Intake Valve Spring for Mk.

[aggettd]

Does anyone know a modern or more readily-available alternative to the Mk intake valve spring? I don't mind machining a new retaining collar if necessary, but it should have a stack height, installed height and seat pressure approximately equal. I'm also putting a wanted note in the "parts wanted" section.

[aggettd]

Sorry, I forgot to mention that it's the outer spring I'm looking for. However I'd settle for a single spring to replace the inner and outer originals if they would give me the same or equivalent performance (seat pressure, stack height, etc.)

[eddie]

Hi Dave,
              Your enquiry begs the question "Why do you want to fit other valve springs?" The original springs seldom suffer from fatigue and/or collapse. All Mark series machines (except the Pluses) use the same inner valve spring, but the outers used on the Mk1 are smaller in diameter than those on later models.
   The size of the outer spring on a Mk1 is: 1¼" O.D. x 1½" free length (shut height 11/16"). The outer spring for later models is the same except that the O.D. is increased to 1-3/8". Sorry but, at the moment, I can't come up with any figures for the poundage.
                                Regards,
                                              Eddie.

[aggettd]

Eddie:

I can't believe you got back to me so quickly. Thanks so much.

The reason I need a new spring is that one of the outer intake valve springs on the two heads I bought a year or so ago was broken when I got it. I knew I was getting an incomplete collection of parts and am only now getting around to taking stock and planning to assemble the bits into a working spare motor. My preference would be to get my hands on original parts as it will reduce fabrication time and the problems associated with incompatibility. However, living in Canada, I am not able to access parts form the LDMCC Parts scheme so have to find/make/buy second-hand anything I need. We don't have autojumbles here, and any parts that do come available are for Triumph, BSA or Norton.

North America is a huge source of used bike parts and in my post was hoping someone might know of a suitable substitute for the original Douglas part. I also posted a note in the Wanted section of this forum for anyone who has an original valve spring surplus to their needs. Any ideas.

[george sutton]

Sorry, I forgot to mention that it's the outer spring I'm looking for. However I'd settle for a single spring to replace the inner and outer originals if they would give me the same or equivalent performance (seat pressure, stack height, etc.)

hi Aggeta, valve springs pressure is determined by the gauge its wound from and the finished free length, provided you have match pairs your ok .    single spring replacement is a no,no.  your double spring setup is to cancel out harmonic valve bounce at various revolutions. your engine wil lnot rev. the same if you change that set up. hoe this helps , Denis. S

[trevorp]

we talking mk1 or later as i think i have some mk1 valve springs u can have

[aggettd]

Trevor:

Greetings mate! I'm building up a spare motor out of assorted Mk 3 parts so that's what I need. I appreciate the offer.

I hope all is well with you.

[Vermont-Ian]

Dave

I see I have 2 valve sets (inner and outer springs) for my Mark III (i.e. larger than a T35, per Eddie) in my parts box.
If that's what you need, you're welcome to one of them.

Ian (Richmond, VT)

Does anyone know a modern or more readily-available alternative to the Mk intake valve spring? I don't mind machining a new retaining collar if necessary, but it should have a stack height, installed height and seat pressure approximately equal. I'm also putting a wanted note in the "parts wanted" section.

[george sutton]

With ref .to aggetted appeal over valve springs posted on the 11 feb. There seems to be some confusion here. I george sutton only added some advice on springs. it is not ME that require them. denis.



Quote of previous post removed - Dave, 16th Feb