Rpms stop at 5k when accelerating under load

[natemoen]

Good!

As Don said the factory setting were a government emissions compliance thing, everything has changed since then so it doesn't matter anymore.

Here is the thread to follow.

http://www.xs11.com/forum/showthread.php?t=36017

No need to dip them, most people don't do that anyways. Just get a few cans of whatever spray carb cleaner you use and some brushes to clean with. I use these brushes from harbor freight and they work great for nearly every passage.

http://www.harborfreight.com/househo...hes-68155.html

Do not pull the emulsion tubes out the top, push them up and out from the bottom. If you pull them out you can damage that lip that is in the carbs air stream.

[WMarshy]

Do you think it's necessary to soak them again? It's really expensive for that carb soak stuff ($35 here and I'd need 2 cans to fit all of the bodies in). I was just going to get some of that Berryman B-12 spray carb cleaner and work with a little bit of acetone I have (making sure to keep it away from rubber seals and what not).

No need to soak them. All you need is a can or two of carb cleaner. High pressure air is also really useful if you have a compressor with hand gun to blow through all the passages. Take everything apart and let it soak in a little bowl of carb cleaner. Blow the carb cleaner through all the circuit hols in the carbs, use eye protection as it might just come back out from a hole facing you. The key is taking the emulsion tubes out. Pound them out with a wooden dowel from the bottom where the main jet threads into. Dont beat up the other end with the little 'fin'. We have good tutorials on cleaning them. Might be worth browsing before you clean... Take the idle screws out and clean them as advised...

[motoman]

No you haven't. You said in one of your other carb threads that you have not pulled the mixture screws out yet. You need to remove that cap and pull the mixture screws, and clean in there and replace the o rings on the mix screw. If you didn't remove the emulsion tube the irst time then there again is another reason you need to go back and clean again. Soaking them doesn't do enough if you are not in there me mechanically cleaning as well. Also, if you haven't leveled your floats out yet so that both sides of the floats are at 23mm you need to get that done as well.

They call it elbow grease for a reason! You are not going to solve this by just doing half the job and then spend your time chasing carb issues. So go back and do a complete disassembly, clean scrub, and blow out every passage.

Exactly what I answered in a response to a PM from him answereing how to remove emulsion tubes, etc.. His choice.......either follow from the knowledgeable here or this is going knowwhere(neither is the bike). Throwing different main jets and such at it ain't gonna cut it.

[motoman]

No offense intended here Downshift, but no getting around it......your not gonna be able to 're-invent the wheel' here. It's already been done.

[D0wn5h1ft]

Ok, so I just finished pulling the carbs COMPLETELY apart, cleaning every nook and cranny, went through 2 20oz bottle of carb cleaner, scrub every part with a toothbrush, cleaned the ports with a non-abrasive brush, and reassembled with precision. Checked my float levels for the 6th time and pre-synced the carbs.

I took her out for a spin and I'm still having the exact same issue. Same chop when I hit 5k, no different than before. I even tried opening up the petcocks to "prime" to make sure there wasn't some weird malfunction happening.

I really didn't want to believe this but I think this bike has inherited the curse of the dual mac 4-2 exhaust. The guy I bought the exhaust from said he could never get it to work on his '80 special no matter how he jetted it, when I took off the 4to1 and put on the 4-2 on my '78 it went from running like a dream to running like crap, and now it's on this '79 and low and behold it runs like crap. The '78 had a similar issue with struggling in the high rpm/WOT range so I think this can only be attributed to this terrible exhaust.

Is it possible that this set just doesn't have the back pressure required for the bike to operate properly? Or maybe there is some subtle difference in the two sets of pipes that causing uneven throttling at large throttle openings?

I guess I could start looking at ways to increase the back pressure or better seal the mac slip ons it has.

[natemoen]

Have you synced the carbs yet?

Plenty of people run the Mac 4-2, it was the only exhaust that was still in production up until this year, and they do not have any issues.

Is there something in the exhaust clogging it so that it creates too much pressure?

[D0wn5h1ft]

Have you synced the carbs yet?

Plenty of people run the Mac 4-2, it was the only exhaust that was still in production up until this year, and they do not have any issues.

Is there something in the exhaust clogging it so that it creates too much pressure?

The carbs have been pre-synced according to the guide and they're dead on. I know that a pre-sync doesn't qualify as a true sync but I think this is much larger that that because it pulls amazingly at low rpms when you roll on the throttle.

I'm fairly certain there's nothing in the exhaust that's plugging it up but I guess I can take off the slip-on turn outs and have a gander down each tube with a flash light. One thing does concern me, though. And it's that there doesn't seem to be that good of a seal for the slips ons. Could a bad seal between the slipon and the header cause enough of a drop in back pressure to create an issue?

[natemoen]

All the bench sync is intended for is to have a base line to start with that will let the bike start and warm up. It is in no way a replacement for a real sync. You need to start with the small things that you know are a problem and work up to the bigger things that are guesses.

Could the exhaust leak be an issue, maybe, I am not there to know how bad it leaks. Try taking the slip ons off once and see how it responds.

[D0wn5h1ft]

All the bench sync is intended for is to have a base line to start with that will let the bike start and warm up. It is in no way a replacement for a real sync. You need to start with the small things that you know are a problem and work up to the bigger things that are guesses.

Could the exhaust leak be an issue, maybe, I am not there to know how bad it leaks. Try taking the slip ons off once and see how it responds.

Big update: So I took the dual mac turnout slip ons off and bam. Cruised straight through 5k rpms like no other. Only issue is that the problem is only about 90% fixed, for several reasons. First, I decided to do a high load gear change and it stumbles a bit if I have to open up the throttle a lot under load. Second, I don't think running open pipes is really a solution because I'm probably going to go deaf if I have to ride this thing open.

So if I took the exhaust off and ran straight pipes and the performance significantly increased, what does that tell us about the real issue? Is it a mixture problem that is getting covered up by taking off the exhaust? If so, does taking going to straight pipes cause the bike to run leaner or richer?

[DGXSER]

Very interesting. Open exhaust will typically lean out the mixture.

However, while it is idleing, take a propane torch, unlit, and wave it around the intakes ad the carbs near the butterfly seals. You mentioned soaking the carbs in dip, the butterfly seals often do not like that, and you may have a big vacuum leak there. This may be causing a lean condition.

I would also suggest checking the markings on the needle jets, and the emulsion tubes of your carbs. Just to be sure some PO did not play mix and match and get the wrong needles for the emulsion tubes you have in there.

[D0wn5h1ft]

Very interesting. Open exhaust will typically lean out the mixture.

However, while it is idleing, take a propane torch, unlit, and wave it around the intakes ad the carbs near the butterfly seals. You mentioned soaking the carbs in dip, the butterfly seals often do not like that, and you may have a big vacuum leak there. This may be causing a lean condition.

I would also suggest checking the markings on the needle jets, and the emulsion tubes of your carbs. Just to be sure some PO did not play mix and match and get the wrong needles for the emulsion tubes you have in there.

Wouldn't it be a rich condition if removing the exhaust leaned out the mixture and resulted in better performance?

If it leans out the mixture then I guess with the old exhaust on I was running too rich in the main circuit? Low rpm power is still great and high rpm behavior is about 80% with a bit of stuttering issues when it's under a lot of load. I do have 120 mains in right now so I could try stepping back down to 110 mains and seeing if the problem goes away.

What gets me is that I had this exact same issue with the '78 with this exhaust on and pods filters just like this '79. When I checked the plugs on my '78 they were sooty and everyone here said that it meant it was way too rich. With the same pod intake and exhaust set up on this '79 it sounds like I might have been in the same situation as before. Too rich and then when I took the exhaust off and went to straight pipes I leaned it out enough to perform semi-correctly. That's my train of thought at least.

I do agree though that there might be some sort of vacuum leak happening somewhere because my idle is a bit erratic. I seem to have to fiddle with the idle a lot because either it will be too high after I blip the throttle or after I make a good run it is too low and will stall. I just don't know where it could be coming from since the carb boots are in great condition.

[bikerphil]

Your mixture is now set up too rich for that restricted exhaust. With the open system, the extra fuel can now be burned and disposed of. The motor can't properly inhale if it can't exhale fuel/exhaust.

[D0wn5h1ft]

Your mixture is now set up too rich for that restricted exhaust. With the open system, the extra fuel can now be burned and disposed of. The motor can't properly inhale if it can't exhale fuel/exhaust.

Woah, my brain is hurting because it goes against everything that I thought I learned from this site. Usually, from what I've read, is that pods increase airflow so your mixture will be lean (+1 for lean) and that 4to2 exhaust has less back pressure than the stock 4to1 which means it's more like open pipes so (+1 for lean).

All the normal indicators would point out that the mixture should be too lean but the exact opposite seems to have happen all with stock jetting! (this was still happening even before I moved the 110s to 120s). I think there must be something SERIOUSLY wrong with those dual mac exhaust slip-ons that I have. I don't know if a critter crawled up and died in one of them or what but logic says that they should be much less restrictive than stock exhaust.

[DGXSER]

To dispel some misinformation you have, the stock system on all XS11s was a 4-2 system. Any 4-1 was an aftermarket change.

You have a point that it seems your running rich, I was just trying to go small step at a time. The fact you had the same POD filters on both bikes and had the same issue may be the common factor. Try putting the slip-ons back on, and removing the POD filters and taking it for a run. Not that running with no intake filter is a permanent solution, but it won't hurt for a quick run. And it may reveal the culprit being the POD filters.

If that gives you the performance back, take a pic of the POD filters and one with them mounted.

[CaptonZap]

As an homage to Mr Wizard, take the slip ons off, and get a vacuum sweeper or shop vac that has a blow hole.
Take the hose, and fix some arrangement that will allow you to insert the hose into the inlet of the muffler without to much leakage, and still allow you to withdraw it and reinsert it.
Turn on the vacuum. Insert the hose.
Listen to the speed of the vacuum. It should increase
Remove the hose and see how that affects the vacuum motor speed
Do the same with the other slip on. Are they both the same as regards the speed up of the vacuum motor?
Place your hand over the end of the hose, and compare the speed increase to the speed of the slip ons.
If that speed is close to the slip on speed, you could have some plugged mufflers.
If you have a known good muffler, compare it's effect on the vacuum speed to the effect the slip ons have.
Gosh-o-mighty Mr Wizard, I bet you can't do that again!
CZ