Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: McCabe-Thiele (Ted) on June 05, 2024, 05:17:50 PM
-
After cleaning out number one carburettor I now have the 500 idling quite smoothly so tomorrow I plan to check & adjust the timing dynamically as the engine is happy to idle at 1000-1200 rpm.
The exhaust on number one cylinder is getting hot although it's clearly not as hot as the other three cylinders at the moment, a big improvement on yesterday.
I have all four side screws set at 1.5 turns out at the moment. I will check the valve clearances again as well. Is it advantageous to reduce the side screws to 1.0 turns first as a starting point?
The float levels were spot on before I dismantled the carbs and are still all equal at the correct setting.
My Haynes Manual talks about having the petrol tank raised to a height of 20" above normal - is this important when setting up the carbs?
I took quite a lot of trouble getting my bench sync as accurate as possible - firstly do the four side screws affect the vacuum reading?
Should I worry at this stage about number one cylinder being cooler than the other three?
-
[...]
I have all four side screws set at 1.5 turns out at the moment. [...] Is it advantageous to reduce the side screws to 1.0 turns first as a starting point? [...]
Try to see the CB500 Four slow jets as acceleration or rather auxiliary jets. Driveability is paramount, so the airscrews should be set thus that you have the smoothest acceleration.
[...] - firstly do the four side screws affect the vacuum reading?[...]
Not in my experience. Out of curiosity I've tried to affect the sync by adjusting the airscrews a couple of times in the past. Never noticed a difference. This may be a different case with twins. Realise that all your four cylinders share one and the same crank, so the piston of whatever cylinder is forced to go down by its three collegues and so will create underpressure anway.
-
Start with all 4 at 1.5 turns out Ted. It's always a good starting point.
-
I found the engine performed differently under load than sat on the stand. Adjusted my screws to get smooth pick up from idle by experimental stop starting adjusting on the road. Bike is running a treat now smoother and smoother as it runs in. Pulls lovely from low revs in tall gears and don’t really need to go over 5 k to make very reasonable progress. I did have to reduce the pilot jet on number 1 to stop it running cooler.
-
That's interesting David - is the Pilot Jet the one that screws into the bottom of the carb inside the bowl? I know mine were all the same number 40 from memory - I did not record the number but all were definitely the same number?
I had to replace one of my needles as it was badly bent at the tip so I did wonder if that was the cause. I will check my build log to see if it was number one.
Updated
I checked my build log - I fitted a set of DS needles & Emulsion tubes - I can't remeber why I fitted new tubes??