My f2 wheel conversion done! Finally!

Ugh! Finally got it done lots of waiting on stuff and weather but I took it out for a quick spin this afternoon. I like! I used Jamie's kit but found some of the pieces did not work together and had to manufacture some spacers my self on my lathe. I am going to show these to Jamie so he can fix the kit.

So I measured the seat height and it is smack on at 31.5 with out modifying the shock. Also I was thinking about lowering the front 5mm instead of raising the rear. This should have the same effect, until I get my twin clicker back. I noticed that with these wheels the bike handles a lot like my old Ducati st4s in the way it falls into turns smoother, less twitchy. Also seems more stable, at speed. I put brand new pilot 3's on, 120/70 up front and 160/70 in the rear, they are sweet and probably add a lot to the handling. I Upgraded the shock to a Olins racing unit as well. Way better.

Next project is installing the Gold Valve Emulators up front, and leaning out the jetting for the 4 into 2 into 1 Kerker. It's running a bit fat right now.

 

Nice, the six spoke wheels really set the bike off.

 

you know nothing about the 86s....poser

 

Nice work! Did you end up using the 750 motor?

 

I like the way the bike looks. Good job!!

 

Looking good!

 

Sharp looking machine, i have the same "saddlebags"

 

you wouldnt happen to remember enough about the whole process to do a write-up or a step by step how-to, would ya? I have a set of F2 wheels in the garage and I'd love to get the ball rolling on getting them mounted onto my bike.

 

No, not yet, I'm going to tear it down, and go through it first. I think its tight, but since I have the time, I'll play around with it, try to eek some more HP from it; do a port and polish. That 4 into 1 made a big difference in bottom end and mid range. I actually can pass without down shifting three times now!

Thanks,
Jason

 

I will, I think its important for all of us, as I had to do some re-engineering on some stuff.

 

They fit great! I relocated the rear blinkers to the fender to get more clearence, and it worked perfect.

 

thanks, I've now put some miles on it, and the decelerating tank slappers are history. Very stable now 125mph+, feels like my 1998 Gen five. Just not as fast.

 

I made little custom brackets that extend off of where the originals mounted, out of the way of the bags and more visible too!

 

What do you contribute that to specifically?

Suspension geometry change? Is the rear ride height lower due to the smaller rear tire, i.e. you now have less rake and more trail? That usually adds stability, but may require more effort to turn.

Is it maybe the radial tire construction just being superior over the bias ply?

I'm going to rule out worn tires as I'm sure you've had a new bias ply tire up front before and it didn't cure the decelerating tank slappers.

You don't have the emulators in yet, correct?

Stock front springs? If not, did you install them the same time as the wheels or before that?

Can you think of any other changes that could be responsible?

 

I believe it has the most to do with the tire. I lowered the front down 5mm, to put the rake and trail back to stock (or close), however this did lower the cG down a little, which is always a good thing.

I did have new tires on it before, BT45 I think, bike was completely stock, with 12000 miles on it, mint condition, never dropped. Taking my hands off the bars while coasting to a stop I would get the slappers.
Bearings were tight, tire pressure good, etc.. I just think it was the goofy profile of the front tire. In the old days, we had no choices(in tires), and accepted the slappers as normal.

I remember in about 1988 watching a guy at SIR (seattle international raceway) bite the dust on the last turn accelerating onto the dragstrip get into some catastrophic slappers on an old FJ600. Poor guy could do nothing but try to hang on. He hit the barrier at about 80, he didn't make it.

That was on Metzlers compound K race tires, best you could get back then. Radial tires are the biggest advancement in bike technology in the last 25 years IHMO.

I'm still working on the instructions for the conversion.

Jason

 

Thanks for the info, that helped me a lot.

I was trying to decide between a front end swap, just a rim swap or putting a new bias tire on the stock wheel. I'm definitely going to swap something so I can run a modern radial tire.

I've got a sweet Kawasaki ZX7 front end, but I'm having trouble getting the steering bearings sorted. If anyone is interested...
http://vfrworld.com/forums/1st-2nd-...d-swap-vfr700-need-some-input.html#post396359

 

All 3 of the bikes I owened had the bar shake at decel.

All 3 times it was a badly worn front tire, and new rubber cured it

 

My wheel conversion

1992 Cbr600 wheels and 94 forks with 1988-89 vfr750 triple.. No need to change spindle as its a straight swap.
No spacer required for front as cbr600 spacers are an exact fit.
Rear spacers are a vfr chuck set.

Roger

 

nice, sounds like a VFR front end swap is pretty easy compared to the F2 front end.

 

I've spent some time applying all of that math I learned years ago and here is what I've come up with for ride height adjustments and the F2 wheel swap.

Here are my findings:
Decreasing the wheelbase, increases the affect the changes make to rake a trail.
At the stock wheelbase of 1477mm the decrease in ~15mm ride height change is .000014 increase in degrees change to the rake.
Raising the rear 24mm << 10mm increase in shock length, decreases the rake by .000028 degrees, for a total decrease of .000014 to 26.9999~
With stock wheelbase and the 17" wheels, decreasing the front forks by 5mm decreases the rake from 27.000028 to 26.99969 or by .00059 degrees, as you can see the front is more effective than rear.
Decreasing the front fork also decreases the wheelbase by about 2mm.
You could decrease the wheelbase by 5mm in the rear and increase the effect the front has even more.
Total ride height is down about .5 inch at the seat, which also reduces the center of gravity (CG), which in theory should reduce transition time and effort from lean to lean.
This method has another benefit, the stock swing arm is designed for a 10.5" shock length, the rising rate ratio is for that length shock, increasing the length increases swing arm travel and causes strain on the counter shaft bearings.
This is caused by the chain being too taught at max tension during normal movement around the arc. To solve you must loosen the chain more than recommended and risk a thrown chain.
As you can see I've put some math behind this, and have hopefully shown a different point of view. I have to admit, the bike looks sexy with the arse end up high though.