'74 Eldo 850 Valve guide Specs

[DaGootz]

Hey Gang, I'm going to be rebuilding my heads with new valves and guides and getting mixed messages on valve guide to stem tolerance. The Chilton manual has a .002~.010" clearance spec and my engine guys thinks that's pretty loose for an air cooled engine, he's thinking more like the .002" range. my main concern is valve seize. Anyone have good luck with the valve guides from MG Cycle? Andrew doesn't have a real good description on his site. Are these guides undersize for fitting or will they pair nicely with his valves? I watched Bill Finnegan series on Mike's Machines on YouTube doing the K-Lining process, which was very interesting and he brought up some good points with regard to stem to rocker alignment/valve seat alignment if new guides are not straight. Hard to find anyone here in the States that does K-Lining, but it's a great process. My engine guy did it back in the 80's at a race shop he worked at in Ohio, doing dirt track automotive engines so he is familiar with that process. Any help is appreciated. Thanks

[Antietam Classic Cycle]

From the factory manual: https://www.thisoldtractor.com/mg_manuals/workshop_manual_700_750.pdf





I've used dozens of the valve guides from MG Cycle without ever having any issues. The guides will need to be reamed to size after installation. Any machine shop worthy of the name will get the guides straight.

[Moparnut72]

I read something about K lining a couple of months ago. Interesting concept and article but I don't remember the verdict. One good thing about Sportsters is that they have a separate cam for each valve. Straight shot to each rocker, valve guide wear is minimal.
kk

[pehayes]

Do you participate at the LoopFrame Discussion Forum?  Might be a lot of people there with good answers for you.

LoopFrames@motoguzzi.groups.io

Patrick Hayes
Fremont CA

[DaGootz]

From the factory manual: https://www.thisoldtractor.com/mg_manuals/workshop_manual_700_750.pdf





I've used dozens of the valve guides from MG Cycle without ever having any issues. The guides will need to be reamed to size after installation. Any machine shop worthy of the name will get the guides straight.

So specs for the 700-750's are the same for 850's?

[Don G]

I run .0015-.002 valve guide clearance on K-Line guides, you want to keep it that range as too tight will cause the valve to seize in the guide.

[guzzisteve]

They are the same for all big twins through the 1100 2V motor 1 spark plug, read your shop manual & compare to other shop manuals to learn.

https://www.mgcycle.com/index.php?main_page=product_info&cPath=68_127&products_id=423

[Antietam Classic Cycle]

So specs for the 700-750's are the same for 850's?

Yes.

[DaGootz]

Yes.

Great to know....Thanks Charlie...much appreciated. That's exactly what my engine guy needs. Now I'll search around for the spring height and that will get us started when we begin this project. He rebuilds aircraft engines in Alaska, so he flies there for a month them comes back to NC for a month. I'll catch him in Dec or Jan...no rush now.

[Antietam Classic Cycle]

Great to know....Thanks Charlie...much appreciated. That's exactly what my engine guy needs. Now I'll search around for the spring height and that will get us started when we begin this project. He rebuilds aircraft engines in Alaska, so he flies there for a month them comes back to NC for a month. I'll catch him in Dec or Jan...no rush now.

Page 20 and 21 of the workshop manual I linked to. Use the V7-750 specs. for your Eldo.
https://www.thisoldtractor.com/mg_manuals/workshop_manual_700_750.pdf
Eldorado supplement: https://www.thisoldtractor.com/mg_manuals/workshop_manual_850_supplement.pdf

[DaGootz]

Page 20 and 21 of the workshop manual I linked to. Use the V7-750 specs. for your Eldo.
https://www.thisoldtractor.com/mg_manuals/workshop_manual_700_750.pdf
Eldorado supplement: https://www.thisoldtractor.com/mg_manuals/workshop_manual_850_supplement.pdf

Thanks again Charlie, you Rock! So I'll assume the only difference between the 7-750 and 850 is bore/stroke? I haven't dived into the specs yet to see for myself....got a lot going on right now. Much appreciated. I did pass along the workshop manual.

[Antietam Classic Cycle]

Thanks again Charlie, you Rock! So I'll assume the only difference between the 7-750 and 850 is bore/stroke? I haven't dived into the specs yet to see for myself....got a lot going on right now. Much appreciated. I did pass along the workshop manual.

The V700 has an 80 mm bore, the Ambo and Eldo are both 83 mm. The stroke is different - 70 mm for the V700 and Ambo, 78 mm for the Eldo.

[DaGootz]

The V700 has an 80 mm bore, the Ambo and Eldo are both 83 mm. The stroke is different - 70 mm for the V700 and Ambo, 78 mm for the Eldo.

As suspected....thanks . I can't remember who, I think it was the boys at Cycle Garden saying they stroked a Ambo with Eldo rods, leaving the bore the same and it gave the Ambo the same displacement as their Eldo big bore kit.....thought that was interesting.

[Antietam Classic Cycle]

As suspected....thanks . I can't remember who, I think it was the boys at Cycle Garden saying they stroked a Ambo with Eldo rods, leaving the bore the same and it gave the Ambo the same displacement as their Eldo big bore kit.....thought that was interesting.

Rods are the same length on all of the Loops, so those aren't going to change anything. More likely they swapped cranks.

[Dukedesmo]

Quote from: Moparnut72 on October 25, 2025, 03:58:29 PM

I read something about K lining a couple of months ago. Interesting concept and article but I don't remember the verdict.

___________________ ___________________ ______________

I had the guides on my LM2 K lined. One reason was that, apparently the old heads can be easily damaged during removal of the guides and of course being made of unobtanium not easy or cheap to replace if that happens. The other being that the shop who did it convinced me it was a better job, that they work better, retain oil yada yada - they actually do them for some of the locally based Formula one race teams so I went with it. This was 10 years ago and I've had no issues so gets a thumbs up from me.     

[DaGootz]

Quote from: Moparnut72 on October 25, 2025, 03:58:29 PM

I read something about K lining a couple of months ago. Interesting concept and article but I don't remember the verdict.

___________________ ___________________ ______________

I had the guides on my LM2 K lined. One reason was that, apparently the old heads can be easily damaged during removal of the guides and of course being made of unobtanium not easy or cheap to replace if that happens. The other being that the shop who did it convinced me it was a better job, that they work better, retain oil yada yada - they actually do them for some of the locally based Formula one race teams so I went with it. This was 10 years ago and I've had no issues so gets a thumbs up from me.     

This is what I watched on YouTube where I was familiarized with the process, episode1 with Bill Finnegan. I emailed him the other day and he got right back to me, nice guy. He said he still prefers K-Lining. He is on Mikes Machines channel on YouTube. https://youtu.be/GEwjFOSDX8E?si=aUWrHAZHrLYFsOT8

[moto-uno]

Quote from: Moparnut72 on October 25, 2025, 03:58:29 PM

I read something about K lining a couple of months ago. Interesting concept and article but I don't remember the verdict.

___________________ ___________________ ______________

I had the guides on my LM2 K lined. One reason was that, apparently the old heads can be easily damaged during removal of the guides and of course being made of unobtanium not easy or cheap to replace if that happens. The other being that the shop who did it convinced me it was a better job, that they work better, retain oil yada yada - they actually do them for some of the locally based Formula one race teams so I went with it. This was 10 years ago and I've had no issues so gets a thumbs up from me.     

I had mine K lined about 2 decades are go and they are still fine (and yes I've lost count of the kilometers it had put on it ) . This was done after I removed the original guides ( I was an MC mechanic for years) and I swore I'd never replace the guides again . Compared to the dozens of Triumph and HD heads that I'd replaced guides on, the MG heads were like hardened lead :) !

[Moparnut72]

When I worked in the radial engine restoration shop we replaced quite a few valve guides. It was quite an ordeal requiring an acetylene torch and a slide hammer. Installing new ones wasn't a picnic either.
kk

[Frenchfrog]

My T3 heads were k lined a couple of decades ago too with excellent and long lasting results.
Same for my LM ones too but I've not accumulated such big miles on that engine.
I would not hesitate to K line again but in France hardly anyone will do it unfortunately.