The story of my Honda Supermono development started around 1997 when I was speaking to Chris Wain, an ex-Spondon Engineering fabricator who knew of a Suzuki RGV250M chassis that he had adapted to accept one of the Honda RFVC single cylinder engines, a few years earlier.
Chris was instrumental in building the Spondon chassis's for the world famous and very successful Norton Rotary race bikes, so I knew if he had adapted the chassis then it would be a top notch job.
Later that year I met up with the current owner to collect the chassis and various Honda race parts that he had been using on a Honda speedway project. The RGV Chassis had never been used since it was modified but had been left a while so was in need of some TLC.
The RGV chassis had been very nicely adapted to take the Honda engine, so much so that it was hard to tell where it had been altered.
As well as the RGV frame and lovely banana swinging arm, there was also a spondon alloy fuel tank, alloy petrol tank, alloy subframe and Yamaha TZ race seat.
The Honda race spares were made up of a bespoke ignition system, new very extreme Megacycle race cam, Wiseco 102.4mm piston, High lift race valve spring kit with Titanium valve spring caps and general clutch spares. A Micron developed speedway system also came with the kit.
I sourced an early Honda NX650 Dominator engine to use as the basis for the bike and spare parts to enable a full rebuild. I fitted a brand new gearbox, had the crank welded by Chris and I tuned the single port cylinder head to take a 42mm Mikuni VM40 (overbored) round slide carb instead of the very sluggish standard Honda carb. The new parts would make this a 675cc beast.
I left the chassis with Chris, to repolish the frame and slightly lower the subframe as this was a little extreme. He also built a battery box to store the battery and electric items.
One major hitch when fitting the engine was that the electric starter gearing on the left hand side of the engine hit the frame and prevented it from lining up with the engine mounts. The chassis was obviously developed for the earlier XR600 ad XL600 engines that had kick starters only and didnt have this problem. To solve it I removed some of the inner wall of the frame. Since Im a trained aeronautical stress engineer I had a fair idea what would be acceptable to remove.
The engine then went into the chassis with just a few spacers required, so I made these out of alloy on my lathe. I hand made a front engine plate form aerospace alloy and this matched up with the T-piece that came with the chassis.
A very tidy set of RGV250N forks were found via a breakers yard. The yokes came with the bike so these took the RGV forks without any modification.
The bike then went to Andy Bacon, famous in classic racing for developing very high quality, low weight two stroke exhaust systems. He took the Micron stainless headers and siamesed these into a very neat collector and megaphone silencer.
The earliest shot I have of the bike, half done is here....
Chris was instrumental in building the Spondon chassis's for the world famous and very successful Norton Rotary race bikes, so I knew if he had adapted the chassis then it would be a top notch job.
Later that year I met up with the current owner to collect the chassis and various Honda race parts that he had been using on a Honda speedway project. The RGV Chassis had never been used since it was modified but had been left a while so was in need of some TLC.
The RGV chassis had been very nicely adapted to take the Honda engine, so much so that it was hard to tell where it had been altered.
As well as the RGV frame and lovely banana swinging arm, there was also a spondon alloy fuel tank, alloy petrol tank, alloy subframe and Yamaha TZ race seat.
The Honda race spares were made up of a bespoke ignition system, new very extreme Megacycle race cam, Wiseco 102.4mm piston, High lift race valve spring kit with Titanium valve spring caps and general clutch spares. A Micron developed speedway system also came with the kit.
I sourced an early Honda NX650 Dominator engine to use as the basis for the bike and spare parts to enable a full rebuild. I fitted a brand new gearbox, had the crank welded by Chris and I tuned the single port cylinder head to take a 42mm Mikuni VM40 (overbored) round slide carb instead of the very sluggish standard Honda carb. The new parts would make this a 675cc beast.
I left the chassis with Chris, to repolish the frame and slightly lower the subframe as this was a little extreme. He also built a battery box to store the battery and electric items.
One major hitch when fitting the engine was that the electric starter gearing on the left hand side of the engine hit the frame and prevented it from lining up with the engine mounts. The chassis was obviously developed for the earlier XR600 ad XL600 engines that had kick starters only and didnt have this problem. To solve it I removed some of the inner wall of the frame. Since Im a trained aeronautical stress engineer I had a fair idea what would be acceptable to remove.
The engine then went into the chassis with just a few spacers required, so I made these out of alloy on my lathe. I hand made a front engine plate form aerospace alloy and this matched up with the T-piece that came with the chassis.
A very tidy set of RGV250N forks were found via a breakers yard. The yokes came with the bike so these took the RGV forks without any modification.
The bike then went to Andy Bacon, famous in classic racing for developing very high quality, low weight two stroke exhaust systems. He took the Micron stainless headers and siamesed these into a very neat collector and megaphone silencer.
The earliest shot I have of the bike, half done is here....
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| Early pic of the Abcon exhaust. Think Id just started the bike. Loud |
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| Nice and sleek. Hard to believe there 675cc's in there |
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| not quite road legal yet!! |
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