Popping out exhaust

[tory]

I pulled the carburetors back off yesterday. Disassembled soaked, boiled. And cleaned them thoroughly. Blasted with cleaner and blew all passages with 100lbs if air. I can see light through all 4 of the idle circuits.
I bypassed the air cut off and replaced the vacuum line with a new tight line.

It started well. Idled smooth with no popping for a good 20 minutes. I tried an idle drop, but hard to hear much difference other than all the way in. Maybe even less noticeable on cyl 1.

But again, no pops as it idled for 20 min. I took it for a 10 minute ride and it still breaks up at 4000-4200 then pulls smooth. After returning home letting it idle the popping returned.

[Whiskerfish]

Tory sorry if I missed it but have you dropped the header and checked it??

The issue we are asking about looks like # 3 in this pic. You can see the swell in the inner liner of the header effectively choking that cylinder. It seems to be happening more often as these bikes age.

[tory]

I have not. I've never seen this happen in any previous bikes (that I'm aware of) but sounds more common than I thought. I'll take a look next chance I get to work on it. Work will take me out of tien again thus week and I'm afraid my wife has next weekend planned. Lol

[redglbx]

Tory, as Steve said as these bikes age the inner pipe collapsing or coming loose seems to be a more common thing, while you have it apart look closely for any cracks or pin holes as those are also very possible. Honda used the double walled pipes on all their bikes “back in the day” to minimize blueing of the head pipes, never understood it on the painted black GL head pipes, just provides a restriction imho,,, but I’ll add that I’ve never seen or heard of the inner pipe coming loose on anything else like the cb750 or CBX’s but they should.

Not sure if the blueing reduction is the only reason of why Honda did this,, but anyway check yours out it was a problem on mine.

[Whiskerfish]

I have seen 3 of these in person now. That is out of maybe 25 or 30 bikes I have wrenched on. I know that is a small sampling but pretty close to one in ten.

[tory]

Assuming the inner pipe us collapsed, wouldn't that make the pipe on that cylinder much hotter? I may be thinking wrong, but if a cat on a car is plug, generally the pipe ahead is very hot.

[Whiskerfish]

I don't know. Remember dealing with a CV flow system. In my head if you reduce the flow out you are reducing the flow into the combustion chamber and that would result in a decrease of energy???

[ericheath]

I’m thinking a tight exhaust valve could cause this. Or a cam out of time. I would check the easy stuff first.

[tory]

I think I'm at the end, and to the "live with it" point.

I dropped the exhuast and see no collapse if inner pipe. I could even shove a foot of fuel line down it.

I check valve clearance again, opening up to the high end.
I verified cam and ignition timing.

This thing starts better than any gl1000 gl1100 or gl1200 I ever owned. I can actually turn the throttle idle down to just a few hundred RPM and it likes it.
At initial start it will idle calm as can be, and you do not get the first pop for a good 5 minutes.

It does seem to pop less with #1 idle jet turned in. And when turning, every once in awhile while turning screw, it seems the engine jumps up for a split second making me think the #1 is not always hitting at idle. Seems crazy considering how good it starts and seems to run.That pipe is cooler at idle than the others by a couple hundred degrees. but not after a ride. It does break up slightly between 4000 and 4200 RPM but smooths back out.
Plugs all look nice and grey.

[Rat]

Fill up with nice, fresh gas … ride 200 miles … fill up with nice, fresh gas … ride …

Gord

[cfairweather]

Tory- Sounds like you have tried everything . It really is hard to say what is causing the issue at this point, but I believe it is most likely your carbs and I am willing to help you know for sure if the carbs are part of the problem, or not. What are the carb numbers of the set currently on the bike? Then let me know the numbers on the spare set. Check each carb to make sure they all have the same number. If you ship me your spare set of carbs and your spare parts, I will fix them and test them on a test engine stand. Even if your second set is not complete, send them to me as I have lots of carb parts and will make them work like new. It will only cost you shipping and any new parts, if needed. I won't be using expensive Randakk parts (unless you pay), but I will use good quality parts. I will pay for most of the new parts like o-rings, seals, etc. I occasionally help people that are at the end of their rope. Send me a PM and I will give you my address. I am in the middle of redoing my shop, so it will take me a month or so to finish your carbs, but since this is your spare set, you shouldn't be in a big rush. Cedric

[Sidecar Bob]

I think that may be the best offer you will see any time soon.

I can actually turn the throttle idle down to just a few hundred RPM and it likes it.

It probably won't like that for long. If the idle is too low the oil pump may not provide enough pressure to lubricate everything properly.

[tory]

I think that may be the best offer you will see any time soon.

I can actually turn the throttle idle down to just a few hundred RPM and it likes it.

It probably won't like that for long. If the idle is too low the oil pump may not provide enough pressure to lubricate everything properly.

Very generous offer indeed. I qill reach out in a PM

I do have the idle set about 1000 RPM. Just was amazed how low it would actually idle down and not stall.

[redglbx]

Tory, the fact that it will reliably idle down speaks well of your tune, I’ve done basically all the same stuff as you, the only difference us that there is no breakup/hesitations in mine when revving it up, just smooth & fast.

Personally I’ve done the whole timing, valve clearances, compression, leak down, new plugs, things and it still pops at idle out of the left bank. I am of the opinion that it has to be something cross talking in the Dyna modules or Dyna coils,so those are on my list if I have a good back day. Part of my plan is to run a straight 12v to a distribution block straight from the battery, maybe something cross talking from the 12v Dyna supply source , just thinking out loud here.

What kind of ignition & coils do you run ?

[tory]

Using MP08 coils and still point ignition.
Keep me posted on your success.