My VFR750F rc24 Track bike aka aajsjinkeracer 4.0

In this thread I'll try and post some pics and a little write-up about my latest project.
Turning a VFR with 60k miles into a track bike for next season.

A little introduction and pics of my other bikes can be found in this tread;
http://vfrworld.com/forums/showthread.php/46552-Joep-is-also-here

Plan for now is to build complying with the regulations of a German Classic Superbike racing series.
So;
CBR 600 pc35 front end and calipers
VFR 750 rc36-2 front rim
CBR 600 pc25 rearrim
Stock swingarm
CBR 600 pc25 Reworked Öhlins rear shock
Pferrer raceseat
Only top fairing
Alu oilcatchtank under the engine

I still have to make some pictures. Will post them here as soon as possible.

 

Pic 1
Test fitting the VFR rim into the CBR front end. No biggy. The calipers need a spacer and two spacers for the rim.

Pic 2
Wacked the Pferrer race seat on there to have look how it fits. Well it does.
(In this picture the gsxr front end is still in there. And you can also see I definitly need to raise the rear.

Pic 3
The way I left it at the end of the weekend.


Next step. Take it all a part. I have to change the frame because this one has a crack. A good clean. Some paint. Work on a whole lot of little things nobody will see in the end. Etc. etc. etc.

 

Great job, you need to do a little of this as well. 3mm difference in carb throat and intake port size.

 

Thanks for the tip. But what do you mean?
Port the heads and take 3mm off? I have two more engines lying around and the plan for now is to do a build up with a stock engine and then take on a second engine and do some work to it. I've learned from the past that all the little things eat-up time like crazy. So first make sure the suspension and weight is looked at before starting with engine work. And maybe it goes really well and fast and I'll start on the second engine for next season and keep this one as a spare.
I also read somewhere to take some sort of silencergear out on the gearbox?

 

Cool build :thumb:
Keep it coming
Nice seat :wink:

 

Yes, if you match the carb throats to the intake you will find that the intake's are 3mm smaller than the carbs. I opened the intakes to match the carbs and straightened the ramps to the valves. Also the intakes are very rough and uneven, smoothing these out will help out a lot. I also opened and matched the exhaust ports as well. There is a lot of rotating mass too, if you can remove some metal from the cam gears you can release some HP and the engine will spin up quicker, Honda did this with their factory bike. JM2C

 

Ah. That's what you mean. Yep. I'm planning on doing that. But with the second engine. I also did this to my VF. It's not that much work, but I just want to be sure that I have a running engine.

 

Hi. Any idea or measurements on how much to take off them gears?

 

Last weekend I stripped it down and removed the frame

I'm going to be using the frame on the left, so the engine in there has to be removend aswell. Had some stubborn nuts and bolts, so I left them to soke. Engine it self is seased, tried to turn the cranck but no luck. Oh well, that will be the parts donor then. I also spotted a difference between the two. On the left one there is a wire with a socket coming off the front cilinderbank. And the black one on the right doesn't have that, but you can see on the cast that it could go on there aswell. I'll look in to that.... someday... when I'm bored... :tongue-new:

But that gave me the opportunity to look at the intakes. And they're already matched to the carbs. There is not 1mm in them. Sure the intake can be 'polished' a bit. But that's all that needs to be done to it.

 

The engine with the wire from the front cylinder is a 1986, the 87 88 89 didnt use the cam sensor for the ignition
There are also 3 styles of ignition box, 1986 has 3 sets of plugs the 87 has two red plugs with 11 wires, the 88 89 has two plugs, a red one a white one but has 12 wires.
I dont think there is a way of swapping units between models because of the subtle differences between models. But as your doing a race bike, some of these differences may not matter.
When you remove the clutch casings you will see the different style of starter clutch. The 86 uses half the pulses from the starter an half from the cam sensor. The others take all the pulses from the starter clutch.
1986


87

Notice the different amount of teeth between the two.
Roger

 

I'm using a '87 for the build and what I've seen all the points you metion are all there. I will scrap the '86 engine for parts and continu with the other '87 engine I have. That should be plug-and-play. Thanks for clearing it up, saves me the read-up, so more build time :smile-new:

This week the triple tree has been made fit. Pulled the stem of the VFR and got it into the CBR600F4 triple tree. Spacers are also made to fit the rc36-2 rim. Just need to service the forks and work out if the springs will do or that I need to swap them or make a spacer to give them some more preload. I'm not going to do the fancy cartridges for now, lets first see how they work. It's already a big improvement, 37mm 'non-adjustable' vs 43mm full-adjustable.

 

I used the 88/89 rc24 41mm triples with1994 cbr600 f2 forks.
No special spacers required. Just bought the oem cbr600 spacer.
Changed the lowers for f3 ones so I could use 296mm discs and brembo calipers. Bought some ready made caliper mounts from Japan.

Roger

 

I'd leave the intake finish as is. Depending on some intakes the air will go laminar and get fuel drop out or clinging to the walls. Check out this write up by Mike Nixon: http://www.motorcycleproject.com/motorcycle/text/cows-porting.html go down to the "polishing" section.

I've found this when porting V8 heads. Here is another idea that actually works. http://speedtalk.com/forum/viewtopic.php?f=15&t=34837 I haven't tried this yet.

Also look up "Short turn radius". On most heads you can pick up a little there and using tulip intake valves along with back cutting the valves. Also easy to do and you will get some small decent gains most of the time. Depends on what you are starting with.

 

Nice write up and project joep, keep us posted. Careful how far you decide to go with the engine work as internals like rod and crank bearings are like unicorns these days, thus the reason I have a dismantled 86 750 in my barn with not much hope of resurrection. I do have some parts though if you go looking shipping to you just might get pricey. Including a set of Cosworth high compression pistons. and the block that was bored over for them. Good luck. Wish I had the time to tinker with shit like that again. maybe someday

 

Hi.
Can you tell me more about the pistons.

 

Work on the bike this week was slow. I wasn’t able to get the bolts off that hold the engine in the frame I want to use. Tried all the tricks in the book, so now some more drastic measures have to be taken. Hopefully by tomorrow evening I can let you guys know if they were successful

Well first I had a GSXR ’88 complete frontend in there, so fork, rim and calipers. And using a flatbar so I could drop the frok to its max . But it was a bit short and I wanted clip-ons on there because most racers had them aswell. And I wanted to use VFRrc36-2 frontrims because again they look like the ones used back in the day.
So…. Got some 43mm clip-ons. Then toke some measurements and calipers had to be readjusted to make them work on either 300mm or 320mm brakediscs which both can be fitted to a rc36-2 rim. GSXR had 310mm discs. Already had some 300mm discs lying around. 310mm discs of a Blackbird would also fit, but aren’t readily avaible secondhand.
So…. Decisiontime.
I had a frontfork which was too short. Calipers needed mounts made. Already had 43mm clip-ons. Etc. I knew about using a CBR600f2 or VFR750 rc36 frontend. But as I am always wanting to do things different (buying a Suzuki GSXR 7-11 for classic/youngtimer racing is a much easier and maybe better route) I searched the internet, looking for a frontend. Asked around for some measurements and ended up with a CBR600F4 complete with calipers. They are long enough, clip-ons fit, fully adjustable, if I want to go crazy race cartridges are available. The rim goes straight in with the standard spacers. I just got the other spacers with a lip on them so they stick behind the dustcover which helps when I need to switch between dry and rain tyres.
Off course the fork will be serviced and maybe change the springs etc. Don’t know what’s in them at the moment.
So…. That’s why hahaha

Yep already read some things about porting heads. But I’m not doing anything major. Just taking out some of the imperfections caused by the casting. But leaving the surface ‘rough’. And when the heads are off I’ll have a look at back cutting the valves. The pictures in that thread are WOW!!! Those completely dimpled heads. Nice read-up for when it gets too cold in the workplace (Simple shed with no isolation or heatsource. But at least the mrs lets me put the fueltanks inside....layful

I’m not planning on doing too much engine work. It’s expensive and the gains aren’t that big if you’re not going to enlarge the bore. Better make sure that I slim down a bit, that’s the cheapest way of tuning hahaha. Send me a pm on those cosworth pistons, thanks.

 

Succes!

It took some welding, some 5 foot pipe and some persuasion but job done!
Threads of the front two bolts are shot. No biggy, I'll use some locknuts instead.
Thread of the lower bolt running across the frame that also holds the side stand had some damage, but it cleaned up pretty well. Still has 6 turns on there. That's plentyfull.

 

Amazing, man !! You're SO nearly-fanatical about your VFR........i mean in a GOOD way of course, yeah !:eagerness:

How many miles on the bike ??

 

Thanks. I think.... hahahaha
Well it's just that I really like/love the V4's. They don't have to look the business as long as they do the business.

The bike I'm using as a starting point has 60.000+ miles on it. But it ran great. So check the valveclearance, new filters and oil, etc. Build the bike back up again and race it!

 

Not a big update as in a lot of pictures to show, but a important one.
I have been fiddling around with the geometry of the bike. Looking at more modern great handling sportbikes in means of rake and trail. Bikes like the Ducati 916, Yamaha R6, etc
With switching from 16"-18" to 17"-17" wheels and tyres some issues had to be adressed. The back was sitting way to low because of the rim conversion. Rake and trail of the original design was okay back in the day, but if you compare it to todays standard it better suits a chopper...

So what I wanted to achive.
Angle of the swingarm compared to the horizontal 12 - 14 degrees
Rake 25 or 65 degrees original VFR 27.5 or 62.5
Trail 100mm original VFR 109mm
Wheelbase I left alone for now. But original VFR 1480mm

After a few hours of fiddling, looking, drinking beer, more fiddling, etc, etc, etc I ended up with
Swingarmangle 14 degrees
Rake 23 - 67 degrees
Trail 105mm
Wheelbase 1460mm
Not all the measurements are spot on, because I didn't have the proper measuringtools and circumstances. But I'm pretty happy with it. If I still want to decrease the rake and trail I can use a 120-60 instead of 120-70 tyre and drop the front some more. Not much because then there will be a conflict between cylinderhead and fronttyre and I'm not looking forward to finding out which one will win, I think I'll be the loser in the end hahaha

So the next stage of the build is due. Get everything disassembled, cleaned, serviced, painted, etc, etc.

I'll keep you posted.