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Discussion Starter #1
My stock rings that came with my Morgo kit are blowing smoke have moderate blow by, which is a bit irritating considering the low miles. The stock rings use a one piece oil ring and a chrome top, which I’ve personally not had great luck with. Does anyone have a recommendation for a quality ring set for the Morgo 750 kit, preferably with a 3 piece oil ring?
 

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Check to see if standard T140 rings are the same size. They are on my big bore 750 kit from Aerco. I use Harris supplied rings and no oil burning of smoke. I change them if i get pushrod tube leaks as it is easy to do at the same time. I pay around £40 for a set now.
 

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Check to see if standard T140 rings are the same size. They are on my big bore 750 kit from Aerco. I use Harris supplied rings and no oil burning of smoke. I change them if i get pushrod tube leaks as it is easy to do at the same time. I pay around £40 for a set now.
The Aerco (Velocette) kit is 76mm bore, but the Morgo is 2.974", or 75.54mm. I actually use the standard Aerco bore pistons to go 1st oversize on a Morgo, but no help here! The last rings I had from Harris were different again, I think from Goetze, which used a backing spring behind a one piece oil control ring, no feedback yet on longevity etc
In the first instance, I would contact Morgo, they are quite approachable.
 

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10 000 km on my morgo rings and they are still running quite well. Possibly a honing / glazing problem?
 

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Discussion Starter #7
Thanks everybody!

I am going to pull the top end and measure the bore. I put the Morgo on in 2012 or 2013 (I don't remember) and have about 4500 miles since then. When I received the cylinder, one bore had a .005 clearance, and the other was less than .0025 (I had that written down), so I had it matched to the other. The guys who honed it are a shop with years of experience with old triumphs. Bores were honed with 180grit. I didn't break it in with Morgo's oil, but used a break in oil that I've had great success with, and it wasn't babied. It doesn't seem to consume an exorbitant amount of oil, but it's smokey. I never really noticed until I had the bike on the dyno when I was tuning my Mikuni last year . It blew a lot of smoke under load. I won't know until I disassemble and measure, but who knows. The bore could be too big. It does have noisy pistons (slap, especially when cold). There are several ring manufacturers that can make any size rings, so I'm sure there are options. Once I get it apart and measured, I'll report back.
 

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Discussion Starter #10
I will. Doubtful, however, that the the guide bores are worn. It smokes a lot under wide open throttle pulls. Though it could be a loose guide in the head, that has happened before. (Many years ago) I don’t think that’s the case, but I won’t know till the patient is open. 🙂
 

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Discussion Starter #11
Update. Head is in great shape. Valves and guides measure good as new. Guides are tight in the head. The problem is quite apparent. My eyeballs can measure this piston fit. The cylinder walls still have cross hatching, and no scores or a ridge. I take full responsibility for not checking the fit after being honed by a shop before assembling it several years ago. You can tell there’s a taper just by wiggling the piston at the bottom of the stroke (noticeably tighter, but still loose). I’m surprised it didn’t make clouds. No wonder these pistons were so noisy. The cylinder is stuck on the cases, so I called it a night.
 

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Looks like you'll have to rebore, so you've now got the choice of either the Morgo or Aerco pistons (roughly 0.020" different in their oversizes). I think you might be using a different machinist next time!
 

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Discussion Starter #13
Maybe its just me, but it looks like after buying pistons, a decent set of rings, and a boring service in addition to shipping the cylinders (no good shops around here), I may as well buy an entire new kit...
 

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You might well be right! You still have the choice of Morgo or Aerco (Velocette manufacture, also being sold as Routt), AFAIK there are no others now, but I stand to be corrected on that one. The visual difference being the fin shape. Not sure about availability your side of the pond, but probably worth shopping around.
 

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Discussion Starter #15
When I ordered my Morgo, I did it through burton bike bits from the UK. Was and is still cheaper than the markup here in the states, even with shipping. I like the shape of the Morgo, but I also like the stock shape.
 

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Discussion Starter #16
Well, the bores look pretty good and measure 2.9745 and 2.9730, and are both round within a few tenths, and the taper is about .0015" or less. Piston clearance is .011" and .013". Pistons look they started galling, with a wear ring that I haven't seen before. Almost like it got hot. I don't remember overheating it or hearing detonation, but that doesn't mean it didn't happen since there was oil in the combustion chamber. I thought about just making it a 650 again, but my two cylinders are not usable.

748334


748335


748336
 

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Hi 68TR6R, Where are you located?
If you ship to good machine shop, you can be assured of a perfect bore & hone.
What rings are best?
For sure you’ll use break in oil again. I’ve had very good success with Torco TBO 40w. Above 45f. Last motor was started New Year’s Day & ran in in a few weeks. San Francisco east bay.
I just visited Engine Dynamics today. They will do my boring. Will install Kibble White C630 guides, black diamond valves, Serdi cut seats. I can’t hone C630 guides. They can’t be reamed. Not sure on rings just yet.
The shop is immaculate. My friend had his 70 Tiger Morgo Cyl bore done there. Many thousand miles now. No oil consumption, no piston noise.
Don
 

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I'm now puzzled, those bore dimensions are standard size Morgo, so have not been rebored. On the piston clearances you have, things would have to be really hot for the pistons to tighten, as it appears they have. What fuel were you using? The "standard" compression ratio with a 0.039" head gasket is 9.5:1, very high indeed for US fuels
 

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Are you measuring piston to bore clearance at the right part of the piston?

Perpendicular to the pin, a little distance up from the bottom edge of the skirt.
 
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