Rpms stop at 5k when accelerating under load

[D0wn5h1ft]

Well, you need to first COMPLETELY disassemble your carbs. Pull the caps on the idle mix screws and clean everything.

Then we will go from there.

I've already done this about 2 months ago. Had the diaphragms, all the jets, float seats, everything apart and soaked it all in carb cleaner that doesn't melt the butterfly seals. I can't imagine that it needs to be done again but if this next couple jet changes doesn't fix it I'm going to drop the emulsion tubes out and go at them with some carb cleaner and a toothpick.

[mack]

advances

try this:
http://www.xs11.com/forum/showthread...anical+advance

Now the maintence for them can be found in a thread three phase did and it is step by step. It took me awhile to find this one, I search again and see if I can find it

[mack]

found it.

Here is Scots thread on mainenance of the mechanical advance.
http://www.xs11.com/forum/showthread...anical+advance

[trbig]

I tried running without my pods on and all I got was back firing out of the carbs! You could see the little explosion where it was happening so I put the pod filters back on. I don't think they are the same emgo pods that most people have because the way they mount is different from the ones that I had on my '78E.

If it's lean should I try bumping up the mains to the 120s I have and give it a shot? Also, I'll check the mechanical advance tomorrow afternoon but this was a good running bike before the PO had disassembled it (I received it in a few "parts buckets"). I'll also wipe the plugs down with some acetone before I go out to see what color they turn and then I'll post pictures.

If it's backfiring out the carbs, something in your timing isn't right. The pod filters in question... Does the rubber collar go onto the intake bell, then neck down and have a filter that attaches onto that, or is the collar/filter a solid one piece unit?

[D0wn5h1ft]

If it's backfiring out the carbs, something in your timing isn't right. The pod filters in question... Does the rubber collar go onto the intake bell, then neck down and have a filter that attaches onto that, or is the collar/filter a solid one piece unit?

So apparently the carb backfiring like that is a symptom of an overly lean mixture according to mikuni's tuning guide http://www.mikuni.com/fs-tuning_guide.html . This would be consistent with the feedback I've been getting about my loss of power at 5k rpms. I have a set of 45 pilot jets that I bought (the stock 42.5 are in the carbs right now) and I have a set of 120 mains that I can try. I'll change out 110 mains for 120s, test it, and see if that helps.

To answer your question about the pods, it has a rubber collar that necks down to the pod not a solid piece. It fits completely over the bell without any overhang into the radius of the bell itself, where it would interfere with the air jet.

[TomB]

Hi D5hift,

I clicked on the link you posted, then clicked on the "backfires through carb" link, they seem to be talking about Hardley's not XS1100's, but they do mention ignition being a factor in backfiring through the carbs, and the lads here have mentioned checking the mech advance, its easy to do and with bikes this age do give a bit of trouble from springs breaking to just be dry/corroded.

It might not be the mech advance but its easy to eliminate.


Tom

[Gallaecus]

Hi D5hift,



It might not be the mech advance but its easy to eliminate.


Tom

how do you eliminate it ? unplug ? cap off ?


I had a similar problem with a rack of carbs,
if i quickly went WOT it would starve, at any rpm.
i swapped the rack with another set and problem went away.

if your problem is at a specific rpm (5k)?
or if your problem happens with WOT and not a slow roll on throttle.?

[natemoen]

I've already done this about 2 months ago. Had the diaphragms, all the jets, float seats, everything apart and soaked it all in carb cleaner that doesn't melt the butterfly seals. I can't imagine that it needs to be done again but if this next couple jet changes doesn't fix it I'm going to drop the emulsion tubes out and go at them with some carb cleaner and a toothpick.

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.

[sparkfly88]

You seriously have to detail clean these carbs...

I soaked mine in cleaner for 3 days, pulled em out, blew em with high pressure air..


And i still had running problems!

I stripped the carbs down to every little piece, and thats when I found out the emulsion tubes come out. You should have seen the funk that came out of them that the cleaner didnt even touch!

[sparkfly88]

See what hides in these things when they arent TOTALLY taken apart?

[TomB]

how do you eliminate it ? unplug ? cap off ?

Ah yes, two nations seperated by a common language

Sorry, I meant eliminate the Mech Advance as the cause of the problem by making sure it is working correctly.

[D0wn5h1ft]

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.

Ok, I'll submit . I just changed out the mains for 120s and it does the exact same thing. It will fight past the barrier eventually but I have to go WOT to do it and that's not a solution.

I'm going to tear apart these carbs again and really get at them to make sure everything is perfect this time. I do have one issue though and it is that the manual says don't tamper with the mixture screw because they are factory set. That combine with the fact that I don't have idle circuit problems makes me believe I should just leave them alone. But maybe I'm wrong.

[DGXSER]

OK, the manual says this because the factory had to set those lean to meet the emissions requirements of the day. That's why they had to put the plugs in place. A lot has changed in 30 years, including the state of the components under that plug, and the fuel we burn. So the factory settings are long past pertinent.

The old saying on here is the carbs are not cleaned until they are "triple cleaned". That saying has been coined because almost every one tries to get by with minimal cleaning the first go around, they start to see the need of cleaning deeper, and then after twice not getting the results, they finally dig in deep and get them clean throughout. Triple cleaned.

So, save yourself some time pulling and installing stuff, look at the carb 101 tech tip, pull them down all the way, clean everything, every passage, every opening, every pinhole as clean as you can get it, then go over it one more time with carb cleaner and a brush, pipe cleaner, wire or whatever to ensure it is clean. THEN put it all back together. The smallest passages make the biggest difference in your performance.

While the pilot circuit primarily effects the low end, it is not completely gone on the upper end.

[D0wn5h1ft]

OK, the manual says this because the factory had to set those lean to meet the emissions requirements of the day. That's why they had to put the plugs in place. A lot has changed in 30 years, including the state of the components under that plug, and the fuel we burn. So the factory settings are long past pertinent.

The old saying on here is the carbs are not cleaned until they are "triple cleaned". That saying has been coined because almost every one tries to get by with minimal cleaning the first go around, they start to see the need of cleaning deeper, and then after twice not getting the results, they finally dig in deep and get them clean throughout. Triple cleaned.

So, save yourself some time pulling and installing stuff, look at the carb 101 tech tip, pull them down all the way, clean everything, every passage, every opening, every pinhole as clean as you can get it, then go over it one more time with carb cleaner and a brush, pipe cleaner, wire or whatever to ensure it is clean. THEN put it all back together. The smallest passages make the biggest difference in your performance.

While the pilot circuit primarily effects the low end, it is not completely gone on the upper end.

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).

[Schming]

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).

Berrymans B-12 and an air compressor is all I use after soaking in Pine-sol for 24 hours.

Using the info from the site, knowledge and suggestions of the fine minds here I get away with a SINGLE CLEAN but mostly I'm known by SWMBO and a few others as ANAL.

For ex:



Here's a couple pics of the mixture screw cap removal on a set of Hitachi carbs but relatively the same as the Mikunis:







When you get the caps out squirt some PB Blaster or similar in the bores that house the mixture screws AND customize a dedicated screw driver to fit the screw heads

Carefully drill the holes in your caps and DON'T let the bit go in too far.
Also, notice I ground off the sharp point on the drywall screw:



When you get done cleaning and assembling you carbs, you may want to bench check the float levels:



And a set of Hitachi's from my XJ 750 Midnight Maxim:



Also, to start off, set your mixture screws @ 2 turns out from LIGHTLY SEATED.
I emphasize the care to be taken with the mixture screws as they are very delicate

Also Again use a light coating of silicone grease on the O-rings and shaft seals during reassembly.

HTH GL