Engine miss at high rpm

[Ecmech]

I posted a problem a month or so about having issues after I desmogged. It was really missing or popping on the right side at idle and higher rpm's. After checking all the clamps, intake o-rings, cleaning all the jets, it seems to idle much better, but now as soon as it reaches 3000 rpm or so it really starts missing and popping. Could I have a coil problem, or is it something else? it is a 97 standard with 51,000 miles. Any advice is appreciated

[Pete]

If it is right at 3000 RPM I would suspect carbs as that sounds like a transition problem from the pilot jets to the main jets.

Carb piston diaphram leak?
Carb piston sticking?

[Bighead]

I would say it is still something with your desmog if it didn't do that before the desmog.

[Ecmech]

I inspected the carb diaphrams on the right side, they look ok, but when I pulled the intakes, there was a lot of fuel present, I checked the spark plugs and looks like the #1 cylinder is running lean compared to #3 and #5 which are running rich, Thanks for your reply Pete

[Ecmech]

It  ran fine before I did the Desmog, I installed the kit from Red-Eye, which I was impressed with, installed the plug in the airbox, not sure what else it could be other than maybe it is running a little leaner now?

[Ricky-D]

If it is right at 3000 RPM I would suspect carbs as that sounds like a transition problem from the pilot jets to the main jets.

Carb piston diaphram leak?
Carb piston sticking?

Not if he is just sitting there in neutral holding the throttle. That would still be the idle circuit. He still has problems with his cleaning job I would say.

***

[Ecmech]

I have removed the air mixture screws and sprayed carb cleaner in the port and installed the screws, per the Honda manual on the 97 is says to install the screws 1 3/4 turns out, but I have them all at 2 turns out, I haven't touched the left side. When I ride it, you can really hear the miss when I give it more throttle, maybe this is a case of messing with things I shouldn't of messed with 

[semo97]

Go to my thread page three(will not go over 4200rpms) read last reply on the fix. You may not have enough air to the carbs or that 3/8 line is kinked.

[Ecmech]

Thanks semo97, I will check that line out

[Ecmech]

I'm messing with the Valkyrie again, when I pull off the #1 and #3 plug wires, the misfire or popping goes away, so maybe I have 2 bad wires or 2 bad coils?

[gordonv]

You have 3 coils. Each fire 2 plugs at the same time. 1 plug would be at the top of the compression stroke, and the other would be at the bottom of the stroke, they by doing nothing. Odd and even.

I believe they are matched, plug 1-2, 3-4, 5-6.

So if coil for plug 1 is bad, so would plug 2, etc, etc.

Your problem is each cylinder, that you identified, 1 & 3.

Could be wires for each of those, but you can change the other wire from the coil to plug that is working, and swap with the bad one. No change, then wire is fine.

I would move on to something like ether or WD40. Some have said stay away from ether. Others says WD will do the same, less harm. Spray around those cylinders, from the engine block up to the carbs. Any change, then the problem is air getting in. Find and fix.

[Ecmech]

Thanks for the input, I swapped out the coils and wires with a different set I had, and have the same result, so I will try the WD-40, I post the results, Thanks again

[Ecmech]

Just thinking about some of the others that have carb issues, mine starts right up, idles fine after warmup, but then misfires like crazy when I give it more throttle, is it maybe possible my right fuel rail as an obstruction? Just trying to think of other causes. I'll check for vacuum leaks again tomorrow, thanks again for the advice!!

[Pete]

I am kind of at a loss as to what to try next.
When at idle if you remove spark plug wire 1 or 3  or both do you see a decrease in rpm?
May want to do a compression test just to eliminate that possibility.

[gordonv]

Personally, I think it's fuel related. But there are processes to follow to figure it out.

Fuel and spark, are about it.

If it was my bike, I would start with 1/2 tank of fuel and 1/2 can of Berryman B12, and take it out for some slow riding. High gear, slow speed. Go through the gears, so you have it up in the 3-4K RPM range, but then drop it down to some lower RPM. Let it sit overnight after about 50 miles. Repeat.

After the fuel is gone, repeat once more. No improvement, then search for something else. But the above is the easiest method to try first.

[Ecmech]

Thanks guys for the responses, I'm gonna get some more gas in it with a heavy dose of cleaner and ride it, Pete, I will look at what the rpm does when I remove the plugs, I'm also gonna check for leaks using some WD-40, I had some minor symptoms before I desmogged then they got worse after, I have checked all the clamps, changed the intake o-rings, changed the plugs, I wonder what I'm overlooking?
Thankful for this site for advice!

[Ecmech]

Hey Pete, I forgot to say that I did a compression check early in the process, and everything looked good, and my valve clearance check was good also, I also cleaned and inspected the jets, which are all the stock ones, Thanks again

[semo97]

What de-smog way did you go? Did you totally take all the stuff off and use the plugs that you tap in, or leave some of the stuff on and rubber cap them? If you did the plugs check those and see if one is not sealed or got damaged. Also if you used the plugs did you put them in the freezer over night then install, helps seating.

[Ecmech]

I used the shiny desmog kit from red-eye, all the equipment was removed, and it came with the plugs and washers, they seem to be sealing well. I'll check them again tho

[3W-lonerider]

have you checked the tubes from the airbox to the carbs to make sure non of them came off the back of the carbs.
your not going to see if they did just by looking at them.

[Ecmech]

I will check all the clamps again, and other connections, I just wish I could find something I missed

[Valkpilot]

I had very similar symptoms on a bike that was forced to sit for 29 months.

1000 miles of riding with high concentrations of various solvents (Seafoam, B-12, Gumout, Techron) couldn't fix the miss around 3000 rpm and never fixed the low circuit stumbling.

Checking for vacuum leaks yielded no good results.

I ended up pulling the carbs and replacing the pilot jets and spray-cleaning the mains.   It ran perfectly after.

I think you've got dirty jets.  If you've got stock 35 pilot jets, it doesn't take much.  The pictures below are NEW jets and illustrate how small the orfice is and how easy it would be for gunk or specks of debris to obstruct or reduce flow.

[Ecmech]

Thanks for the input, I have had the jets out and soaked them in cleaner, being the orifice is so small, I thought they were clean, maybe replacing them is the way to go, I know these are the original 35's

[Hook#3287]

Thanks for the input, I have had the jets out and soaked them in cleaner, being the orifice is so small, I thought they were clean, maybe replacing them is the way to go, I know these are the original 35's

On my first go around with cleaning jets, I really thought I had them clean.  Put it all back together and same issue. 

I now replace instead.

All my girls have 38's and I know some have stated that could cause a carbon build up, but, I know 35's will most likely give me trouble again and carbon build up will probable not.

I won't live long enough.

[Harryc]

Hook#3287
All my girls have 38's and I know some have stated that could cause a carbon build up, but, I know 35's will most likely give me trouble again and carbon build up will probable not.

I won't live long enough.

Where's the like button here anyway. . I think I'll be putting 38's in mine as well.

[Ecmech]

Thanks Hook, I think replacing might be the way to go, The jets really aren't that expensive, and I really am  done messing with it instead of riding it!! Thanks for your advice

[Ricky-D]

Cleaning the jets themselves can/may help, but you have to realize the idle circuit passages are also small and restrictive and they can clog up just as easily if not more easily that the jets. If you pull an intake riser and look at the carburetor venturi area you will see a small aperture at the bottom. That is one of four apertures that make up the idle circuit. This is the aperture which is controlled by the idle mixture screw. Farther up into the carburetor you will find the other apertures located closer to the butterfly valve. These remaining apertures are controlled solely by the idle jet. If you do not have all these passages clean and open you'll have trouble with your idle characteristics.

If you can remove a spark plug wire from a cylinder and have that action cause no discernible difference to the running engine you can infer then, that that cylinder is not contributing to the idling effort of the engine. The most obvious correction after verifying there is no fuel problem would be to synchronize the carburetors to get all six cylinders back into equal participation.

***

[Ecmech]

Thanks Ricky-D, It never really occurred to me about the small passages being clogged, I have had the intake risers off and never really paid attention them, Thanks for your advice and knowledge