Topic: ** First CB750 - Starting Trouble - help needed **

[Ericcb750]

Hey Guys, sorry to keep this going but I'm still having problems here. I've tried so many different things now, Switching the yellow/blue wires adjusting the timing, cleaning carbs, etc. I'm getting real frustrated on this thing but i'm not going to give up. I put so much work into this thing and it looks great but I just can't get it to idle. I don't know what else it could be, I went through and adjusted the valves again to make sure they were all correct.  I'm just stumped, I pulled the carbs again to make sure the floats are correct and that the Little o-rings are under the fuel screws (hondaman recommendation).  I don't know if there's anyone from CT on here but I would really appreciate the help. Any tips would be appreciated, I also want to Thank everyone who has helped already.

[Ericcb750]

Hey Calj737, The PO said the battery was "new" but I have not checked it yet, how would I run a test on it? Also, for the bike I have the stock airbox - brand new air filter, stock 4-4 pipes. I have put in all brand new 35 pilot jets, 110 mains. I actually shim'd up the needle with one very small washer in each carb. The Accel pump works perfectly. I'm just at a loss at this point.  it's strange because if i give it a few pumps from the accelerator it will start, then if I twist the throttle it will rev rev but then once I let off it will dies. This makes me think it's fuel. but I'm going to get into the carbs again tonight and make sure the floats are correct. I have my manual so I'll check the heights on them. I'll clean all passages again. 

[LesterPiglet]

You are letting it reach operating temperature before you try to let it idle?

[Black 750K8]

Are you sure the choke is working correctly? Are the butter flies working as they should? Is the fast idle cam setup correctly?

[Ericcb750]

Hey Fellas, Thanks for all the help. I haven't been able to keep it running long enough to get up to normal oper temp. yet. I have a feeling i'm close. My choke is a bit tricky. The spring that holds the two halves of the choke setup's together (1-2 choke plates on 1 half and the 3-4 on the other). The linkage where they attach the spring is weak, however when I pull the choke the plates close about 80% of the way. When I work on the carbs tonight i'm going to try and fix this.  I'll check on the battery too to see what the deal is there.  Where exactly is the Fast idle cam on the carb setup? It's the 78' PD keyhole carbs.

[Ericcb750]

Hey Guys,   I Finally got the bike running/ idling ! I had to fix the floats in the carbs and when I hooked it back up it fired right up. I do have to tune it a bit thought. When I fired it up I pulled the choke all the way out, which I also fixed the choke so that the plates close completely now! I gave it a few twists of the throttle and it rev'd up to about 3000 rpm and kind of sat there for a few seconds before slowly coming back down to about 1200-1500 or so.,  I'm now trying to figure out how to get this corrected. When I pull the choke and start the bike, what should the RPM's be (give or take)?? I know at idle it should be about 1100 +/- 100 right?  I also have a timing gun to check the timinig on this now that it will actually idle for me .   I'm just not sure if this is something that I have to adjust the Idle Adj screw, and the fuel screws to fix or if this may have to do with the little fast idle cam screw? Thanks for you help guys, I appreciate it.