Found my next BIG project...

boomshakalaka

Over 1,000 Posts
thats really cool that you can rebuild the top end while the motor is in the bike. Also cool that you can just use an engine crane to lift the thing out the bike if you need to. Sure these motors are relatively light, but its still a bitch wrestling that thing out of the frame by hand.
 

Swagger

Putting boot to ass since 1967!
I wouldn't bother trying to find measurements for a couple reasons. First off, they were all hand made so that in itself injects a bit of variation. BUT...the main reason is that the Drixton frames were built for vertical twins so if you're looking to build one for your 550 (L4) you're in uncharted territory as far as I know. Not that it cant' be done...I think it can be, but your numbers are going to ALL be different from an actual Drixton frame (tolerance not withstanding).

If you're going to build your own frame then you'll need a good solid frame fixture to build from. As for geometry...that depends on your choices, not the least of which will be the suspension components you want. Are you going to try for a true retro build with old 35mm forks and vertical dual shocks out back? USDs and monoshock?
If you are building truly old school, mimic the stock 550 geometry. With upgraded bits they handle pretty well.
If you're giving it a little newer flavor...pick your favorite sportbike and steal the geometry as suits.

in the end though...you're going to have to forge your own path mate....
 

Bobdot

Coast to Coast
Great insight Swagger, I knew I loved this site for a reason... Very good points, I decided today that I am going to use a 500 Twin and bore it out a little. It'll be more compact, lighter, and much easier to work on and tune, which is why I've always loved twins in the first place. I like the thought of a mono in the back but I'm more into the old school, so dual shocks out back, attached to a boxed out swingarm.

As for the front suspension, I'm still looking into possibilities, I do like the inverted forks...

So my real first step is now to locate a donor 500 frame and motor, just dont tell the woman.
 

Bobdot

Coast to Coast
ah, also came accross this pic for good frame building reference:


thats for an XS650 engine...

and this for general change-you-pants-ness:



Trying to decide between a dual front disks or dual drums. Both look awesome but there's something about the giant dual drums with those super short spokes that make me want to do bad things (see: 1st page of this thread, fourth pic down). Anyone know what bike I could steal dual drums off of?? If I do go drum, I would stick with traditional 35mm forks.
 

Bobdot

Coast to Coast
holy monkey...


my guess is that is part of an oil cooler attached to the right side crankcase cover?
 

Tim

Administrator
Staff member
Dual drums are hard to come by, unless you have the $ to fork over.

I think the cheapest option (and the one I went with) is to find one from a Suzuki GT750 or GT550 (same hub).

They typically sell for about $300-$400 on eBay in used condition. New pads will run $100 a set, cables $40, dual-pull lever $50+... you get the idea. Worth it in my opinion. It just adds value to the bike - like doing a reno on your kitchen or bathroom - it's an investment ;)

You can buy new from Grimeca for $800 or so. You want the 4-leading shoe (4LS) for best stopping power. My GT750 hub is pretty good. Not as good as my BMW's single disc, and nowhere near anything modern, but they can be made to stop really well with Ferodo shoe's and proper tuning.

My front wheel - 1972 GT750 front hub, Buchanan stainless spokes, XS650 shouldered alloy 18" rear rim, 100/90 Avon Roadrider:

 

Bobdot

Coast to Coast
Tim - I love it, thanks for the info, I'll be adding that to the list, and shouldered rims are a must. Are those gt750 forks as well?
 

Drewski

"Invictus Maneo" - I remain unvanquished!
DTT SUPPORTER
DTT BOTM WINNER
I'd say start with a quality coffee maker. You're gonna go through MANY cups of java figuring this one!! ;D

Fun times!! 8) 8)
 

Bobdot

Coast to Coast
Yup, it will be a challenge, thats what I like about it.

So I came accross some shouldered rims on eBay today for a good price. 19" front, 18" rear. Is there any dramatic signifigance handling-wise between a 19" and a 18" rim on the front? I run a 19" on my CB350 now and love the look of it, but for the Drixton I'm really trying to get the best performance out of it. Thoughts?

bob.
 

boingk

Standard gearhead.
You'll notice the difference between the two. I've ridden a few bikes, one of them being my GS850 which has a 19" front wheel. Let me tell you, its as stable as a rock but it doesn't want to turn in or change direction that fast. Its worlds apart from my 17" front wheeled rides, but makes for a nice cruising bike. Not saying you can't ride it hard, but there are limitations.

I'd opt for 18" wheels, my man.

- boingk
 

chrisf

Over 1,000 Posts
Bobdot said:
ah, also came accross this pic for good frame building reference:


thats for an XS650 engine...

Since you plan to model this up in SW, I recommend running FEA on the frame. Looking at it, it seems pre stressed in the worse possible location. I know they run a neck support to the engine, but I don't think that's going to do much. If you happen to hit an bump that bottoms out the forks, the frame may just buckle. Remember, straight tubes will be stronger than bent.

I think the most difficult part of the project is determining the geometry AND building the jig. The pic above does give you a pretty good starting point though. The critical part is making it rigid enough to withstand the torque of the metal cooling.

For brakes, I would definitely do disks over drums.
 

phrige

I'm a pig, I'm A dog so exuse me if I drool.
Love that video, Its great to see his perspective like that. Like how many times he's looking side to side to side. ;)

Good luck on the bike! I love the look of these drixton bikes. Def ganna be following this thread closely.
 

pacomotorstuff

Coast to Coast
Figure out what hubs you're going to use before you buy the rims - the spoke angle out of the rims is different for drum versus disk hub, but I think you already knew that, right?
For my tuppence worth, go with the Suzuki 4LS front brake - looks really period-correct even though it is blessedly heavy. A good machinist can get a few pounds off the assembly without sacrificing strength, though.
Check with Walridge Motors (Mike Partridge); he used to carry a spoke kit for the Suzuki 4LS brake / 18 inch rim combo, but don't know if he still lists it or not. I think he had 2 versions - one cad plated (which is what I used, it being a race bike and all) and one stainless for you guys with deep pockets.
Don't know what rear hub you're thinking about using, but the CB450/500 twins' rear hub is remarkably heavy, so maybe something else?
As far as the tank and seat, I believe replicas are available from a number of suppliers, so unless you have a tremendous urge to fab it yourself, might be an easier way to do it?
Have fun with your project. The Drixtons were a fabulous bike back in the day and there are a bunch of replicas being raced today.
Pat
 

VonYinzer

Over 10,000 Posts
Haha... Bob has been MIA from the forum for a few years. He and the Mrs had a kid, he got a new job, etc... This all does remind me that it's been too long since I've checked in w the guy though. A phone call is in order.

Sent from my SM-G920P using Tapatalk
 

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