Dowels or no?

A

Alexb83

Full member
Location
Northumberland
Good morning all,

Time is coming round to check and adjust valve clearances as required on my '77 triple.
Now, this is going to be my first time carrying out the procedure (and indeed taking the timing drive apart) and I refer back to the previous owner's notes, which include a service report from a well known retailer of Italian bikes in the Wiltshire area.

There is a comment on the service report to the effect of 'cam tower dowels are missing, not a major issue but may wish to replace'.

Should a triple of this vintage have dowels to site the cam tower blocks onto the head?
Is it actually not a major issue?
Referring to the parts catalogue (https://www.laverda-paradies.de/shop-1000-44-en.html) I think this may be the part referred to as '28, locating pin, middle camshaft support' - am I wrong?
 
a lot of replacement bearings (years ago) came with the borings to suit the dowelled type head, so don't have concerns unless you also have the over bore/dowel recess on the head studs, and then in that case........
CLEM
 
Surely the towel would be 44. 03?  Not the pin in the centre bearing which you should surely have. I don't know when the heads changed to no to weld but at a guess would think if the space is there in the bearing you should have them? I have always thought that the way the bearings locate in a soft alloy head I.e on a narrow ledge is pants :D. Get yourself a digital micrometer...soo much easier to read. Don't drop anything down into the engine.dont over torque. Push down on the cam wheel when measuring gaps with feeler gauge and cam chain is off.Allow enough time.New spring link or at least clip?
 
nick7 said:
Surely the towel would be 44. 03?  Not the pin in the centre bearing which you should surely have. I don't know when the heads changed to no to weld but at a guess would think if the space is there in the bearing you should have them? I have always thought that the way the bearings locate in a soft alloy head I.e on a narrow ledge is pants :D. Get yourself a digital micrometer...soo much easier to read. Don't drop anything down into the engine.dont over torque. Push down on the cam wheel when measuring gaps with feeler gauge and cam chain is off.Allow enough time.New spring link or at least clip?
Click to expand...

I would've called 44.03 a spacer for a bearing stud!
A dowel is a cylindrical peg used for holding things together, no?

In any case, we'll see what I find when I get it apart.

I read in another thread: 'the earlier version, i.e. the version that makes use of a centralising bush/dowel to locate the cam block in the cylinder head' and feedback to the effect of 'The earlier heads don't have the locating slots that the newer pillars locate in.'
 
You can call it what you like..but the parts cateoghe doesnt agree with you and nor do I.A pin is a pin...when you get it apart and fi d hollow to weld missing, let us know?😁 and ignore my other comments T your peril..I am no engineer but have had my Jota 18 years, and one learns painfully and expensively!!
 
nick7 said:
You can call it what you like..but the parts cateoghe doesnt agree with you and nor do I.A pin is a pin...when you get it apart and fi d hollow to weld missing, let us know?😁 and ignore my other comments T your peril..I am no engineer but have had my Jota 18 years, and one learns painfully and expensively!!
Click to expand...

I'm not disagreeing with you, that this is the 'dowel' (you know better than I do)
Also, I don't want to get into a semantic argument about what 'dowel' means. I'm just puzzled by inconsistent language - even the parts fiche I linked there calls it a 'centering bush'!

@CLEMTOG I saw had written at http://www.laverdaforum.com/forum/index.php/topic,80530.msg132720.html#msg132720 that these were used 'no later than 74/75' - is this just another case of whatever was on the shelf making it onto later bikes?

When fitting, is the 'dowel' supposed to sit proud of the head and slot into the base of the block? Or does it fit flush and just stop the stud from wandering?
 
Hi Alex

I would think that the note 'probably' refers to the 2 small locator dowels within the split centre cam bearings. The intention of which is to ensure the halves go together correctly 'as machined' [and then you have to position them so the oil relief hole points outward to the adjacent cam-follower face]. So, yes, my guess [because of the word tower] is also that your 'item 28' is what the note is referring to.

28976078147_e3b69448e9.jpg


HTH
 
Which dowels are you referring to?

Early heads had hollow dowels placed over the 8mm studs to locate the bearing blocks.  The dowels for the centre studs also located the top half of the split bearing block.  Later bearings that were positioned in a machined slot in the head, had 2 dowel pins to locate the 2 halves of the centre bearings.  Either way, the bearings need to be properly located so they can be replaced in exactly the same position as before.

In both cases, it is not a particularly good idea to omit them.  Omitting the bearing locating dowels (if the bearings are not positioned by the slot) will have you chasing your valve clearances for the next fortnight... at least. :D  Every time the bearings are replaced, they will assume a different position, throwing any measurement straight out the window.  Omitting the locating pins between the halves of the centre bearings can cause the top half to move when nipped up, thus jamming the cam journal, just what you need to fuck the cam journal.

The early dowel method of locating the bearings has the disadvantage that parralellism isn't guaranteed, the bore for the 9mm stub can allow the bearing to swivel slightly around the dowel.  The slot in the head with the corresponding spigot on the bottom of the bearing block eliminates this problem, at least as long as no ham-fisted bodger manages to totally fuck the locating slots by inserting and tightening the bearings at an angle!

Dunno what sort of mechanic can describe this as "no major issue".  Miserable wrenching at its best.  ::)

piet
 
Alex, take measurements & determine the next course of action. If disassembly is required then you will be able to see what may/may not be missing.
 
Piet as ever clarifies...anyway we have hollow dowels and dowel pins :D and I guess the need to translate from German or Italian doesn't help...
Haven't looked again but hope the hollow dowels as we shall now call them and which it is likely you are missing can be got. If you want to do the job in one hit, it is stating the obvious that you may need some shims! Of course hopefully not...but if you do consider where to get them? I bought a full set from RichardSlater one time..when I bought the RGS head from his display engine. Ah plus billet cam blocks I recall..nice things.So, have not needed to use my digital micrometer in anger as all gaps unchanged. Have measured the shims I bought..not all quite the size it says on the packet so it's worth measuring first. All you engineers will laugh at that..but for those that aren't...
 
you have clearly demonstrated Nick that you are not familiar with the early set up of cam bearings being located on the cylinder head with dowels. these are "tubes" with a lead in taper (both ends) and compressible, so fit over the studs, and locate in an overbore of the thread holes in the head, and the through a similar overbore of the holes of the bearings. very different to the highly accurately machined 22mm abutment on later engines. I can show you a set next time you are here.. This system is great for a 360 degree location finder, and works very well on flanges such as primary chain cases (which Laverda do not have and why?) and also gearbox covers (same applies but more so) not entirely good at locating  small items especially with a single or two bolt  fixing and close together.
CLEM
 
sfcpiet said:
Every time the bearings are replaced,
piet
Click to expand...

Piet,

Does this mean that some Lavs used white metal split shells for cams? If so...
I've been looking at a number of 650 Zane heads with chewed out cams and wondering if there is a split white metal bearing I could use. What are your thoughts?

Regards, Greg

 
nick7 said:
Haven't looked again but hope the hollow dowels as we shall now call them and which it is likely you are missing can be got.
Click to expand...

Available here for starters, part #44-03

https://www.laverda-paradies.de/shop-1000-44-en.html

My 76 has them fitted.
 
Clem
You have clearly demonstrated that you haven't  read the thread carefully enough! I am fully aware of the early head cam bearing location methodology..you might recall you got me one many years ago..which turned out to be scrap as it had been decked unevenly and now resides in Richard Slaters show engine..so don't be tempted to buy that, anyone! So I will be over for a cuppa and an apology asap Clem...can tell you are feeling better! :-*
 
ghwallice said:
Piet,

Does this mean that some Lavs used white metal split shells for cams? If so...
I've been looking at a number of 650 Zane heads with chewed out cams and wondering if there is a split white metal bearing I could use. What are your thoughts?

Regards, Greg
Click to expand...

No, Greg.

Simple alloy blocks cut in half, similar to the top caps of the Zane cam bearings.

The Zane heads will only work if you manage to extract the heat faster/more efficiently, no matter what type of bearings you install.  The stock type bearings work OK in the 500 and 600 engines, the Zane guys just pushed the envelope that little bit too far...

piet
 
Thank you all as always for your constructive comments and advice.

The bike has recently done an 1100 mile round trip including very hard riding, and had no compliants (aside from a little rattle at the top end after cold starts that has me concerned and thinking this check is now overdue)

We'll see what I find when I get it open, although now I am thinking I should resolve the 'dowel issue' before I start checking clearances, rather than after.

If I just assume that it's going to be a complete cams out/replace the dowels/renew cam chain (can't hurt?)/measure and re-shim as required job, is it going to make my life simpler? Would refreshing the bearings as a precaution be advisable if they have not been positioned with the dowels previously?

I don't want to measure clearances, potentially re-shim, then alter the cam position and end up having to re-measure for a fortnight as Piet suggests.
 
Dellortoman said:
What's the fix for that problem? Greater oil flow perhaps?
Click to expand...

The factory tried that with a pump about 4 times the flow volume as the original Formula/600 pump.  Even added an oil channel between the exhaust valve seats and a pair of monstrous coolers and fans, heads still collapsed under the exhaust cam.  Just too much heat being generated, too much power expected from an air-cooled twin.  Reckon if the factory had put their ceiling at 60-65hp, all could have been good.

piet
 
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