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CB750 Barn find project - First Timer
Underdog1:
Finally going to have some fettling time today so going to sort the petcock and carbs.
Running on the rich side so need to raise the needle clip either 1 or 2 notches. How long do I need to run the bike for before looking at plug colour again to see if I need to move needle position again? And do I need to clean up the plugs if they’re already a bit blackened from rich running or does this get burnt off?
Underdog1:
Okay so pulled the carbs off and raised the needle clips one notch to lean out the mix a bit, I’m at one clip from the top so still got some further adjustment if needed. Checked the floats and they are all bang on 26mm and operate smoothly. I’ve replaced the float valves with the original ones incase the cruzin image ones aren’t sealing properly. The aftermarket ones go into a point whilst the original ones are blunted off at the tip. I also noticed that the air mixture screws were no longer at the 1 turn out, on was at about 3 turns out.. no idea how these have worked themselves out but put them back to 1 turn.
Got them back on the bike and synced with a carbtune pro which was pretty easy but then noticed I had a significant leak around the front sprocket cover. Whipped the sprocket off and seen this
The drive seal wasn’t sitting flat as it should and was leaking at the bottom where it protruded out slightly. Unsure whether it wasn’t lined up correctly when I closed the cases or not but it’s not leaked for the first 50 miles until now. I even put a smear of hondabond on it as recommended in hondamans book so perhaps this held back the oil until now.
Rightly or wrongly I carefully tapped it back in flush and it doesn’t seem to leak any more. Am unable to ride as the seats with the upholsterer but fingers crossed it’s fine
Still getting a bit out the overflows so don’t think swapping the float valves has done anything. I’ve not got any sort of washer beneath the float valve seat and carb body, none was supplied in the rebuild kit and none were on it when I stripped them.. have seen in some pictures that some sort of washer is present - did this appear on certain years only or am I missing them possibly?
Laverda Dave:
I feel your pain underdog :(. I suffered a similar fate with my CB250RSA drive oil seal. It was fine for 10 miles and then just let go in the same way dumping oil all over the road. I had to split the cases to replace the seal. Hopefully yours will be OK, good luck.
Trigger:
Do your air screws have springs ? They should not move ;)
Underdog1:
--- Quote from: Laverda120 on September 09, 2018, 08:19:25 PM ---I feel your pain underdog :(. I suffered a similar fate with my CB250RSA drive oil seal. It was fine for 10 miles and then just let go in the same way dumping oil all over the road. I had to split the cases to replace the seal. Hopefully yours will be OK, good luck.
--- End quote ---
Yeah time will tell, it’s a new seal so no idea why it’s happened.
--- Quote from: Trigger on September 09, 2018, 08:24:28 PM ---Do your air screws have springs ? They should not move ;)
--- End quote ---
Yeah they do, it’s possible I had a brain fart at some point but I’ll keep an eye on them to see if they move at all in the future
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