Well carburators were spotless

[shadowmagic]

So the carburators are clean, jets are clean, floats are clean, float needles are springy, I'm at a loss now for why its backfiring. The only left is to up the jets i guess? It has stock jets on it, 100 and 35. If I move up is there a possiblity that would eliminate the backfires? My cobras have baffles if that matters. Any help would be greatly appreciated. There is just nothing left to try but a rejet as far as i can tell.

[Bighead]

You need topost a video where we can hear what you are calling a backfire. Does it sound like a gunshot or a slight popping on decel? If the latter I would say you are chasing a ghost.

[shadowmagic]

The warmer the bike gets the louder and more frequent the pops are. They muffled at idle and always pop on decel. Some get loud like a muffled 22 gunshot.

[shadowmagic]

To clarify, actually my pilot jets are 35s which if I understand correctly means the air holes are smaller? There is literally an "s" after the 35 on the jet. This is supposed to create a richer mixture but since I'm backfiring on decel thats probably because I'm running lean. Maybe I need bigger pilot jets.

[sandy]

Popping can be caused by other things. An air leak is the main culprit. Vacuum hoses, intake runner O rings, clamps on the carb intakes, exhaust gaskets cover most all the reasons. Set your pilot screws at 2 1/2 turns out for your cobra pipes.

[98valk]

To clarify, actually my pilot jets are 35s which if I understand correctly means the air holes are smaller? There is literally an "s" after the 35 on the jet. This is supposed to create a richer mixture but since I'm backfiring on decel thats probably because I'm running lean. Maybe I need bigger pilot jets.

all u have to do is open up the idle mixture screws btwn three and four turns open and most of the popping will go away.

any PJ is good for up to 4.5 turns open.

[Foozle]

To clarify, actually my pilot jets are 35s which if I understand correctly means the air holes are smaller? There is literally an "s" after the 35 on the jet. This is supposed to create a richer mixture but since I'm backfiring on decel thats probably because I'm running lean. Maybe I need bigger pilot jets.

IMO, don't mess with the jets - they're fine.  I once installed 38 slow jets in response to a problem that really didn't exist (clogging) and never could get them dialed in correctly.  I'm now back to 35 jets set at 2 1/4 turns (the factory setting) and the bike is much happier.  I run a bottle of Technron through every 10th tank of gas and make sure it's ridden regularly; I've never had an issue with clogged jets. (I have no idea what the "s" designation on your jets means, if anything).

Sorry if I missed this, but are you running the Cobra needles?  If so, where are the clips set?  Cobra pipes come with adjustable needles that are more tapered than stock (if memory serves); if you want to richen the mixture, try lowering the clip (raising the needles).  OEM needles are not adjustable in this same fashion.

Terry

[shadowmagic]

After reading countless articles and watching numerous videos, I've corrected every issue that it could potentially be. I've fixed every air leak, replaced orings, and now the carburators. I've read in multiple articles it could potentially be the jets so thats my next step. I'll put in 105s and 35s to see how it goes. I really was expected to find my pilot jets gummed up but they are spotless. I suppose it could be the one way valves on the carburators but I'm not sure how to check them. I'm worried if I take them apart I may screw some thing up worse lol I'll keep you guys posted, my jets and high flow filter will be here friday.

[The emperor has no clothes]

After reading countless articles and watching numerous videos, I've corrected every issue that it could potentially be. I've fixed every air leak, replaced orings, and now the carburators. I've read in multiple articles it could potentially be the jets so thats my next step. I'll put in 105s and 35s to see how it goes. I really was expected to find my pilot jets gummed up but they are spotless. I suppose it could be the one way valves on the carburators but I'm not sure how to check them. I'm worried if I take them apart I may screw some thing up worse lol I'll keep you guys posted, my jets and high flow filter will be here friday.

I think you are messing with stuff that doesn't need to be messed with. Any kind of clogging in the jets or passageways is not going to result in backfiring. It will result in rough running, doggedness, etc.

[98valk]

After reading countless articles and watching numerous videos, I've corrected every issue that it could potentially be. I've fixed every air leak, replaced orings, and now the carburators. I've read in multiple articles it could potentially be the jets so thats my next step. I'll put in 105s and 35s to see how it goes. I really was expected to find my pilot jets gummed up but they are spotless. I suppose it could be the one way valves on the carburators but I'm not sure how to check them. I'm worried if I take them apart I may screw some thing up worse lol I'll keep you guys posted, my jets and high flow filter will be here friday.

MJ is from 3/4 to WOT, does not affect backfiring when off the throttle.  it will be too rich on the top end thereby reducing power.

it is very simple open up the idle mixture screws to reduce popping.

[shadowmagic]

I tried the idle mixture screw and it didnt help, trust me....I've tried everything. The only things left are the jets, or possible those one way valves on the carburators. Possibly one of my cylinders losing compression. Those are the only 3 things I can think of or I've read about. So lets see which one it is lol

[Bighead]

I tried the idle mixture screw and it didnt help, trust me....I've tried everything. The only things left are the jets, or possible those one way valves on the carburators. Possibly one of my cylinders losing compression. Those are the only 3 things I can think of or I've read about. So lets see which one it is lol

A set of stock pipes will cure your worries.

[shadowmagic]

Now you tell me 

[Willow]

I tried the idle mixture screw and it didnt help, ...

As you spoke in the singular and he in  the plural I think you're referring to the idle speed screw and he's referring to the mixture screws, one on each carb.

[shadowmagic]

Yes, those are used to sync the carbs. I'll be doing that as part of my jet replacement.

[The emperor has no clothes]

Yes, those are used to sync the carbs. I'll be doing that as part of my jet replacement.

I think you are getting them mixed up. The synch screws you are referring to don't control the fuel mixture. They basically control the set point that the carbs start from. The pilot mixture screws (the D shaped ones are the ones Willow is referring to. (I believe) Then there is the single idle adjustment screw.

[shadowmagic]

Ok, yes I bought the d tool but I havent counted how many turns yet they were set at on the carbs. I'll do that this evening. when I completely clean out all the holes just to make sure. Then i'll set them at 2 turns with the new jets and put them back in. Then I guess I"ll have to adjust them from there.

[SCain]

I once tried the 38 pilot jets, went back to stock. At our elevation it just wouldn't run. Changing the high speed jets I don't think will solve your problem. Adjust the low speed circuit pilot screws, sync the carbs and see where you are at.

[98valk]

This was posted by J. Orr, 3/27/1998, on the GWRRA BBS, valkyrie section.
The following mods were done by Marc the owner of Factory Pro on a valkyrie that had cobra 6x6 pipes.
K&N filter (w/o prefilter)
Air box mod (remove plastic welded baffle)
38 pilot jet
3.5 turns idle mixture screw
front needles set on #3
mid and rear needles set on #2
115 main jets all carbs
this picked up 5 hp over the base run with the cobras.

this HP is still down from the stock pipes or almost the same.

[trantony]

Hate to hear of your problem shadowmagic. The problem you are having with the backfire on deceleration is indicative of a bad  air shut off valve. It is a round black plastic valve on side of each carb that has a short vacuum hose attached to each carb. Just my 2 cents worth. this may or may not be your problem. Hope you get it figured out, good luck.

[shadowmagic]

Thanks trantony, ultimately it was the previous owner fiddled with the carbs and messed up a spring on one of the idle screws so it was twisted sideways. I also changed the jets to bigger ones and now she runs perfect, no problems whatsoever.....except for the next problem which is my ignition switch lol