Honda-SOHC

I used a vorlux kit on a Kohler lawnmower engine last summer, only issue, if you dont centre punch the insert or similar to retain it the insert comes out on the plug - mildly annoying if you aren't paying attention.  Actually came with 4 inserts of varying length so potential  for 4 plug threads repaired depending on length required. Otherwise a nice quick cheap and easy repair.

I've had top boxes or racks on most of my cb550 bikes. No idea of who made them, I think most were universal, one did cause problems with the shock absorbers as it was on the rear shock mount bolts and contacted the top of the shock which  was fine in most use but ag some point I geuss the bike was heavily loaded on a rough road and the shock wasn't able to pivot I geuss - anyhow I did notice bent damper rods and leaking rear shocks after  a few years. Only them that I really looked closely at the fitting arrangements- the bike had come ready fitted with top box and crash bars, chrome, gone rusty and painted gold - so were the spokes and rims -  That was a classy looking bike! Worth the £220 I paid though, leaked oil, didn't like to start if hot and when I investigated the oil leak I found it had no top rings in the pistons and a chewed up head.

I have a set of S&b ( similar to k&n ) conical filters with chrome end caps, I had them fitted to my 500/4 for a few weeks, bloody awful things, fit fine etc, but, outside pair get damp and the bike then runs rough, even worse in snow and ice. Not sure where they are exactly now, handy to bench test an engine but truly a pain in the backside to live with. Also a job and a half to get jetting right. Best system I have had was a stock setup right back to the filter box, then a genuine K&n filter  that is about the same size as the stock filter box. That released a few more horses, though I suspect it was rejetted to suit and ran a very free flowing exhaust.

I assume it is what reduces the speed, probably possible to bypass the switch and run direct but very fast or by a new board. I think the board may be replaceable for not a lot - if it's what I think it is its less than a fiver, but not had mine appart to look. I know the led worklamp I had from there the board packed up, a generic replacement was 80p delivered, a few days of solder and a £15 work light was saved from landfill.

I just use Lidl  /  parkside drillbits most of the time, if they snap I top us using cheap drills off Ebay, I think it was about £9 for 99 drillbits, lots of the small sizes, less as you go up. I was using one of these cheapie to centre bore stel bar on the lathe, managed about 1.5 metres in total before sharpening was needed. I often find drills are not properly sharp when new and need a tickle, and the wings also chip easily on rounded Phillip's screws until they are properly eaten into by the drillbit, I go for a 7 or 8mm drillbit to start off taking the heads off m6 panhead or Allen screws if they round. If a good lot of swarf isn't spoiling off the drillbit, stop and sharpen, never persist as a drillbit, once it's got hot needs s lot of effort to sharpen and get back to properly tempered steel that will hold an edge. My pet hate is blunt drillbits, spent 18 months in an engineering firm where no one sharpened drillbits and the pedestal grinder was miles from the drill, I have bench grinders 2 foot from the pillar drill, running several grits of stone right down to a really fine, water cooled whitestone. A shap drillbit should have the head off a m6 panhead in 30 seconds, using a basic cordless drill.
After practice I now tend to be able to fairly consistently drill bolts out well enough to pull the thread if the bolt out like a helicoil gone wrong leaving the trapped hole intact.

If you can remove the valve cap and see if it comes out freely that might be a good first indication. Depends on having the right tool to get the collects out though. Possible without correct tools but can be a fight.

My 500/4 came with black and white plate, never changed it, never attracted comment. Did get stopped by s traffic cop once and she was busy filling out her paperwork, looked at it and was about to tick the box saying no tax or mot because she thought it was too old to need it - back in 05 this was. I was quick to say, no its taxed and tested, look at the sidecar window, theres s disk on clear display. Very noticeable that police dont like looking closely at old vehicles, too many age related exemptions for them to want to get involved in inspecting them.

One of mine gave a clear sighn this was the issue, the tappet and top of valve both went blue with heat discoloration. To ride it was ok for maybe a mile, then rough as a badgers rear end. Was mostly ok again if allowed to cool.  That engine still sat in a corner someplace. If that's the problem I geuus the effected valve and guide need replacement. Should be easy enough to spot by rolling the valve stem along glass and testing if a feeler gauge can slip under it at various points as its rolled. Is it viable to ream a valve stem rather than replace and then ream the new one? Probably not.

Guy I bought my first 550/4 from said he had on some bikes stereightened valves that had bent when camchains had let go and got the bikes going again, but given the dammage a dropped valve can do it's a step too far even for me.