Honda-SOHC

I wonder if the 13mm (?) AF bolt heads are slightly pushing the chrome ring off centre, perhaps a reduced outer diameter washer underneath would allow enough play to allow better centreing?

Have a look at Paul Goffs emporium: http://www.norbsa02.freeuk.com/index.htm, I've used stuff from him on a couple of my bikes and my experience was fine.

Wow Alan, that's quite something for a spot of tinkering, well done.

I posted some time ago about fitting ceramic pads to try and fix the well known squealing problem, and also to see it they helped with the wooden feel of the front brake. 150 miles (none in the rain) and I'm pleased to report that there are still no squeals, the brake feel is rather better and there's more retardation. Not tried in the wet yet. Pads are SBS 501HF from flea bay. I did also reprofile the brake lever where it presses on the master cylinder piston in order to bring the lever closer to the bars and let me use the stronger parts of my fingers, so the feel thing may be related to that.
Regards,
Arthur.

Hello there.

Put the 400/4 back on the road after winter sleep about a month ago and after dealing with the yearly petrol leaks from the carbs by sternly ignoring them (yes, I drain the fuel when I put it to bed, and it's got a nice set of nurse Julies viton o rings, and I carefully cleaned the float needles and pivots and set the float heights....). After a ride the petrol had cleared and the bike was feeling very nice apart from the very harsh front forks and the dreadfully wooden and squealing front brake. Just for info the bike was entirely overhauled by me 3 years ago. So I had a good look through the stuff on this very useful forum and did the following:

Front forks- changed the oil for 150cc each side of 5W fork oil (was ATF at first fill) that i happened to have around. The result hasn't transformed it to magic carpet status but it's a lot better than it was, the previous post on the forum recommended 7.5W so that may well be better still. For the expense and time taken it was a very worthwhile bit of tinkering.

Front brake- I've tried two previous sets of organic pads from different suppliers and the rest of the front brake set up is new. For both the previous pads squealing starts after about 50 miles and gets more pronounced as time goes on. Cleaning the disc does help for a while. The real problem is the very wooden feel at the lever and the high lever pressures needed to get any realistic retardation. For info I'm used to riding a number of different bikes including pre war machines and I used to have a 400/4 back in the day which was ridden very frequently with a pillion and, apart from the wet, I don't think it was ever this bad. Anyhow, I got hold of a set of SBS 501HF ceramic brake pads from flea bay (Trumpet Tyres) and fitted them. The result after 80 miles is no squeals yet and a rather better retardation. I had a think about the hand lever compared to the span of my fingers, removed the lever and reprofiled the radius where the lever presses on the master cylinder piston, opening the clearance to around 1.5 mm, giving a free play on the lever tip of perhaps 8 to 10mm, rather similar to the clutch when fully warm. This brings the lever a bit closer to the handgrip on first bite and means that I can use more grip more easily. This has improved matters a bit further. Although the woodeness persists it is better and I'm certainly getting better retardation now, much more tolerable. Pads were about £30 including postage so it wasn't the most expensive fix, although it's my third set in 1500 miles! I should also say I haven't tried it in the wet, so be warned. I'll let you know if the squeals stay away.

So thank you to the original contributors on both these issues and I hope that it's useful to get some feedback.

Regards,
Arthur.

First thanks to all contributors and moderators for the help and encouragement that you've wittingly or unwittingly given to me. A great forum in a world of (mostly) dross, well done.
I had one of these back in the day and the Force was strong. So, a 1977 400/4 was purchased a few years ago in substantially complete and original condition. After a while it became clear that not all was well with the engine, it turned out that the detonation problem had done for a couple of piston rings and pistons, and also damaged inside the cylinder head. Rebuilt it was including things like laser welding of the heads to take out the pits, dynamic balance and I couldn't resist a yoshimura 455cc kit either, plus full cosmetics on the rest of the bike. Your various contributions were most useful to me for example at the time Nurse Julie was posting on her rebuild. I only carefully cleaned the carbs as a set, and did go through three iterations of main jets for the Yoshi kit.

Fast forward and after a thousand miles or so I'd had a couple (or 3 or 4) of instances of leaks from the carbs which were down to various things including swelling or shrinking of the O rings- I drain the fuel in winter when I park the bike up. Because I needed to do something else to the bike (don't ask) I thought I'd strip the carbs right down and check and rebuild. I won't tire you all with the four or was it five times that I've fitted and removed the carb bank in the past couple of days or so but I thought I'd give you the condensed tips below. Some of these are borrowed from other contributors. The carb to head rubbers on my bike are still reasonably flexible, the airbox is standard as are the airbox to carb rubbers. The latter have gone a bit floppy over time.

Removal. Put masking tape over frame tubes near airbox on RHS. Remove airbox drain tube from the airbox, the elbow holds it up. Slacken the carb rubber clips. Remove airbox top, air fliter clip
air filter. Slacken the hose clip on the filter box to airbox adaptor. From inside the filter box take out the metal tube then the tapered (conical) rubber, the hose clip and finally the airbox intake rubber adaptor. Remove the airbox out of the RHS of the bike. Remove the throttle cables, pull the drain tubes up and pull the carbs back. Remover the carbs from the RHS of the bike.

Carb rebuild. I wasn't convinced by the DS carb rebuild kits (Keyster?)partly because the float chamber o rings had swelled or shrunk, or both. So I purchased a nice set of Viton rings from Nurse Julie. Quite a few of the o rings on the carbs were in very poor condition. I refitted all new brass ware from the DS kits and used the stainless float pivots, resetting the float heights as required and bench synchronising. I checked that the float valves were working properly by extending the feed pipe and blowing down it operating each float in turn, checking it again by turning the carbs over when the float chambers were on. On the first refit two carbs leaked from the drains. One had a brush hair in the float valve only found after using a magnifying glass, the other no fault found. Next refit all four leak. So I had a good look through the forum. I recovered the OE float valve assemblies from their bags, polished the seats, cleaned the needles carefully (small wear ridges on tips), took out the DS valves and replaced them, resetting the float heights. Interestingly there are some dimensional differences- on the DS kits the needles are longer. Checked valves worked as above. Refit- leaks from 1 and 2! Quick tap with hammer handle on float bowls stopped that. Warmed the bike up and synchronised the carbs with vacuum gauges. A ride of 10 miles or so this morning showed no problems, phew.

Carb refit. Fit the airbox to the carbs on the bench as another contributor said. This showed me that it was impossible to get the intake rubbers to fit if I tried to do it in the bike. Using a sturdy screwdriver and pressing from inside the airbox it is just possible to get a snug fit of all the rubbers. On my bike they are decidedly uncooperative, a smear of engine oil inside was helpful and working along the bank and back again eventually worked with various adjustments to the clips.

Pop a couple of~450mm lenghts of wire between the engine and the swing arm where you want the drain pipes to go. Rub a bit of engine oil on the inside of the head rubbers. Fit the carb assembly from the RHS, keep the intake stubs level with the rubbers. With a bit of fore and aft twisting to start with you need to compress the airbox to get the intake stubs past the rubbers without the stubs popping into the wrong rubber. The stout screwdriver is handy between the frame tube and the airbox for this. Once you're a couple of carbs in from the RHS the process gets a lot easier. Once in the right place push the carbs into the cylinder head rubbers, making sure you don't push the bike off the mainstand. On my bike carb 1 (LHS) goes in first, followed by the rest in a sort of fore and aft rocking motion. Tape two of the drain pipes to one on the wires and carfeully work them through, then repeat with the other pair. Refit the rest of the gubbins, tighten up clips etc.

Phew, hope that's helpful.

Arfa.
 

Not particularly helpful I should say up front but... I've just restored my 400/4 and this included a Yoshi big bore kit, yoshi advise rejetting to suit, but don't suggest how much. I had a look at the this site and the US site, and there was rather more advice on the US one as one would expect with rather more people racing etc. An unscientific review of the advice was that for sea level use an 85 main jet was about right, and all the rest of the carb settings remain as standard. so that's what I've done. I've just given it the first service, bearing in mind I'm up to 7000 rpm steadily, with excursions to 8000, and plugs look to me to be on the slightly rich side, so I'll stick with 85 for present. Otherwise the bike runs really well with clean carburation from tickover upwards.
Main jet really only affects mixture at large throttle openings, so I might suspect that you've got some other thing going on if it won't run at all. Perhaps somebody better versed on here may be able to help?
Arfa.