Building a race bike

Concept is a lot clearer now that I've read your explanation and gone back over your pics, Julian. Am I correct in assuming shaving so much off the head has in effect raised the seat/s? Your flatter top pistons will have deep pockets for valves?

Marty, when I say 95% on the roof, I really mean I won't be removing material from the floor, other than to shape. Julians inserts actually address an issue I see with my OSd small valve head and re-angled inlet port: the original floor 'ramp' could have an upward curve leading to the radius entry to the cc. I could profile it with JB Weld or see how it goes before I go there. It might not be ideal for a race motor but might give me what I'm after for a broad powerband road motor. FCRs are going to help a lot regardless.
 
Really nice, Julian.

You're addressing the shortcomings many of us have found in these heads, especially the tight radius at the port bottom/valve seat.

Are you leaving the skulls in situ and building them up with weld to attain your envisaged chamber shape, or removing them altogether?

How will carb/frame rail clearance work out?  Stock frame already has issues with bell mouth clearance on stock carbs, seeing you're lengthening the intake tubes at a steeper angle will aggravate things further.  Completely new frame?

Reckon a complete revision with altered valve angles, rocker and cam geometry would be the next step... :D  Not so easy considering the given positions of cam and rocker axis.

piet

 
"reminds me of something...not that I want to compare your skills really with - let's say - autodidactive experiance of a well known Laverda dealer from southern Germany , who tried similar things in the 90's, ending up putting all heads on a flow-bench just to find out that the head with the best result was - actually the standard factory one... it just reminds me of the same route (changing the inlet angle to a more down-draft one), for sure the excecution was different."

I basically wouldn't care at all, BECAUSE it just looks the absolute bollocks, even if it gave 40 BHP, no one would know as I rode away from the pub having spent the evening talking about it!
CLEM
 
 
How will carb/frame rail clearance work out?  Stock frame already has issues with bell mouth clearance on stock carbs, seeing you're lengthening the intake tubes at a steeper angle will aggravate things further.  Completely new frame?
Click to expand...

Hi Piet - i was going to ask that question - With 10? of downdraught i can get my 36mm D/o's in and clear everything with a slight angling of the carbs. Wont be able to do that with the 40millers. have got a couple of SU float chambers and will use one or both of them and  then can angle the carbs a lot more.  - regards - Phil
 

Attachments

  • carbs-frame,.jpg
    carbs-frame,.jpg
    131.1 KB · Views: 409
  • D-O+SU sm.jpg
    D-O+SU sm.jpg
    134.6 KB · Views: 407
chrisk said:
::) How quickly we forget, Julian has the spine frame for this race bike. The frame was built before he started playing with the engine.
Click to expand...

That's good - thinking of putting my special  motor in my Sidlow frame - save a lot of messing about - Regards - Phil
 

Attachments

  • Sid - carbs.jpg
    Sid - carbs.jpg
    166.1 KB · Views: 391
Morning all,

Carbs are 40 PHM Dellorto (may have to remove the accelerator pumps),  certainly not allowed CRs but I don't like the look of them anyway, far to modern, I want my bike to look really period when finished. NO modern stuff at all visibly.
I will make special shaped bell mouths for the carbs, been experimenting with shapes and have had some very large increases in flow from the right shape trumpets in the past so am confident.
The frame should clear ok but may have to slightly tweak it for full clearance.  The inlet manifold in the pics is longer than I will be running by about 25mm, this is just a prelim mock up.  The plastic combustion chamber will first be laser scanned, then the skulls will be completely machined out and then the combustion chambers welded up and then CNC'd to shape.  Valve angles are being changed, (we did the rough valve angle cad drawings yesterday actually) and the valves will be swung outward and make a flatter combustion chamber than you see in the pics.  Pistons will only need a max of 3mm dome to give me 12.5:1 CR.  With the shallower chamber to come I envisage even keeping the flat top pistons.  Valve cutouts will need to be at least 8mm deep as I have 6.5mm of lift at TDC and this is with C6 cams,  these will be changed as I am not happy with the lift curve at the moment.  Still masses of work left to do here.  I calculated that I would like 12.5mm Lift on the inlet and 11mm on the exhaust.  Rockers will be new ally ones with a little change in ratio and flat pads. 
Spring platforms will be welded up and re machined, I have some very trick light weight valve springs and retainers to use so actually don't need as much room as std.  Solves a few problems. The valve angle will change so all spring seats need to be re machined anyway.
As I said, lots of work to come.

Will be a little dead for a few weeks as we have just signed a contract for a new building at work.  This will be a new sales showroom and a room to house my bikes so now need to start painting and decorating.  Lots of work needed to do in about 2 weeks as the new epoxy floor will then be laid.  need to then design and make a car photo turntable.
Not much "bike time"  for a while I am afraid.

Thanks all for the interest, I will try to post some more pics in the next days before the work starts to get in the way.
Anyone welcome to visit if you are in the area.

Happy New Year to everyone,
Jules
 
Just got me a set of these little beauties coming in the post!!!

http://caferacersuspension.com/ceriani-type-gp-35mm-front-forks.html

Fully adjustable 38mm versions  GP38R

Looking forward to opening the box  :D 8)

Jules
 
absolutely! and if you compare it to getting a fork redone to roughly similar adjustability, they are fair priced, too.

The caliper mounts look a bit low on the pic - what kind of discs (diameter) will you be using?
 
Laverdalothar said:
absolutely! and if you compare it to getting a fork redone to roughly similar adjustability, they are fair priced, too.

The caliper mounts look a bit low on the pic - what kind of discs (diameter) will you be using?
Click to expand...

Oh, how quickly we forget: Julian is using that big mutha 4LS front.
index.php
 
I had a look through that fork site and it looked like the only 38mm forks were for disc brakes. Do they come with bushes, that would be interesting? Chris is that pic Julians bike, looks like tubeless type spoked rims?
 
julian said:
Just got me a set of these little beauties coming in the post!!!

http://caferacersuspension.com/ceriani-type-gp-35mm-front-forks.html

Fully adjustable 38mm versions  GP38R

Looking forward to opening the box  :D 8)

Jules
Click to expand...

I?d also be very interested in this fork replica. I'm just not sure if the handlebars on a 3c could still be mounted as intended:
49828465973_7e4bb282d0_c.jpg

 
they have triple clams with the mounting points for the "Brevetato" handlebar (or any other handlebar that is mounted on top of the yokes).

Paul: thanks for reminding me, yes, I tend to forget details sometimes...    :-[
 
Laverdalothar said:
they have triple clams with the mounting points for the "Brevetato" handlebar (or any other handlebar that is mounted on top of the yokes).

Paul: thanks for reminding me, yes, I tend to forget details sometimes...    :-[
Click to expand...

Lothar, I mean the part of the fork that protrudes above the upper fork yokes (see picture)!
 
Jo said:
Lothar, I mean the part of the fork that protrudes above the upper fork yokes (see picture)!
Click to expand...

Hi Jo, looking at the pix of the 38mm fork, you will need risers for the Brevattato bars - and thats absolutely forbidden on a 1000 3C!!!
Ciao, Gert
 
Jo said:
Lothar, I mean the part of the fork that protrudes above the upper fork yokes (see picture)!
Click to expand...

I assume these are the pre-load-adusters. they look like fully put to the soft side, they will screw in a fair bit. All you might need is a distance piece between the yoke and the clamps for the handle bar. Maye 5mm will be already enough, depends on how much the pre-load goes into the top screw of the fork.

something this way maybe: https://www.louis-moto.co.uk/artikel/lsl-riseup-clamps-distance-bucks/10021303
 
You must log in or register to reply here.
Back
Top