I need some back-up

[Chrisj CMA]

A friend has a 97 std.  Was complaining about loud exhaust popping.  He has unbaffled cobras, I told hime they will probably always pop a bit, but he replied this is new and bad on the right side.

So after tightening all the intake runners and changing vacuum lines we removed the exhausts and carefully replaced them one by one with new gaskets.  The exhaust tone was improved and no popping could be produced until the test ride.......popping still there

Heres my latest diagnosis.  See, immediately after replacing gross vacuum lines....soft gooey flat, not able to pass any air I dont think.......he said he noticed new sounds....ticking on one side and a kind of swooshing on the other.  I figured these sounds were comming from the pair valves/other smog equipment that is now getting vacuum, but is still not operating properly. 

My question- Can the smog stuff cause harsh popping at decel from highway speeds through the exhaust.  Im thinking it can but not sure what to suggest we do next?????

[SANDMAN5]

Desmog got rid of my popping %100!! All the other stuff you tried
will/can help, but for me the popping didn't completely disappear
until I desmogged.

[Kaiser]

Chris - I pulled this from Normand's (QueExpress) Desmog write-up in Shop Talk:

"Our Valks have been equipped with a secondary air supply system in order to reduce engine emissions .
Whenever there is a negative pressure pulse in the exhaust system (i.e.: when you close the throttle), fresh air is drawn into the exhaust port in order to promote burning of unburned exhaust gases.
This is fine until you experience an increase in rapid, annoying, popping/gurgling sounds when throttling down. With aftermarket exhaust systems, glass pack mods, etc., lower backpressure seems to make this annoyance even worse.
A permanent fix to this is the removal of the PAIR (Pulse Secondary AIR Injection) system as shown below."

Seems like you are on the right track with the desmog.  You and your friend should come on down to Gainesville.  I'll be desmogging mine soon, too.  Frosty adult beverages are on me if you show up.

[Chrisj CMA]

Hey Kaiser, thats a mighty enticing invite............Ill see what we can get goin on........Thanks guys for confirming my track of reasoning

[Chrisj CMA]

Is there anyone out there that desmogged and removed perfectly good pair valves just because they wanted them off?  Would you be willing to part with them.........could you pm me?  My friend may not want to desmog, but changing out bad junk for working junk may be helpful

[Chillerman]

Chrisj, check your messages.

[Chrisj CMA]

Thanks to Chillerman....looks like Im gonna learn the ins and outs of life under the Carbs.  I assume we have to remove the air box and the carb bank to change out he pair valve blocks..........is there any other way or is this our future?

[Chillerman]

Thanks to Chillerman....looks like Im gonna learn the ins and outs of life under the Carbs.  I assume we have to remove the air box and the carb bank to change out he pair valve blocks..........is there any other way or is this our future?

That is correct!  Better you than me!      Be careful what you ask for 
Seriously though, I hope that is the problem. 

[Thunderbolt]

Once you get in there, you will see that it's not that bad of a job.  9/16" freeze plugs and some epoxy, some fireproof gasket material.  There is one of the bolts that attached the pair apparatus to the engine that must be put back in the top of the engine, if not it pumps oil out, someone posted a picture of that.  I just put them all back in.  I set the pilots to 2 1/4 out while I have the carbs out for cleaning and of course clean all the orifices and jets while there, not much more trouble.  Then sync carbs when done. 

[Blackduck]

All I did with mine was to take the valve assembly off and cut a bit off the tubes the hoses go on, then put a ball bearing into each hose and refitted the valve assembly.
Looks stock but all blocked off. No popping and no way anyone can  tell by just looking at it that it has been modified.
Cheers Steve.

[GOOSE]

you need to look at xf6-custom, and the de-smog kit that he has.  he custom machines the plugs (4), and the 2-block-off plates (2)/gaskets that go on the bottom of each head.  the freeze plug route is definately cheaper, but.......(1) it looks cheaper, and (2) when you put a metal freeze plug in you make a bigger hole, and you now have two different metals working against each other (electrolyss)....eventually the plug rusts, nad the jb-weld cracks.  daryls plugs are stainless, and add two things to this picture:  (1) they look like factory plugs, thus don't draw any attention to a de-smog, and (2) they don't ever rust or crack, and fall out.

[fudgie]

Thanks to Chillerman....looks like Im gonna learn the ins and outs of life under the Carbs.  I assume we have to remove the air box and the carb bank to change out he pair valve blocks..........is there any other way or is this our future?

You leave the carbs in.

[Chiefy]

My question- Can the smog stuff cause harsh popping at decel from highway speeds through the exhaust. 

Don't have enough time in with Valks to comment much.  But on other carb'd bikes I've had, a lean mixture will do that too.

Just sayin'...........

[Earl in Pensacola]

Chris, you know if it were up to me, I'd try the method that "Blackduck" said worked for him. )The "ball-bearing" trick.  It sounds like the simplest, fastest and just as effective!   

[GOOSE]

chiefy..... not to change the subject, but what kind of exhaust are you running on that thar bike of yours?  it does look good.

[Chiefy]

chiefy..... not to change the subject, but what kind of exhaust are you running on that thar bike of yours?  it does look good.

Two brothers racing

[Chrisj CMA]

OK, like I said.........this is a new "popping"  Nothing was changed lately except new vacuum lines and at that time that cause him to start hearing new noises........ticking on one side (normal) and a weird noise on the right (same side as the popping)

I think he has a bad pair valve.  We are going to try to just replace a bad pair valve with a good one and see what happenes

[Sodbuster]

Hey ChrisJ - Just out of curiosity how many miles are on that '97 ??