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Bobbing a -67 Bonneville

46092 Views 175 Replies 55 Participants Last post by  Johansson
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Hi guys, Anders is my name and I am new to both this forum and vintage bikes. I´ve been riding sport bikes up until now (tuned Hayabusa) but as I want to spend more time in the workshop than on the road I figured that I needed a change of machinery. The damn jap fours never break down!



I dug a hole in my workshop funding and bought a Bonneville -67 with a NOS 750cc kit and some other reliability-enhancing mods like external oil filter and a new set of bearings in the engine. I took it for a 150km maiden ride and almost missed a friends wedding since I had no idea that I couldn´t have the light switched on while trying to start it. After pushing it up and down a hill for 30 minutes it started the same second as the throttle wire snapped...



Needless to say I had to give it a complete overhaul before I dared take it on any longer trips again, the wiring had seen better days and I had some plans made up for it so I started taking it apart.



The most gorgeus bike style in my opinion is the bobber, a minimum of parts which are mostly home made and looking like it has been stored away in a barn for the last 20 years was the look I was after. A 2" stretch 2.5" drop hardtail was ordered and while waiting I gathered up some bike parts I had laying around the workshop that might just fit.



When the hardtail arrived I eagerly bolted it on and threw some other stuff I had found on as well just to see where this was heading, I had some handlebars from a Skidoo REV 600 snowmobile that I inverted, shortened some and bent a bit on the hydraulic press, a set of home made headlight mounts from my old turbo-GSX750 build and used the front fender as the rear fender even though it needs to be widened 10mm to fit the tyre.



It actually started to look like the image I had in my mind so I continued by cutting out a seat pan.



An old hinge from the dog house gate became the front seat mount, when I have welded the spring mounts in place I will glue some foam to it and dress it in leather.



The handlebars turned out really well, the best part is that I can use the original steering head without doing any mods to it. I won´t do anything to the bike that cannot be restored to its original state in case I would like to one day. It wouldn´t feel ok to destroy an old vintage bike.:(



With some styrofoam blocks under the seat I took it outside to see it in daylight and get some footage of the driving position, my feancee gladly helped out since I think she secretly disliked my 176RWHP Hayabusa.:D







As you can see I haven´t lowered the front yet, and the more I look at it the more I think I will keep it this way. The inverted handlebars makes it look pretty low in front anyway and the hunchback-look it gets with the tank as the highest point isn´t bad.

Back in the shed I took out an old 3 litre fuel tank from an old Brittish 2-stroke engine, I found it years ago on a local scrap yard and knew that some day it will come to good use.



Almost every Triumph bobber has the oil tank fitted sideways under the seat, I considered this first but dislike that I will have to remove the seat to check the oil level. A loose drivechain might also wear a hole in the tank if it cannot be mounted high enough so I found an alternative place to fit the tank.



A pair of leather straps and a sturdy mount hidden behind the tank gives it a nice vintage look, I haven´t decided whether I should paint the tank black or leave it as it is yet.



This is how far I have come since I bought the bike a couple of months ago, right now I am waiting for a Sparx module and some other bits and pieces for the ignition from Lowbrowcustoms.



Thanks for giving me the inspiration to start this build and tonnes of advice in the various threads here!:)

Best regards //Anders Johansson - Sweden
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Damn fine work there Anders, but before you get to far,,, please read the stickys & do an Introduction before everyone flames you for breakin the rules. We like to know a bit of your history & experience, as it is valuable to all!!!
Cheers & Welcome
Thanks for the advice, I honestly thought I had made an introduction when I signed up but since my post count is 1 I must have forgot to post it or something. Will get to it immediately!

Edit: Introduction written and stickys read!:)
great start stance looks good also and I like how you mounted your oil tank, keep us posted on your progress
Good looking start, i am on the fence about the oil tank, but we'll wait and seen.

Thanks for the advice, I honestly thought I had made an introduction when I signed up but since my post count is 1 I must have forgot to post it or something. Will get to it immediately!

Edit: Introduction written and stickys read!:)
These are the people we like around here; he even read the stickys
looking really good so far!

like the idea with the strapped-down tank - looking forward to the further progress

keep us posted!
Thanks guys, this build is on a quite short budget since I am building a land speed bike which absorbs most of my workshop fundings so the goal for this winter is to make it road worthy and completely rewire the bike with new coils, point breakers, Sparx etc.

Later I will probably get a Boyer electronic ignition for it, I absolutely hate everything electric so I figure the better the ignition is the less I will have to worry about it.:)

The same goes for the appearance, I won´t worry about any detail flaws at this point but live with them until next winter when I should have a pretty clear view on what I want to keep and what I need to change.

The bike will never see any powder coating or shiny paint, it will be a good weather ride which I will wash off with the garden hose when it gets too dirty from the gravel roads around here. Keeping a perfect polish on everything would sort of ruin the whole idea with a bike like this in my mind.

Cheers!
/Anders
Damn Anders that is looking pretty good. I wish I had thought of using snowmachine bars. I guess I need to start hitting Craigslist for cheap pieces.

Dawg
Leave the ride height like it is, That way you can go through curves without scraping to bad,
That is true, another reason to stay clear of the front forks.

Damn Anders that is looking pretty good. I wish I had thought of using snowmachine bars. I guess I need to start hitting Craigslist for cheap pieces.

Dawg
Thanks! I guess many motorcycle bars would have fitted as well after some tuning, it just so happened that I had the sled bars hanging on the wall so I figured I´ll save me a few bucks by using them.
I'm not too fond of the low oil tank placement, as far as function goes.
I'm not too fond of the low oil tank placement, as far as function goes.
Why not? It is still way above the pump level so I see no reason why it shouldn´t work.
Nice hardtailing, sure one of the kind oiltank placement:) Keep the good work up!
Why not? It is still way above the pump level so I see no reason why it shouldn´t work.
i like the design of the oil tank too but even though it will function in that location, imho and pardon my french, it looks like ass in that position.
while i'm all for pushing the design envelope and wait with baited breath for the first "it's his fuking bike to do with as he pleases" reply here, you did ask for comments on your build and that's mine ;-)
Cool oil tank find there. Bike looks great so far. Welcome to the board even though I should have posted that in the into section.
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Nice hardtailing, sure one of the kind oiltank placement:) Keep the good work up!
i like the design of the oil tank too but even though it will function in that location, imho and pardon my french, it looks like ass in that position.
while i'm all for pushing the design envelope and wait with baited breath for the first "it's his fuking bike to do with as he pleases" reply here, you did ask for comments on your build and that's mine ;-)
One of a kind placement it sure is, nothing is set in stone as far as the placement is concerned but I think it looks better there than under the seat so its a keeper for now. I appreciate any comments about it, good or bad. :)

Cool oil tank find there. Bike looks great so far. Welcome to the board even though I should have posted that in the into section.
Thanks!

I got the set of 3" springs I ordered for the seat last week so tonight I spent a couple of hours fitting them. A pair of lower spring weld mounts were cut out of round stock in the mill.



After that I turned the end down in the lathe and threaded it 5/16-24 UNF, in Sweden we have the metric system so it is a pain in the ass to find any UNC/UNF assortment of bolts and nuts around here but I will have to live with that since I don´t want to mix in yet another thread standard in the Whitworth/UNC/UNF mess...:rolleyes:



After some shaping up on the belt sander I had two mounts ready to be welded to the rear frame.



Here they are tigwelded to the frame.



After that I measured out where the holes in the seat would be, drilled them and welded in a pair of 12.9 bolts that had got their heads turned down in the lathe so I won´t feel them through the padding on the seat.



This is what it turned out like, I have seen bikes with the springs the other way around (loop pointing backwards) but it looked like shit when I tried it so I´ll keep them like this no matter if it is right or not.:)



The next step will be to drill some holes around the seat edge, sand blast the seat, give it some paint and start dressing it. I will only put on a thin 10mm layer of foam padding since I am satisfied with the ride height as it is.



Cheers!
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Why not? It is still way above the pump level so I see no reason why it shouldn´t work.
I'd like to see the routing of the lines.
I love the oil tank my friend. Good build goin on.
I'd like to see the routing of the lines.
Aha. Well I need one outlet and one return line on the bottom and a vent on top, that shouldn´t be overly hard to fit.

Since we are at it, there is one thing about the oil tank design I have a hard time getting my head around, namely the need for an internal oil return tube that routes the hot return oil to the top of the tank.

The reason for this tube compared to just a plain return nipple in the bottom of the tank similar to the feed line is said to be to avoid the pressure head of the oil inside the tank, but that doesen´t really compute in my mind. If there is a 1cm2 hole in the bottom of the tank the pressure head will be just the same whether there is a thin tube with 1cm2 cross section area or an ocean worth of oil the next 20cm above the hole.

Another reason for the internal tube is to get the hotter return oil as far away from the feed line as possible, that sound a bit logical to me at least.

Cheers!
There was an external automotive oil filter on the return line when I bought it so I´ll use that one, figured I won´t need the intank-screen filter then.
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