SOHC.co.uk Forums > CB750

750 F2 carb problem?

(1/2) > >>

sonsman:
Seventy five miles into a ninety mile ride my F2 went on to three cylinders. Got home and number one spark plug was oily but sparking nicely and then realised that the carb on that cylinder was piddling petrol from the overflow. I did the usual thwack to the carb body but no joy. I am assuming it will be carbs off and a clean out but before I do that anybody else had a similar problem and what was the outcome?

royhall:
Had a lot of these problems over the years. Has the bike been standing with fuel in the carbs. If so it will be a carb strip and clean, be careful if you change the float valves as some of the pattern parts are rubbish. Another common problem is dirt in the fuel from deposits in the tank. Best thing to try first is an inline fuel filter in the fuel delivery pipe. Put that in then drain the carbs and let some clean fuel run through. That has fixed a few of these problems without the need to remove the carbs. Good luck.

Sent from my Nexus 6 using Tapatalk

neat street:
Hi, Could be a couple of things, but either way, I would suggest carbs off. the float needle could have some goo stopping it from sealing when the float is up, damaged float needle or seat, float not adjusted correctly (on a CB750F1 it should be at 26mm). These would be my first checks. you may be able to just take of the bowl and let the fuel run, gently lift the float and see if it cuts off? if not then check the seat or crud around the float needle/seat. if it does seal, then possibly suspect float height (could also be a small hole or crack in the float so not working as it should?
I hope this helps?
John

royhall:
It's an F2 so will be hard to get the bowl off without taking the carbs off. Not likely to be goo as you were okay for 70 miles, I would try the fuel filter first as resealing the carbs on old rubbers is not easy and new rubbers are not available.

Sent from my Nexus 6 using Tapatalk

sonsman:
Thanks guys, the bike has been in regular use so I don't think it will be gummed up or stale fuel from being laid up and it's been running fine over the couple of years I have had it until now. I'll let you know how I get on.

Navigation

[0] Message Index

[#] Next page