Commando 850 petrol tank capacity and mileage

[johnm]

This MKIV has the stock cam with 32mm amal premiers tuned in. It gets a shade under 60 miles per imperial gallon. That is mostly cruising 100 or 120 km/ hrs with small towns scattered here and there with speed limits. And it is an average, so wind etc. is factored in. It is the most economical vehicle, other than a bicycle, that I have ever had on the road. Couldn't be more happy with the operating cost

Thanks. Very much in line with mine.

Regards John

 

[MexicoMike]

Back in the day my 750 Commando's mileage was typically low-mid-30s MPG. But I was young, mostly rode as fast as I could at all times, and fancied myself as the next great pro motorcycle racer. I discovered after several years of competition that I wasn't!

I don't seriously check mileage nowadays though with my 850 I refuel at around 100 miles and it usually takes about 2 gallons. Back then my Roadster was out of gas at 90 miles! I know that from personal experience! I also know that the "reserve position" meant I had only about 8 oz of fuel to work with. I learned that the first day I owned the bike on I55 southbound from Memphis. It sputtered, I flipped to reserve -only 10 miles to the next gas station - NO PROBLEM!. And it wasn't a problem for nine miles but pushing the Commando for that last mile was tough ...

 

[milfordite]

That's a single Mikuni ?

Very good mileage for that kind of usage I think. 22 sprocket may help I imagine.

Yes, single Mikuni, 34mm. The 22 gives my bike a sweet spot around 65-70 so that's where I ride on long trips. Usually 2 lane roads.

 

[CanukNortonNut]

"Air cleaner is a standard hamcan but reduced in diameter to fit above a CNW starter." From post 1
HI Johnm, could you show us a picture of your hamcan setup? what filter you are using?
Thanks in advance for your input.
Cheers,
Tom

 

[johnm]

"Air cleaner is a standard hamcan but reduced in diameter to fit above a CNW starter." From post 1
HI Johnm, could you show us a picture of your hamcan setup? what filter you are using?
Thanks in advance for your input.
Cheers,
T

Post in thread 'Alton on a MK2A 850 with full plastic OEM airbox?' https://www.accessnorton.com/Norton...ith-full-plastic-oem-airbox.26137/post-476415

Plus some photos I took just now with Roadster sidecovers.

Back when I posted in the Alton thread I hadn't used it much but a couple of years later it seems to work fine. I'm not racing the bike obviously but it accelerates very happily up to 90 mph and is still accelerating quickly when I back off. Mixture seems fine as I described above. I might go photograph a plug just for kicks.

OK. Added photos of the plugs. I will admit they look a bit rich especially soot on the plug body but the bike was at 50 km for the last 3 km and sat idling in the driveway for a few minutes as I opened the garage so maybe I should check after an open road ride.

 

[CanukNortonNut]

Thanks johnm,
Nice work on matching the bottom of the rolled edge.
Great Idea on modifying the original filter.
Cheers,
Tom

 

[Café au Lait]

With this thread in mind and having set out on my Commando to meet with some friends with 74 miles on the trip a deliberately kept riding to the point of needing to switch to reserve which happened to coincide with a stop at lights. 117.7 miles. It was a further 8 to my favourite station for ethanol free petrol and filled up, 10.04L or 2.2 imperial gallons. I’d reckon my roadster tank is 2.5 gallons. 56.8 mpg of mixed riding but mostly spirited. I can live with that.

 

[johnm]

With this thread in mind and having set out on my Commando to meet with some friends with 74 miles on the trip a deliberately kept riding to the point of needing to switch to reserve which happened to coincide with a stop at lights. 117.7 miles. It was a further 8 to my favourite station for ethanol free petrol and filled up, 10.04L or 2.2 imperial gallons. 56.8 mpg of mixed riding but mostly spirited. I can live with that.

Getting a bit of consistency around the 55 60 mpg Imperial for mixing riding. Not too bad.

 

[Café au Lait]

Getting a bit of consistency around the 55 60 mpg Imperial for mixing riding. Not too bad.

I guess so especially running FCR35s

 

[johnm]

I guess so especially running FCR35s

Modern carbs should improve things I imagine.

I think I got OK at tuning Mk1 Concentrics when I was racing my Dommie 500. Plus I have been helping out a team of guys racing Velocettes running MoteC lambda meters for mixture tuning so seeing lots of plugs under different conditions.

Their carbs are mostly old fashion Amal GPs and Gardener flat sides. With the occasional Mk1 and M2 concentric.

Have to say I find GP carbs particularly messy to deal with. With the right needle Gardeners are pretty easy.

 

[kerinorton]

I rode from Little River to Kaikoura one time 144 miles, with my steel roadster tank 2 1/2 imp gallons. Probably averaged nearly 60 mpg. Just cruising back from the Akaroa Rally on the way back to the Far North.

Not sure why people get hung up about worn carbs. Mine still has the original 32 mm carbs. They are worn, but hardly noticeable. Did quite a lot of work about 10 years ago getting the bike to do the 60 mpg. Someone mentioned my right carb is slightly leaner, but that's getting really finicky trying to get that right as it is far less an adjustment needed than raising the needle. Mostly my bike will idle ok, but I live a long way from traffic lights so never have to be concerned. Idling a bike is not riding in my book. Depending on conditions riding from one end of NZ to the other, it can be anywhere between 53 and 73 mpg.

 

[johnm]

I rode from Little River to Kaikoura one time 144 miles, with my steel roadster tank 2 1/2 imp gallons. Probably averaged nearly 60 mpg. Just cruising back from the Akaroa Rally on the way back to the Far North.

Not sure why people get hung up about worn carbs. Mine still has the original 32 mm carbs. They are worn, but hardly noticeable. Did quite a lot of work about 10 years ago getting the bike to do the 60 mpg. Someone mentioned my right carb is slightly leaner, but that's getting really finicky trying to get that right as it is far less an adjustment needed than raising the needle. Mostly my bike will idle ok, but I live a long way from traffic lights so never have to be concerned. Idling a bike is not riding in my book. Depending on conditions riding from one end of NZ to the other, it can be anywhere between 53 and 73 mpg.

I have my original 32s in a box in the shed. My memory from a good 25 years ago now was fuel consumption was very bad , it was very hard to start and plugs were black. But I was pretty broke and hopeless back then so maybe it was me more than the carbs.

Actually I'm pretty sure it was me. Back when I was a student and broke I was a very poor mechanic.

When I started racing my 500 around 1998 I learnt an awful lot in 3 years. Often by testing on the dyno with lambda sensors. Plus lots of reading of people like Gordon Jennings, Blair Irving Kevin Cameron etc. Much of the information talked around the pits was seriously misleading and I soon learnt I needed to ignore most of it.

But all of that just serves to remind me how hopeless I was with my Commando back when it was my daily transport.

Still my old carbs can stay in a box until someone wants to convert everything back to original. Won't be me.

 

[worntorn]

It's the worn brass that causes old carbs to put through too much gasoline, mainly the needle jet.
When the fuel mileage starts to drop it really goes off a cliff.
Renewing the needlejet will bring it right back.
The slides can be quite worn and the carbs will still work OK.
My 850 carbs are originals with 47,000 miles. The slides are worn but the bike runs nicely. The needle jet and needle have been renewed at least once.

Glen

 

[frank73x89]

It's the worn brass that causes old carbs to put through too much gasoline, mainly the needle jet.
When the fuel mileage starts to drop it really goes off a cliff.
Renewing the needlejet will bring it right back.
The slides can be quite worn and the carbs will still work OK.
My 850 carbs are originals with 47,000 miles. The slides are worn but the bike runs nicely. The needle jet and needle have been renewed at least once.

Glen

Hi Worntorn. I've had one slide break while running at highway speed (110 KpH). I knew both slides were pretty darn well worn but decided to keep them there. Well, one of the two broke with imaginable consequences to the engine... I was lucky the engine didn't lock up. Just my 2 cents.

 

[johnm]

Hi Worntorn. I've had one slide break while running at highway speed (110 KpH). I knew both slides were pretty darn well worn but decided to keep them there. Well, one of the two broke with imaginable consequences to the engine... I was lucky the engine didn't lock up. Just my 2 cents.

Unpleasant.

I have also found worn slides mean poor to nil idle and poor transition from idle to low speed.

But certainly agree with Glen that needle jets are often the reason for heavy fuel consumption.

I beleive it was John Healy who said. "It's the needle jet stupid"

 

[850commando]

back in the day (1970's) i'd see about 100 mile to reserve.