their website and a dream to order parts with their super easy setup.
    They do offer clutch metal spacer plates of various thicknesses for adjusting stack height which usually fixes hard clutches. Mine's a two finger pull when before it was a bear.
  18. rvich

    rvich VIP MEMBER

    Jul 25, 2009
    Every bike has its own story to tell, but my experience is that the original harnesses are pretty good quality so long as they haven't been melted or butchered too badly. Moving to EI you will find some wires are no longer needed. When I installed mine I went through the process of taking the old tape off and wrapping it with new tape. It didn't take very long to do it a section at a time and I was able to remove wires that were no longer needed. It gave me a chance to inspect everything and work on improving all the connections. Then I went to the local NAPA store and bought some grounding straps. I ran them from the positive post on the battery to various places on the engine to improve the ground circuit.
  19. Nater_Potater

    Nater_Potater VIP MEMBER

    Apr 7, 2013
    Is that a two-wire, high output setup, or a three-phase kit? It makes a difference in low-speed (low rpm) driving. I'll have to do some deeper searching, but there's a rather lengthy post about this very thing somewhere in the archives. Suffice it to say; if you're looking for better low-speed performance from your alternator, you'll need to go with the three-phase setup.

  20. walt_mink

    walt_mink VIP MEMBER

    Feb 10, 2013
    I have a box due to arrive from OldBrits today. It's full of cables (brake, clutch, speedo, tach, and throttle) and various smaller bits and bobs. I've also get a new clutch set from Barnett on recommendation from a local owner who reached out to me - thanks Douglas!

    You're right - as I dove in more on the wiring, I found that the cables themselves were in pretty good condition. The issue was the wire butchery that happened when it was installed. Now that it's all cleaned up, I feel pretty good about it. I did add several more grounds during the install of the new ignition and rectifier.

    Three wire. I ordered the whole setup from CNW which included the ignition, alternator, and rectifier. The output is excellent at every speed. I rode around with my meter on the tank to verify. :)

Share This Page