Stray

Bit more progress, albeit minor. Got to measuring and designing the subframe. For the record, the stock subframe sits under the NSR250 fairing. I’m using this as a guide/template to measure the new one before fabricating parts. Was thinking about extending the seat to follow the tank crease at the knee - what do you think? Also thinking of following that seat line with the fairing so it’s one clean line, parallel with the frame. This part of the 5th gen always seemed untidy to me, like they had a plan but changed it. Again, what do you think? I’ve even been thinking of covering that lower triangle on the tank (under the green pen) in the same material as the seat for continuity. Here’s what the seat pan looks like in situ. Need to think about how I want to deal with the hole where the rider’s butt goes. Might just seal it with plastic plate. Also got me thinking more about why the NSR cowl/cover has all these holes. Turns out the two on the side (where the blue end of the pen sits) are for a passenger seat pan that slots in. Will have to weld those shut. But what about the NACA duct on top (where the pointy end of the pen is)? What purpose could that possibly serve other than to let rain into the battery box? It’s absurd! I was working late at night and couldn’t break out the angle grinder so cut the ends of the stock subframe off by hand with a hacksaw. No joke, it took over 30 minutes (with cutting oil!) and I was sweating like a galley slave at the end! Finally, if anyone wants to do this mod the stock subframe will fit if you cut the rear corners off like I did. You don’t have to even cut the Frankenstein bolt (I did but you don’t have to). Only a very small part of the stock subframe shows (where the yellow pen is pointing) if you kneel down low. You’d have to weld on tabs for the fairing and lights but that’s easy on steel. Interestingly, the NSR fairing mounts are a hot mess. If you look at a stock NSR MC21 subframe you’ll see what I mean. I’ll have to recreate that hot mess of welded tabs to make this work...wish me luck!

Thanks mate. Can’t wait to see the finished product either but my God she’s taking her time! Just saw pictures of your RS850 - got to be one of the most beautiful motorcycles I’ve ever seen! Unfortunately I’m now committed to the MC21 seat and am measuring up subframe parts. But I’d still love to see your bike in the flesh. I’ll be racing in Mallory Park on the 8th if you fancy coming for a jaunt. The Triumph, Norton and EMRA boys will be there - should be a hoot! Free to watch if you come early enough before the racing starts. It’s an odd circuit and you can only access it by riding the wrong way round the track. So once the racing starts there’s no way in until the next break.

I love the lean angle you can achieve on that RC45, BLS!

Another minor bit of progress - initial trial fit of NSR 250 MC21 tail fairing (Chinese plastics) and cut down 5th gen seat. Still needs a great deal of sculpting for both seat and fairing, but it’s a cautious start. Now just need to settle on the rear fairing angle and build a subframe. Which one do you prefer? Slightly upward pointing tail: Or slightly lower pointing tail: The MC21 is a much smaller/narrower machine than a 5th gen and the tank is narrower too. The MC21 fairing sculpts inwards at the front and fouls against the 5th gen frame, making it impossible to line things up properly. So I cut the offending pieces off and straightened them with a heat gun, some old angle iron and a clamp. You can see where I cut them off in the previous picture; there’s a gaping hole just where the fairing meets the main frame. Below you can see the grey plastic piece sandwiched between two black angle iron pieces and a blue Irwin clamp. By the way, these Irwin clamps are amongst the most useful tools I’ve ever bought! Came out straight enough with minor ripples that will sand out. Can’t tell it was ever “sculpted” in the photo. The idea is to glue them back on (solvent welding) but if I was doing this again I’d just have bent them on the fairing without cutting them out. Now can somebody please tell me why the MC21 has a NACA duct on the rear fairing cover? What purpose does that serve other than to let rain water in? And one more thing: why does the 5th gen have a sculpted crease on the tank (where the seat meets the tank) and no fairing to go there? It seems like they initially planned to extend the rear fairing and cover that hole where the rear cylinder is visible but then changed their minds. Maybe to let hot air out and stop the rear cylinders overheating?

I bet there was an air bubble trapped in that run. Air bubbles can cause poor cooling. Otherwise distilled water is a better coolant than “coolant”. The only reason we mix water with other stuff is to stop internal corrosion.

Minor bit of progress, but an important step made this weekend: got rear brake bracket welded for 848 wheel/caliper conversion. The 848 brake torque arm is a cast & forged aluminium piece fixed with a 12mm lug in the swingarm. The 5th gen equivalent uses a bracket and a dogbone fixed with a 10mm bolt that’s about 47mm too far for the 848 bracket to reach (depending on how the eccentric is situated). I tried making various brackets and bolts but there isn’t enough clearance. So I extended the 848 bracket with a piece from another 848 bracket. Traced it on paper and drew out the design crudely in pencil. Then cut out the piece to add as a stencil and traced it on the donor part. After that, a tiresome couple hours of cutting, grinding, filing and shaping to make it match the profile of the other part for welding. It’s a thin piece of aluminium with lots of complex angles so had to make sure the welding gap was minimal. Then bevel the edges and get welding. Came out quite nice in the end with minimal distortion. Hope you like my plait welds! Not the prettiest job but it’ll hold. Maybe some paint to smarten it up... Few notes: the internet is so full of sh1t and misinformation it gets me every time. Every source I’ve read (including dedicated welding sites) say cast aluminium wants 4043 filler rod because of its ductility to avoid stress cracking as it cools. They also say 5356 is unsuitable for cast because it’s prone to cracking and difficult to work with. They also say to never mix the two rod types: if you apply one and then decide to apply another the first should be completely ground off first. Well, that’s all horse sh1t. I started with 4043 and it cracked before my eyes. So I tried the 5356 over the cracks and that went on a dream. So I went over the whole thing again with 5356 (no grinding) and used the side-to-side method to cover more area and deposit more rod volume. That’s why it looks like a plait. In short, it was EXACTLY THE OPPOSITE of what the welding forums were saying. So don’t believe what you read on the internet. Don’t even believe me! Get proper professional opinions and make up your own mind.

Sorry Mike, I haven’t got that far yet. Still battling with subframes and bodywork. The injection system will be the last bit to get done. Still have electrics, new coolant system, suspension upgrades...and so on. Mightbe a while before I post an update but certainly will when the time comes.

Jim, have you put spark leads on correct plugs? Many of us have got that wrong and engine won’t fire.

Pics of the SP1 race tail as promised. Got the rear wheel and front fairings off so it’s hard to picture. Will need some trimming at the tank. Not really the period look but not bad. Any good? Compared to the previous ones?

Thanks bmart! Do you mean the half-naked without the lower fairings? The one with a chin spoiler? Love the FJ, by the way. One of the greatest bikes ever made. Really solid air cooled engines!

Thanks for your input, Dangeruss! It’s good to know you’re in this rabbit hole with me. Can’t wait to see yours with the SP2 tail. Please post ASAP!

Hello All, Stumbled across this motorcycle journalist from Bennetts Insurance doing a test on single layer vs double layer motorcycle jeans. I sometimes wear motorcycle jeans when it’s hot so watched it. Turns out he’s got a 5th gen in the garage. Fantastic endorsement that his own bike is a VFR. Although it looks like he’s servicing it with what looks like supermarket oil... Spoiler: double layer jeans are better than single layer, regardless of safety rating. Wearing armour with the jeans is better still. Enjoy!

One more thing: I’d been reading up on tyre pressures and heat for track days and when I came off each session I’d put my bare hand on the tyre to check temperature. Tyres were cold each time, even when I jumped off in the pit lane right after my fastest session. Dead cold. Tyre tech told me touring rubber is designed to warm up quick but stay quite cool in all weather as it deals with a wide range of conditions. Track rubber is designed for a much narrower temperature range and is designed to get really hot with speed. This is why track tyres are lethal when cold - they haven’t reached operating temperature until you’ve tortured them. Touring tyres are fine from the get go but tend to get slippery when worked hard in the heat. The gap between street and track rubber has narrowed greatly over the years though.

Ducnut, that filter looks nasty!

One thing about Avon tyres: the tyre tech told me they need bigger weights to balance because they’re not as precisely manufactured as the bigger brands. If you’re one of those bikers who doesn’t use wheel weights then you may want to steer clear of Avon.