Done this before!

Chris

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Hi
I'm posting this to keep me at this build. I've done this before but didnt finish & I need to this time.
Originally a 750 with a big single Dellorto carb. It's now an 850 built on a Mk3 electric start. Strengthened cases., Venolia hi comp pistons, 7s cam, belt drive,. Currently 33mm MK1 carbs but I have 34mm MK2s & thanks to Fast Eddie it will end up with FCR35mm carbs. I just want to ride this by the autumn! So no bling or paint just keep nailing bits together. Added indicators! As I so love wiring.
Chris
20210617_114025.jpg
20210617_115509.jpg
 

Craig

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You almost there , August sounds better ! Going to be a real nice ride by that time !
 
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Intresting front end, lookin' good! Posting it up here is the right idea, keep the creative juices flowing and all that. :)
 
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Hi Chris, I've just joined and just up the road from you.
I started building a "Lockdown project" a few months ago (Haven't had a Commando for about 40 years TBH.).
Fitted a very similar front end, though realistically I'm looking at another 18 months when my finances might catch up with the blingy stuff I've got planned.

If someone will let me know how to post pic's on here..........
 

Fast Eddie

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Looks nearly there Chris, you can do it mate !

You need to control the ‘scope creep’ though… I mean INDICATORS !? Wasn’t aware they made ‘em any faster… it’ll be heated grips next…
 

Chris

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Gell seat. Eddie. Going to use it so being practical for club night
Paul pm me & I will give you any help you need
 

baz

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Hi
I'm posting this to keep me at this build. I've done this before but didnt finish & I need to this time.
Originally a 750 with a big single Dellorto carb. It's now an 850 built on a Mk3 electric start. Strengthened cases., Venolia hi comp pistons, 7s cam, belt drive,. Currently 33mm MK1 carbs but I have 34mm MK2s & thanks to Fast Eddie it will end up with FCR35mm carbs. I just want to ride this by the autumn! So no bling or paint just keep nailing bits together. Added indicators! As I so love wiring.
Chris View attachment 80528 View attachment 80529
Bike looks looks ace ,do you know what make that 2 into 1 is?
I had one of those systems
I just couldn't get the bike to run well with it
Despite re jetting etc the bike just felt flat
I fitted standard downpipes and pea shooters and that really woke the bike up
 

Chris

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Hi Baz it's a period race 2 into 1 from the period. I brought a lot of Norvil Proddy spares some years back. Someone was converting it back for the road. & I brought all the bits they didn't want! They were all well worn, it was a well used bike. The exhaust system came from it so I believe it must have run ok, although I don't know how the carbs were jetted. Short mega inside the silencer! It will be loud. This is the man who cut the end of the Gus Khun footplates & folded up the brake lever to fit a disc back end. Belt & braces racing.
 
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Here's some of that interweb unsolicited advice everyone hates:

If you plan to keep that 2:1 exhaust, you might consider adding about 4 inches of exhaust pipe between the collector and megaphone. The Bubb 2:1 I'm using was too short initially. Makes a big difference with the added length if you like nice town manners and top end. I gutted the megaphone and put a SuperTrapp arrangement in the end of it. I have 21 plates in it. Wife says it really isn't that loud, but I put put around the neighborhood. She never hears it when on the cam.

7S might be kind of overkill on the street. Yowser!!

Great stoppers and front fork. Should make for a great hooligan bike if you plan to ride it on the street.

The FCRs will be a nice touch. Very street friendly IMO, but they definitely work better when the RPMs are up. I get over 60MPG with them on my 750. I'm sure that will be different with your hot rod 850. Might take a little tuning, but they are very tunable without a lot of effort.

Enjoy
 

gortnipper

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Hi Chris, I've just joined and just up the road from you.
I started building a "Lockdown project" a few months ago (Haven't had a Commando for about 40 years TBH.).
Fitted a very similar front end, though realistically I'm looking at another 18 months when my finances might catch up with the blingy stuff I've got planned.

If someone will let me know how to post pic's on here..........
Look at the Resources menu item.

 

baz

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Hi Baz it's a period race 2 into 1 from the period. I brought a lot of Norvil Proddy spares some years back. Someone was converting it back for the road. & I brought all the bits they didn't want! They were all well worn, it was a well used bike. The exhaust system came from it so I believe it must have run ok, although I don't know how the carbs were jetted. Short mega inside the silencer! It will be loud. This is the man who cut the end of the Gus Khun footplates & folded up the brake lever to fit a disc back end. Belt & braces racing.
My exhaust was completely open it sounded good but I'm guessing on my stock 750 it needed more work to get the best out of it
Your bike should handle really well with that front end you have as the offset of those yokes looks reduced and with 750 frame it works really well
 

baz

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Here's some of that interweb unsolicited advice everyone hates:

If you plan to keep that 2:1 exhaust, you might consider adding about 4 inches of exhaust pipe between the collector and megaphone. The Bubb 2:1 I'm using was too short initially. Makes a big difference with the added length if you like nice town manners and top end. I gutted the megaphone and put a SuperTrapp arrangement in the end of it. I have 21 plates in it. Wife says it really isn't that loud, but I put put around the neighborhood. She never hears it when on the cam.

7S might be kind of overkill on the street. Yowser!!

Great stoppers and front fork. Should make for a great hooligan bike if you plan to ride it on the street.

The FCRs will be a nice touch. Very street friendly IMO, but they definitely work better when the RPMs are up. I get over 60MPG with them on my 750. I'm sure that will be different with your hot rod 850. Might take a little tuning, but they are very tunable without a lot of effort.

Enjoy
Wish I'd known about extending the collector pipe !!
 

Fast Eddie

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I think that without knowing how long the headers actually are, how long they need to be, what diameter they are, what diameter they need to be, and what the differences are, then adding 4 inches into the headers would be a real stab in the dark for Chris!

Add to that he’s running high CR and a 7S cam and I see no reason on earth, other than random chaos theory, that a 4 inch extension would do any good at all.

All only IMHO of course.
 
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I think that without knowing how long the headers actually are, how long they need to be, what diameter they are, what diameter they need to be, and what the differences are, then adding 4 inches into the headers would be a real stab in the dark for Chris!

Add to that he’s running high CR and a 7S cam and I see no reason on earth, other than random chaos theory, that a 4 inch extension would do any good at all.

All only IMHO of course.
Everything during R&D is a educated stab in the dark until it is successful. Once successful it's called a better design.

After the collector, not lengthen the header pipes. No welding required. Simple thing to do/try with a slip-on piece of straight exhaust, and a longer stay for the rear exhaust mount on the megaphone.

I can tell by the pic it is a typical period short 2:1 low exhaust. I'm sure it works somewhere in the RPM range for that cam. I know for a fact making one of those short 2:1 exhausts longer after the collector makes a tuning difference. It's not random chaos theory.

What I did worked and made a difference on a similar "period" 2:1 exhaust. It's not my opinion.

All that said, I doubt Chris will try it without the clubhouse nod of approval. lol
 

Fast Eddie

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Well let’s agree to disagree.

In my experience, unless you have specific knowledge of a particular pipe / cam / head / CR combo, or the software to run simulations, it is no more than a stab in the dark.

The same pipe that works great on one set up can be rendered ineffective simply by reducing cam duration a few degrees. I know this from my own dyno testing with a Maney 2:1 pipe and radiused followers.
 
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OK with me to disagree.

That Maney pipe is not in the same league as that cheap thing on the bike pictured. For what a Maney pipe costs they should self tune the entire engine. ;)

Obviously everything related to the motor configuration makes a difference. That is a given IMO. I wasn't aware that there would be anymore motor changes. And for all I know the pipe works great. My suggestion was just in case it does not work well everywhere on the "street".

I don't have any simulation software, or a dyno. Would be a waste of my money. I can tell when a motor is working. I can't tell what the HP and torque is, or make a chart though.

I made the modification to my 2:1 exhaust, because the top end was terrible with it as delivered. Similar to what baz experienced. Extending the 2 inch diameter pipe section between the collector and megaphone, gutting the megaphone, and using the SuperTrapp disc arrangement made a positive difference. If people don't want to believe it, their loss. The total extension is 3.5" on my setup. The length of the 2" slip-on is 6.5".

I doubt Chris needs any advice from anybody anyway.

I got caught up in thinking I knew what I was doing there for a minute. Whew, glad that's over. :)
 
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Chris

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Hi
I will see what we end up with.
I might even measure it up for you all.
The only alteration it's going to get is a touch of the acetylene torch to tuck it up a bit.
 
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