Beefing up the 850

Hi

I am about to buy an 850 in parts. I intend to renovate the entire bike in details, and wondered if there is a good way of increasing the performance of the engine. Bigger bore, larger valves, a different cam shaft? Will it cope with higher revs? Or will the bottom need changes too? - Or should I just keep it as it was designed?

Regards Finn

Have you ever ridden an 850? I had one when I raced a TZ350 and as a road bike it was quick enough and I used to make it fly. The engine is well torquey as it is. I only advise as it's easy to waste money on something you don't need.

Having said that I once has a go on a 920 and would like one....

Hi Finn,
Of course your Norton can be beefed-up, any engine can. Check out offerrings from http://www.jsmotorsport.com and/or
http://stevemaney.com , its all available and all that it takes is money. Personally, I'd go for the modifications that would increase reliability and drivability before I went chasing after more power. There are plenty of carburetion, ignition, drive train, and brake mods that can be done.

ludwig said:

mc finn said:

.. increasing the performance of the engine..

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What about increasing the performance of the BIKE ?
Is it power or speed you're after ?
Before trying to squeese a few extra hp out of the ingine , invest in chassis , suspension and brakes .
Brakes = speed .

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Ludwig is wise. These bike are a unit and when all is well, all is great. Although other bikes will have a highter torque rating, Nortons seem to utilize every inch pound. I have a 750 now, having owned a MKIIa in the past, and I have never experienced a motorcycle of this size that when taking on a second rider made so little difference in the performance.

I guess what I am saying is, bring it all together, brakes, handling, motor tuning and of course, polish. You can find quickness or top end speed in gearing. As most Cafe Racers know, the easiest way to increase performance is to reduce weight. If I go on a diet and loose 20 pounds, I will probably net 2 to 3 horses and 5 to 10 foot pounds of torque.

That being said, you can dump a lot of money for a few hp's (I am) but it's what you already have that pulls the front wheel off the ground and that is torque. Increase braking, handling, sound engine machanics and a "Ton Club" membership is all but guarenteed......safely. Many nortons, if not all, are capable of a ton or better, yet are uncontrollable over 80mph.

In the '70's, in my "I'm gonna be the next Mike Hailwood" amateur road racing days, after being passed on the inside on the track by guys on 250s while was on my '71 750 Commando, I figured out that the bike didn't need improving, I did!

More Power Scotty!!

850's just need the stuff to allow em to rev for some horse power out of their torque. 5 lb lighter steel flywheel, lighter pistons and bump CR up to 10-ish so it can enjoy a more agressive cam like 2S, 4S, PW3. Put on single bigger carb like standard 34 Mukuni. Lighten up valve train by grinding away rockets till about arrow head thin and stick in 7 mm valve with race level spring kit. Add belt drive in 2:! ratio.

A Combat head could be adapted or extra cost FullAuto head. You will not lose the slow poke big twin short shifting torque but gain 60 mph in 1st and almost 90+ mph zing in 2nd. Modern bikes can't keep front down to pull as hard as a Commando which can just leaps ahead rather than backing off. Pisses modern off royally, though they can usually take ya after 120 mph or so but not shake ya off the game till turns appear again and their sprint only limits shows up in spades.

Then it will be extra dangerous entering turns on ligthened front into fish flop onset. So while engine and tranny out weld up the mounts for rear rod link and its secondaray helper top/front, then order Gregs or John's fork up grade kit and an RGM fork brace and go hunt down them sports bikes to show them what real corner handling is about and show supermotards what they are missing out on power to fly.

$1000+ crank shaft + work, $400 cam shaft, $700 pistons, Norton rods fine but for Jim's steel set add ~$800, Cases reenforced welded ~$100, Valve train parts $600 w/o rockerts dealt with. Belt drive $500-800. Rod links need a few more $100's. Boyer rev limiter a vital over sight or protection $140. Micky carb $400+ or JIm's flat slides. Rest is mostly extra for looks or ligher bits in tank and seat and such. Rear sets really make Cdo's more comfortable besides allow more lean. Might remove center stand, worth about 2 hp mass gain and fouls LH leans.

A combo above would give past Ms Peel a run for the money and requires her another $6-7000 big block boosted engine to get away fast enough to matter
and special fork tuck down mod to take it w/o just going skyward.

A good stock mid model 850 loaded with cross country campping gear and big rider can give my light ass on SV650 scary fits to follow in twistes at legal speeds and above, with 850 tires aired low for the comfort zone not ballarina contact.
ugh. Impressive. Main down fall w/o the full links are fast powered sweepers.

I used to think owning a sailboat was expensive...

All these mods will produce lots of extra power, make sure that you do things like balancing and shot peaning, they are that "ounce of prevention" that will help you avoid a "pound of cure". Make sure that you test fit and check clearances with all new parts (and old ones), don't assume that anything you get is clean enough to be fitted without a through cleaning and examination. Your engine's rotating and recriprocating parts weigh someting less than 30 pounds, at 7000 RPM they contain more energy than a stick of dynamite, if that stuff breaks and gets loose you could end up with bloddy stumps where your lower legs used to be, in less than one second.

Oh, and be careful not to make your Norton too powerful lest you end up like a Supermotard and can't keep your front wheel on the ground :mrgreen:

RS

Make sure the junctions of the manifolds to the heads and the carbs to the manifolds are smooth. Quite often, they are uneven and the steps in the transitions can cause poor intake flow. This a completely free power-enhancing procedure that only requires a little emery cloth and some trial-and-check handwork.

It would be a lot cheaper to just buy a new Ducati...

I'd do a complete rebuild of all the wear parts of the standard gearbox if you plan to use it.
Original gearbox design was probably for 30HP and your talking maybe 70.

Yep tranny can break but it can take a lot of fun first. Keeping in lower gears for most the acceleration and some care in throttle snaps can go a long way further faster. I'd also cryo tempered many parts in engine and tranny plus dry friction coating. With the rod links and right attitude you can take on supermotards in their element and not lift front before out leaping them while they watch out for wheelies. All 850's have tad slower steering angle than 750 so a bit more effort to fling around but fling around they sure do. Just watch the longer sweepers where oscillations build up destructively with out rear and other links and fork mods.

Exhaust systems can make all the difference I found in getting the bang out of what's ahead of it.

I would at least think about MexicoMikes remarks. A fairly new Ducati on Craigs list will run you 4 - 5k. Far more performance for much less than you will have in the 850. The real question is "Do you really want to go that fast?".

Diablouph said:

I would at least think about MexicoMikes remarks. A fairly new Ducati on Craigs list will run you 4 - 5k. Far more performance for much less than you will have in the 850. The real question is "Do you really want to go that fast?".

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true, picked up a 2003 Monster 800 w/ only 1700 miles for $4300 and just ride it when I want more performance than what my 850 Commando has (like a fast group ride, etc...), waay faster.....still ride the Norton the most but having the pair works really well for me

The 850 I have now - I've owned it for the last 18 years - was my daily rider and workhorse for a long time.
It now sits in partial retirement and only gets ridden on occasions - 3800 miles this year.

My bigger bikes are ( Dollar for Dollar ) a Lot faster, more comfortable and more durable. BUT.........
the torque of the Norton is hard to beat - it eats up TT100's. Spins the rear tire at just about every stoplight, even when I'm not trying to roar off the line like TC Christensen used to do.

It's stock except for a Mikuni, Boyer, and upgraded suspension bits.
.