Inconsequential ramblings of an Old Git

[mangocrazy]

Can't you shave 50mm off the downpipes? (Once it's all apart)

The downpipes on the VFR are an absolute twat to fit or remove, being a V4 layout. The rear downpipes are especially twattish. The front and rear downpipes on each side merge underneath the engine and then plug into the collector box. This is an ebay listing for the left hand rear downpipe for my MY of VFR750:



So there is no scope to shorten the downpipes as everything has to fit together in some Frankenstein jigsaw puzzle. The only way to get around the problem is either to fabricate a shorter collector box or fit a different system. I'm intending to do the latter. But may also need to do the former...

I have made progress today; the collector box is now off the bike, but I had to make creative use of the Skylift along with using a ratchet tie-down round the subframe and through the rear wheel to take the load off the suspension linkage so I could remove two of the linkage bolts and allow the swingarm to pivot freely.

It's all back together now (sans collector box) but torquing all the bolts up can wait for another day. Getting all that done in a small shed with two bikes in it was an exercise in frustration and bruising.

[mangocrazy]

Finally got round to making the trip to the welders with assorted pieces of aluminium tube and this was the result once Chris had done his thing:

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And here's a closer view of the welded bits:

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Next step is to head off to the platers/coaters and get them Xylan coated in satin black.

[Supermofo]

Surely you're missing about 8 inches off them risers for you (as the bishop said to the actress)

[mangocrazy]

Surely you're missing about 8 inches off them risers for you (as the bishop said to the actress)

Hah! These ali bars are basically a clone of the steel ones I'm currently using, so I can test which material offers the best vibration resistance. Here's the current (steel) bars and the much-maligned MT-09 risers:

[Mr. Dazzle]

I strongly suspect any difference will be in your head.

Which, TBF, isn't a bad place for it to be, 'cause that's the bit where you feel annoyed about vibrations too.

[mangocrazy]

I strongly suspect any difference will be in your head.

Which, TBF, isn't a bad place for it to be, 'cause that's the bit where you feel annoyed about vibrations too.

I'm reasonably sure any difference (if indeed there is any) will be felt in my hands and forearms.

If my head is in contact with the bars something has gone seriously wrong.

[Skub]

Shirley the heavier bars will dampen the vibez best? Or is it more complex than that?

Or maybe it matters little which material the bars are made of,because bar end weights will do the dirty work.

[mangocrazy]

Shirley the heavier bars will dampen the vibez best? Or is it more complex than that?

That would be my guess, as well. But the ali bars are made from heavier gauge tube (i.e. more material) so that may have an impact. Or not.

Or maybe it matters little which material the bars are made of,because bar end weights will do the dirty work.

Nail head, meet hammer. I've had to modify both bars so they will accept the OE Aprilia bar-end weight system (discussed at length somewhere on here, not in this thread) so that will probably make the major difference.

I'm also going to check throttle body synchronisation, just to rule that out.

[mangocrazy]

After my customary January/early February hibernation I've (sort of) woken up and started doing stuff. In a lazy, rather disconnected way of course. The object of my attentions has been the VFR. It was ferried back from France last October for a good dose of looking at the front end and clonking issues. I'm hopeful these have been resolved (time will tell) so now I need to do something about the exhaust collector box being approximately 50mm rearwards than it should be. I've resolved this problem by the simple expedient of taking the fucking thing off, pending surgery (of it, not me).

One of the benefits of being a hoarder is that stuff that I stopped using 30 years ago is still lying around somewhere. This is/was the case with an aftermarket exhaust system I had fabricated to fit the VFR (same model, different model year) that I had in the mid-90s. It was somewhere in the loft of spiders but was still in remarkably good nick and (better yet) still fitted pretty well. It completely dispenses with the collector box (yay!) and just has one pipe and one (carbon) can per side. It also sounded pretty good, if memory serves. Here's the RH side of the bike with the old/new zorst fitted and the bike on the Skylift:

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And a closer look at the carbon can. It's survived remarkably well and still looks pretty good to my eyes. I'm pretty sure I got the system made up in 1995 so for a 29 y.o. can it's not too shabby. But it was made at a place that also fabbed F1 exhaust systems (Parallel Motion, unfortunately no longer in business) so that would possibly account for its longevity. I have had to get db killers made for them though - the V4 open pipe wonderfulness isn't appreciated by everyone, especially MoT testers...

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But removing all that silencing restriction and back pressure does bring its own set of complications. Hondas of that era (in fact most Hondas) are famous for running as lean as possible and today's petrol is vastly different to that of 30-odd years ago, so I think I will need to richen up the mixture somewhat. I'm debating whether to take a stab at it myself and bung some bigger jets in, or take it to a dyno and get it done properly. Are there any 'old skool' dyno operators that know how to fanny about with jets rather than just do it all on a laptop? All recommendations welcome.

Here's what faces you when you take off the seat and tank on a 1988 VFR750...

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[Skub]

Drunken Ferret Repairs get a good name among the classic boys,I think the shop is around Portsmouth.

[mangocrazy]

Drunken Ferret Repairs get a good name among the classic boys,I think the shop is around Portsmouth.

Cheers - it's a bit of a trek from Sheffield but I might be able to fit it in on the way to France. I normally sail from Portsmouth.

[mangocrazy]

Having thought about this for a bit, I messaged Dave Whattams (the guy who dynoed my LC with excellent results) and asked him if he was prepared to dyno a diesel and this was his reply:

I don't do 4 strokes, my extraction system isn't able to handle it without being fully cleansed of old 2T oil etc - its a major fire risk for me as 4 stroke exhaust gases are way hotter than 2T's

The only guy I would recommend is John Warrington in Malton, tell him I put you onto him, he will sort it for sure - his number is 01653 698258

So I rang John up and I'm booked in for Monday 25th March. John used to race VFR400s (NC30s) back in the day so knows all about jetting V4s. He's based in North Yorkshire (between York and Scarborough) so not too far to go. Looking forward to this.

[KungFooBob]

I'd have given Swinton Motorcycles a call, they have a rolling road and tune for at least one BSB team. They're local too.

I've no idea how hot they are with carbs tho'

Edit:

https://www.swintonmotorcycles.co.uk/

Lol, they only do carbs in winter!

[mangocrazy]

I'd have given Swinton Motorcycles a call, they have a rolling road and tune for at least one BSB team. They're local too.

I've no idea how hot they are with carbs tho'

Edit:

https://www.swintonmotorcycles.co.uk/

Lol, they only do carbs in winter!

Bugger, wasn't aware of their existence! But trying to get booked in before end of Feb would probably have been a no-no anyway.

I do understand what they mean about 'carbs only in winter', though. Changing jets or needles on a VFR is a complete PITA. It's seat/tank off, airbox off, plenum chamber off, then try and wrestle the banks of carbs off fighting 35 year old carb rubbers and no space. And a hot engine. Only then, with the bank of carbs on the bench, can you get at the jets/needles. Then it all has to go back together for the next dyno run.

Compare that to making a few fuelling changes on a laptop...

[mangocrazy]

So while I'm waiting to stick the VFR on the dyno, and the weather is still shit, I thought I'd bugger about with the LC. Just because.

The LC has a YSS shock on it, which is a massive improvement on the 40 year old thing that supported the rear of the bike before. But after a fair amount of running, I've realised that a) the spring is a bit on the harsh side for my tender little botty and b) I'd like some more weight on the front to make it feel a little less vague.

As regards the spring, YSS ship the shock with an 80 Nm (or is that N/mm?) item. They also offer a 70 and a 90 spring in the same sizes for lighter and heavier riders respectively. So I've placed an order for a 75 Nm with a local spring supplier, just to be a fussy bastard. Delivery should be mid-March.

To try and fix the perceived 'weight on front' problem, I've acquired some 25mm alloy round bar and handed it to my local engineering place, along with a CAD drawing and asked them to make it happen. This is what I got back:

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These fit in between the top shock eye and the shock body and increase the overall length of the shock by anything between 25 and 40mm, thereby jacking the back end of the bike up by a similar amount. The piece with the shorter nose gives a minimum increase of 25mm in shock length, the one with the longer nose and thin nut gives a minimum increase of 30mm in shock length. If you really wanted to you could increase the shock length by at least another 15mm, but frankly it's all getting a bit silly at those settings. This is a pic of the shock with short extension mounted on the bike:

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To be honest, the extension piece with the short nose is probably at the outer limits of sensible modification. With that fitted, the centre stand is largely redundant as it needs to be stood on a piece of 18mm ply to actually get the rear wheel off the ground. I'm also planning to drop the forks through the yokes by 10mm to lower the front and hopefully bring the centre stand back into use. Thankfully the LC also has a side stand, but the bike now sits at quite a jaunty angle when using that (see below). At least it won't blow over in the wind...

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And after all this I still don't know what effect these mods will have on the handling. I'll learn that in due course... But all the mods are completely reversible, so not all is lost if it fails horribly...

[Le_Fromage_Grande]

If my memory of 1987ish is correct LCs handle better with the front end dropped by 20mm and it doesn't make a noticeable difference to ground clearance, as it's the fat part of the pipes that scrape in corners.

[mangocrazy]

If my memory of 1987ish is correct LCs handle better with the front end dropped by 20mm and it doesn't make a noticeable difference to ground clearance, as it's the fat part of the pipes that scrape in corners.

Cheers. I'll start at 10mm and add droppage as required...

[mangocrazy]

As an illustration of how the spacer has lifted the back end, here's a photo of the bike on an 18mm deep ply board, and the rear tyre is just clear of the ground (by about 5mm). There's also a lot more air between the rear tyre and the mudguard than previously...

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[mangocrazy]

Today dawned bright and sunny (as forecast) and so the LC was wheeled out blinking into the sunlight, had its tyres pumped up and we then went for an enjoyable little jaunt around some south Yorkshire/north Derbyshire scenery. None of which I can show you, as I didn't take a camera and my dumb phone doesn't have any photographic capabilities (or any other capabilities, if I'm honest).

This was the bike's (and my) first outing this year and it was the first time I'd ridden it with the lengthened shock and slightly softer shock spring. I was also wearing new boots and helmet so was taking it steady until I had a few miles under the wheels. But within a hundred yards or so it was obvious that the shock felt much better - more compliant and no sharp kicks up the spine over harsh bumps. To be honest the handling and steering wasn't that much different with the longer shock, just a more composed and balanced feeling. There were certainly no vicious tank-slappers or terminal instability, in fact the whole plot (if anything) felt more stable than previously.

Anyway, here are some photos of the old girl in the back garden, but fully clothed this time.

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and side view:

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And in other news, I've finally bought a phone with a camera!


But it's still dumb, and a flip-phone...

[mangocrazy]

Today was dyno-day...! At 9 am I pulled up outside John Warrington's emporium in Malton (on the A64 between York and Scarborough) with the VFR in the van. I've fitted a pair of aftermarket exhausts and was a little concerned that they might have made the bike run lean, plus I've been twatting about with a Sigma jet kit and wanted to know whether the carburation was OK or miles off, and if it was off, in which direction (rich or lean).

I'd scarcely popped my head round the door before I was offered a cup of tea, so things definitely got off on the right foot. And then before we got down to running the bike, John talked me through the technicalities of the dyno and the principles of how it all worked. Maths and physics, basically. Then it was time to get the bike strapped down and screaming for mercy. John warmed the bike up in stages and was initially interested in seeing what the low speed and mid range fuelling was like. Seriously on the rich side, it transpired. Not at all what I'd expected. It also highlighted that there was an exhaust blow on the LH side of the bike that will need sorting, that side running noticeably leaner than the RH side. But still rich, IYSWIM.

I don't know how many of you have ever removed and re-fitted a bank of V4 carburettors, but trust me - it's an absolute twat of a job. You really don't do it unless you absolutely have to. So John suggested we just work on the (relatively accessible) rear pair of carbs. Without removing them from the bike it's a simple job to take the carb tops off and remove the diaphragms and needle assembly. As part of the Sigma kit, they had supplied washers to fit under the head of the needle (the needles dont have any adjustment notches - thanks Honda...), thereby richening the mixture. I'd fitted two washers per needle which had the approximate effect of rasing the needle by the equivalent of one notch.

The Sigma kit also supplied a drill bit with which you were instructed to drill out and enlarge the two small holes in the base of the needle holder. I'd followed orders and done this, but John was not at all impressed. His view was that the extra hole surface area would mean that the slides would be less likely to lift with the intake air pressure, thereby further richening the mixture. There wasn't much we could do about that at that time, but I will need to look around in my spares box and see if I can find a set of unmolested slides/diaphragms.

With the back needles effectively dropped one notch it was time to run 'er up on the dyno again. This time the Air/fuel mixture was noticeably less rich than before, but still too rich for John's liking. This was with the needle washers removed on only 2 of the 4 carbs, so there were still improvements to be found by correcting the other two needle positions. I'm also intending to renew all the float valves and seats, as doing that on the LC made a big improvement. Lastly I may also try and find some NOS emulsion tubes on the basis that the current ones must have some wear after 50k miles and that would also contribute to richening of the mixture. Unfortunately they've been discontinued by Honda and are rare as hen's teeth.

So it was a really instructive day, and has definitely shown me a way forward. And to leave on a positive note, the 36 year old bike with 50k + miles on the clock, rich fuelling and a leaky exhaust registered a very healthy 94 bhp! I was expecting mid-80s, so that was a nice surprise.

Time to dig out the big box marked 'VFR stuff' and get ordering carby parts...