Chris Harris’ BMW R80
Germans are well known for their precision but, bugger me, I didn’t expect Accuracy Level 99. While trawling the web for the right parts to turn my 1986 BMW R80 into a hard-nose cafe racer, I couldn’t resist looking into performance gains – not that its performance was lacking. The biggest benefits came from slashing as much as 60 kilograms from the original bike, top-notch Wilbers suspension and an equally top-notch suspension tune, but I couldn’t resist the temptation of a 1000cc kit. Screw it, why not?
Chris Roberts at BM Motorcycles in Melbourne said the big-bore kit from HPN (of 1980s Paris-Dakar fame) was the one to go with as he’d fitted plenty over the years with very good real-world results.
Interestingly, HPN claims a 25 per cent increase in maximum power output as well as a 30 per cent boost in torque over most of the rev range. Those are serious performance claims so, in the name of journalism, I decided to put it to the test.
As a before and after test, the bike was dyno’d around the corner from BM at In-Tune Motorcycles in Ringwood. Luke gave it three runs and the magic figure was 42.2 horsepower at the wheel. Not bad, given these 800cc units left the factory in 1986 with 50hp at the crankshaft.
The kit comprises two Nikasil-coated barrels, stainless steel pushrods, high-compression pistons (9.5:1), rings and gaskets, and there’s no need to alter the original exhaust, head or jetting, according to HPN.
I got it fitted but now with higher compression, the original Bosch starter motor just wasn’t up to the task so in went a later-model Valeo unit for a higher kilowatt rating while drawing a third less current from the battery.
The 1000km run-in period took what felt like a lifetime as I don’t exactly ride it far or often, but it did prove the best excuse to slip out for a cheeky afternoon ride.
After the painstaking 4000rpm rev ceiling for the first 500km and 4500rpm thereafter using 75 per cent throttle it went back to BM to adjust valve clearances, tighten things up and fresh oil. Even within the run-in parameters, the extra dollop of torque was immediately noticeable – it’s simply quicker while using fewer revs.
Now for the real test: the dyno.
Luke gives it another three runs and after fitting slightly larger jets manages 51.4hp and 44Nm, which are increases of 22 and 31 per cent respectively. That’s pretty damn close to HPN’s claims but then they are German. More beneficial is how much earlier the power and torque is produced and how linear the delivery is. Look at the graph – no asphyxiating dips and no dropping off cliffs.
On the road the bike simply has extra muscle no matter which gear you’re in.
Even Pat, my ever-skeptical friend who helped me put the bike together, could only manage to blurt out a grinning “F-yeah!” when he returned from a flat-out blockie.
Some of you are probably scoffing at the bike’s modest outputs and my floral descriptions while caressing your modern 200hp sportsbikes. “That’s not a knife…” But it’s pretty damn good for a bike almost 30 years old and originally intended to haul old farts for miles on end.
For perspective, I signed up to run down the quarter-mile at the classically inspired Geelong Revival – the only drag strip with a hairy kink and rather short braking zone. This involved a dull 100km commute to get there, melting in the hot afternoon sun in black leathers in the staging area while the exhausts of two-stroke widow makers sand-blasted my face.
Ideal conditions to extract maximum performance from an old airhead these were not.
Of the three runs I managed times of 13.5, 10.28 and 13.8 seconds, the latter of which was slowed by a missed gearshift.
My questionable second pass was certainly my quickest as well as proving to be the fastest in class, which comprised a sea of fire-breathing Kawasaki Z1000s and even a McIntosh Suzuki.
Grabbing the trophy and making a run for it certainly crossed my mind, but the thought of angry riders on even-angrier bikes chasing me down the freeway back to Melbourne proved too great.
I suspect the ‘10’ should’ve been a ‘13’. Unfortunately terminal speeds were not recorded over the weekend.
Despite the timing glitch, I’m pretty damn pleased with the results of the day and the 1000cc kit. It’s been money well spent. The piece de resistance, however, was immediately going from the torturous rigours of the track to comfortably and reliably cruising 100km home. Gotta love that.