Fortnine RG500
Discussion
Stevemr said:
Not trying to change any one’s mind about Fortnine. Just did not know how close to a gp bike the RG was, and found the part about developing expansion chambers and the V1 connection v interesting.
Padgetts raced one in TT Formula 1 using a Harris frame and won the title in '86 with 'Captain' Mark Phillips and '88 with Darren Dixon.Performance Bikes tested the '86 bike at Bruntingthorpe at something like 170mph
trickywoo said:
Tango13 said:
Performance Bikes tested the '86 bike at Bruntingthorpe at something like 170mph
Are you saying a production RG500 went a true 170mph?Yes, they were derived from the race bike RG but in reality, the performance was a look g way off. A comparison with the latter RGV250 which made about 65bhp in it's final Aprilia RS250 iterations with a little bit of breathing on.
A friend of a friend in SA engineered the rgv barrels and pv's onto an RG500 bottom end and it still didn't make mad power. The crankcase volume and scavenging was just poor at best and even the later 570's engines struggle to get over 100bhp .
Edited by Steve Bass on Monday 28th April 02:23
trickywoo said:
Tango13 said:
Performance Bikes tested the '86 bike at Bruntingthorpe at something like 170mph
Are you saying a production RG500 went a true 170mph?The '86 title winning race bike was tested at something like 170mph. PB tested a VFR750 with a cut and shut crankshaft at the same time and that also hit about 170.
Edit to add...
The road bikes didn't hit 145 on 78bhp, it's well known the road test bikes in the UK had been 'fettled' to about 80~85bhp, possibly more.
See also E Type Jaguar...
Edited by Tango13 on Monday 28th April 10:25
Tango13 said:
trickywoo said:
Tango13 said:
Performance Bikes tested the '86 bike at Bruntingthorpe at something like 170mph
Are you saying a production RG500 went a true 170mph?The '86 title winning race bike was tested at something like 170mph. PB tested a VFR750 with a cut and shut crankshaft at the same time and that also hit about 170.
Edit to add...
The road bikes didn't hit 145 on 78bhp, it's well known the road test bikes in the UK had been 'fettled' to about 80~85bhp, possibly more.
See also E Type Jaguar...
Edited by Tango13 on Monday 28th April 10:25
trickywoo said:
So the road bike is nothing like the GP bike?
Nope, different stroke and the race bike having one of the first cassette gearboxes are the main differences I can think of off the top of my head but there were almost certainly lots of small details too. Getting a road RG500 up to 170 or so took an awful lot of work but it did result in a weird anomaly where you could race an F1 bike in GP but you couldn't race a GP bike in F1
Tango13 said:
trickywoo said:
So the road bike is nothing like the GP bike?
Nope, different stroke and the race bike having one of the first cassette gearboxes are the main differences I can think of off the top of my head but there were almost certainly lots of small details too. Getting a road RG500 up to 170 or so took an awful lot of work but it did result in a weird anomaly where you could race an F1 bike in GP but you couldn't race a GP bike in F1
Drawweight said:
Mark dent is the guy for RG500's.
With modern technology and machining you can get pretty close to GP performance from the road bike and be reliable as well.
I would seriously question anyone who says they're getting late 2T era power from the RG engine. With modern technology and machining you can get pretty close to GP performance from the road bike and be reliable as well.
Sheene's bike was rated around 125bhp and the XR14 around 114. It wasn't until the end of the 2T era power was up around the 180/200 mark and that needed special fuels, pv engines and a hair trigger power band.
It's only recently that ground up modern bikes like the Suter 500 or Ronax are making big power and their engines are night and day to the RG.
Great in their day and emblematic of an era but it seems like the glasses get more and more rose coloured every year.....
I'd kill for a Suter mind......
Acuity30 said:
If you're a fan of motorbikes I'm not sure how you couldn't be a fan of Fortnine
I like motorbikes (watching more than riding now as nearly died on one!) and also Fortnine videos. Only discovered the YouTube channel in the last 6 months or so, I don't understand why bike people wouldn't. They seem very well made videos to me. I was a greenhorn mechanic at a Suzuki dealership when these came out,
had owned GT185 and RD250 aircooled but that 4 was definitely something else.
The boss of dealership had some two-stroke tuning experience from his racing days
and modified some of the 500s for all-out customers,
with aggressive intake timing, raised crankcase compression ( with Scotch Weld stuff ),
machined heads for more compression and some carb fine tuning.
He claimed mid-90s hp but the powerband was small and way up the rev range.
It was quite an experience to do test rides with those bikes as we were in the middle of town
and had to drive to the next Autobahn strip to test the engine setup.
That 1st gear was loooong and stalling was oh so easy, very embarassing when I filtered through
the cars waiting at red lights and giving it throttle blips with blue cloudbursts before.
WENNNNNGGGG, WENNNNGGGG, WENNNGGGG.....childish but fun, and felt like Mr. Sheene himself.
Those were interesting days, working/riding on the RG and then the 1400 Intruder with it´s damn lean carbs.
had owned GT185 and RD250 aircooled but that 4 was definitely something else.
The boss of dealership had some two-stroke tuning experience from his racing days
and modified some of the 500s for all-out customers,
with aggressive intake timing, raised crankcase compression ( with Scotch Weld stuff ),
machined heads for more compression and some carb fine tuning.
He claimed mid-90s hp but the powerband was small and way up the rev range.
It was quite an experience to do test rides with those bikes as we were in the middle of town
and had to drive to the next Autobahn strip to test the engine setup.
That 1st gear was loooong and stalling was oh so easy, very embarassing when I filtered through
the cars waiting at red lights and giving it throttle blips with blue cloudbursts before.
WENNNNNGGGG, WENNNNGGGG, WENNNGGGG.....childish but fun, and felt like Mr. Sheene himself.
Those were interesting days, working/riding on the RG and then the 1400 Intruder with it´s damn lean carbs.
Steve Bass said:
Drawweight said:
Mark dent is the guy for RG500's.
With modern technology and machining you can get pretty close to GP performance from the road bike and be reliable as well.
I would seriously question anyone who says they're getting late 2T era power from the RG engine. With modern technology and machining you can get pretty close to GP performance from the road bike and be reliable as well.
Sheene's bike was rated around 125bhp and the XR14 around 114. It wasn't until the end of the 2T era power was up around the 180/200 mark and that needed special fuels, pv engines and a hair trigger power band.
It's only recently that ground up modern bikes like the Suter 500 or Ronax are making big power and their engines are night and day to the RG.
Great in their day and emblematic of an era but it seems like the glasses get more and more rose coloured every year.....
I'd kill for a Suter mind......
The FIM mandated a big (relatively speaking) weight increase to 500 GP bike of 10kg, the factories just made the crankcases and barrels from aluminium alloys instead of magnesium alloys. The more robust engines could be worked much harder for more power.
The RG having disc valve induction was always at a disadvantage to the reed valve engines of Honda and Yamaha hence the big jump in power from the RG to the RGV.
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