running 10-1 pistons

Status
Not open for further replies.
So I bought the Mikuni carb set up, the motor gets a pair of new 9:1 pistons and life with a Norton will be a lot easier for her.
I think we discussed this different compression pistons before. There is no compression difference with 750 pistons, with the exception of Powermax. Combat engines achieved 10:1 compression by milling the head by .040”.
 
In my 70 years I have yet to see a woman in person kick start a cold Norton engine.

Any chance there will be a video of the owner starting the Norton up stone cold after you get it put back together?
 
BTW - the SRX600 was a very cool bike.
Indeed it was. I raced one for several years back when Sound of Singles racing was popular. It did everything well, and I really enjoyed riding it.

This is a picture of it in it's final configuration, just before I sold it back in 2012. Not a Norton, so I won't hijack this thread with a lot of detail, but couldn't resist just one picture.


running 10-1 pistons


Ken
 
With modern fuel you should have no issues at all. Many modern 4 stroke 125's run far higher compression than what could sensibly be achieved on a Commando.
Apples & beef stew. Modern engines (like the 420 hp Chevy LS engine in my pickup truck) run on low grade fuel ONLY because the computer engine management compensates for it. WITHOUT the knock sensor, TPS, MAP, MAF etc., it would not be possible.
 
  • Like
Reactions: baz
Apples & beef stew. Modern engines (like the 420 hp Chevy LS engine in my pickup truck) run on low grade fuel ONLY because the computer engine management compensates for it. WITHOUT the knock sensor, TPS, MAP, MAF etc., it would not be possible.
Also you can't compare water cooled (ie modern) with air cooled or a 125 that has a much narrower bore (flame front travel) to an 850?
Also in terms of the original question, having high comp pistons (with all the attendant issues outlined by others) on a single carb bike is adding a little bit of performance and taking away more.
 
  • Like
Reactions: baz
So I bought the Mikuni carb set up, the motor gets a pair of new 9:1 pistons and life with a Norton will be a lot easier for her.
Good plan.
In all of the period road tests, the stock 9 to one 750s accelerated really well and were quite tractable.
I have a book of about 30 roadtests from that time. There is very little difference in 1/4 mile performance between standard compression/cam 750 models and hi compression Combats.

Glen
 
In my 70 years I have yet to see a woman in person kick start a cold Norton engine.

Any chance there will be a video of the owner starting the Norton up stone cold after you get it put back together?
Back in the 80s I knew 2 young women who both rode 74 850 Commandos their dad was a Norton man and both girls grew up with Norton's, the were also very slim and pretty girls and they had no problems with kicking their Norton's to life even on cool mornings, its got nothing to do with size or shape of the body, its knowing the knack to kick start a Norton that is the most important thing and they were taught well as they both had the knack to kick them to life they didn't even use the stand to kick them over.
I have a short video of kicking my Norton over on first kick from a major rebuild on here, you might have to go back 12 years to find it.

Ashley
 
Back in the 80s I knew 2 young women who both rode 74 850 Commandos their dad was a Norton man and both girls grew up with Norton's, the were also very slim and pretty girls and they had no problems with kicking their Norton's to life even on cool mornings, its got nothing to do with size or shape of the body, its knowing the knack to kick start a Norton that is the most important thing and they were taught well as they both had the knack to kick them to life they didn't even use the stand to kick them over.
I have a short video of kicking my Norton over on first kick from a major rebuild on here, you might have to go back 12 years to find it.

Ashley
Well said sir, i know plenty of females who can not only kick start there own bikes, but show up i lot of male boy racers. role on ladys
 
There is always a balance to be maintained between comp. ratio, ignition advance, jetting and fuel octane ratio. Those factors can compensate for each other. If you fit the 10 to 1 pistons, you might need to use about 2 degrees less ignition advance, then jet to suit it. Almost anything can be made to work.
Back in the olden days, British road racers could get their low comp. Manx Nortons going as fast on pool petrol , as Australian riders could using 12 to 1 comp. with methanol fuel. But tuning with petrol takes much more patience. The margin for error is less.
 
I think we discussed this different compression pistons before. There is no compression difference with 750 pistons, with the exception of Powermax. Combat engines achieved 10:1 compression by milling the head by .040”.
Yes we did, but different circumstance....

He says it had a pair of 'Powermax' pistons in, not that it was a Combat with skimmed head!
 
Back in the 80s I knew 2 young women who both rode 74 850 Commandos their dad was a Norton man and both girls grew up with Norton's, the were also very slim and pretty girls and they had no problems with kicking their Norton's to life even on cool mornings, its got nothing to do with size or shape of the body, its knowing the knack to kick start a Norton that is the most important thing and they were taught well as they both had the knack to kick them to life they didn't even use the stand to kick them over.
I have a short video of kicking my Norton over on first kick from a major rebuild on here, you might have to go back 12 years to find it.

Ashley
Were they 10:1 compression motors? LOL

Anyway, if you and these ladies can 1 kick start a 850 Norton in 30 degree weather it must be very easy.

Makes me wonder why it is so popular for all the taught well exerts here to put electric starters on their Nortons. ;)
 
Some people do not know how to kick a motor over, and jump on the kick start without pushing the piston well up towards to dead centre before shoving it over the top. I have kick-started a Vincent twin which was on 13 to 1. High comp. does not make much difference if you use the right technique. Do it slow and you won't break your ankle. Just hold the piston hard up against compression before you try to make it fire.
!0 to 1 is nothing.
 
Indeed it was. I raced one for several years back when Sound of Singles racing was popular. It did everything well, and I really enjoyed riding it.

This is a picture of it in it's final configuration, just before I sold it back in 2012. Not a Norton, so I won't hijack this thread with a lot of detail, but couldn't resist just one picture.


View attachment 79614

Ken
WP_20190420_17_54_10_Pro.jpg
Gratuitous picture of Yamaha single engined yellow bike....also a hoot to ride.....if only SR500 power in modified BSA Fury/Triumph Bandit frame....
 
I'm thinking the boys and apparently girls from down under could probably kick start a 14:1 Big Block Chevy. Must be something in the water and all that taught well goodness. ;)

Edit: Obviously, I have been doing it wrong for a very long time. Somewhere along the line I lost track of the feel for the compression stroke when the motor and oil is really cold. Everything feels like the compression stroke. I'm also not getting any younger, which might have a lot to do with it.

I had a pre-kick ritual with my previous incarnation of the motor. (I'm rebuilding it now.) It actually would always start on the kick that counted, but I usually kicked it 3 times with the throttle wide open before that. The intake tract is not stock so it took a couple of kicks to get fuel in the combustion chamber. Also turned out when I got the head off and put a degree wheel on the alternator rotor what I thought was 31 degree BTDC was actually 40. Kind of made it hard to start. Anyway, now that I actually know where 31 degrees is I can get the timing at 28 for the TriSpark ignition. Maybe it'll start a lot easier. Kidding I know it will.

Sorry for running off track into the weeds again.
 
My Norton motor is not standard my cam has been built up to combat specs, still running original valve but has been ported the head has been shaved and 40thu Hepilight flat top pistons the final rebore to hone was done tighter than recommended so my motor was very tight on the first kick after the rebuild but knowing my own Norton it still fired it up on the first kick, I have only used a timing light once on my Norton as really the rota marks are never that accurate in the first place, yes I do use the timing marks to set my ignition as close as I can for firing, if I get kick back I just slightly retard it till the kick back is gone, tune my carbs in then take for a ride and do minor adjustments when needed, I have been doing it this way for all my Norton life and works for me, all my mates can't kick my Norton to life on first kick, and they have owned British bikes most of their lives, have had a drinking contest in my shed and after many beers I give the mates 5 attempts to kick my Norton to life and they always fail, I run a Joe Hunt maggie and the longer folding kick start, then of course they say go on smart arse and even sitting on the seat it will fire up first kick every time for me and to show off I turn it off and back on and kick it back to life every time, but after 46 years of ownership and know every bit on my Norton, I have the knack.
When I first bought my 850 new when I was 17, I was built like a match stick skinny as and it did take me some time, well a month anyway to get to understand what is needed to do to kick start a Norton and my mate who got me into Norton's always said there is a knack you just got to learn that knack, I have owned a few older kick start Triumphs in my time and they are not the same as kicking a Norton to life, they are easy.
The first kick in the morning or day is the most important kick, it will be the biggest swing on the kicker, but once started for the day I can sit on the seat and kick it to life, but that first kick for the day is one you got to get right, I have seen so many riders who have just got into Norton's and watch them kicking them to start them and usually 5 or 6 kicks and sometime longer, they just do everything wrong, one of my old riding mate that I been riding with for 49 years he bought a Norton 750 Commando back in the late 70s we were at Lakeside Race way in my home town his Norton had Mikuni carbs and he was kicking it for over 30 minutes trying to start it, I was watching him and he was kicking it like his old Japanese dirt bikes, straight away I told him he was doing it all wrong and using throttle on every kick, so he said give it a try, pissed him off when I fired it up on the first kick, he didn't keep the Norton for long after that and he also had a Norton tatto on his left arm when he bought it, to this day we still ride together and every so often I will ask him about the Norton tatt on his arm while with the mates as not to many know about that tatt that is under his shirt sleeve lol, love stirring the old mates up LOL.
As I say experience Norton owner will know what I am talking about and I have seen many Utube from people on this site as well others who just do everything wrong when kicking a Norton to life and why so many spend the money on E starters, as for getting old if you don't have the knack then the ES will be for you, my Norton will never have one fitted, but I do have the knack ;)

Ashley
 
Interesting.

I would sell my Norton if I went out to start it and could not kick it over anymore. I've been hauling it around from house to house for 50 years. I know it well enough. I don't try to tell anyone anything to make myself look or sound experienced. I just am.
 
When I first began road racing, all races were run and bump start. If I cannot get a motor to start, I resort to that. But the truth is, if the motor is not going to start by kicking, it usually will not by run and bump. I now have a 240 volt portable electric starter, It works well, but I have to make sure the gearbox is in second gear or higher. The starter is built around an angle grinder. It has got a couple of rollers and a chain. It cost $700. My Seeley has a TTI box which has no provision for a kick starter.
 
I don't know what all the fuss is about. If you motor is well tuned, all you have to do to start it, is make it go over compression. But if you take too big a bite of mixture, the motor will probably kick back. If you stand on the kick start and wait until the piston is well up the stroke, then bounce it over compression, the motor will usually start. If it doesn't, there is usually something wrong.
 
Status
Not open for further replies.
Back
Top