Dennis, right now I have the carbs off, the float bowls off and the carbs upside down and dripping a little seafoam into the slow speed jets (rubber buttons removed of course) every now and then. Of course the seafoam drains down somewhere - all drain evenly (at the same rate). I'll do this for a couple of days then I'll do some spraying as per your advice. Graham
On May 14, 2009, at 11:18 PM, Dennis Hammerl wrote: > You are in the most complex and troublesome circuit. The fuel path > is from the bowl supply up the primary main and over to the slow > speed jet (the hole from pri main to slow is only a small distance > up above the removable pri main jet. Look for the passageway, it's > blocked off after drilling with a small brass "BB") The fuel flows > forward to a junction and on to the holes. It is controlled by the > idle mix screw. ALSO, air is mixed in at two places. The rubber > buttons insure that fuel is channeled from the pri mains by > blocking off any direct path. Sprying into the slow jets should > come out the main discharge in the bore as it is the path of least > resistance. Blocking that off with a finger should direct the > cleaner along to the right place / path. Opening the mix screw will > allow more cleaner through. SO, spray into the open screw hole and > into the slow jet with the main discharge blocked off. It would > seem that the tiny discharge holes are open but the path to them is > gunked up. There are so many passageways in this circuit to clean > out all I can say is be diligent. Trace out the flow paths by > examining the casting and seeing all the cross-drillings that are > plugged with small round brass BB's. The horizontal passageways are > the most difficult to clean, but it can be done. If you block off > the main discharge in the bore and spray into the slow jet, it > SHOULD spray out the three small holes. Then, there's always the > Sea Foam soak... I want to look for the photo you sent. I may be > able to indicate the flow path. > > --- On Thu, 5/14/09, Graham Rogers <[email protected]> wrote: > > From: Graham Rogers <[email protected]> > Subject: [Nighthawk Lovers] Re: Graham's 1980 CB750F > To: [email protected] > Date: Thursday, May 14, 2009, 3:13 PM > > Okay Dennis, I have the carbs off the CB750F once more. Here's > what I have observed after removing the black plug covering the > slow speed idle jet. When I blast compressed air through the jets > the air returns up through the primary main jet. A very small > amount passes out the tiny hole(s) in the carb body. There are > three holes in each carb body - two side by side covered by the > throttle plate and one one the outside of the throttle plate. The > amount is so slight I could only tell by holding a piece of tissue > in the throat and watch for it to move when the air came through. I > cannot tell whether it comes through one or more of them. It > seemed the same amount came through on all four carbs. Spraying > carb cleaner through the slow speed jet did not result in spray > coming through those same holes. What now? Graham > > On Apr 24, 2009, at 11:10 PM, Dennis Hammerl wrote: > >> My other E-mail rejects LARGE files. Total limit is one meg. >> With a long lay-up, I'm still going to stick with the carb >> malfunction. To do what you say, it has to have a blocked circuit. >> Large throttle openings dump fuel and the vacuum slides will >> control it. So much for acceleration. Steady speed requires the >> contribution of fuel by selected circuits. One of yours isn't >> doing it's job. >> >> --- On Fri, 4/24/09, kiwi <[email protected]> wrote: >> From: kiwi <[email protected]> >> Subject: [Nighthawk Lovers] Graham's 1980 CB750F >> To: "Nighthawk Motorcycle Lovers!" >> <[email protected]> >> Date: Friday, April 24, 2009, 6:38 PM >> >> Hi Dennis, yes, I repaired the broken idle mix screw and set them >> all at >> one and a half turns. It has four into one, air box is >> original with clean air filter. This is the way the bike was when I >> got it and probably how it ran before I got it. The bike sat for a >> long time. It started and ran when I got it but I didn't ride it so >> I'm assuming it had the same problem. Sent pics to your other >> address >> Dennis but everything came back. Don't know how to post them here >> >> >> >> >> > > > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en -~----------~----~----~----~------~----~------~--~---
