Author Topic: Monza questions?  (Read 1448 times)

Vasco DG

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Monza questions?
« on: April 26, 2015, 01:55:33 AM »
Rather than reiterating the gist of the message I'll copy and paste this email I got from my mate Peter's pal who is a smallblock tragic in Townsville. Essentially I have the same manual as him so I'm as much in the dark as he is. If anybody has ACCURATE,(As opposed to factory supplied via 'Manglish'!) figures for spring free length and possibly seating poundage it would be a great help!


Hi Peter,
                       I hope you and Jude didnít get clobbered in the hail storm too badly.
         I have made a small start on the assembly of the 2 monzas under the house, beginning with cylinder heads, I have measured the valve springs free length and the measurements are substantially different to the measurements in the manual I have and I have found no specs in my copy of Guzzioligy that relate to the Monza valve spring lengths. The  inner valve springs I have measured (free length) are around 33.5mm for one engine and 34.5 for the other, the outer springs are 35.5 and 36.5mm respectively.
             My issue is the manual has a free length of 36mm for the inner spring and 40.5mm for the outer, this seems to be too much of a discrepancy to be just rooted vale springs on both engines. I would like to know what the free length is really supposed to be as well as the loaded lengths, the manual has a couple of lengths to test at different loads which I will do when I am confident I know the correct lengths free and loaded. Also the assembled height of the valve inclusive of the spring seat/spacer to the top of the valve spring is close to 34.6mm, the manual states 37mm ! All the valves are well within the length tolerances so that is not a factor. 
      I would like to shim the valve springs to the correct length but I need to know what it is first, Peter and I had a look on the internet and have so far come up empty handed, if you have the correct lengths or know where to find them I would be greatly appreciative, cheers



Online Muzz

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Re: Monza questions?
« Reply #1 on: April 26, 2015, 04:20:11 AM »
Hi Pete, suggest you give Kev (Steamdriven) a pm.  I think he still has some Monza bits left over from his Monzada creation.
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Vasco DG

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Re: Monza questions?
« Reply #2 on: April 26, 2015, 04:34:50 AM »
Thanks, parts aren't the problem though really. Most of the bits are available. It's just getting good info on what is actually *Right*. Early smallblocks had a history of shedding valve heads. I'm wondering if the valve length discrepancies and possibly the wire diameter would indicate some sort of modification to address the problem?

I'm asking here because there are a whole heap of far more knowledgeable smallbock nutters here than I could ever hope to be. Someone must have some sort of a clue ' is I don't! :D


Offline SED

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Re: Monza questions?
« Reply #3 on: April 26, 2015, 09:52:02 AM »

Not sure this will help, as it doesn't really answer the original question.

As I understand it the fix for the Monza valves is to replace the valves and springs with the Nevada single coil version.  It is what I did and it's worked great.

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Offline steamdriven NZ

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Re: Monza questions?
« Reply #4 on: April 28, 2015, 05:56:42 AM »
Sorry all, I only have the same factory manual and supplement as you appear to have. The part number for the early V50 springs 61 03 76 00 and 75 00 don't change with the Monza / V50-3 so I don't think that accounts for any changes in free length. I did change the valves on my 500 engine along with everything else at 96K km (yes really, all that way and nothing dropped or blew up...but I am a nana rider  ;D) when Dave Currie built that engine for me. Some 25K km later one ex valve closed up and I replaced the two exhausts. From memory the springs were *OK* as in very close but what they actually were is not recorded and anyway they had done 25K km.

If they are original springs they are now 30 years old and are likely to be just sacked out. I'm not as experienced in this field as you Pete but I would guess the best course of action is to set the spring seat to collar underside to 37mm as the book, fit some new springs and new valves. The old springs being shorter will be prone to float but I hardy ever revved mine past 6 as it didn't make any more power, just more noise and it might be fine to just run the old ones!

Just noticed the 37mm seat to collar figure is from the UNDERSIDE of the spring seat to the underside of the spring collar, there may be 2.4mm in spring seat thickness there to make his 34.6mm actually the 37mm is says it should be? That detail in the drawing is easily missed, as I have just done until now  ;D 

Alternatively email Pete Morecombe at Reboot and buy a Nevada engine and gearbox, carbs and exhaust (or find a wrecked Nevada locally) and make the bike a 750. A friend of mine rode mine years ago and also rode it after the conversion. He said "it was now the bike he had always hoped it would be" and he rides a 1200 Buell Thunderbolt these days. Being able to accelerate from 100kmh in top gear, uphill, into a headwind by just rolling it on just makes it SUCH a nice thing to be on............ and all for a gain of only 1.8kg including going back to factory mufflers from ...lighter ones (I've grown up... :)) For all the effort of resurrecting these wonderful looking and handling bikes it's worth the effort to make them go to match the look. You won't regret it.


« Last Edit: April 28, 2015, 06:03:38 AM by steamdriven NZ »
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