Commando Shortstroke tuning experience

Hi,
All new to this forum but have read a lot of interesting stuff and here and as I´m into a rebuild of my dad´s short stroke Seeley Norton Jim S that we got some real nice parts from though there might be an interest for this so we´ll se the.

It all started in 99 when me and my dad started racing. I built a T140 racer with the oil in frame. We did´nt know anything about racing back then and had to go as totally beginners. The machine I´m totally rebuilding was bought from L Sandberg in Sweden. It was a shortstroke 750 with a Nourish crank in a Mk2 Seeley frame.
Floating Norvil/seeley disc in front and a conical rear wheel that barely was worth braking with.

Anyways back some 6 years ago when we were practicing the top yoke broke and going of at 75 mph he broke his leg real bad shortening him some cm because of the parachute kind of landing.

Taking a break from racing a couple of years I got a little curious testing his bike but we had to get it together first after that crash. When we left the scene we had some 70 rear wheel Hp on both the Triumph and Norton but for 2015 test I can´t says there was much left in that Norton package from those days.

We got some good laps around the race track but never did finish because of battery failure ignition problems and lots of oil blowing on the left hand side.
Obviously we had to do something about this.

Stripping down everything and starting from all over. As so many times before the plan was to do something minor but that turned to a total rebuild and change as so much obviously needed being taken care of.

I will post some of the strip and successively the rebuild.

Any ideas tips help on the way to make this Norton a potent twin Norton racer will be appreciated.

Cheers

Mats Malmö Sweden

Re: Norton Seeley shortstroke Racer rebuild

Hi Mats

Brilliant. Anything to do with racing Plenty of short stroke advice on this forum. Another Seeley out there that can only be good. Looking forward to reading about your build.
All the best Chris

Re: Norton Seeley shortstroke Racer rebuild

Looks great ! Have you seen this page ? :

http://seeleynorton.com/technical/specifications

Re: Norton Seeley shortstroke Racer rebuild

Very nice! It looks a little low at the back though - how much do the springs (both front and rear) compress with a rider seated (what we called the '1G position' in GP racing) and what does the fork angle end up at?

Re: Norton Seeley shortstroke Racer rebuild

acotrel said:

Looks great ! Have you seen this page ? :

http://seeleynorton.com/technical/specifications

Click to expand...

Yes, seen it. It´s a nice report and pictures.

Re: Norton Seeley shortstroke Racer rebuild

Paddy_SP said:

Very nice! It looks a little low at the back though - how much do the springs (both front and rear) compress with a rider seated (what we called the '1G position' in GP racing) and what does the fork angle end up at?

Click to expand...

Hi there,
I think it´s misleading picture as the lower stand is so much lower than the front.
The front and rear height and springs have been set according to the recommendations from öhlins.
The specify non seated rear 5-10 mm and front 25-30mm. Seated rear 30-40 mm and front 35-48
The rear is a shock unit made specially from Öhlins parts by stötdämparexperten in Stockholm. The front just before the crash was a std interior damper unit with manx stanchions (shorter) but I had an extra unit that I had rebuilt with parts from RGM that was suppose to get better tolerances.

It did work better not digging skewing the side of the tires as it did when the front end didn´t get contact with the surface and bumped.

However there is a problem with the weak 34.5 mm fork that twist and turns at high corner speeds and in braking zones as the single disc twists.

Cured that partly by bendin a stainless steel plate inside the front fender preventing in some way the twist.

Will be working on getting a cartridge damper unit into that fork in a month or so

Re: Norton Seeley shortstroke Racer rebuild

Starting the teardown checking everything. Head is an 850 Maney ported stage 2. Not a very good job done on those seats as the contact area was slim and vacuum test proved leaking. Some Hp lost there.

The big issue though explaining why my left leg got soaked in oil was that the left side of the left cylinder liner was severely wear damaged which there was no explanation to. Usually it´s front and back that gets the wear. In this case the front and rear was good but there was 3/10 of a mm clearance at the side. Obviously the oil blew past the ring at the side and back through the carburetor and the left exhaust.

Additionally the heat had been quite extreme inside the engine case making the piston pins blue and also heating the small end of the carillo rods.

Had to solve this problem and talked to chis at Nourish so I checked the endplay of the big ends which was a little to big but still can´t really explain everything, the oil pump and the release valve all seemed fine

Maybe the rods were´t straight so made a dowel for the rods to line them.

Re: Norton Seeley shortstroke Racer rebuild

Swetune said:

Paddy_SP said:

Very nice! It looks a little low at the back though - how much do the springs (both front and rear) compress with a rider seated (what we called the '1G position' in GP racing) and what does the fork angle end up at?

Click to expand...

Hi there,
I think it´s misleading picture as the lower stand is so much lower than the front.
The front and rear height and springs have been set according to the recommendations from öhlins.
The specify non seated rear 5-10 mm and front 25-30mm. Seated rear 30-40 mm and front 35-48
The rear is a shock unit made specially from Öhlins parts by stötdämparexperten in Stockholm. The front just before the crash was a std interior damper unit with manx stanchions (shorter) but I had an extra unit that I had rebuilt with parts from RGM that was suppose to get better tolerances.

It did work better not digging skewing the side of the tires as it did when the front end didn´t get contact with the surface and bumped.

However there is a problem with the weak 34.5 mm fork that twist and turns at high corner speeds and in braking zones as the single disc twists.

Cured that partly by bendin a stainless steel plate inside the front fender preventing in some way the twist.

Will be working on getting a cartridge damper unit into that fork in a month or so

Click to expand...

I'm delighted to hear that you're doing things properly! On Kevin Schwantz's GP500s we used to work on 45 mm sag at the front and 25 mm at the rear, with the rider seated - so very similar to what you're doing.

Re: Norton Seeley shortstroke Racer rebuild

Swetune said:

Additionally the heat had been quite extreme inside the engine case making the piston pins blue and also heating the small end of the carillo rods.

http://s1168.photobucket.com/user/matsbhall/media/B71FE8C1-5023-4659-B3AB-982B4B83B5FD_zpsfdtcefho.jpg.html

Click to expand...

That much heat may have deformed the pistons. You can see that there was a lot of wear down the center of the piston (machine marks are gone). But now the wear has shifted to the side as if the skirts have changed and are now too out of round. You may have come close to melting a piston (this can happen in a Norton). A good running short stroke can create too much heat. Ron Wood had problems with the motor getting heat soaked. Those look like heavy long skirt forged pistons with severe wear. Any brand and design of piston is going to have a lot of wear (and cylinder wear) at extreme RPM (shortstroke). I would switch to Castrol R 40 bean oil and also consider carbide impregnating on the cylinder walls. Many racers use bean oil in their Manx's and the same consideration should be given to twins. To bring the heat down you need a big oil cooler, richer jetting and maybe bring down the compression ratio. You can pump these motors up as much as you want but when you see problems (impending disaster) you need to address them in some way. The lighter pistons/longer rods and lighter radiused BSA lifters will help bring down the heat (reduced friction) but it might not be enough. When I had overheating problems I resorted to a fuel mix of 75% alk and 25% race gas (which required a much richer ratio). But alk is generally illegal in most race clubs.

Re: Norton Seeley shortstroke Racer rebuild

If you have a look at the specifications for Kenny Cummins bike in the link I posted above, he gives the offset figure for the fork yokes. The suspension sag affects the way the Seeley frame handles in corners. Kenny's figure is very close to what I use. If you get it right the bike will tighten it's line in corners. This means you will get on the power earlier coming out, and can ride much more aggressively. Judging from the photo you probly have about 5mm too much offset. It is really critical, and if you are playing with it - take care, the mishandling can come from nowhere and grab you.

Re: Norton Seeley shortstroke Racer rebuild

If using methanol is illegal in most clubs, are regular fuel checks done ? I got myself a nice new ELF fuel drum, just in case methanol becomes illegal in the class which suits my bike. Racing is about having fun and my 850 loves methanol. I have never raced with anything else.

Re: Norton Seeley shortstroke Racer rebuild

jseng1 said:

Swetune said:

Additionally the heat had been quite extreme inside the engine case making the piston pins blue and also heating the small end of the carillo rods.

http://s1168.photobucket.com/user/matsbhall/media/B71FE8C1-5023-4659-B3AB-982B4B83B5FD_zpsfdtcefho.jpg.html

Click to expand...

That much heat may have deformed the pistons. You can see that there was a lot of wear down the center of the piston (machine marks are gone). But now the wear has shifted to the side as if the skirts have changed and are now too out of round. You may have come close to melting a piston (this can happen in a Norton). A good running short stroke can create too much heat. Ron Wood had problems with the motor getting heat soaked. Those look like heavy long skirt forged pistons with severe wear. Any brand and design of piston is going to have a lot of wear (and cylinder wear) at extreme RPM (shortstroke). I would switch to Castrol R 40 bean oil and also consider carbide impregnating on the cylinder walls. Many racers use bean oil in their Manx's and the same consideration should be given to twins. To bring the heat down you need a big oil cooler, richer jetting and maybe bring down the compression ratio. You can pump these motors up as much as you want but when you see problems (impending disaster) you need to address them in some way. The lighter pistons/longer rods and lighter radiused BSA lifters will help bring down the heat (reduced friction) but it might not be enough. When I had overheating problems I resorted to a fuel mix of 75% alk and 25% race gas (which required a much richer ratio). But alk is generally illegal in most race clubs.

Click to expand...

Hi Jim,
well the pistons were ok all the same measurements all around. However you are correct in that we had much heat. Börje, my dad, started with a compression on 12:1 which of course created big Hp but also big heat. It was really fast and the pull was tremendous. However the left piston always failed. Never the right one. We started having more trouble when noice restrictions required us to go below 104 dB creating additional heat.When we had 108dB ok we had 90 Nm on the rear wheel and about 72 Hp. The case went in to halves though...
So we had to reduce compression to 11:1. Then we had welded an additional squish which when it works creates more heat as well.
We solved this by using a oil cooler that you probably can picture on the stripped first picture. That helped a lot.

Now I´m very fond go light moving parts so I bought your long rods and your pistons which is a huge weight improvement to the pistons from Steve M.

They weighed at least 100 g more per piston than yours. THIS WILL reduce wear heat and all get this engine smoother. This I know. I have a lot of experience of this since my friends and the swedish Malmö motor renovering engine shop do some serious tuning and dragracing in the US as well. Thats Adam Flamholc if you recognize that name.

I never liked the S Maney pistons as his way to go was raising compression by doing a higher crown keeping the rod length and thus a heavier piston.

On the Triumph Rickman I used std cast alloy pistons and machined a 6 mm squisband on the pistons, skimmed the head for squish and bigger inlet valves then changed the ring depth using total seal. And with that hemi Triump we got 70 rear wheel Hp.

So it´s not in the forged alloy. It´s in the head and matching the piston correct. Those new cast alloy production pistons from the orient worked well.

Will post a picture on these further on

Re: Norton Seeley shortstroke Racer rebuild

jseng1 said:

Swetune said:

Additionally the heat had been quite extreme inside the engine case making the piston pins blue and also heating the small end of the carillo rods.

http://s1168.photobucket.com/user/matsbhall/media/B71FE8C1-5023-4659-B3AB-982B4B83B5FD_zpsfdtcefho.jpg.html

Click to expand...

That much heat may have deformed the pistons. You can see that there was a lot of wear down the center of the piston (machine marks are gone). But now the wear has shifted to the side as if the skirts have changed and are now too out of round. You may have come close to melting a piston (this can happen in a Norton). A good running short stroke can create too much heat. Ron Wood had problems with the motor getting heat soaked. Those look like heavy long skirt forged pistons with severe wear. Any brand and design of piston is going to have a lot of wear (and cylinder wear) at extreme RPM (shortstroke). I would switch to Castrol R 40 bean oil and also consider carbide impregnating on the cylinder walls. Many racers use bean oil in their Manx's and the same consideration should be given to twins. To bring the heat down you need a big oil cooler, richer jetting and maybe bring down the compression ratio. You can pump these motors up as much as you want but when you see problems (impending disaster) you need to address them in some way. The lighter pistons/longer rods and lighter radiused BSA lifters will help bring down the heat (reduced friction) but it might not be enough. When I had overheating problems I resorted to a fuel mix of 75% alk and 25% race gas (which required a much richer ratio). But alk is generally illegal in most race clubs.

Click to expand...

Hi Jim,
well the pistons were ok all the same measurements all around. However you are correct in that we had much heat. Börje, my dad, started with a compression on 12:1 which of course created big Hp but also big heat. It was really fast and the pull was tremendous. However the left piston always failed. Never the right one. We started having more trouble when noice restrictions required us to go below 104 dB creating additional heat.When we had 108dB ok we had 90 Nm on the rear wheel and about 72 Hp. The case went in to halves though...
So we had to reduce compression to 11:1. Then we had welded an additional squish which when it works creates more heat as well.
We solved this by using a oil cooler that you probably can picture on the stripped first picture. That helped a lot.

Now I´m very fond go light moving parts so I bought your long rods and your pistons which is a huge weight improvement to the pistons from Steve M.

They weighed at least 100 g more per piston than yours. THIS WILL reduce wear heat and all get this engine smoother. This I know. I have a lot of experience of this since my friends and the swedish Malmö motor renovering engine shop do some serious tuning and dragracing in the US as well. Thats Adam Flamholc if you recognize that name.

I never liked the S Maney pistons as his way to go was raising compression by doing a higher crown keeping the rod length and thus a heavier piston.

On the Triumph Rickman I used std cast alloy pistons and machined a 6 mm squisband on the pistons, skimmed the head for squish and bigger inlet valves then changed the ring depth using total seal. And with that hemi Triump we got 70 rear wheel Hp.

So it´s not in the forged alloy. It´s in the head and matching the piston correct. Those new cast alloy production pistons from the orient worked well.

Will post a picture on these further on

Re: Norton Seeley shortstroke Racer rebuild

acotrel said:

If you have a look at the specifications for Kenny Cummins bike in the link I posted above, he gives the offset figure for the fork yokes. The suspension sag affects the way the Seeley frame handles in corners. Kenny's figure is very close to what I use. If you get it right the bike will tighten it's line in corners. This means you will get on the power earlier coming out, and can ride much more aggressively. Judging from the photo you probly have about 5mm too much offset. It is really critical, and if you are playing with it - take care, the mishandling can come from nowhere and grab you.

Click to expand...

Hi thanx for your advice.
I did my yokes myself I have to check what offset I did. I´m sorry but I did my yokes 6 years ago when I was active racing. Hav to check.

What is the offset you use.


Thanx

Mats

Re: Norton Seeley shortstroke Racer rebuild

Swetune, here is a pic of an alternative way to mount a steering damper. Scott unit fully adjustable
Upside down on the the bottom yoke
Regards Mike

Re: Norton Seeley shortstroke Racer rebuild

acotrel said:

If using methanol is illegal in most clubs, are regular fuel checks done ? I got myself a nice new ELF fuel drum, just in case methanol becomes illegal in the class which suits my bike. Racing is about having fun and my 850 loves methanol. I have never raced with anything else.

Click to expand...

The methanol is illegal but the bike was run with methanol before. We saw that since the main jets were 320. We used to use race fuel Sunoco before but it was to expensive so we went for shell 99 octane. Can´t say if we lost so much Hp.

But maybe all mixture is good.

I have no experience whatsoever.

Thanx

Re: Norton Seeley shortstroke Racer rebuild

Just sending some pics on the check up on rods which I really recommend a specially if you use std alloy rods. Carrilo principally never breaks and bends.

We had to check as I couldnt explain that side wear in the bore.

Re: Norton Seeley shortstroke Racer rebuild

Nice looking bike. You should find at least a few more years of pleasure out of it at the track.

Your mention of it always being the left piston that wears, as well as running hot, reminded me of something Axtell told me when I first started building engines for my Norton PR back in '75. He said the left side runs hotter because it gets less oil flow than the right side, because the oil is fed from the right end of the crank, and lubricates the right side big end first, losing some pressure in the process. He always honed the left cylinder another .0005" because of the extra heat. I've always followed that advice on my own race engines. Just something you might consider in your rebuild.

His original advice was for standard stroke 750 engines using Powermax cast pistons. We used .004" for the right cylinder and .0045" for the left. Later, when I switched to the short stroke 750, I used the stock Omega cast pistons, and ran them at .0045" and .005", and two pairs lasted several seasons, with no wear problems. I used them with a factory nitrided iron cylinder, and the bore never seemed to wear (until the rod broke). When I started using 920 engines and forged pistons, I had to go with more clearance. I had good luck with .005" and .0055" clearance with several brands of forged pistons, but did see significant bore wear over a season. I haven't road raced a Norton for a long time, but still do some landspeed racing. I ran a 920 Norton for several years at Bonneville, and set the piston clearance at .006", because the engine sees full throttle right from the start to the end of the third mile, and gets pretty hot.

Please keep us posted on your progress.

Ken

Re: Norton Seeley shortstroke Racer rebuild

A 320 main jet sounds as though the fuel was a hydrocarbon/methanol blend. Back in the 50s methanol was legal for road-racing in Australia. So our guys were accustomed to a fair level of speed. When some of them went to race in the UK, they found the Brits had their Manxes going as fast on petrol as ours' went using methanol. The trick with methanol is to use the same tuning procedure you would use with petrol. Most of our guys still run methanol too rich. It still gives good power like that, but in comparison with the situation where the jetting is properly leaned off, the bike is usually sluggish. If you don't know how to tune, methanol is very forgiving as long as you use big jets. The allowable margin for error is twice that of petrol.

Re: Norton Seeley shortstroke Racer rebuild

Might be the idea that the left hand cylinder gets to little squirt up the liner, but I do think that´s odd as just if you get some pressure and above all oil in to the end of the crank the centrifugal force takes care of the rest. There must be something else to it as well.

I went for going as light as possible by getting Jim´s pistons that has the pin moved upwards closer to the oil ring. By doing that we had to have even longer rods to compensate for the distance between old a new piston. After som math and sketching studying it seemed ok and I would´t even have to skim cylinder o head. Dad had place 2 spacers under the cylinder so when these came out the squish distance could still be good.

It was a good thing to that all moving parts got lighter so I could lighten the nourish crank and rebalance it to what I want.

It took some time on the mill but I think I lightened the crank about half a kg at least. Then static balancing and last I did a dynamically balancing to perfection at the machine shop Malmö motorrenovering in Malmö.

The picture shows 2 of the lightened holes on the side of the std balancing plug hole. Then I did two more big holes in the weight on the sides not shown