New bike running rich/rough

[klutch77]

i just bought a 77 cb750 k7 and im having problems with it running right. the guy i bought it from ran it with no filters on the carbs (thinking about adding some pods) it has what im guessing is original exhaust, just cut off under the pegs. its been fouling the standard NGK D8EA plugs pretty easy, and puffs out black smoke when i give the throttle a quick twist which im guessing is soot, the plugs are also flat black. today i put some D7EA's in today in hopes that a hotter plug might help with the extra fuel, but it honestly seems to run rougher than before. im not real keen on this bike quite yet, so im not at all sure what approach i should take. i was wondering if anyone had any advice on what i should do or how your carbs are tuned if your running close to the same setup. pilot screw adjusting? smaller main jet? where i can find filters for my carbs? weak coils or timing off possibly?

[klutch77]

ohh, forgot to mention that the RPMs seem to drop slow after a rev also...

[TOOLS1]

First thing is to download the manual from the home page here. Then put an air filter on it. I am also guessing that the PO has messed with the carbs trying to get it run with the open carbs, and exhaust. I would bet he has drilled the main jets. I would get some complete carb kits, and start from scratch with them.
Welcome to the forum. TOOLS

[klutch77]

i appreciate the input, any recomendations on filters or carb kits? im planning on going with pods because the stock airbox wont fit because of the hardtail frame modifications.

[TOOLS1]

Spring, for the K&N pods. They are a lot better then anything else on the market.
TOOLS

[seestheday]

Lots of links to part sources in the Links section of this site.

Welcome to the forum.

[Lucky 1]

You will of course have to take off the carbs and clean them and write
down the size of the main jets and the idle jets.

Who knows what has been done to it and how it was done.????

You will have to make sure the accelerator pump and nozzles are functioning.

Are they the stock 1977 carbs???

THEN you might want to read my article about jetting.
http://honda-cb750-s.456789.n3.nabble.com/1977-78-CB750-jetting-for-pods-td3900695.html

If they are 1977 carbs with the accelerator pump system I would put in #120 main jets.
I would put in #45 idle jets.
Put in brand new float needles. A MUST DO. Then check the float level.
Make sure all of the mixture screws are backed off one full turn.
Make sure the CHOKE is not stuck closed.
Get some kind of muffler if it has none.
Put some pods on it. find some way to support their weight.
Or you could choose to just put on the stock #35 idle jets and stock air box and stock air filter.
Go back to a stock #110 main jet.
Get a stock set of exhausts, or a 4 into 1 pipe.

[Lucky 1]

Yes I agree...It needs a complete work up. A 33 year exam.

[klutch77]

Yeah, theyre the stock carbs. I took them partially apart yesterday and wasn't to surprised to find some sediment in the bowl. The jets didn't look to clean either so I soaked them down pretty good. I found out I'm running 130 mains and they dont exactly look drilled like tools said they could be. I haven't got to crank it up yet because I got done with it pretty late. Before I cleaned the carbs I had the pilot screw set at 1 full turn and it seemed a little better (still black smoke and when I got on it changing gears it bogged down initially) I'm thinking that the float setting is too high and letting too much gas in. It looks like it would be running more lean than rich with the setup I have?

[TOOLS1]

130 is a pretty big jet. The float level would not cause the engine to run rich. If it was too high gas would be running out the over flow tubes on the float bowels.
TOOLS

[klutch77]

I think I'm going to try what lucky said and go with some 120 mains and pod filters. I'm going to double check on what my idle jets are when I get a chance today. Anything else I should look for while I'm in there?

[shinyribs]

*post deleted*



                                                                                                 i'm dumb.

[mitchell.lee.miller]

This maybe a silly question, how do I tell what number my jets are?  

[TOOLS1]

They should have a very small number stamped on them.
TOOLS

[mitchell.lee.miller]

Mk, is that the size of the opening for fuel then?  Do you know what is stock?

[klutch77]

I may be wrong, but I think 110 or 115 is stock. You can find the number stamped on the end of the jet where the hex is. By the way, I cleaned my carbs real good, and messed with my pilot screw a bit and it seems to be running alot better. Its still rich but it seems to lean out pretty good after it up.