Backfiring on 1 side

[Wood Butcher]

Another newbie here joining your forum. On my 2nd Valkyrie, bought a 2001 IS new had it 5 years traded it for a new Goldwing in 06 and sold the Wing in 2011. Been without a bike for past few years until 2 weeks ago I bought a used 98 Valkyrie Tourer. Bike has 42,000 miles on it and honestly looks like a new one, has been well taken care of. On the test drive I noticed the backfiring on decell and figured it would just need a desmog. Rode it home, ran great other than the little puffing on decell. Tore it down, snatch all the extra weight out of it, drove some 14mm plugs down the 4 top holes then ground the nipples off on the tubes so they would fit back down in there holes on top of the freeze plugs. Did this to keep water from entering the new depressions and put back a little chrome. I just capped the 2 bottom tubes off. I pulled the carbs apart and cleaned them piece by piece. I broke 1 of the low speed jets off at the top so got a replacement 35S and put it in. Put everything back together, blocked off the front hole in the airbox, ran a line from the petcock to #6 intake tube, and checked and replaced the fuel lines and drains. Took a quart bottle of gas and primed the carbs thru the tank line then installed the tank and fired it up. Ran perfect, no decell popping, idled great, plenty of power. Drove about 15 miles and as I was pulling back into the driveway it started popping at idle and all the way up the scale. Went to the hydraulic shop, got some Viton #123 o rings for .12 each and installed them under the intake tubes. Checked to make sure all my boots where installed correctly and tightened everything down. I also changed the plugs and exhaust gaskets while I had it on the lift. So, I just got back from a short test run, depression is setting in but I'm not a quitter and am determined to whip this thing. It's now intermittently backfiring on the left side only. It runs good, no popping on decell, then it's there, then its not. If I hold the throttle at any steady rpm it starts popping constant just from the left pipe. So I need some input to help me whoop this thing. Thanks in advance for the help. Oh and I also tried running it with the gas cap open and no difference.

[gordonv]

Hi and welcome to the forum.

It's a little hard to read the one large paragraph, but I'll try a suggestion.

I'm not fully sure of what the issue really is, but I do think I know what you are saying. I would check by tightening my exhaust bolts. But be VERY CAREFUL! They are very small stubs and you only need something like 7 inch pounds to tighten. So that means with a wrench, just a little pressure, to see if they are loose, you aren't even tightening them. There is a crush washer there for a seal.

[Pappy!]

First off....welcome to the Valk forums! So, a second Valkyrie adopted you ! Good deal.
Now, on the popping, couple easy things to check would be the exhaust seals. Make sure they are not leaking. Edt)-Gordon beat me to it!
Try and richen the mixture on the cyls on that side and see if the popping goes away. There is no hard and fast number of turns you have to set your mixture screws at, just good ballpark figures.
check the vacuum lines that go to the decel valves on each carb. Did you check them while off? Lots of those old hoses are loose, cracking now.
This will give you a couple places to start. Good luck and keep us in the loop.

[Flat6Valk]

95% Chance it is the exhaust bolts.  like said before do not over tighten.  Good Luck

Greg
Flat6valk

[Wood Butcher]

I had the popping before I changed the exhaust gaskets, just put new copper rings in there today and no change. I rode it and got it good and warm then re torqued them again. I have a 2 post lift in the garage so I can raise it up over my head to work on it. Made the exhaust gaskets a breeze to do. I'm not an expert by any means but to me it seems like more of a spark issue or valve? I think I'm going to try and find something on the coils for testing them, unless you guys think that would be a waste of time? I did not change the short vacuum tubes on the sides of the carbs, but I will tomorrow.

[Wood Butcher]

Yes sir Pappy, I guess you would say it adopted me. My 68 year old neighbor has a Harley and has rode well over 100,000 miles on a bike. No, not that Harley, it would take at least 10 Harleys to get that far, but he likes to strike out about twice a year and travel on his bike. Anyway we were talking a couple months ago and he ask me to get another bike that he wanted me to come along on his last big ride. So I started looking and came up with another Valkyrie. Heading out from here in Fl. around the Texas border up along the Calf. border to Utah where we are meeting our wives who are flying out and then riding back after we tour the Grand Canyon. Not sure I'm up for it, but dang sure gonna try it. If I can knock the cough out of the old phat girl.

[Pappy!]

Am a Florida boy as well. Join us on the Florida section of this and say hello.
What part of Florida are you out of? Am located in Lake County, North of Orlando.
Try the simple things before you start messing with the coils. Doubt it is the coils for one and for two they hardly ever go bad on these bikes. Try the mixture screws and see what happens first.

[Wood Butcher]

I set them all at 2 1/2 turns out but can try another 1/2 out I suppose, can't figure why they would need to be out that far with stock pipes and all? I'm originally from Dunnellon, Fl. , moved up here between Perry and Tallahassee to my 150 acre hunting tract about 3 1/2 years ago. Big change in lifestyles. We are just getting 911 here. The last real frontier of Fl. Nothing big here but the sceeters.

[gordonv]

It sounds like you have enough knowledge that I don't need to say this, but I will. Some have said they found multiple exhaust seals crushed under their headers. Since you have a good look up under there, I wonder if there may still be an extra set wedge in the head?

Pappay mentioned the other thing I was thinking of, but couldn't remember, the vacuum lines.

You did say you did replace the intake runners O-rings?

[Wood Butcher]

Yes I did replace the o rings under the intake tubes, I did that at the same time as the exhaust gaskets and plugs. I'm going to replace those vacuum lines today and see what that does. I started to do that when I had the carbs out but they didn't look all that bad and I thought they part of the choke. I didn't study them to hard to see what their function was, guess I should have. I have that problem a lot, should have, could have, would have, but now it's do over. Guess I'll throw it up on the lift again and swap out those lines and pull the header pipe down on that side and take a close look at those gaskets again. Hope they'll seal twice, I don't have another set to put in there. That's the bad part of living in the middle of nowhere, its a 70 mile round trip to the closest town no matter which way I go. Sure appreciate all Y'alls help on here, this is great to have somebody to push thoughts back to ya. You got me thinking

[Ricky-D]

Sounds like a synchronization problem.

***

[Wood Butcher]

Well I stuck it back on the lift this morning and pulled the left side exhaust down. No double gaskets and all looked as though the header pipe had seated well on them at least no carbon signs bypassing them. I was in the process of putting it back together and my neighbor called and asked me to help him hook his tiller to his tractor. So I figured I would just jump on the bike and run down there. It's about 6 miles to my neighbors. I start it up and it seem to run fine, a little blue smoke rolled out it then cleared up. It ran almost perfect all the way and back. I think it sounds like a good excuse to get out and exercise the tires a bit. Not sure whether it had picked up some trash while reassembling the carbs or if the exhaust header was tilted one way or another? I tightened the bolts all evenly both times, so not sure what went right? Either way it seems fixed for now. Gonna ride it a bit and see if she starts acted crazy on me again. Got some of those honey doos to catch up on first, the old lady got some new chicks hatchin got to get the brooder up and running. Thanks again you guys for all the ideas, think I'm going to enjoy being a part of your group as long as you'll have me. Thank you

[Wood Butcher]

It could be a little synchronizing problem Ricky, it's not running 100% right now but seems to be getting better. Here in Fl. we have all this sand that blows into everything and instead of rebuilding the carbs in my shop I carried them up on the back porch to the picnic table and did it. You know just being sorry and wanting a sit down job. I synced them by setting the butterflies to all the same place to match the lead carb with the idle adjustment on it. I really only moved 2 less than 1/4 turn trying to make them perfect. It will have to work for now until I can build a set of gauges to set them with. For now I guess a little fuel treatment in the tank and add a few miles to the clock in hopes it will work itself out.

[Pappy!]

Ricky is probably on the right track. A bench sync is nowhere near as good as what can be done with a good set of gauges on a running engine. Go for it.