Memories Of A Simple 2-Stroke

by Sverre Helgesen

Very erudite discourse, factual, to the point. But I'm not.

I'm a lifelong 2-stroke fan and ex-MX rider. Sweden in the 70's had the best and toughest race-courses in the world, and this reflected on the standard of the riders. You got tough fast or died, back in those days. Crap 'B-grade' rider as I was, after a mere 5 years of racing my lap times on four GP courses here was as fast as the heavily-sponsored pro Brit GP riders! (The guys were very disappointed with lackluster much-hyped Neil Hudson, but a very young unknown, Dave Thorpe, got the thumbs-up, and later did very well).

It helped we had the Husqvarna factory at hand. Though not perfect they were the best MX bikes ever made. Because they were evolved and tested by US, the riders, not slide-rule toting engineers who never swung a leg over a motorbike, a la Japan, and, often, had never actually seen one.

I met Gordon Blair at the factory once. Ruben Helmin wanted to see if he had anything to offer HVA. Answer: no. Blair knew the maths but never fired-up a bike in his life, let alone ride one on one of the toughest tracks in the world, the fearsome Drattinge track a mile or two from the factory. ALL of the young engineers working under Helmin (who had raced earlier in his life) raced MX and enduro, testing the very bikes they were working on, sharing their experiences directly with each other and Helmin. And those same engineers chatted with we riders at the races, offering advice, helping out spannering and repairing if needs be ... but most importantly; LISTENED to our woes, thoughts and ideas.

Their economic director and sales manager, Bror Jauren, was also a much-loved man about the scene, quietly listening to often rather loud, er, abuse. Sometimes, it has to be said... (Wound-up, tight riders who'd suffered a breakdown, or been thrown onto somewhat hard ground in a violent manner due to a failure, could be rather abrupt.) He never got angry at being told the harsh truth, but took it to heart. And always left you with a kind word and a rubbed back. And passed on the information. But it was this that took us from the original 'Silverpil' based design to the fabulous magnesium 6-speeders (I bought my Mikkola Replica in '76, the '75 cracked frames and blew clutches.) And HVA did this on an annual development budget that a Jap factory would use up in one week.

Helmin took a lot of flak for still using twin-shocks when all others had gone over to single linkages. But there was a sound engineering base to this. Twin-shocks were better (at the time). HVA's were never the most powerful bikes on the tracks, but they always put all that power on the ground, where it counted.

One area that caused a few shouting-matches was the need to run-in a HVA for 30 hours before racing. You could race a Jap bike out of the crate. Many a rider ruined a HVA in a few weeks, throwing the # crap to the ground, bad-mouthing it. "Effing Smalands s##t!" Not all riders were as intelligent as we others... Why they raced fast for a year or two, then quit. HVA always used the best materials for the job, these materials needed time to bed in ... and these materials didn't like the wrong lubrication either.

"Always use a mineral oil, NEVER one of these new-fangled synthetics, and ABSOLUTELY a 20-25:1 ratio. A simple moped-oil from the gas-station is perfectly ok to use. Anything that needs lubricating needs a cushion of oil to rest on, a thin layer, yes, but a reliable film, a bog-standard mineral oil will do this, but a synthetic won't. It's there, yes, but too thin a film to give that cushion.

Whatever ratio you use. A bottom-end will run on 100:1, but a piston won't like it one iota even though it runs. Use Bel Ray in a HVA and it'll seize as the rings gum up instantly, our ring-clearances are half what the Japs use. Crank lifespan is cut in half on 100:1 and pistons wear out like there's no tomorrow. It also affects the heat-dispersion. Only the 'thick' film left by mineral oil will allow heat to disperse, acting as a cooling-fin on the engine. Frankly, if you're out of oil and desperate, run into a supermarket and buy rape-oil, sunflower oil, olive oil, anything like that, that will sort you for the transmission, gearbox, and even the engine-oil. Though be sure to only fill a few seconds before the race and give the can a good shake. You will have to strip and clean the engine afterwards as it does gum-up easily after heating. (B#gg#r that, we filled the crankcase with petrol and gave the bike a good shaking, then upended it to empty out the residue. Well, it works! I once drove my Transit van from Stockholm to Gothenburg on sunflower oil. No, I just drained it and filled it with real oil ... and crossed my fingers...) You've tested it in your frying pan enough times to know that. But it's only a problem around the rings and plug. But up to that point it's as good as Castrol-R as far as being a lubricant. Sooner that than Bel Ray...

A lot of the oil is condensed out of the petrol when entering the engine and the petrol suddenly being heated, why an engine smokes on startup and when not being revved hard for a few seconds, more oil being held in suspension by the petrol and being burned in the combustion-chamber. And a lot of THAT oil condenses when cooled in the expansion-chamber. So when being revved hard not that much oil goes out of the tailpipe. Split a pipe sometime, and look. Very interesting. Most of the oil merely 'wanders' about in the engine, being slowly blown through it by the air-currents. Bit hit-and-miss, yes, but the various bits DO get the lube they need. Some oil drifts up the walls of the transfers and into the bore, lubing that area (even the bore above the piston needs lubing, the same applies for 4-strokes) and slowly finds it's way out to the exhaust port. Some of the oil gets blasted by the combustion and is seen as carbon deposits in various places. These places are HOT areas that you should study. Might save you a seizure, sometime? And, of course, there is always some oil that gets burned with the petrol and goes out of the exhaust with the hot result of that. How much isn't known, but I've had it suggested about 10-15 percent. I've also had it suggested a simple charcoal-filter in the front of the silencer might deal with a noticeable amount of that. A charcoal-filter attached to the petrol-tank breather takes care of evaporating gases there, my '66 Mercedes 200 car had one just inside the filler-cap.

I've seen pictures of the Uddevalla track I used to race on, one of the 4 toughest in the country - the world (Harry Everts said so, "But it is too smooth, I prefer rougher.") It had been, lovely and rough, but the organisers, not being actual racers, bulldozed away all the good bits, thinking about all the dead bodies and the insurance costs, not listening to the local racers telling them merely to fill-in the ruts, they being in the wrong place for the serious GP riders - let them dig out their own - and I was devastated. Gone was the track I once knew, now there is something likening a circus and an American freeway. All the rough bits were gone. All the hard bits were gone. None of the old track exists. I can see why, all to make the track easy enough for the feeble 4-strokes to go fast on, not having any of the acceleration the rip-snorting 2-strokes had, and to have all the huge jumps the stars need for their circus-antics in the air. Even at my age (63) and out of shape, I could ride the new track. Wouldn't make a lap on the old one, let alone at race-speeds.

The future is direct fuel-injection for the 2-strokes. I'd love a bike with digital engine management, one that adjusts the carburation and ignition all by itself 256 times a second. No more re-jetting each training-session, no more desperately trying to work-out out what settings to have so the engine will survive a hot day on a sandy track, sensors will read-out the actual temperature of the exhaust-port, plug, amount of air entering the engine etc., and do it all for you. Imagine during a race, hearing 'Stephen Hawking' in your Bluetooth ear-piece; Beep. "Computer to operator: Plug not at optimum operating temperature. Please change to hotter plug ... or ride faster." Beep.

The problem is the 'bean-counters' don't like spending money. They are so stupid they can't see that throughout history it has been proven you simply cannot make money without SPENDING money. And changing over to another power source is a major investment.

I honestly don't see it happening.

I once heard an interesting story, overheard an ex-Rolls Royce engineer talking to a German whiz-kid electronics engineer from the war. It seems when Rolls were mulling over a new engine for their cars after the war it was suggested they make a 2-stroke V-8/V-12 based on the proposed RR-design for Barnes Wallis' Victory bomber, the one he needed for his ten-ton bombs. The engineer suddenly found himself 'considering a new career in the USA'. And NOT for RR. A pneumatically-controlled sleeve-valve, direct-injected, blower 2-stroke with piston and conrod as one unit (a type of 'Scot-crank'?). Very small unit compared to a 4-stroke, light, much better fuel consumption. And I've met 2 other guys over the years who've repeated this to me, none seeing each other since splitting up after the war. Same team who were working on it, you see. They got their asses kicked, too.

- Ha.. A brilliant read thanks Sverre! I'll keep a bottle of sunflower oil in the car for long trips from now on.


Comments for Memories Of A Simple 2-Stroke

Average Rating starstarstarstarstar

Click here to add your own comments

Mar 11, 2010
A V8 2 stroke ... Awesome!
by: Anonymous

About now would be a perfect time for a manufacturer to produce a nice veggie oil burning 2 stroke for sure.

Nov 30, 2009
Two-Stroke Oil Requirements
by: will

Hi Sverre,

Liked your comments very much... so informative. Your experience with Bel-Ray mirrors my own... over-rated and didn't work at 100:1 or even 50:1.
On my TZ 350 Yamaha which was raced for some years successfully on Castrol R at 24:1, Bel-Ray was an expensive flop... never worked at any ratio.

When my TZ was stripped after yet another seizure, (using Bel-Ray) all the internals were found to be 'dry'!!!

After standing for several months over the winter period for a re-build for the new season, my TZ internals were still 'wet' with caster oil after using the 'old fashioned', gummy Castrol R.
It took me several years to overcome the hype and return to Castrol R at 24:1.

It now seems that even the 'super synthetics' at twice the price are required at 30:1, or even 27:1.

I'm still pottering round on a Suzuki T20 in classic racing and have to use Castrol 747 (an expensive synthetic oil) at 27:1 to ensure it doesn't seize.

Good luck to all two-stroke riders and roll on the 'new generation' of strokers. Also, great article, Tim, can we have some drawings/diagrams, please?

Nov 03, 2009
No Rough Tracks Left
by: Anonymous

Have to agree about the condition of motocross tracks since the 70's. Everywhere you look the face of MX has changed to emulate supercross.

MX used to be about racing on 'irregular', 'natural' terrain. There is certainly nothing irregular left to the modern MX track. It is sad to see that aspect gone the way of the dinosaur.

Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to The Future Of Two Strokes.

Get The Basics RIGHT! And Watch Your Bike Skills & Enjoyment Increase. Over 800 Copies Purchased & Growing.. The Dirt Bike Garage Manual

Site Search