popping on decel...

[MAD6Gun]

 I have boon working on my brothers 97 Valk for the last few weekends. He has had a long term popping noise on decal. He says he thinks its coming from the right bank. He had it before he changed to MarkTs exhaust but not its louder because the exhaust is louder. We just did the Desmog. After we got it back together yesterday Chris took arould the block and it still has the pop. I have not synched the carbs yet but I will be doing that soon. I have heard that if the carbs arnt synched that this could cause the pop. I am not sure. Either way is there any other things that can cause the problem other that the smog crap,sync and intake seals. (they have been replace as well).

 Any help would be greatly appreciated. Thanks....

[JC]

Any air leaking into the intake side can cause this problem. Check the orings under the intakes, You might find that all is needed is tightening the bolts holding them to the top of the crankcase. Also, check how tight the 3 hose clamps are on each carb (yes, there are 3 on each one).

[nogrey]

+1 on what JC said. You said you desmogged. Did you use all new vacuum caps on the intakes? Is the vacuum line on #6 to the petcock in good, non-leaking condition?
Personally, I'd do a carb sync. It only takes about 30 minutes and I've had it clear up issues like this.
Other things to look at are:
1) Hoses on air-cut valves are notorious for being overlooked and leaking. Will cause popping on decal (that's what the cutoffs are designed to do, enrich fuel during decal.)
2) O-rings on intakes should be "tall" enough to seal properly.
3) Did you seal up the air hole in the air box created when you desmogged? It would be the one that used to go to the reed valve assemblies that were removed.
4) Pilot screw adjustment can cause this as well, and the Pilot screw "O" rings can leak. The only way to really tell is to replace them. They cost about $4 from redeyetedh. (look on ebay).
5) Clamps on the 6 Rubber intakes that go from the air box to the tops of the carbs. Check the back sided of those for a possible crimp condition that could allow air leak. These are sometimes difficult to get seated on top of the carbs properly.
6) Check for tightness of the black connectors on the chrome intakes. There are two clamps per intake.
NOTE: My terminology may be a bit confusing when I say "intakes". There are two sets: The air intakes to the tops of the carbs, and the chrome intakes to the manifold from the bottom of the carbs.

I'd check those things. I'd also consider the possibility of replacing the slow jets with 38's. I know you said that the problem existed before you installed the "Mark T's", but it is still usually necessary to reject after putting low restriction exhausts on.

Hope this helps.

[wiggydotcom]

When you re-installed the pipes after the MarkT conversion, did you go with new exhaust gaskets?
Did you get the old ones completely out?

My bike was popping due to the exhaust nuts coming loose during the 100 mile breakin of the gaskets. I retightened the exhaust nuts that were loose and all is well.

And don't overtighten them.

[Thunderbolt]

Nogrey's item 1 the small lines to the air cut valves are often overlooked.  They will look good on the outside, but when you remove them and squeeze the end between your fingers they will have a lot of small cracks.  Some are easy to replace, but a couple are difficult without removing the carb bank. They are only about 1 1/2" long and are on the left side of each carb.

[Lazy]

Nogrey's item 1 the small lines to the air cut valves are often overlooked.  They will look good on the outside, but when you remove them and squeeze the end between your fingers they will have a lot of small cracks.  Some are easy to replace, but a couple are difficult without removing the carb bank. They are only about 1 1/2" long and are on the left side of each carb.

Are these lines something that are bought individually from Honda or like a regular vacuum line?

[nogrey]

Nogrey's item 1 the small lines to the air cut valves are often overlooked.  They will look good on the outside, but when you remove them and squeeze the end between your fingers they will have a lot of small cracks.  Some are easy to replace, but a couple are difficult without removing the carb bank. They are only about 1 1/2" long and are on the left side of each carb.

Are these lines something that are bought individually from Honda or like a regular vacuum line?

You could do either. I would just remove one and take it to an auto store and buy a couple of feet of vacuum line.

[whitestroke]

I bought them from redeye, They come in a kit but if you ask they will sell you the 6 hoses.

[R J]

I have boon working on my brothers 97 Valk for the last few weekends. He has had a long term popping noise on decal. He says he thinks its coming from the right bank. He had it before he changed to MarkTs exhaust but not its louder because the exhaust is louder. We just did the Desmog. After we got it back together yesterday Chris took arould the block and it still has the pop. I have not synched the carbs yet but I will be doing that soon. I have heard that if the carbs arnt synched that this could cause the pop. I am not sure. Either way is there any other things that can cause the problem other that the smog crap,sync and intake seals. (they have been replace as well).

 Any help would be greatly appreciated. Thanks....

Hey Mark.

If you know which side is popping, it sounds like you might have a screwed up gasket in one of the holes.

I fought that on MGM when I put my Viking pipes on it.    One gasket had gone in catty wampus and I had a good sized exhaust leak, and it made it pop like a SOB on deceleration.

Pulled the side down, replaced all the gaskets again and tightened her up.   Was careful not to bust a stud.

Poppin went away, then I got a slight bubble on deceleration, went back around the nuts again and it went away, 100 miles later I did it again.    Haven't messed with them since.     I think it was at InZane 4 or 5 that I got the pipes.    Vell, it was the last InZane at Zanesville.

Dragbars, LaMonster, a couple of other guys helped put them on in the parking lot around back.   We got them on and we went for a ride.   Came back and put a couple of turns on the nuts and headed MGM for home.    Stopped in Peoria, IL and tightened them the last time.

[Psychotic Bovine]

Ok, Mark and I are at the end of our rope on this thing.
It still pops on deceleration and also pops when holding steady RPM (while riding or just sitting).
So far this is what has been done:
desmog
sync carbs
replaced all vacuum hoses including the ones that go to the air control valves on each carb (the short hoses)
re-torqued the header bolts

Things we have found out:
It only pops out of the right bank.  
it pops like a machine gun on decel, at constant speed, not so much (but quite a bit).
If you apply a little choke to richen things up, it runs perfect.
It pulls hard on accel, no rideability issues.

No dealers are open in the area on monday, so I have to wait until tuesday to put it o a sniffer to see if it's running too lean to hurt it.

Future ideas I have considered:  shimming the needles to richen it. Has anyone needed to richen while running Mart T exhaust?  I was told it didn't need it.
replacing the air control valves if we can isolate which cylinder is doing it.

Does anyone have any ideas at all beyond what you helpful blokes has already suggested?
thanks much!

[big poppa pump]

When did you last check/replace the intake manifold O-rings?

[Psychotic Bovine]

When did you last check/replace the intake manifold O-rings?

sorry, forgot to mention that.  did that when we desmogged.

[R J]

Hey Chris, is this pop pop pop on one side?

Do you know wht cyclinder?

I'd look at the intake o-rings first.   Sounds like maybe one got rolled over at installation.

Trust me, tell Mark it is not hard to do.

[Psychotic Bovine]

we can't determine which cylinder it is.  But, Mark is bring his mechanics stethoscope home and I figure we can listen to the header and determine which cylinder it is.
We checked and double checked the o rings during install and they are fine.
We put seafoam in the tank last night to hopefully clean the carbs..  This morning I took it out and beat it like it owed me money.  Quite a number of times to redline at full throttle through first and second.
Problem is still there.

[R J]

I got faith in Mark, he should be able to find the problem.

I know when I replaced my o-rings I screwed one up and it did a lot of backfiring.

It was in the groove properly, but an 1" of it did and extra roll, which left air holes to suck raw air.

I also had a exhaust gasket in rooster eyed.

Between the 2 that was my problem.

Chris, after your SeaFoam treatment, you were supposed to ride it a few miles, like 30 to 40, under 2,200 RPM's before you twisted it tail big time.    Otherwise all you were opening up was the main jets, instead of the slow jets.

Good Luck.......

[Thunderbolt]

I've told this one before but bear with me.  I have a 1972 International Cub tractor that I had to run the choke partial on to get it to run at all.  Turns out that the previous owner had torqued the 4 screws that secure the top to the bottom bowl section of the carb so hard that it was warped and sucking air between the two halves.  Once I got it to fit correctly problem solved.  Point here is that it must be sucking in air and leaning out the mixture if it runs better with partial choke.  Keep looking for a vacuum leak.  You might try in a well ventilated area squirting some WD40 or carb cleaner using the aiming tube in different possible areas that could leak and see if rpm's increase at any point.  If they do you might have found your source.
I also think that someone reported that they had a defective air cut valve.  Another possibility.

[Psychotic Bovine]

Ok,  Mark and I worked on it again.  We sprayed carb cleaner at every potential leak point and no change in sound.  The popping is getting worse at constant throttle, so until we find the issue, the bike is immobile.  Dad is loaning me his 'strom for the PA trip.  Ironic that I have two bikes, but have to borrow a third!  There is no way I can ride the Triumph for that distance, and it would be far past the 500 mile break in service when we returned even if I could.
When we return, will be rebuilding the carbs, since we have checked everything else.
Thanks much to you guys here!

[fudgie]

Can u put the oems back on and see if its still there? Heck id run on ur trip i dont think it would hurt it.

[solo1]

I think that Mark and Chris made the right decision.  One cylinder is running too lean and could result in predetonation, heat,  and a holed piston.

Putting the original exhaust back on probably wouldn't help as it was doing that with the old exhaust too.

[MAD6Gun]

I worked on it for two hours last night. Pulled all three intakes tubes and check the seals All were ok. Sprayed brake clean around all intakes and vacuum lines. Was unable to detect any change. As it gets warmer the popping gets worse. We found that the popping goes away if we put the choke on a little bit. So it is running LEAN for sure.

 I called my Buddy DOGG in Maryland and ran if for him on the phones. He said that it is running way lean. He suggested trying to run a whole can of Seafoam through it and see if it cleans it out. If not he thinks there is something in the carbs. So tonight I will put the Tank back on and have Chris ride it tomorrow. If it does not clear up than its stays home and we go into the carbs later. Chris will ride Dads Strom to the POWWOW. Thanks for everyone's input....

[fudgie]

Would adjusting the pilots help?

[Ricky-D]

You may have thought the bikes carburetors are synchronized but

to me it sounds as if that is still the problem.

The cylinder is loafing, which in turn is causing the popping.

Get a good synchronization and all will be well.

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