Sputtering and backfiring after desmog

[Chiefy]

Rode it to work today and it ran just fine. It's only when raising the throttle in neutral or decelerating that it pops.  I will try and make some blockoff plates on Saturday. Do I need to get an actual gasket or do you think a high-temp RTV would be ok?  Because if so, I will put a thin bead under the top caps.  After putting the freeze plugs in, I cut the tubing off the caps and shaved them down closer to the o-ring so it would look nicer. I just put them in so the holes are facing away from view.

There was a recent thread that discussed this particular problem and the consensus was that it is a normal occurrence when the motor is free turning.

I feel you are worrying too much about the the plates, etc.  This stuff has no influence on how the motor runs, and you could actually leave the plates and freeze plugs (or whatever) off with no ill effects.

***

Here's that thread, MO

http://www.valkyrieforum.com/bbs/index.php/topic,33453.0.html

[Warlock]

Just finished getting the tank back on and did a test fire.  Had to turn the idle up a bit and my '97 valk is sputtering and backfiring.  Does it worse when applying throttle.  Would the bottom smog pieces cause that if they aren't sealed perfectly?  The gasket was a little chewed since it was factory.  I wasn't sure if the flow went in or out on those.

I made sure everything was tightened down.  Anyone have any ideas?

I still think it needs a carb sank. Some will run like crap after a De-smog. You will be surprised to find some off pretty good. Some I've done I didn't have to touch and some needed it. What you described seems it needs sanking.
David

[Mo_Corley]

Well, I will just quit worrying about it, then.  I'll wait and see if I can come across a good deal on vacuum gauges and look into doing a sync on the carbs.

Thanks everyone for your help. I am gonna take the long way home tonight!

[fudgie]

I occasionally get some popping when I 'high' idle my bike in the mornings. Not alot. Usually that tells me to check my header nuts. You might do the same.

[John U.]

There are rubber sleeves that connect the chrome intake tubes to the carbs. They have band clamps on the tops and bottoms which can loosen over time and cause vacume leaks.
I don't think what you've done to block off the desmog tubes is causing your problem.
I'll add my vote to use some Techron. The slow jets are very small and ethanol will clog them.

[CRASH]

This is timely info, my 98 std has been out of service for a year now after we flipped over on her back, but I have started it every 2 weeks. I now have a kustom built radiator on her and with the air filter removed, warmed up & at 3K on the tach you can watch each small burp out of the different stacks inside the air box every 2-3 sec. I thought I might have more problems but this info helps.

[partsiam]

Mo - you said, implied, that you had the decel pop before you did the desmog. And I think you said you did the desmog because of it. You also said you put the 2 brothers on back in June. Someone else had mentioned exhaust leaks will cause a pop (sucking in air around the gasket on decel). You might want to give the exhaust nuts a check just in case. I believe they need no more than 7 ft lbs of torque, they are fragile. Youmay take them down to be sure the exhaust gasket isn't kinked somehow too. All the other checks are well noted as well, check intake rubber adapter clamps for tightness, etc..

Sometimes it's the forest thru the trees thing

[YoungPUP]

I chopped up my stock air tubes for under the exhaust, filled and reinstalled them almost 6000 miles back, and not a problem with them since. Did you remove the exhaust to do the desmog? if so check to see that the header nuts are all torqued. 7ft/lbs ONLY these break pretty easily if you get rough with them.

[Mo_Corley]

I bought the bike in June and it already had the cobras on it.  I tightened down the header nuts a couple weeks later hoping that was the problem.  I did not remove them for the desmog.  The thing is, it will softly pop at idle, too.  It didn't do that before the desmog.  I am wondering if there was something in the emissions junk that was leaking and making the bike run leaner than now, but that doesn't make a whole lot of sense to me.

If the carbs being out of sync would cause popping, I will fix that when I get a chance (had a lot of bad luck lately.)  Might have to finish up the season trying not to be too embarrassed about sounding like a war zone when downshifting.

[YoungPUP]

The popping ( and the noise) are why I ditched my cobras. Never could tune it out. Maybe due to a lack of backpressure?

[fudgie]

I bought the bike in June and it already had the cobras on it.  I tightened down the header nuts a couple weeks later hoping that was the problem.  I did not remove them for the desmog.  The thing is, it will softly pop at idle, too.  It didn't do that before the desmog.  I am wondering if there was something in the emissions junk that was leaking and making the bike run leaner than now, but that doesn't make a whole lot of sense to me.

If the carbs being out of sync would cause popping, I will fix that when I get a chance (had a lot of bad luck lately.)  Might have to finish up the season trying not to be too embarrassed about sounding like a war zone when downshifting.

With it running spray something into all the desmog parts and see if it blows it back out.

What about them tiny vac lines on back of the carbs?

[R J]

This is  somewhat messy, but it finds vacuum leaks.   Just steal a roll of the SO's paper towels.     We use them in the shop for all our rag needs.     Sure cut down on the commerical laundry service, for some reason we always lost about 40 of those damn towels a week.    Seems like we paid $2.50 a dozen for the lost ones, and when they found them, they just kept them and still only delivered us 500.

Get a can of WD-40, insert the little red hose into the nose of the nozzle on the can and start the unit up. 

Spray a little bit around a tube ending, if the RPM's advance, you have a vacuum leak there.    Keep up the short spurt on each junction, end of hose, air filter intake tubes, top and bottom,  terminated desmog ends, if no slight advance of rpm for a short second, then you got other problems.

I'm betting my $$$$ on a vacuum leak somewhere..........    Good Luck in finding the problem, just be patient Grasshopper you'll find it eventually.   Don't go spraying around and no place in particular, as you never will find the leak.   That was the way one of our Sexual intellects did it, yes, he no longers works for us.   He was the 1st one my son, who owned the shop with me fired.   He has the shop all to his own now, so he has learned how to be a owner/manager.   Instead of my being their everyday, I make it out about twice, maybe 3 times a month.    September I never stepped in the door once.

Back to your problem, please keep us posted on what ya try and what finallt fixes the problem.

[sugerbear]

when your ready to sync the carbs, let me know i have the guages and can help.

i'm just outside st louis. about 3 1/2 hrs from you.

[Chiefy]

Mo_Corley....... Check this out:

http://www.valkyrieforum.com/bbs/index.php/topic,33871.new.html#new

[Mo_Corley]

I am not sure I can find ethanol-free gas in Missouri.  I think they passed a law a few years back to where it's all e10.

[Chiefy]

I am not sure I can find ethanol-free gas in Missouri.  I think they passed a law a few years back to where it's all e10.

Says here:

http://pure-gas.org/index.jsp?stateprov=MO

[YoungPUP]

Most of the time ( atleast here in indiana) 97octane is ethanol-less  Corn juice may be good for the enviro  but not for these bikes....

[Mo_Corley]

Hmm. Shows a spot about 15 miles away. I'll hit that up this weekend since I had to go on reserve coming home tonight.

[salty1]

Check the synch on your carbs. If you don't have an air leak(s), you may also need to turn out the pilot screws and richen up your fuel mixture, 3 turns max. I got 6 into 6 Cobras and they will pop some.

[Mo_Corley]

I have been messaging back and forth with sugarbear and I think I have a gummed slow jet or 2. I am going to run some heavy cleaner through it this weekend and mess with the spark plugs. Even at idle, it will pop every now and then.

I went looking for the station with raw gas and it is no longer there.

[Chiefy]

I have been messaging back and forth with sugarbear and I think I have a gummed slow jet or 2. I am going to run some heavy cleaner through it this weekend and mess with the spark plugs. Even at idle, it will pop every now and then.

I went looking for the station with raw gas and it is no longer there.

Take my heart-felt, friendly advice........ If the cleaner and spark plugs don't work, find another member and meet up somewhere.  Let him listen to your bike.  No offense intended, but your descriptions of the problem have gone from severe to minimal, and now you're drifting back towards the middle.  It's easy to lose perspective when you have nothing to compare things to.

It'll be a nice excuse for a ride, hopefully set your mind at ease, and you make a friend in the deal.  Win/win/win.

[Mo_Corley]

I had started to just shrug it off as one of those things until a couple co-workers came up the other night asking what was wrong with my bike.  If anything is starting to go wrong with it, I don't want it to come back and bite me.  If the cleaner and spark plugs don't do it, I am done wasting time and money with it.

As far as riding with someone, it seems so far that sugarbear is the closest and he is 3.5 hours out.  These last few weekends have been some of the only ones I have had off this year and I found out Tuesday that we are going back to 7 days at work next week.  So that means I just get to ride 13 miles to work for a couple days a week, again.  It bugs me that I don't have much free time to mess with it.