To correct the rough low/mid range running, I bit the bullet and bought 2 Keyster refurb kits and then pulled the carbs off the bike yet again. When I started this recommissioning I think it took me about 45 mins to get them off but I've now practiced it so much that I reckon I have it down to about 20 minutes!
The kits are actually for the CB360 (250 version was unobtainable), which has a slightly bigger main jet, but when I came to fit them it was the same as was already in the carbs and seemed OK according to the spec in the Haynes manual. As it has been running OK on the main jet, I decided to install the new jet and see what happened.
So, it was a fairly easy process to swap over the bits and then reinstall the carbs - I expected to kick the engine over and it would settle into a nice smooth idle .......
What actually happened was that I kicked it over 3 times and then something went "clunk" and the engine locked up solid! I put everything away and came back to start again another day ....
Once I started pulling things apart, it fairly quickly became obvious what the problem was. A week or so earlier, I had been trying to fix the starter motor, which has never worked since I got it. I removed the motor and fitted new brushes and also noticed that one of the screws holding the magnets in place was missing. I found an appropriate screw and reinstalled but the motor still didn't work. I can only think that the spinning motor against a loose magnet has caused internal damage, so I sourced a working second hand one. However, when I pulled the motor out, I assumed (incorrectly) that the cog the splined end of the motor engages with was retained in place in the engine casing. It wasn't and had dropped down with the chain that engages with the crankshaft. When I tried to kick it over, the chain had wrapped around the alternator rotor and jammed. No damage was done and all was soon back in order.
Having sorted that out I again kicked the engine over and it did indeed settle into a nice smooth idle.
So I went out for a spin and it felt great, accelerating strongly right through the rev range. At that point I got cocky and decided to head out further afield - only about 10 miles away across country lanes, but as I slowed down into a village where I planned a stop for a pot of tea, she started running roughly at low revs again. I got to the cafe and sputtered to a stop. Being an eternal optomist, I thought that things might be OK once she'd cooled down a bit. I hoped so, as I had no tools with me!
Of course once the tea was downed, things were no better because motorbikes don't generally fix themselves, and whatever I did I just couldn't get her running again. Shamefully, I had to call the recovery service to take me home.
I felt like I'd kind of reached the level of my incompetence now and was all for getting a proper mechanic to look at it, but once I'd calmed down a bit I thought that all they would do was strip the carbs and check all the settings and ditto with the ignition side, so why didn't I do that one more time first? As an aside, I've found that retirement has changed my approach to stuff like this - when I had a very limited amount of "play time" at weekends, I would rush and get agitated but now I kind of think "oh well, let's try again!"
I pulled the carbs yet again and then very carefully set the float heights. One of them wasn't really quite engaging properly with the new float valve and I think as a result was flooding at low revs. I reassembled everything and also balanced the carbs again, just to be sure. I also spent a couple of hours checking all the ignition side and tappets etc - all was good, which it should have been as I'd only done less than 100 miles since setting it all up. I also installed the replacement starter motor at this point. (She starts so much better off the electric start than with the kick start - it obviously gives the engine a much better initial spin than you can manage with a kick.)
And she fired up and ran really nicely. But, after a short ride, started overflowing fuel from the RH carb again! I'm managing to ride around that issue at the moment - it's OK above idle and so I just switch the fuel tap to off as I approach a red light etc, and then turn it back on as I set off. Everything seems to be running fine like that (fingers crossed) and I managed a really nice 50 mile bimble around the Wirral Peninsula that way. I made sure that I had my tools with me this time!
Parkgate
West Kirby
I have seen a couple of articles now saying that new float valves can take a little bedding in, so I'm hoping it's that, but I also have one last thing to do to try and sort this properly (because, as I said earlier, I'm old and wise enough to know that motorbikes rarely fix themselves.)
The inside of the tank on the bike is pretty good and quite rust free. The fuel flowing from it looks clear, but I am aware that there could be very small bits of rust or other debris still getting through and that could be causing the valve to stick open. So I have bought a couple of fuel filters and I'll pull the carbs again, clean the float valves meticulously and then install the filters. I may also just tweak the floats by 1mm to try and put a bit more pressure on the closing action. Watch this space....
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