Bike hits a wall at 5000 rpm

[whale]

Bike runs well . Starts and idles well, runs normal until you get to 4500 to 4700 then by 5000 rpm the bike hits a wall. Thanks in advance for your thoughts. Carbs VB 64, 79 bike rebuilt carbs stage 3, DG Exh. No flat spot.......a wall. Bike will not go past 5000 rpm. What controls the fuel at that rpm level? Thanks, wayne

[asacuta]

How do you know it's fuel and not ignition? Just curious.

[steve murdoch icoa #5322]

What air filter are you using, Wayne?
Even with pods i wouldn't think you would need the Stage 3 using the DG system.
On my '79 with a DG system and stock airbox/filter no rejetting was required.

[Rick Pope]

The real experts will be along shortly, but until then, I'll do my best to lead you astray.

Sounds to me like you have too large main jets. As the slides raise, along with the needles, you are getting more and more fuel, until finally you have way too much. Bigger jets do NOT necessarily make more power.

[whale]

Thanks to all......air pods are K and N, one filter for every two carbs. New Dana ign system including coils ' plug wires and plugs. The plugs are lean, if it was to much fuel they would be wet. I have riden the bike and used the choke while in a 5000 pull with the same results. Also, when under a load and I let up on the the throttle there is no change. That would point to too much jet. But again the plugs are white.

[daves79x]

Sounds like too many changes at one time. Those carbs are from a late model and I haven't seen a 'Stage 3' kit for late model carbs for a long time. Pods are an issue. The Stage 3 jetting, if that's what you really have, involves a new, adjustable needle and different main jets to pick from. With pods, you can still end up way too rich with stage 3 kits. If someone just upped the stock sizes, then it might not have been enough. Stock mains are 105 on those carbs and you'd need to go to 125-130 range with pods.

But the bike should still rev past 5000 with jetting that far off. I'd be looking at the new Dyna ignition and coils. You could have anything from a sticking, or incorrectly installed, advancer to mis-wiring to or from the new coils. I'd make absolutely sure all the primary side wiring was correct and that the plug wires were all in the correct order. I think you'll find most of your problem there.

If all the above checks out, then check your fuel flow. Do you still have the vacuum valve in place or do you run straight into the carbs from the petcock? Bypass that if you do and see what happens.

Let us know what you find out.

Dave

[80 cbx dude #6216]

Could it be the carb vents are blocked and not allowing the carb bowls to stay full? Had this happen on another bike a while ago....-Mike

[whale]

Not all changes were done at the same time. Bought the bike it ran but the carbs leaked. Swapped the carbs at a well known and trusted bike (CBX) place. Bike ran well but it a wall. Found all three coils cracked and replaced them with new Dana stuff. Also have a Pringle petcock with duel lines. Flow is good. Is anyone going to Charleston?

[80 cbx dude #6216]

Does it hit the wall in first gear? It ran ok with the original carbs-no wall?-Mike

[daves79x]

If you check the Rally section, you will find your answer to 'Is anyone going to Charleston?', but I find it curious you would wait until the rally week to ask. So are you coming?

Dave

[whale]

Sorry I have not been on this forum in a while. Family and work load have taken most of my time. Yes we are coming, should be there on Wed eve.Yes to the other question it hits a wall in first gear also. I never rode the bike it had bad tires and leaking carbs.

[daves79x]

Wayne:

Look forward to seeing you Wed eve - we'll be there in the PM.

Dave

[whale]

Broke thru the wall by re adjusting the timing. Now have a flat spot from 4700 to 7500 . Then it screams!!! So now its a known problem and how to make it a smaller flat spot.

[cross]

I have '82 with DG pipes, stock ignition, airbox and jets. Always had flat spot around 4700-5700, no after I adjusted the valves, flat spot is more noticeable and it seems to go all the way up to mid 6000.
Please post if you find resolution.
Thanks
Sasha

[daves79x]

Are you running the stock paper filter or a K&N? DG pipes with a K&N are notorious for producing a flat spot in the mid-range that you can't jet out. Going back to a stock Honda filter will help.

Dave