R80 Mono Project Build

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Graeme
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R80 Mono Project Build

Postby Graeme » Wed Apr 04, 2018 11:20 am

Hi guys,

I thought I'd start a build thread for my bike to log changes as they happen. Hopefully it'll be of interest to those on here who like to see modified bikes as much as original machines.

The Plan - I like the Cafe Racer style, but the wife likes to come out on the pillion from time to time... What I need is a rear subframe that can take two different seats that can be swapped as simply as possible. Also, I'd like to keep the bike on the road as much as possible so I can enjoy riding it - I've fallen into the issue of completely stripping vehicles before and not being able to use them for years at a time.

The Bike - I like the clean look of the mono bikes and wanted a running & riding bike as a base point. I finally found a nice clean example for a sensible price up in Yorkshire. It had been off the road for a few years, but had been re-commissioned and MOT'd by the current owner. The bonus is that it only appears to have done 20K miles in it's life. Borrowed a bike trailer and collected it April 2017. After a few teething problems associated with it having been standing for so long, I enjoyed it all through the summer as standard .

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The Modifications Begin - I tried a cheap seat off Fleabay, but it was miles away from fitting with the width totally wrong for the main frame rails at the back of the tank - back to the drawing board...

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I gave a well known Cafe Racer parts supplier a call and they were developing exactly what I needed - one common subframe with two seat options. The prototype was being done for a guy in the states and I would get the first set in the UK. The quality if the GRP parts made the wait worthwhile when it all eventually arrived, but it would still need further trimming to fit the bike as neither seat sat down fully on the subframe!

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After messing with the seats a couple of times, I still wasn't happy - what I really wanted was the seat and tank to have a common straight line through the base of the seat into the base of the tank. As supplied, the seat was sitting too high and too flat (even with the tank packed up 25mm as specified by the supplier). I bit the bullet and cut off the rear stays and dropped the front by cutting and re-drilling the mountings. With the tank packed up 35mm, I was able to re-weld the rear stays at the correct angle. A bit of a faf to do, but well worth the effort in my eyes. The "straight line through the whole bike" base line styling is now in place and I can push on with the rest of the build.

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That's as far as I've got for now (apart from bolting on a pair of flat bars and an after market exhaust) and it's currently got the original seat back on so I can get the freshly rebuilt carbs balanced.

Next on the list - Mount rear light and indicators to the subframe to allow "2 minute seat swaps", mount the number plate either under seat or behind the rear diff, then ride and enjoy while I move the attention to the front and that massive OE mudguard and messy brake line routing...

I can't promise that this will be the fastest moving project or thread, but I'll update as things move on.

Cheers for now,

Graeme
Last edited by Graeme on Wed Apr 04, 2018 12:08 pm, edited 1 time in total.
Cheers,

Graeme

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george baker
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Re: R80 Mono Project Build

Postby george baker » Wed Apr 04, 2018 11:43 am

Hi
good to have an idea of the destination before starting the build, my K single seat/hump are a 20 minute swap

George
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Bav
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Re: R80 Mono Project Build

Postby Bav » Wed Apr 04, 2018 11:46 am

Looks great. Is it a Vonzeti rear unit?


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Graeme
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Re: R80 Mono Project Build

Postby Graeme » Wed Apr 04, 2018 12:06 pm

Hi Bav,

Yes, It's a T18 subframe modified to take both T63 & T20 style seats. Nice quality parts, but just didn't fit how I wanted.

Apparently I'm a bit CDO - it's like OCD, but the letters are in the correct order...

Cheers,

Graeme
Cheers,

Graeme

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Bav
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Re: R80 Mono Project Build

Postby Bav » Wed Apr 04, 2018 12:14 pm

Apparently I'm a bit CDO - it's like OCD, but the letters are in the correct order...
Is that why you bought a BMW and not a BSA?



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Graeme
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Re: R80 Mono Project Build

Postby Graeme » Wed Apr 04, 2018 12:42 pm

:lol:
Cheers,

Graeme

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Graeme
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Re: R80 Mono Project Build

Postby Graeme » Fri May 04, 2018 11:14 am

Just a quick update to log a small, but significant step forward - it's now on the road as a "Cafe Racer" (of sorts) \:D/

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Considered different brackets bolted to the subframe to mount lights, number plate & electrics to, but in the end decided to plate the complete underside of the rear loop by stitch welding in a plate. Gives it a really neat look and I get a tray under the seat for a tiny bit of storage.

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To try and achieve my target of "2 minute seat swaps", the seat already has 4 off M8 captive bolts in the underside. I've cut these just under flush with the new base plate and made sleeve nuts out of M12 button head screws.

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I'll cut down an 8mm allen key to keyring size so I can get under the seat when out and about if I need to...

Next on the list - Progress has been a little slow as I've been fighting with a missfire for the last few weeks, but for now I can ride and enjoy while I move the attention to the front and that massive OE mudguard and messy brake line routing...
Cheers,

Graeme

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george baker
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Re: R80 Mono Project Build

Postby george baker » Fri May 04, 2018 12:01 pm

Hi
keep an eye on those screws to see they dont vibrate out, it may be worth making a spare to keep under the seat

George
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Re: R80 Mono Project Build

Postby Mike D » Fri May 04, 2018 12:48 pm

It may just be the angle the photos were taken, but can you see your rear lights from a position further aback, say sitting in a car?

Mike

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Graeme
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Re: R80 Mono Project Build

Postby Graeme » Tue May 08, 2018 10:12 am

George - Great minds think alike. After my recent experience of loosening fixings, I've ordered some wavy washers to make sure.

Mike - I think it's just the photo's. The wife followed me out of work the other day and commented on how bright they were for the size...
Cheers,

Graeme

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Re: R80 Mono Project Build

Postby Quzzy » Fri May 11, 2018 12:17 pm

Dont get me wrong, I really like it, but I couldnt live with being able to see the tank tunnel where it meets the seat.
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Re: R80 Mono Project Build

Postby windmill john » Sat May 12, 2018 2:02 pm

I don’t like cafe racers, but you need to reduce the size of the front mud guard to balance it out; aesthetically.
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Graeme
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Re: R80 Mono Project Build

Postby Graeme » Mon May 14, 2018 10:25 am

Quzzy - thanks and I agree with you about the tank tunnel. It will get at least a blanking plate, but I'm considering putting the ignition switch in there...

John - I couldn't agree more. Next stage of the project is to clean up the front, so watch this space for more (slow) progress.
Cheers,

Graeme

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george baker
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Re: R80 Mono Project Build

Postby george baker » Wed May 16, 2018 6:35 pm

Hi
putting the ignition switch in there could smack you in the nuts with a sudden stop

George
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Re: R80 Mono Project Build

Postby Quzzy » Sun May 20, 2018 9:52 pm

1971 R60/5 ex Gendarmerie
2002 1150RT ex Gendarmerie

Pattern emerging?

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Graeme
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Re: R80 Mono Project Build

Postby Graeme » Mon May 21, 2018 4:50 pm

George - don't worry, I wouldn't risk the crown jewels. If I do put it in there, it'll be "under flush"

Quzzy - thanks for the link. I'd seen this type of seat unit, but the bottom edge sits too high for my taste. Don't worry, this is all a work in progress and that tunnel is definitely on the list.

Next to do is the front mudguard and brake line routing - I'm toying with the idea of taking a single line from the master cylinder down the hollow steering stem and mounting a tee piece under the bottom yolk, then running symmetrical twin lines down to the master cylinders. Thought it might look like the fuel tank vent pipes on 70’s / 80’s / 90’s race bikes (and my old NC30). I’ll mock it up and see if I like it…
Cheers,

Graeme

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Re: R80 Mono Project Build

Postby bwprice100 » Mon May 21, 2018 6:06 pm

Looking nice but the standard tank looks too big in proportion to the seat.

Brian

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