Re: Idle's fine, boggs down with high rpms

Posted by CMGoldie on Jul 02, 2013; 6:36pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Idle-s-fine-boggs-down-with-high-rpms-tp4042962p4043151.html

Ok, got the carbs back on and synced. I started working on the tuning. I also noticed when checking my plugs that they were not fully in. I got them tightend up, along with my headers. We tightened down the screws to adjust the fuel. It seems to run better, didn't get much done after that. I ran it down the highway to see how it would do. It ran better but still didn't run very good. It seems like rpms get higher now before it bogs down. 1st and 2nd gear were bad about it. 3rd was too but not as bad as the other. I didn't get the rpms high enough in 4th and 5th. It seems to be happening when you are accelerating hard. I am going to work on it again later this week.

 

What is blowing my mind, is that it ran fine before I changed batteries. The carbs were still synched when I put them back on. I don't understand how it would go from running fine, to running as fast as a 3 legged dog, by changing the battery and sitting for three weeks. It sat all winter and didn't have any problem with running. My theory, I am not a mechanic, is that the battery could have something to do with it. Or the wire that we ran pass the coupler and spliced together. My friend, who is a mechanic, told me I am wrong. So I will continue to work on the carbs and adjusting them.

 

Also I don't know how good the sound quality is. I made this prior to adjusting the pilot screws.

 

http://www.youtube.com/watch?v=PnUuV6Twvzo

On Fri, Jun 28, 2013 at 5:48 PM, trapper [via Honda CB750'S] <[hidden email]> wrote:

Hard to really tell cuz none of us here can actually hear what your bike is doing but I'll take a shot. There's a lot of great techs here so, hopefully we can help ya trace it.
I'm not leaning towards an electrical issue. Though not impossible, seeing as it idles fine and revs better (but not good) in neutral but not as well once under a load (in gear) I'm still going to lean towards carbs.
Sounds like you may not be getting enough fuel.
You say you cleaned them but, a real cleaning should involve pulling the jets and tubes and really cleaning them out. Take a small wire, an e string from a guitar works great, and poke it through all the holes in the tube gently. do this until you can put the little hose that comes with a can of carb cleaner, spray it and see a steady spray coming out of all the holes. Make sure you spray through all ports and clean the bowls completely. Any little bit of schmeg can clog up a jet. Next, after you assemble them and get them back on work on your pilot screw adjustment. This puts more or less fuel in your crabs. I believe stock on these are 3/4 turns out from gently seated. Do this, clean your plugs then take it for a quick ride. Then check your plugs again. If they are white you're running a little lean. Turn the screw out a little. If excessively black you're a little rich. Turn them in a bit. You'll have to adjust each carb to how the coinciding plug looks. Of course, getting them properly sinced will help a lot too.
Try this and let us know how it turns out.
One step at a time my friend. But no, it doesn't sound like you'll have to go as far as pulling the whole motor out. :)
Good luck  

It ain't a custom till you have customized it yourself.

1981 CB750c (current daily ride and build)
1980 GL500 (Stripped and rebuilding)
1981 CM450 (Stripped and rebuilding)

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