Down under, an idiot and a 400F

Also kicked off my seat build today. Always preferred steel to fibreglass but didn't know how I was going to do the bump stop.

Decided to just start and see where it took me. Used the upside down frame to trace the seat pan out. Cut it out with the angle grinder:



Plan is to weld these bits together at the end with some bracing behind. Next up I needed to bend the sides down, a tough job as I could only do it by hand and in the end I used the angle grinder to help start the process. Here it is post bending with extra long sides so I can trim them back:



On the bike:



Next up was cutting the seat pan back further to bend up the rear of the seat area, the plan was to curve it up like Benjie's seats so I used my rear hub to get the curve:



Next up was cutting the bent up rear seat section, I used my grinders disc as it was almost the perfect size:



A nice line from the tank through to the bump stop:



Afterwards I cut the first of the segments, made an error here as I really should have made both sides out of 1 piece to minimize the welds, might redo it tomorrow. It needs trimming too as its a bit too wide still:









This first section will probably get cut by about half so I have enough room on the end to get a nice rounded end piece. Then need to French in a rear light.

Great work man! like it!

Bit more seat work done today. First question was how much of the frame rails do I want to expose. I cut the edge to 1" first as I could always cut again, I do like this look though so it will probably stay at 1":



Just the slightest amount of frame visible and it gives a nice sharp edge to the seat area. Test fit with knee scoops to check the lower lines:



Everything so far:













I suspect the rear bump is a little on the tall side. It's quite large and seems a little goofy. I was playing with the idea of trimming approx 15mm off the height as most nice looking bumps seem to be slightly shorter than the top of the tank (Bonita Applebum and GoingsMoto's to be precise). Anyone got some inputs? Estimated new line:



New shape:



Old lines:



All the electricals and battery will be going in the bump but I plan on getting an antigravity battery so I don't need a huge space.

So I went a stage further this evening and mocked up the rear section in cardboard and masking tape to see exactly what each of the options above looked like. Needless to say I think it is waaay to big in its current form, it looks like the right height is shaving a good 30-40mm off the height as it is now. Took some photo's and did some jigging in Photoshop to see what the end result would look like:



I think the smaller version looks much better. What are people's thoughts? Is there a standard height for a bump seat? I feel I could even shave a bit more height off.

What about my seat area, is it too long/ok?

That it was too high was my initial thoughts, then I read that you thought it matched the tank so I let it go. your "after" looks better to me, the seat height will change when you add the foam, might be about right.

Swivel, thanks for the smack down, I had to get a few tissues to wipe the tears as I read.

I am pretty comfortable with most of the choices I have made but was wondering what peoples thoughts were on 2 comments you made.

1. Are there genuine concerns about the top triple? If there are I will look at a proper flat aftermarket one.

2. Are the Alu frame braces an issue? Stock steel width is about 1.2mm and the Alu is 3mm. Again happy to use the stock ones and get them powdered with the frame, but was going to polish these. Don't want the motor to move though.

I've made heaps of chain gaurds out of aluminium. No problem there - and better than plastic IMO.

OK now it's getting confusing. I cannot see the issue with an Al chain guard, are you being critical of everything just for the sake of it?

The top triple I am happy to know the risks, but I think you might be being a little critical when you question my choice of material for a chain guard.

Can you keep your feedback about genuine concerns? That way I can ensure I focus on addressing those.

Neevo, check this out.
http://www.denoonsp.com/user/image/cb400f-stress-analysis.pdf
There is virtually no movement around engine cradle, it's all on steering head top tube
Thanks to Rick for the analysis.
http://www.denoonsp.com/user/image/cb400f-stress-analysis.pdf
He has a LOT of information on 400f

Maybe take this conversation somewhere else. Keen to keep this thread on track.

neevo said:

Maybe take this conversation somewhere else. Keen to keep this thread on track.

Click to expand...

Done and , done, I removed the posts as irrelevant but left the Denoon one with links

That top triple will be fine as long as it's welded up to fill the holes. In reality the top triple doesn't take a lot of force and doesn't need to be anywhere near as thick and heavy as people think. They do need to be 'complete" though. By that I mean that they have to be ribbed to have strength so if a hole cuts through a rib, the part is weaker than stock.

Check out a TZ250 top clamp - it's more air than metal, but the metal is in the right places. If you want the triples to be stiffer, replace the lower one - that's the one that takes most of the forces in normal riding situations.

And plastic is fine for a chain guard.

No champions told me I was wonderful, but I did stay at a Holiday In Express last night..................

crazypj said:

Done and , done, I removed the posts as irrelevant but left the Denoon one with links

Click to expand...

Thanks PJ, amazing how a cat amongst the pigeons can stir things up.

PJ? I have been using this guide to see what tyres can go on different rims.

http://www.dropbears.com/u/utilities/tyrerim.htm

I am looking at 90x90 for the front and 120x80 for the rear, does it matter what rims I put these on?

Buchanans doesn't do a WM4 and I would have liked to put the rubber on WM3 and WM4, could I use WM3 and WM4.5 without adverse affects?

I probably wouldn't have that much size difference front to rear.
With WM3 (2.15") & WM4.5,(2.75") go 100 f and 120 r.
I have no idea how it will handle though ;D

Thanks PJ. It's a big thing buying the rims, they are incredibly expensive with anodizing and SS spokes. Don't want to bugger it up.

You should try and ping the 400f guys about rim and tire sizes. (yahoo group - I was one of the earlier guys on that group) Or even 350 twin guys. It's a similar chassis.

http://www.eurospares.com/tires.htm

You can go WM3 front and back (and save some $$). For tires, you can go 90 and 110. It's better to go with a size that handles better rather than just go as big as possible for cosmetic or appearance reasons. I guess it depends what you want to do. If you want to go railing around corners, rim and tire sizes choices will be more critical. Going too big will affect handling. Just MHO.

I've built a few wheels in my past. Whenever I did, I always searched ebay, cl, etc for used ones. Borrani, Akront, DID all made wm3 alloy rims. Heck, they even came stock on early XS650 rear. I've never bought a new one. Get a used one and polish it or have it polished. I always went with WM3 rims since that size is so plentiful.

I did buy new stainless spokes only because they were thicker than stock. If going with the old ones, just blast them and get them zinc plated. Honda went with bigger gauge spokes on bigger bikes. So, if the length is correct, you can use spokes from a 550, 750, etc.

I'm not sure if I missed it or not, but did you install tapered roller bearings for the steering stem and bronze bushings in the swingarm? These should be essential since they are the main pivot points from the frame front and rear.

Eric

We already went through the rim sizes
I recommended getting 36 hole WM3 front and back then fitting 90/90 and 110/ (80~90)
They are available much cheaper than Buchanan prices
Buchanan's will make sure everything matches if you buy from hem though, may have to do a few mods if getting mismatched parts, plus, remember, it all has to be shipped to Oz.
400F frame is a lot more like CB360 frame than 350 twin
Did you get oil pump yet?
I'll pull the one off 'ded' CB350F and check it in next few days

Eric the bike is getting taper bearings and bronze swingarm bushes.

PJ, will probably get them off Buchanans as they know their stuff and the quality seems top notch.

No oil pump yet, funds are very low and I bought some carbs off eBay as I didn't want to miss out on a set. Not many come up and the same seller had another set that hadn't been cleaned that I snapped up.

Trying to accumulate parts now so that I can build in 1 go rather than tiny bits here and there.

Just fabricating stuff at the moment like my seat and tank. Will be welding up soon, then need to get forks fixed and cam issue sorted.