750 power improvements

Best bang for the buck power mods?

Year of bike ?
And what do you intend to do with it ?

Better brakes.
Best single thing you can do to go faster, safely...

Cam, head/valve work, Carb, exhaust and any supporting items like wheels, tire, brakes, bearings, a reworked/rebuilt gearbox etc, etc, etc.

Buy gas and ride it , spend less in the garage and more on the road :lol:

How much money do you have? How fast do you wanna go?

IMHO anything much more than combat specs is treading on thin ice with stock cases and the 750 cylinder.

Let me rephrase....(for the street).....of headwork, cams, etc.; which gave the most improvement in streetable power? For instance...2s cam?

750 with over over bore, trim flywheel down or put in a few lb lighter steel wheel, 2S or above cam, 10-11 CR, small port standard head, big valves, 34+ mm carb/carbs best with accelerator pump and 2-1 headers into long megaphone, PowerArch ign. Then lighten-remove mass as practical, especially wheels.

'streetable power', to me that means torque, and what hobot said about port size, carburettor and exhaust pipe, I agree with. I'd use the 2s cam, but broach two more keyways into the cam sprocket, and progressively advance the cam timing until it is optimised to suit the pipe. The standard commando never had a two into one pipe to my knowledge, and the cams were probably developed to run with separate pipes. The tail pipe of the exhaust should be twice the crossectional area of one header pipe or you will lose too much top end. After this modifying the engine becomes the law of diminishing returns.
Hobot's comment about flywheel weight interests me. When Triumph produced the Saint 650 which had a lighter crank, it never performed well, and that particular crank is always cheaper to buy than the one with the heavy flywheel. You don't always get the result you might expect when you modify engine parts.

It depends on your year 750. They were fast enough, but really needed a disc brake. Then a resleeve of the master cylinder to make lower the effort. Generally, vernier iso's adjusted, an aftermarket head steady, pin the swing arm shaft. A good set of shocks and forks that are working well. I'm satisfied with my power, it's nicer to be able to apply it and reel it in when necessary.

It also occurred to me that stopping is more of an issue than going with the Commando. The kit that madass sells to replace the front disc with a 1320mm six pot brake is about the best bang for the buck at the moment. If you look at how quickly the $thousands slide away when on the hunt for a few more hp, the brake makes total sense. On top of that, brake improvement is felt at all speeds whereas engine mods for more hp usually give you a few more hp right at or near the top rpm but deduct hp down low where most roadbikes get ridden.
In that same way it seems more advantageous to work on weight reduction because the cost is generally not all that high, and the increased acceleration is right thru the range. You also get the added benefit of improved handling.
And if the bike falls on you it hurts less :mrgreen:

Glen

+1 on reducing weight. I have trimmed my 850, my avatar photo, down to 300# dry. Still working on it, so it will go down a little more.

On the plus side, the reduced weight doesn't reduce reliability like many engine mods can.

If you are set on engine mods, go for the JS lightweight rods and pistons. at least a 2s cam, large head ports usually don't help.

Cost vs bang was an element so to get the escalations possible out of the way a real full race best there is combo engine costs like 12-14 grand. So sticking to old school factory and common after market stuff can still make ya grin with some money to spare. Most the full race engine benefits would only show up near top out speeds anyway and even they are straining to sustain 8000, I'd go for the torque gusto so its all in by reline and time to snick up again and again with enough pull on tap you keep on snicking for the over drive to lessen the throttle response.

Acetrel your exhaust clues are sinking in for a bit of a redoing of Peels 2-1. I can garantee the 2S cam can fall in love with a good 2-1, but it falls on it face until dialed in on length and exit size. I'm fond of the 2S but the PW3 cam is popular but any over lapping cams craves CR or a annoyance down low instead responsive. Cam degreeing is definitely free horse power where you want it most but cost is labor tedium.

Brent I'm floored you've got a road goer down to 300# dry. Its said that each 7.5 lb off is worth one more hp in thrust forward. Peel's most trim past was somewhat below 340 # with a full 6 gal tank but still mud guards and flaps and signals and luggage rack and steel rims with tubes.

I was told all sorts of bad things about a lightened crank, bad idle, stalling between shifts and less pull through or out of turns. Well my 9000 rpm P!! drag only definitely had lightened crank and would hit 9 grand before I could snap to full WOT BLATTT! Ridiculous Radical, but a pussy cat in loose stuff and stop go town traffic or pit lanes. Peel got ~5# lighter crank and was a dream to lug or snap throttle for rear kick steer and I think helped her roll rate to full leans.

If retaining the cast iron crank triming some off helps reduce its sling loads to resist fractures. Lossing mass can easy cost as much as it does for another hp.

Best advice for best power per bux is get Jim Schimdts Racing Notes for ~$25.
Then Paul Dunlop Tech Notes

Btw a peashooter weighs ~6# and a length of a 1 3/8" header ~3# and the mounting brackets ~1.5#. IS fiber tank ~6, steel Roadster tank ~6, on and on..,

Buy a modern bike to go fast and keep the Norton stock! :idea:

The one that seemed to work best for me was;

I went on a diet. :mrgreen: :mrgreen:

Snakepit said:

Best bang for the buck power mods?

Click to expand...

You did not supply the present specification of your engine.

The most common Commando engine is the plain 750 which was put in the 68-72 non-combat bikes. It has head with the good small ports and 9:1 compression from the factory and a cam that works great at street rpms.

For these engines the most power for the least trouble and outlay of cash would be to remove the head, ship it to Jim Comstock and have him rebuild and port it. If he knows it is going back onto a stock engine he would keep the ports the stock size and maybe just do what needs to be done from the valve seat back to the guide. Tell him you are going to switch to 32mm concentrics and their matching intake manifolds as was used on the 1974 850, where the manifolds neck down to fit the smaller ports. Have him put in a new set of stock valve springs which he will of course make sure are installed correctly.

Put the head back on and you are done. You will not have had to spend a dime on anything below the head gasket. You will have more power where you will enjoy it and at an rpm where the engine will live happy for a long time, further stretching your dollars.

Once you go to a big cam and take the rest of the engine apart, you are going to spend a lot more money and end up with an engine less fun on the street, and less reliable. If that is your choice go there just realize the price you will pay in cash and rapid parts wear/failure.