RE;setting up Mark two’s on their Norton’s (2004)

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Apr 7, 2004
I thought this might help people setting up Mark two’s on their Norton’s

The set up on my Norton Commando for Mark 2’s follow, the carburetors on mine are 34mm. Jetting is fairly typical. Needle jet is a 106, needle is 2A1. Main jet 250, Slide # 3 cutaways, pilot jet 25.
It’s all the other things that make them run right. Other things; the slides are 2 cycle parts, brass with chrome plating. The floats are also 2 cycle parts much larger than four cycle floats. I elected to blend the 34mm size down into the head but it will work if you just blend the size difference in the manifolds. The aluminum bushings at the air entrance of the carb are removed to defeat this circuit. The air cleaners are huge K&N's this requires a notching of the oil tank for clearance but since this mod is at the top of the tank one doesn't loose much oil capacity. . Also these carburetors do not clear one another and require grinding were they touch at the unused idle screw bosses in the casting. This set up needs dampening support without it the carbs will not stay on the rubber spigots but that’s not the worst part. The needles and their jets will wear very soon without dampening. The mark 2 carburetors have a semi flat spot above the intake throat in the casting that must be machined flat. There are two tapped holes on this flat spot. One just makes a piece out of aluminum 3/8 thick by1/2 tall by 1and 3/4 long. Than drill clearance holes to line up with the tapped holes that are already in the body. Than drill and tap 10-24 hole in the middle of the aluminum key for 1/4 shoulder bolt 3/8 long shoulder on the same plane as the mounting screws. Now just install hardware hooks in the frame above the shoulder bolts and use O-rings to suspend and dampen the carb assembly. On a Commando these holes are in the slanted sheet metal gussets that are mid frame use the threaded hooks with nuts and washers. Custom made very light gage throttle and choke cables need to be used. Also use straight cable fittings at the top of the carburetors. I use an after market throttle mechanism for dirt bikes that has the cable coming out parallel to the handle bars and the cable adjusters are underneath the tank near the splitter boxes. Don’t put the adjusters out in the air. Cable routes are very important so take extra time to get this right or you will be constantly fiddling at adjusting later as the system wears in. Start rich and work to lean till she's nice and snappy mine gets 50 MPH and no dead spots or sick rich out of the plugs. Starting needs half choke most of the time with a two block warm up. I had to buy some of the knurled idle adjustment screws and than add small springs to get it to hold idle. All my other bikes will be single carbs don't care about 120 MPH so much any more. Most of these modifications were necessary because my bike has a some what higher compression ratio and a higher balance factor and a Winy Eads’s rose joint head steady. You can't win, you can't brake even, and you can't quit. Norbsa48503

Got a photo?

I'm interested in the mounting of the carbs with the rubber manifold and the O-ring dampening.

The mark two carbs are on my alum. bike the 72. I will try to get some photos on a site for you soon. norbsa

I just read your essay on Mark IIs and was absolutely stunned by the brilliancy of the last line.

Please alow me to repeat it: YOU CAN'T WIN, YOU CAN'T BREAK EVEN AND YOU CAN'T QUIT.

I love it! It's so poetic and so befitting of the British bike experience; pure literature! All the joy, frustration and pride of owning a British bike neatly wrapped into one succinct sentence! Peter Egan would be proud. Not only is this sliver of literature befitting of Norton ownership but of life in general!

Great work,

Jason, It's the second law of thermodynamics as taught to me by a college physics proff and it stuck. That was way back in 1974 I was driving a 1971 TR6C as my only transport. Got to ride with a racer on the Ohio back roads who is 72 years young this last week at the Norton rally He was on an 500 single BSA that was borrowed and his riding gave us all a lesson He wipped are asses in the turns. I could get him in the straights but no way on the turns. I hope I can give a lesson like that when I am 72 what a hoot. norbsa

None of my college professors ever said anything that profound. Thanks again for sharing it with us.

Now, your 72 year old motorcycle racing buddy sounds interesting!


Norbsa _ Thanks

Great, thanks for the MK 11 info! Thats what the forum is all about.

I have MK 11's as well. I like the idea of adding the bracket to join and support the 2 carbs. I'll do that later.

I have been running my MK 11's for about 3 years and have my first problem. The left hand float had a small hole in it and eventually wouldnt float, so I have 2 new ones on the way. I put it down to todays fuel.

I am running a 25 pilot jet, not a 20, otherwise the same.

I welded a stub in each MK 11 manifold and added a balance tube.

Otherwise the same setup, and I am very happy with the performance and slow running,

Jerry, I had to change to #25 pilot jets for an easyer start but now I find that it's too rich for campground first gear work with a hot motor. I think I will try drilling a #20 to half way in- between and than polishing the hole with small cotton string and Auto-Sol. The latest thing I have found and you may what to try is spark plugs. I always liked Bosch Plat WPR 7's because of thier toughfness to gas fouling. My bike is geared tall and dosn't red line in third gear it stopped at 100 MPH I was playing at improving this and found that Auto Lite AP63's got me to 105 MPH and Auto lite AP64's took me to 110 MPH. The bike runns better all around now and these plugs also are easy to read and don't foul out easy. All platnum plugs are resistor type and so the need for the hotter set ups. It's the cheapest HP I have found. Jerry some time ago I asked if you could find the K&N air filter # that you are using for me because it looks like you have no need to Knoch the oil tank with the ones you are using. Could you post the #'s Also did you have to lathe down the belmouths like I did to get a good fit on the air cleaner side of the carb? norbsa
K & N c-1082

Good deal on the plugs.

I got my K& N air filter from British Marketing (Norton Dealer) near where I live. I just called them to get the number and it is C-1082.

I have to remove the battery to fit it in behind the carbs. It's a squeeze, but once it is in works well.

British Marketing is under new ownership now. My friend Albert owns the shop. I will be giving them a good plug from the main page of the website soon if I can ever find time.

Anyhow you can email Albert for the K&N if you like: (Make sure you tell him where you came from and he might work you a deal) :wink:

NORBSA, would it be possible to repost this photo? I am unable to access the msn site. I am setting up Mark 2s on a 72 combat and would like to see what you did.

I camped next to Greg last summer at the Michigan rally . Try contacting him through his website. He has not been here since 2015.
Interesting, I had to mount the Dellorto's on my race bike the same way. It does help keep them in place. I was running 11 to 1 compression in a featherbed frame.
Building a motor now that will get MkII's so good info!
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