NC750 Track day

[spaaz 60]

Dear NC's, 

I am a Newbie with an NC750 DCT, I can't ride a manual bike because of fused ankle and lack of co-ordination from brain injury.

This week I finally had a chance to ride a bike again, after a 17 year gap, I had an accident at the 2004 TT which left me with life changing injuries.

I have never been a fan of riding bikes on the road, in the 90's I had a rolling road business in Croydon, with a customer base of 300-500, we use to lose, dead, 2-4 a year due to accidents, so I knew riding at the TT was nearly as unsafe as road riding in South London.

I bought a NC750 earlier this year. As soon as I rode it around the car park at my unit. I knew I had to remove a lot of weight.

I removed all road gear, ABS.

Then found out that in removing the ABS stopped the DCT from functioning.

On the dyno we soon found that the ABS stopped the DCT as well, with the front wheel not turning.

But an ABS tricking box soon allowed me to see, we had a massive 55hp ish.

Plenty enough for a reserved track day bike.

The heavy rear subframe was removed and replaced with an aluminum tubular bespoke made by Plymstock race fabricator Pro4m. To allow the use of CBR600RR 03-04 Tank cover and race seat, at the correct height, to get the rider weight further forward.

The fuel tank was shortened and moved to over the engine, air box junked. Electrics modded to move the battery below the seat.

I initially was going to use the std NC forks but soon realised that they were not suitable. The std NC has the longest headstock I have ever seen, so using another front end would not be possible.

In the 90's I used to track day a Honda VTR1000 firestorm, nicknamed the "FireYorn" by my friends and customers. It was totally std apart from revalved fork by Ron Williams(Maxton), 320 discs with Brembo goldline race calipers and Super Corsa tyres. 

I could ride the wheels off it. 105hp but torquey and predictable. Unbeatable at most circuits with short straights.

So the VTR forks are 41mm same as NC and very similar in length, std have small pre load adjustment and rebound damping adjustment.

But I soon realised that putting the VTR forks in the NC, the forks would need more mods, I had to pre load the std springs by an extra 25mm and heavier fork oil.

The NC has a head angle of 27 degrees, which is not suited to the track, but perfect for non nervous road riding.

Though changing the head angle is not insurmountable, it takes time, so by dropping forks and raising back end, you can emulate the same, as changing the head angle, but with associated problems though.

The problem is that by dropping the forks through the yokes, the front wheel starts to come in contact, radiator easily moved. Then rocker cover, not so easy to mod.

So I will have to investigate ways I can get the head angle closer to the recognised 23-24 degrees used on most sports bikes.

In dropping the forks through and raising the back, lessens the trail, documented at 110mm for the NC, which is huge against the trail of 95-98mm on sports bike or 82mm on the super flickable TZ250, I loved riding/crashing in the 90's, when I was young, dumb and thin.

In raising the back end up with different shock length or shorter dogbone link, can cause other problems, chain clearance on swinging arm and power on and power off problems loading up the front end, when large changes in ride height changes are made.

I will break this report in to two as to make it not so boring.

Nick turner

 

 

[jeremyr62 2,559]

Keep it coming. 

[SteveM 706]

You got any pics of your mods? 

[Trev 18,644]

NIce one Nick, look forward to reading more 👍

[MatBin 5,085]

Nick, not boring at all, please post pt 2 as soon as you are ready, I am sure all of us that run stock bikes are fascinated at the thought of a track tool based on an NC DCT, definitely an unusual thing.

On that note have you been in contact with any magazines to reach a wider audience?

[spaaz 60]

Dear NC’ers,

Please excuse the lack of photos, I have no idea how to post pictures. With only half a brain, from my crash, I am a drag and drop WhatsApp merchant. If someone could explain how I can post photos from my phone.

But it will have to be simple.

Nick

[SteveM 706]

6 minutes ago, spaaz said:

Dear NC’ers,

Please excuse the lack of photos, I have no idea how to post pictures. With only half a brain, from my crash, I am a drag and drop WhatsApp merchant. If someone could explain how I can post photos from my phone.

But it will have to be simple.

Nick

Your more than welcome to send me the pics and I can post for you. 

[spaaz 60]

How do I send them to you ? WhatsApp ?

 

[SteveM 706]

12 minutes ago, spaaz said:

How do I send them to you ? WhatsApp ?

 

Either that or email. Pm for either 

[SteveM 706]

 

[spaaz 60]

Track day NC750

Continued account.

With the modified VTR forks installed, I now concentrated on the front brake.

Because of the losing 60kg, I assessed that a single 320mm disc should be enough, with 50hp, short circuit speeds of 100mph approx.

I could not find a VTR front wheel in stock, so picked a Ducati 916 front wheel and 320mm fully floating Galfer wavy disc. Mated to a Brembo 4 pot caliper via adapter plate to suit Honda forks. It was not as easy as I thought, I had to make spindle spacers and sleeves, due to the forks being so widely spaced. Unfortunately unable to find a front mudguard to fit the wide forks.

 

Managed to pick up a bigger bore header pipe, which had to be “adapted” to suit a 2” Scorpion titanium silencer, fitted high up and away from the mechanical noise from the engine, noise tests should be ok. It will be sufficient for the first ride. Unfortunately Akrapovic don’t do a full race system yet ?

 

I fitted an AP GP radial pull master cylinder, with adjustable span and ratio. Excellent Brake.

Footrests were a bit of a guess for position, used std CBR600rr footrests, picked up the top NC footrest mount and fitted M8 threaded insert in frame for lower mount.

CBR600RR rear calliper, master cylinder and used the NC brake pate.

I was running out of time before the track day 17-6-21 at Llandow.

So rear std disc, and back end complete, std shock. Now with big chunk of overall weight removed rear unit seemed not so squidgy and lacking damping.

Thursday arrived. Llandow is a simple circuit about 6 corners. Flat and smooth. Ex airfield. 2 ½ hours from me in Devon.

Perfect for the Mentally and physically challenged ?

I should explain, I am 60 next week, in the last 17 years I have had over 53 general anaesthetics for my injuries sustained in my 2004 TT accident. So fat, 30kg heavier, unfit, old man.

The first few laps were very slow, I have no short term memory, ever lap was a new circuit for me, but I soon picked it up. Never been out in a novice group before, shame they didn’t have a less than novice group !!

I am very lucky I have good friends, who have been with me, through thick and thin.

At Llandow 3 friends came from London, Cheltenham and Exeter for which I am very grateful, for their physical and emotional support.

The day went in a Blur, we tried a few changes, sorted a few niggles.

But on the whole the bike performed as well as the rider.

Over weight and underprepared.

 

Debrief.

 

Performance, is enough. Torque a plenty. Enough to get the rear wheel squirming and sliding.

Handling. Bike has a weight distribution of 80 front and 97 rear. The trail is 110mm. The head angle is 27 degrees.

Proposed changes. Lose weight from back end to push more weight distribution to the front.

Needs to be 50/50 if not more 55/45 front bias weight, makes a more predictable front end. As it was there was no heat in the front tyre, 15mm gap to edge of tyre unused. Gave a very vague feeling of understeering, no confidence in slow corners.

When riding, found my self trying to sit on the tank, a sure sign there is not enough weight to the front.

The head angle is 27 degrees, normally I would re-jig the headstock to 24, not so simple with the NC, as we have no room to tighten head angle before the front wheel hits the rocker cover.

Also another problem is the NC is too long, 1525/1535mm to 1370-1390mm for a modern 600 or 1340 for the super twitchy TZ250.

I know I need to make modifications to the frame. If I decide to steepen the headstock, I will have to sever the headstock completely and remount it further forward and steeper( not as difficult as it seems, I have a friend who is not scared of this sort of mod). Thus not increase the wheelbase and so that the front tyre will hit the rocker cover.

But before doing this large undertaking, where a jig will have to be made.

I shall investigate how much I can drop the forks through, maybe forks with less travel. Fork travel NC std 183mm, VTR  120mm, CBR/R6 109mm, TZ250 102mm.

I need to research how much I can drop the vtr1000 forks through, without coming in contact with rocker ?

My other fork options are more offset on yokes?

That would reduce the too large trail at the same time, but from my experience of riding Yamaha Classic race bikes where we changed the yokes from 65mm to 30mm offset transformed the bike in to a predictable racer, but it will make the wheelbase longer and possibly more unstable.

I know that yoke offset can be a big change and I am not confident that my garage chassis analysis is correct ?

It is a balancing act of head angle, trail, offset, wheel base, weight distribution.

I know that the bike works as it is, not totally right but maybe change easy things first like rear end weight savings, drop the forks as much as I can, maybe limit fork travel ? raise the back end, longer shock or shorter dog bone link or different rocker ratio ?

To Shorten Wheel base is harder, shorter swinging arm, I know that there is no room in the std arm for wheel go much further forward.

That would mean making a new swinging arm. I am not really prepared to go that far now.

 

It comes to a point where I should just take the engine package and put in to a CBR600RR chassis, which I have.

This is a massive undertaking, financially and in time.

 

Or do I modify this chassis as much as I can without doing major mods ?

Just learn to ride it within the constraints ?

 

Only more track days will tell.

 

Thanks for reading this account of my first track experience since head butting a wall in Kirkmichael Village.

 

Alive and laughing.

 

NT

[Tel 4,712]

Good on you Nick! I always respect anyone who gets on with whatever life throws at them and doesn't feel sorry for themself or whinge.

Are you in north or south Devon?

Wishing you all the best for your future biking, and life in general. 👍

[Tonyj 6,907]

I did wonder about the feasibility of transferring the lump and gubbins to something else but you are more aware then me so I’ll shut up , keep on keeping on :0)

[Defender 3,837]

Thank you for taking the time to put all that down in print for us, I found it very interesting indeed, I think I recall one other forum member having done a track day on an NC, but that wasn't modified like you've done.

I have to say that it looks a bit odd, but then 'Honda San' never envisaged the NC being used as a race bike?

The details of the changes and modifications are particularly interesting as it illustrates the differences between the NC and more sporty/race bikes.

All the best in your future track days and with the NC's development :0)

 

[wjvh 999]

Holy moly ... this must be the most tricked out NC in the world! If you want to save weight from the backend try locating an Integra Alloy swing arm, will save about 3-4kg of unsprung weight. Won’t do anything for the wheelbase though. Good luck and enjoy.

[wjvh 999]

Getting rid of the side stand might save another few hundred grams ... 😉

[Andy m 23,540]

Great thread and thanks for posting @spaaz 👍

 

Glad you got the dyno sorted. Totally agree on the brake, the single has enough power to put you over the bars and in this use will use pads faster, but is ultimately lighter. When bedding pads you are going to be in a slightly different time frame IMHO. The peak performance will typically come sooner but just the usual case of cycling heat and pressure together to clear anything on the surfaces and match pad to disc. 

 

The list of mods to me highlights how close (yet no cigar) Honda got to making the NC a great road bike. Small tanks, twin discs, tyres that don't last a decent holiday etc. annoy the **** out me because we get stuck with race fashion on the road. 

 

Good Luck and keep in touch. 

 

Andy

[MatBin 5,085]

One of the best threads, if you include pt1, on this Forum.

Thanks and best wishes for the future.

[Johnnie Mototrans 2,766]

Round of applause.

 

[t5er 74]

thank you spaaz for the great topic.

i was sorry to hear of your life changing injuries especially that they were motorcycle related.it makes me wonder what you would have created if you had not only had "half a brain".

i very much appreciate off the wall creations and look forward to any updates regarding your" frankenstein monster"