450 DESMO - HAIRPIN SPRING REMOVAL

[Santiago]

Hi from New Zealand. I'm currently putting a 450 Desmo race bike together and also returning a 450RT that has been cafe'd back to MotoX for VMX racing. I've had a valve spring 250 Mk3 in the past as a road racer. I'd like to remove the hairpin spring arrangement from the road race engine, i've seen these springs advertised and would like some guidance as to the modifications required to install them please. My goal now I'm mid 50's is to circulate not win, so am not going all out modifying the bike for racing (having toyed with the idea of a Misano head). I have other bikes to race as well including a highly modified CB350 and a CB450 also modified.

[graeme]

Hello Santago,

I had some springs made, same as bevel twin / pantah but half the strength.
Have used them in many Desmo singles, pantah and belt 2 valve engines.

You have to turn the closing rocker end down to about 13mm and check that the spring doesn’t bind when compressed, if it does it will break the tang off.
If you want more info pm me

Graeme

[Jordan]

Some have run desmos with no springs at all.
I think a spring on the exhaust side must help keep the valve face cool.

[Santiago]

Hi Graeme, cheers, will send you a PM, these springs from MotoGuzzino look like ordinary Ducati 2V desmo springs, not sure about the wire size or tension, maybe they have been made especially, anyway I've ordered a set, once they arrive I'll see if I can work it out, turning down the rocker end makes sense now I think about it, will have a look at my 907ie set up and see what needs to be done to make them fit. Cheers.

Hello Santago,

I had some springs made, same as bevel twin / pantah but half the strength.
Have used them in many Desmo singles, pantah and belt 2 valve engines.

You have to turn the closing rocker end down to about 13mm and check that the spring doesn’t bind when compressed, if it does it will break the tang off.
If you want more info pm me

Graeme

[graeme]

Do you have access to a lathe ?
The closing rockers are hard to hold.
Best way I’ve found is to use a 10mm dyna bolt, the “cone” end of the bolt fits neatly enough into the rocker pin hole at the end you want to machine
A washer and the nut will lock the rocker onto the bolt.
The threaded end into the chuck.
Take light cuts on the rocker, they are not hard.
Cut a small radius at the end of the cut to prevent a sharp edge that could crack the turned piece.
Most important,,,, make sure the spring can be compressed more than it would in operation so it doesn’t bind.
As you compress the spring the hole in the spring will reduce and can bind and transfer the movement to one of the spring ends. The ends aren’t meant to bend, only the coil.
When you get your springs measure the hole in the coil.
Let’s say it is 13.5mm, find some 13mm rod and put it in the coil hole, compress the spring and see if the coil hole is still free to compress more.
This will give you an idea of what the finished OD of the rocker needs to be.

Hope this makes sense ?

I have spare light springs if you need.

Graeme

[graeme]

Also, don’t over tighten the dyna bolt as the cone end may crack the rocker
Another reason to take small cuts in the lathe.

[Santiago]

Hi Graeme, I'll PM you, would like some springs. I have a lathe and can do the machining as you have said.

[Santiago]

Hi Graeme, I PM'd you with my email address let me know if you received it, the message shows in my outbox but not the sent folder, not sure if you have it or not.