hesitating

[cb500bobber]

Okay so what is happening is when im cruising along at whatever speed and I go to get in it harder it hesitates and then kicks in. This only happens when im cruising. If im sitting still and rev it up it does just fine. I was thinking that it could be that I need to increase the main jet size, because I have pod filters on and a 4into1 exhaust and I haven't done anything with the jets. I think the jets that are in there are 100 so I was gonna take them to 115 or 120, but I didn't know if that would fix the problem.

[felkman]

I would make sure those termites haven't migrated from your kickstand up to your carbs!

[cb500bobber]

Hahahahaha real funny there

[tango911]

I saw this quote from another thread/forum.

"Basically you have to get the idle a bit richer, so when the throttle is opened and the throat vacuum dips, there is an abundance of left over fuel still available for the engine to pick up. Engines that "peak lean" the air screws at idle also (usually) have an accelerator pump to shoot raw gas into the carb throat for engine pickup when the throttle is opened.

Anyway, here is what you need to do. From the stock Air bleed setting turn the air screws inward (all of them) about 1/8 and drive the bike to see if it improves enough. If not, go inward another 1/8 turn. In top gear, just crawling forward at low speed, you should be able to twist the throttle up to 1/2 the total available travel and the engine should pick up smoothly (if a bit slowly) and reliably. You should never be able the whack the throttle full open from idle because of the physics involved. Sudden throttle opening allows air in, but the loss of throat vacuum severely reduces the pull on ALL the fuel jets sucking fuel up from the bowl chambers, starving the engine. I call it "wheeze".
After you get some good air velocity through the carbs, say above 4-5000 RPM, the venturi effect is the more significant source of vacuum pulling from the fuel jets, rather than just cylinder suction. So, sudden throttle changes don't starve the engine pick up nearly as much."

[gr1976]

Mine does the same. I also blame the pods and header. It only hesitates for a second if i slam it open. I have trained myself to roll on the throttle and it doesn't do it.

In a car I would tune the accelerator pump or power valve but since mine are purely vac cum delivery I don't have that option. I assume yours are as well. I'm not sure if upping the main jet will be a benefit since it doesn't really start working until the engine is under a real load and you are experiencing problems in the transition from part load to full load.

I'd first make sure the idle circuits are set, cabs synch'd, and the timing is right and advancing properly. Then do do a plug chop to see if it is running lean at the upper end. If so, change the main jet accordingly. If you still have problems you may need velocity stacks to smooth the air entering the carbs. I've often heard these bikes run a lot better with the stock air box.

That's basically how I would attack it. Someone else who has actually fixed it may have a better approach. Like I said, I just roll the throttle to allow a little longer transition.

[gr1976]

I see I was typing my dissertation the same time Steve was.

It looks like we are saying the same thing.

[cb500bobber]

Okay thanks guys I will try that out tango

[williamc89]

hey remember what we just went on my old 650, try to set you fuel air mix up a little and if that dont work change the jet if all else fails , i agree that there may be other things but u had 2 cylinders to each side now u have all 4 to 1 and its like a car it will change back presure to the motor a little,,,,, does it feel like it is wanting to die out

[tango911]

correct anytime you change mufflers / air filter setup, you will need to change your jet size on the idle jet and the main jet.

[gr1976]

Dont you agree though that the jets won't make much of a difference for rapid throttle openings?

[tango911]

each throttle position uses different fuel routes, and they over lap with each other.

[gr1976]

I did some internet research since this has resparked my interest in trying to get rid of my quick opening stumble. Someone wrote that new needles from Honda fixed his. It would make sense per that chart since it looks like they have the most control from 1/4 to 3/4 opening. Maybe this winter I'll pull them off and throw in some new needles.

I did notice a few drops of gas out of the overflow tubes this morning. I am hoping that it was just expansion from the heat, but if not I may have to tear into them sooner than later.

[novafrk]

I've been told the only way to get accurate jetting is to do plug chops... Since you only have a hesitation as you increase throttle while cruizing it may not be as helpful. But it will give you a good picture of how it is running over all. Trial and error works but is expensive in my experience. The plugs will tell you what you need to do.

My first thought is to agree with you that since you have free flowing intake and exhaust that you need to richen the overall fuel mixture. I'd pull the plugs and if they are very white then it is definately running lean. If they are more black and sooty, need to lean it out. You're tail pipes can give an indication if you are running rich as well. If they are sooty it's injesting too much fuel.

My $0.02

Eric

[73cb500]

How did that exhaust end up sounding??

[cb500bobber]

It sounds great man I just use the header