E: Engine Comet Mongrel

[Bill Thomas]

That's all I do is look at my Poss' 560, Someone came round the other day and said, " I remember seeing those flywheels there ".
But I have been getting some miles in on my Comet and ex L/ning rep'.
Keep up the good work, Bill.

 

[vibrac]

Glad to hear you are making progress. My plates seem to be working out ok so far. I spent a lot of time trying to keep everything as compact as possible and not stretch out the wheelbase any more than necessary. I'll have to make up a bell rank of sorts to get the exhaust valve lifter to work.... although I think it was Bill who told me that only a pussy would need one to start a Comet.

Meeyow!
Royal Enfield decompresor.........

 

[Cyborg]

Meeyow!
Royal Enfield decompresor.........

Yes that would be a logical option because the head is already set up for twin plugs, but it would not be in keeping with my propensity to do things the hard way.
As previously mentioned, you also have to factor in my ancestry..... I basically started with bare lumps and had to purchase all new lifter bits, so I'm damn well going to use them. Kidding aside, it looks like it would be relatively easy to add a small spring loaded bell crank. The spring pressure would assist the internal lifter return spring keep the valve lifter washers sealed. Just an idea rattling around in my head, so who knows.... I might change my tune when time comes.

 

[Bill Thomas]

Meeyow!
Royal Enfield decompresor.........

I thought you had one of the new type decompressors, Ron's does not seem to fire, And I have bought one for my 560, To save fitting all those small bits. But even if they don't work on Vins, It should be easy enough to turn the Engine until compression, Open the new type, Get it over com', Then close it, Then give it a kick.
It will mean taking your gloves off !.
Cheers Bill.

 

[Cyborg]

I have spent the last three days staring at the nether parts of my empty cases with a view just like that trying to decide which of the 10,000 ways to mount a Norton gearbox I will use. Nice to see all these old Comets coming back to life. You have a good attitude. Nice work. As Bill says, all in good fun!

View attachment 22802

When you are contemplating the 10,000 ways..... you may already know this.... the belt drive gives you some flexibility as to where you locate the Commando box (side to side). Your use of the Comet primary drive case will make your situation different than mine, but I would suggest including the rear wheel, sprocket, swingarm, etc in your staring sessions. Before I started, I assumed I would have to trim some material off the rear wheel cush drive in order to keep the rear sprocket aligned and the wheel centred. Not so.... I actually have to space the rear sprocket out a bit. Not a show stopper, but had I chosen different path, I wouldn't have to make the spacer. I also spent some extra time removing bits of material from the right side plate, thinking I would have to get the gearbox farther to the left because of the Honda rear wheel assembly. I can see why folks like CAD.
None of it turned out to be an issue, just different results than expected and a few more days making shavings.

 

[davidd]

I would have been surprised also. I had to reduce the sprocket carrier quite a bit.

David

 

[Oldhaven]

When you are contemplating the 10,000 ways..... you may already know this.... the belt drive gives you some flexibility as to where you locate the Commando box (side to side). Your use of the Comet primary drive case will make your situation different than mine, but I would suggest including the rear wheel, sprocket, swingarm, etc in your staring sessions.

My path is hopefully a bit easier than yours since the gearbox is butted against the stock inner chaincase lug, which (I think) no one ever has to modify to use the box and newby clutch. That will be my datum and I will shim the engine belt pulley to the clutch. I am also using a frame designed for a Vincent engine and a somewhat contemporary rear hub, thankfully, so I should have only minor difficulties with the rear chain and sprockets. We'll see. I won't be doing skyhook engineering like you are. (And doing it well. I am not as brave as you appear to be.) I do have to be a bit creative about what to use for a F106 substitute, thence the gazing ball sessions.

 

[Cyborg]

My path is hopefully a bit easier than yours since the gearbox is butted against the stock inner chaincase lug, which (I think) no one ever has to modify to use the box and newby clutch. That will be my datum and I will shim the engine belt pulley to the clutch. I am also using a frame designed for a Vincent engine and a somewhat contemporary rear hub, thankfully, so I should have only minor difficulties with the rear chain and sprockets. We'll see. I won't be doing skyhook engineering like you are. (And doing it well. I am not as brave as you appear to be.) I do have to be a bit creative about what to use for a F106 substitute, thence the gazing ball sessions.

I'm not sure it qualifies as bravery... probably closer to plain old stubbornness. Why else would I make my life difficult by insisting that I use whatever has accumulated in the shed or the dumpster at the local bike breakers.... but thanks for the compliment. Never heard the term skyhook engineering before, but it sounds about right. I will refer to my exhaust lifter bell crank as a momentum exchange tether from now on.

 

[Cyborg]

I would have been surprised also. I had to reduce the sprocket carrier quite a bit.
David

This photo is with the wheel centred in the swingarm and the sprocket shimmed out slightly, but still fully engaged on the carrier. The centre of the tire aligns with the centreline between the cylinder studs. The front mount in the frame puts the centreline of the studs directly in line with the centre of the steering head, so in "theory" all is good. Now I just need to stick everything together for the umpteenth time and make sure the wheels align. Once that is done, I can finalize the width of the spacers for the gearbox mounts and the rear wheel spacers. If this thread goes silent and you see a want ad for an Egli frame, you'll know I overlooked something.

ps. if wondering about the length of the swingarm, its not finished yet. Just tacked together and needs to be shortened by about 1/2 mile.

 

[Cyborg]

Working on the rear suspension. Fabricated a fork that connects the rocker to the swing arm. Rocker was borrowed from a Ducati Monster and shock from a Yamaha R6.