Topic: 'Kerby' Honda 500 Racer.

[Doc.]

Posted a few details of this in the new members section, and elsewhere, someone suggested giving it it's own topic . . .


Kerby Honda 500 (Dave Kerby Frame Kit).
Belongs to a (new) friend of mine, he's kindly letting me ride it at the Belgian Classic TT at Gedinne,  23rd/24th Aug.


I've been doing a few bits and pieces to it.
When I first saw it (Classic Meeting at Brands last month), I noticed a few faults, and fixed them for him.
Screws missing from front hub (3 of 5!), things not wire-locked, loose locknuts, etc.
So I decided I'd like to check it all over before I rode it in earnest.
There were lots of 'niggly' little things that bugged me as well, poorly thought out brackets, spacers, mountings etc.

Stripped it down to the Frame and Engine a couple of weeks ago, and started making a few little mods and 'improvements'.
Made a new Caliper mount, the original needed two spacers, which were easy to drop/lose when removing.
I think you'll agree, the Mudguard needs dropping a little too . . .


Made new Foot-peg mounts, lifting the Pegs a little, and made an adjustable 'reverse' gear lever to replace the original sloppy lever and linkage arrangement, I prefer the 1-up ~ 4-down pattern anyway . . .


Re-bushed the Shock Mounts, the originals were quite worn, and the Bolts were too small, there was a lot of play in it.
I made Delrin Bushes for it, nice and 'snug' now.
Added a grease nipple to the pivot tube . . .


There's no lock-nut under the top Yoke on the Headstock, just the one thin nut on top . . . which was only on finger-tight!
I machined up a thin spacer to sit underneath the nut, so I could wire-lock it more easily.


Lectron Carb, that'll be a steep learning curve.
Had to make up a fuel screen for it (small cylindrical foam piece that sits round the lower end of the metering tube), the original crumbled to dust when I removed the float bowl  . . .

[Doc.]

The original rear Brake layout had the torque-arm attached to the frame below the swing-arm pivot, yet there's no bearing or bushing in the back-plate.
With the wheel spindle torqued up, the torque-arm was forcing the back-plate to move (due to suspension movement), which was causing wear on the spindle spacer and back-plate.
Explains why the original torque-arm was such a heavy-duty item.

I've machined up a mounting bracket, which clamps round the R/H end of the swing-arm pivot tube, and made a lighter weight torque arm to suit . . .

[bwaller]

Good work Doc. I don't blame you for wanting to "go through" the bike before your ride. I hope you enjoy yourself.

[scottly]

Thanks for starting this thread, Doc! I recall Suzuki RM's (MX bikes) in the mid '70s that had a floating brake plate; the claim was that the torque reaction helped keep the rear wheel planted. Can you fit a bushing or bearing into the hub of the brake plate large enough to accommodate an axle spacer? If that is not an option, perhaps there is a more solid way to anchor the torque arm that clamping around the pivot tube? I can envision that nicely machined bracket rotating under heavy loads?
Is that an XR, XL, or FT motor?   

[Doc.]

Cheers Bwaller, I'll try 

I might bush the Brake back-plate at some point Scottly, but for now I just want to get it ready for a Track-Day (shakedown) next Monday, and for Belgium.
The clamp is very tight on the Swing-Arm pivot tube, I made the bore slightly undersize, plus it's more or less in line when fitted, if it did rotate, it would only be by 10° or so.
Also, with the rear Spindle torqued up, the back-plate is held fairly tight anyway.

Not sure what the motor is from originally, I'll ask.
Most likely XR, as it doesn't have the electric starter mechanism.

[Doc.]

Engine number PD01E-******* puts it as an XL500S, the bottom end at least.

Got the Clutch casing off tonight to get ready for the new Plates and Springs, hopefully they'll come in time to be fitted for the Track-Day on Monday (18th).
If not, I'll machine up some spring spacers, and/or find some stronger springs for it.

[scottly]

The XR head has a rectangular manifold connecting the carb to the head, with 4 attaching bolts, while the FT, and I believe the XL has a round manifold, with 2 attaching bolts. What were the readings when on the dyno? Can you post a graph? Here is a graph from my mostly stock FT:

[Doc.]

It didn't get a run on the Dyno, the clutch was slipping while they were trying to start it!

The owner thinks they tried to start it on the roller, without taking it back against compression first, he thinks it probably just over-powered the Clutch.

Quick question about Scitsu Tachos . . .
Both Bikes (this and the 750) have them fitted, but they're not working.
I know they've probably be sat unused for a while, and I also know they've been run (the Engines) with the 'dummy' plugs in place, which I know is not meant to be done, but can't find any info on what happens if it is done.
Are they likely to be 'kaput'?

Anyone know the capacity (mAh) rating of the internal Ni-Cad, and the polarity of the charging jack plug?

[Bill/BentON Racing]

Nice work! Always pays to check it yourself! K.

[Doc.]

Booked in for a Track-day on the 18th now, Bedford Autodrome SW circuit, same as last weekend.
Hopefully the new Clutch parts will arrive in time, if not, I'll try packing the springs a little, or find stronger springs . . .

[Stev-o]

Subscribed, keep us posted.  Safe to say the Kerby was manufactured in the UK?

[Retro Rocket]

I'm in...

[Doc.]

Subscribed, keep us posted.  Safe to say the Kerby was manufactured in the UK?

Yes.
Dave Kerby is a Brit.
Not a lot of info around, but I'm finding little bits here-and-there.
Seems he raced himself, maybe still does?
Sometimes spelled 'Kirby' on various sites, so try that too if you're searching.

One thing I found out about him . . .

Don't have any memories of Joey as such, but I do know an old road-racer, engine tuner and frame builder called Dave Kerby who was with him at the Pirita-Kose Circuit the day Joey crashed. He was his Pit Board guy and travelling buddy that weekend, Dave was sheltering under Joey's pitboard at the time!

[Doc.]

Working on it today threw up another little gem . . .
I decided the bolt holding the tacho-drive blanking-plug in the head should be wire-locked.
Put in a drilled bolt, and when I pulled the wire tight, the bolt and plug just pulled out!
The section the bolt threads into should be cast as part of the head-cover, but at some point, someone’s glued in a threaded boss.
I can only imagine they stripped the thread, so they then machined off the threaded part and glued the replacement boss in . . .



I'll be making up a small angle bracket to hold it in place, clamped under the two right-hand cam cover bolts.

Clutch friction plates arrived, so I've fitted them, along with a washer on top of each spring, fingers crossed it's enough.
Up-rated springs may still arrive before we leave for Belgium . . .

[simon#42]

yes dave is still about , and still racing [ or was until very recently ] 
ask about in the paddock at  jedinne , i know he was doing the belgium rounds .

kirby and kerby are two different frame makers both english .

oh and that lectron carb wont be a steep learning curve . they are the easiest carbs on earth , no jets you just alter the hight of the needle or the needle itself .

seems odd to spend all that time making a nice frame and then putting a ditch pump engine in it .

[Doc.]

Ooooh! That'll stir up some comments   
The Frame has been used for many different Engines as I understand, 400/4s, two-strokes, triples, etc.

Is Mr Kirby a Dave as well, only I've only ever seen it that way, which made me suspect a spelling mistake/typo?
There's only one other Kerby on the list at Gedinne, (they've spelled it Kirby, as they have with this one), in one of the Sidecar classes, Yamaha Engine.

I've read up a bit about the Lectrons, and they seem to illicit either unswerving devotion . . . or fear and loathing!
I suspect the latter is more often than not due to lack of research/understanding of them, and how to set them up.

To me, it's a no-brainer, and the basic principle is sound.
I'll just have to put all the 'usual' Carb set-up and troubleshooting info/knowledge to the back of my mind . . . 

[simon#42]

sorry my memory is rubbish , there are two kirby's both spelled the same . tom kirby [ kirby matchless etc ] from the 60's  and dave kirby who made mostly honda frames in the 70's
that frame of yours was specifically made for the ditch pump engine . the frames for the four cylinder bikes where much different .

with regard to lectrons you do not have to forget all your usual knowledge at all . the needle will have two numbers on it e.g. 5.1
the number 5 refers to the top end  mixture . number 1 refers to the low down mixture  [ like main and pilot jets ]
if the bike is weak low down you change the needle for a 5.2 if the bike is weak at the top end you use a 6.1 needle
if the mixture is weak all over you turn the needle in[ making it shorter ] , if its rich all over you turn the needle out [ making it longer ]
you probably wont have to change the needle as four strokes are not that sensitive to change and i would hope that someone would have
worked out the correct needle in the last 30 or so years . so basically you will just be turning the needle in and out

if you do need a different needle let me know i have boxes of them .

[Doc.]

Thanks Simon.
It's been run on a Dyno before, and was fine, so I'm not expecting any major issues with it really.


This is my quick solution to the Tacho plug issue . . .

Front bolt wouldn't come all the way out, it fouls on the Frame tube, so I had to slot the forward hole.
Also meant I couldn't put a spacer washer under the bracket, hence it's sitting a bit wonky, but it'll do for now.
Not sure what I'll do as a permanent fix yet, I'm wondering if there's enough 'meat' in the cover to drill and tap it . . .


Anyhow, it's loaded in the Van with the 810, ready for the Track-Day tomorrow 

[Doc.]

So, another perfect day for a Track-day, but another cut short by mechanical gremlins.

Took the 810 out first, just to check the oil leak was cured really, and to put a few more miles on it to make sure nothing else cropped up . . . well it did!
http://forums.sohc4.net/index.php?topic=140214.0

As for the Kerby, well what a great little Bike 
So light compared to the 810, obviously, and so 'flickable', for the first couple of laps I was braking and turning in much too soon, had to re-calibrate my brain a bit!

Once I'd gotten used to it, it felt really good.
No working tacho on it (like the 810), so I was being a bit cautious on the massively long straight, but on all the corners it could hold it's own 

Went the whole first session out without a hitch, other than the gear lever being a bit high.

Came in and adjusted the lever, then went out in the next available session.
Got to the first corner, and it just coughed and clanked and wouldn't run 

As I coasted off onto the grass to sit and watch the group go round, I looked down at the Engine, only to see fuel pouring out onto the Crankcase!
Fuel off then, and wait for the trailer.
Looking closer, the float bowl was full (right up, it's a clear plastic one), so suspected a stuck float valve.

Back in the pits, we whipped off the tank, and Carb.
When we removed the bowl, it looked like a small strand of the fuel screen (a small foam 'cylinder' that sits round the base of the fuel tube) was sticking out slightly, catching the float tang.
Great, we thought that was it, so we re-fitted the bowl without the screen . . . only for it to do the same as soon as the fuel was on again!

We could also see that fuel was coming out from the front of the bowl at the join with the body, it looks like the edge has distorted slightly, probably due to there being no heat-shield, and it's pretty close to the head there.



I've stripped it down and blown through the float jet, it's shutting off OK.
I'll be adding a fuel filter in the line, as it doesn't have one at the moment, silly oversight on my part really 
I've made up a heat-shield, and I'll have to seal the bowl up with a little sealant for now, it's that or try reshaping it while heating it (very) carefully, but that could go very pear-shaped . . .

[Retro Rocket]

I would make up a long washer to go across between the bolt holes on the fuel bowl. that way the whole side of the bowl has support...

[seanbarney41]

Lectron is still in business and may have a new float bowl/gaskets.  I don't think they use the slear plastic bowls anymore.
http://www.lectronfuelsystems.com/carburetor/

[Doc.]

I would make up a long washer to go across between the bolt holes on the fuel bowl. that way the whole side of the bowl has support...

/that was my first thought RR, but with the choke tube section in the way, plus the fact that the plastic is very rigid, really rules that out.

I've fixed it by bonding the gasket to the bowl with a two-part rubber compound, and pressing the gasket down onto a surface plate.
The compound has filled the slight gap, and it's leak-free now.
Only a temporary solution for the meeting this weekend, we'll be getting a new bowl for it.

I also made up a thin Stainless Steel heat-shield for it, that's secured by being sandwiched between the carb and the mounting rubber, should keep most of the heat off the bowl.

[scottly]

seems odd to spend all that time making a nice frame and then putting a ditch pump engine in it .

Simon, you must be mistaking the Honda thumper for a BSA 441 Victor??
Doc, take a look at Joe's posts on my old FT thread; he has probably forgotten more about pumping these motors up than I've ever known.
http://forums.sohc4.net/index.php?topic=124417.0#lastPost

[Doc.]

Well, what an absolutely brilliant Weekend! 
Full report when I have a bit of time, but right now I'm still buzzing, even after a 350-mile drive and a Channel Tunnel ride.

Kerby is a stonking little Bike, absolutely blinding!

[Retro Rocket]

^^^ who's a happy chappy^^^