'03 misfires between 5000-7000rpm on cylinders 2 or 3. Help!

[wildweasel_pt]

Yes....you would be replacing all of the electrical components that could be causing the misfire.

Not really as the TCI is the same one Eric. He can try to use a different TCI and see if it solves the problem.

 

[Traumahawk]

Don't understand why you can't rev it above 4k without airbox?

Ive been told that without the airbox...you will have TOO MUCH air going to the carbs....thats why with Seans kit....or stage 7...you have to put in air correctors into the main air bleeds.

 

[Traumahawk]

Not really as the TCI is the same one Eric. He can try to use a different TCI and see if it solves the problem.

Sorry I wasnt specific enough....I was meaning, the coils....spark plug boots...etc...anything with THOSE electrical components.

 

[TheFleshRocket]

Don't need to remove the coils just swap caps and wires and connectors in order to maintain firing order. The reason for the misfire to seem to be less noticeable on third gear might have to be with the moving inertia of the bike due the gear ratio? Don't understand why you can't rev it above 4k without airbox?
I've read somewhere that theres a wire that goes from the VBoost controller to the TCI so that misfire range may have something to do as well but this is just a WAG. The VBoost entering in action may also be the culprit but you can't check it visually.

When you says caps, wires and connectors, do you basically just mean the wires? There's the coil, then the wire, then the plug, so if I'm not changing the coils or plugs, it would just be the wires, right?


'99 VFR800, '08 1125R, '06 1050, '03 Vmax, '03 DRZ400

 

[TheFleshRocket]

I've swapped the rear wires. Not gonna bother with the fronts--don't feel like trying to dig my hand up in there that far. If this doesn't make a change of some kind, I'm probably going to throw up my hands and take the bike to a shop.

The rubber covers over the plug wires (not the plug wires themselves) look heat-cracked. The exhaust headers don't have any kind of heat shields on them so I wouldn't be surprised if they're putting a lot of heat into surrounding components.


'99 VFR800, '08 1125R, '06 1050, '03 Vmax, '03 DRZ400

 

[vbober]

mine dose the same thing but it is intermitant all stock 97

 

[wildweasel_pt]

Coils + HT lead + plug cap
The front headers are double skinned, the rear ones have a diagonal heatshield fixed to the headers covers by the heads

 

[TheFleshRocket]

I swapped the rear plug wires from side to side with no effect--misfire still comes out the right muffler.

Yesterday morning (upper 60s), the misfire was almost unnoticeable with the Vboost set to 3000rpm but in the evening (mid 70s), it was more noticeable.


'99 VFR800, '08 1125R, '06 1050, '03 Vmax, '03 DRZ400

 

[wildweasel_pt]

How did you do it? Did you unplug the cap and moved it to the adjacent plug? if so you messed up the firing order. You should have swaped the coil connectors and then swaping the plug caps you would be swaping the whole group of coil, ht lead and cap from one cylinder to the other and see how it worked so you could rule out the group... Isn't this clear?

 

[TheFleshRocket]

I completely disconnected everything between the coil and the spark plug and swapped them for both of the rear cylinders. Yes, I understand that just swapping the plug ends would have messed up the firing order. I'd be surprised if the bike would have even run like that.

I changed the #3 (right front) carb needle from position #3 to position #1 (the richest setting). The bike would sputter every few seconds at cruise, and it still has the misfire from 5-7k, completely unchanged.

So I put carb #3's needle back to position #3 and changed carb #2's (left rear) needle from position #3 to position #1. The engine still sputtered frequently at cruise, but the misfire from 5-7k is almost gone, even with the Vboost off.

So it seems apparent that the misfire is due to a lean condition in #2. Leaving the needle at full rich isn't a solution--I need to figure out what's causing the lean condition. I feel like it's related to the occasional squeaking (exhaust leak?) coming from the right side muffler (which is used by cylinders #2 and #3).


'99 VFR800, '08 1125R, '06 1050, '03 Vmax, '03 DRZ400

 

[TheFleshRocket]

Previously, I had changed all four carb needles from the 4th notch out from the pointy end to the 3rd notch (slightly richer), and I'd also changed cylinder #2 (left side rear) to the 1st notch (full rich). As mentioned in my previous post, with #2 at full rich, the bike ran sloppily at cruise but the misfire between 5000-7000rpm was just about gone, even with the Vboost off completely (which is where the condition was most noticeable).

Tonight (after the bike had sat for almost a week) I decided to put all of the needles back to the 4th notch (how the bike had been when I got it). I unscrewed #1 (left side front) and #2 at the same time and pulled out the #2 slider first. It was very hard to get moving, like the slide was under vacuum, but once I'd gone about half way, it slid out easily. So I did the old in-out in-out with it several times and it slid nice and easily. The slides from the other three carbs came out easily.

I don't think it's a coincidence that the #2 slide felt like it was under vacuum--in fact, I'm just about positive it is tied to the lean condition that is making the bike misfire on that cylinder between 5000-7000rpm. So my question is this:

Specifically what part of the carb affects the vacuum that causes the slide to move?

I'm sure that something is still gummed up in #2 and that's what's causing my problem, but I'd like to have an idea of what I'm specifically attacking before I shotgun or peashoot the carbs (both of which have been done by me, with a reasonable degree of thoroughness, I thought).

 

[TheFleshRocket]

I decided to redo the shotgun, mostly because the first time I did it (with the carb rack off), I just sprayed a bunch--like 3 cans--of carb cleaner through the orifices but never followed up with the 100psi air.

I found that the #3 (right side front) mixture screw was missing its washer and had a torn o-ring. I feel like that shouldn't be causing my misfire between 5-7k, but I'm going to replace them nonetheless. (As mentioned above, the misfire appears to be on #2--left rear--as the misfire goes away when I change the needle clip to the full rich position.)

Also, both right-side screws have corrosion on them, but it's only on the outer half. I suspect it's from water getting stuck in there, maybe after the bike was washed or rained on. Do you guys think there's any reason for concern?




'99 VFR800, '08 1125R, '06 1050, '03 Vmax, '03 DRZ400

 

[alorio1]

Usually when the bike gets washed it's on the side stand and the carbs on the right are tilted up and thats why the right A/F screws are usually seized up on these 2 carbs. You can go to Home Depot and search for some plastic covers that fit the A/F screw holes well, problem solved.

Also, both right-side screws have corrosion on them, but it's only on the outer half. I suspect it's from water getting stuck in there, maybe after the bike was washed or rained on. Do you guys think there's any reason for concern?

View attachment 44735


'99 VFR800, '08 1125R, '06 1050, '03 Vmax, '03 DRZ400[/QUOTE]

 

[TheFleshRocket]

The problem is solved!

I noticed that one of the slides moved slowly when it was sealed but slid freely when not. I pulled the pilot air jets and inspected them. The one at the top of carb #2, the cylinder that was misfiring, was mostly plugged--the hole was the size of a pin. I rogered it out with a metal twist tie so the hole looked like the other jets. I also replaced all four idle mixture screw assemblies, but I don't think that helped.

Now the bike pulls strongly through the 5-7k range where it used to misfire.

I'd shotgunned twice and peashootered once, and that didn't fix it, so apparent those fixes aren't necessarily the holy grail of fixing carb issues.

 

[TheFleshRocket]

Followup--the problem wasn't entirely gone. The bike didn't misfire at all with the Vboost set to come on at 3000, but it occasionally would with it set to 6000. Since it was K&N filter oil that had gummed up the air jets, I took some K&N filter cleaner (which does a fantastic job at de-oiling filters) and poured it down the PAJ1s while the bike was running. That helped, but it's still not perfect, so I'm going to buy some more cleaner and have at it again.