Honda-SOHC

David Silver sells those, should be easy to find as they are used on quite a few bikes. 77204-292-000

The round ones are 77206-329-000 and the oblong one at the back is 77204-312-000. Just in case you need those as well.

Having split my 400 crank case 3 times I became more skilled at applying a nice thin layer of Hondabond each time.
Following advice from Julie the secret appears to be - don't squeeze  it onto the crankcase directly out of the tube - obviously apply to the inverted upper case only
I wore surgical type gloves - applied a small amount less than half an inch directly onto my fore finger then spread it onto the crankcase starting at one end repeating once the finger full had spread as far as it could. Repeat until all applied. I actually put the Hondabond on my left  finger then dipped my right fore finger and spread it nice and thinly.I then removed any excess that had spilled over the inside edges. It spreads so thin I found using this method. Sorry if I'm being over descriptive & stating the obvious.

Then assembled making sure I bolted up in correct sequence as per manual keeping my eye on the primary drive assembly etc.

After perfecting this method Ted found that he was quite proficient at doing Prostate exams and now works for the NHS as a freelance poker.

400, 500 or 750.

400 can be a little small if you're of a big build but parts are easier to get than any other model.

500, same as the 550 but easier to get parts for, exhausts for instance are available whereas the 550F ones aren't. Not many models of them so easy to work out what's correct for the model.

750, reasonably easy to get parts for, Yamiya do quite a few parts. However the differences between each model can get a little confusing for an original restoration, the early ones are more valuable but then your initial price goes up as well.

I'd ride the 550 and see if it suits you, if the power is ok then maybe think of a 500, if you think smaller and buzzier is ok go for 400, if you want bigger and slightly more powerful go for 750 but be aware they don't handle as well due to the extra weight.

Do you strain the waste veg oil or just burnt it with all the impurities in it?

I watched that Vid and it looked fine. However you then start to read some of the comments and things start getting complicated, stuff like routing the exhaust pipe wrong, drawing outside air in as opposed to using inside air. After a bit my head started to throb trying to decipher hat exactly they were concerned about.

It also say £120 but buggered if I can find one for that price in the UK. I'd love to have a toasty garage so this looks ideal, I'd also like to know where he's buying red diesel, it's hard to find a supplier due to changes in the law. 

I’ve had a few 4 into 1 systems Ted, a Piper system that howled like a Banshee having a prostate exam, had to remove it to change the oil filter though and it rusted for fun. A Yoshimura that was much quieter until you wound it up but it didn’t stop you working on the engine etc.

For best performance though the OE system takes some beating, sure the Yoshi performed better but only at the top end of the rev range, it lagged at mid range though, the Piper sounded better but it also had a hole in mid range, the 4 into 4 system looks awesome, it performs excellently and it just suits the look of the bike better.

For me it’s the exhausts that make the 500 so appealing, there’s just something about them that floats my boat in a BIG way.

Don't forget you need to space out the caliper bolt on the new side Roo, if you don't the arm sits at an angle and the pads wear funny. It's because the new caliper mount sits ON the mudguard brace whereas the old side it sits under the brace, you also need to ensure the arm sits directly above the disc like the other side does. IIRC you need some washers between the top mount and the brace and a thicker one on the bottom mount bolt. I seem to recall I put the new caliper onto the new arm complete with pads, pushed it onto the rear of the disc not the front as that movable and left the bolts out, swung the arm until it was level with the mounting bolts and measured the gap. I ended up welding the washers to the brace and then having it chromed so I wouldn't lose them if I dismantled the front end.