Opinions on my acceleration issues.

So for some background, so far I have:

- Fully disassembled the carbs, boiled them in lemon juice, tested the starter circuit, polish the slide bores, passes clunk test
- Fixed and confirmed there are no vaccum leaks (propane test)
- Polished the float needles, adjusted the float height (might still be 1-2mm off though after having the carbs apart several more times?)
- Sync'd with a homemade manometer, and roughly colortuned/ear tuned the idle. My mixture screws ARE concerningly far out though, like 5+ turns and still not turning fully yellow

It idles pretty well around 1000rpm, has good off idle throttle response, revs freely... But when accelerating in the lower rpms it feels a bit down on power, and when I hit 4000-5000rpm the transition from the pilot circuit to the mains is bog/stutter/shudder then SURGE. I get great power from then on.

The one thing I haven't fixed yet is my valve clearances, they are:
E1 .127 E2 .178 E3 .127 E4 .102
I1 .102 I2 .102 I3 .127 I4 .152

Now, are those clearances bad enough to cause this kind of issue? I assumed it might just cause a lack of power. Could this still be mis-adjusted floats? Bad gas? I do have some seafoam, and it's diluted old gas from last year. Need new plugs from tuning? What do you think this sounds like. I'd really like to avoid pulling the carbs again if possible, but I'll do it if needed! Just would like to know a possible offender.

 

Re: Opinions on my smooth running issues.

YOU GOT SOME OUT OF SPEC VALVES THERE.

YES, they're "bad enough" to cause issues; at least two of the exhaust valves are teetering on the edge of the danger zone.

Assuming those are "American" measurements, you've only got three (E2, I3 and I4) that are IN spec.

You cannot, repeat, cannot get a "valid" vacuum sync on CV carbs with valves out of spec. As bad as your exhaust valves are, I'm surprised it's running well enough to ride.

Getting the valves in spec is the first step in carb tuning; not a last-ditch "thing to try."

Gotta fix that first.

 

Re: Opinions on my smooth running issues.

As I suspected. I knew the valves were out of spec based on the FSM, but not the degree or how severe. Thanks!

I'd read all the testament about valves then sync then mixture, but I'd been putting valves off mainly due to stubbornness. I got my bike with a crankcase full of gas, and once I got it running it had/has some concerning clattering in the bottom end (feared spun mains). I suppose it's running well/long enough now to warrant the expense of a valve job.

Hopefully with everything in spec my fueling will improve without having to check the float levels again.

 

I, like you, did everything except the valves first. I don't have a lot of issues on power or ride-ability but I am sure I could stand to get the valves checked out and in spec. There are awesome write ups on there that can guide you through it with little issue.

Just out of curiosity, how many miles are on the bike right now? Mine is just over 13K and maybe 35 of those by me in the past 2 weeks.

 

Yeah I'm not worried about difficulty at all, just the costs involved. Plus like you say the guides on here are fantastic.

Seems like the odometer says something like 45,000, but the speedo didn't work when I got the bike so who knows really.

 

Ahhh! Well if it has that many miles on it, I would definitely believe that it needs a valve adjustment. I too am not looking forward to the cost of shims. being in Southern California, no one gives or swaps shims for free here.

This place is a great resource. Free info from people who just love sharing their knowledge.

I will give you a tip right here and right now...keep your hands away from the exhaust pipes after they have been running. That crap hurts!

 

Re: Opinions on my smooth running issues.

Just made the connection in this comment, did you mean to say Metric instead of American? My measurements are in mm (should've listed that). You're evaluation that only 3 are in spec matches with mine, so unless I'm missing something or you had a hidden meaning I'll assume typo

 

Look for "Power Robbing" Gremlins.

Non-Vacuum Hose to the Petcock.
Petcock Vacuum Membrane Puncture
Petcock Screen clogged.
Petcock Screen Missing.
Foreign Matter in the Petcock.
(Use Weed Whacker Line to probe Petcock.)
Inline Fuel Filter's Paper Element Non-porous. (China-Taiwan made N.G.)
Kinked Fuel Line

Beenie Screens not cleaned.

 

Forgot to mention that I rebuilt the petcock, line is good, beanies were cleaned when the carbs were torn down.

I hadn't thought of the inline filter, might as well replace that again. Though with the power being great above 5k once the mains kick in, I wouldn't think fuel supply would be the issue.

 

If it runs great over 5k fuel supply is not the problem. If it was it would loose power up there and run fine down low. Is it blowing any black smoke? By the main jets start working about 1800 by 2500 your completely on the mains . Did you check the diaphrams for pin holes hold up to a light . It almost sounds like a vac leak but you said you checked it

 

No black smoke, or any really.

Wow that low? I thought I read it took up till as late as 3000 for the mains to kick in, and you weren't fully on them till 4000. Aka my problem area.

I didn't hold them up to light, but the diaphragms were soft supple and didn't appear to have any damage. I won't rule that out but it definitely won't be the first thing I check haha.

 

I just type a list.

Things it might be.

Take it out for a Test Run.

When you get ready to start the Test, ...
Put it on PRIME and see what happens.

 

it all depends on where your throttle is as soon as the diaphragm starts to rise starts sucking fuel thru the main. pilot system is less then 1/4 throttle 1/4 to 1/2 is using the slide and needle off the main jet and 1/2 and over its running on the main completely. If you wack the throttle down low as the slide raises your pulling off the main. So technically cruising it might take 4k to be running completely on the mains but as soon as you touch the gas those slides move at all your pulling off the mains

 

Re: Opinions on my smooth running issues.

Mis-type, yes. Sorry. And you don't need a "valve job" (well, let's hope not anyway) just a "valve adjustment right now." Keep running the motor with tight valves and you WILL need a valve job. Checking clearances and swapping shims is a normal maintenance procedure required at 5000 mile intervals; a valve job is a major remedial process. Cost to do the adjustment is minimal compared ot a full-on valve job.

That being said, you still need to get the valves in spec BEFORE trying to sync the carbs.

 

Yeah, adjustment is what I meant. I've got a local Yamaha buddy with the shim bucket tool, so all I have to track down is a local source for shims and I'll be in business. I'll be sure to update with my results.

 

Alright well I just did my valve adjustment, did another sync, and tried to colortune. I will say it does idle smoother than it ever has, but it's STILL doing the stutter/surge when it transitions from the pilots to the mains.

When I colortuned I was able to dial in carbs 1 2 and 3 perfectly, but I couldn't get any change in color on carb 4. I haven't replaced the mixture screw o-rings, could they be the culprit? If not I guess the only possibility is clogged pilot passages.

Could that one carb having pilot circuit issues be causing this kind of symptom?

 

Yes and yes. Did you PULL the pilot screws out, at least? If not, you didn't get the carbs clean.

I love how the factory was so hell-bent on keeping us from fiddling with the mixture screws lest they run afoul of the EPA that they had to leave one of the most important steps out of the carb service procedure.

Save me reading back up the thread, what method did you use to set the float levels?

 

Yep, pilot screws removed and flushed with carb cleaner, and I prodded the pilot hole and bypass holes in the throat. Floats were set with the wet method.


Side note: What would happen if the little washer wasn't between the spring and the o-ring on the mixture screw? I had it out of the carb last night and can't remember if the washer was in there. Also, what usually happens when the mixture screw o-rings are worn out?

 

If the washer(s) are missing and/or the o-rings worn out, the pilots could suck air thru there, which could cause your symptoms.

 

Alright well I'm at the end of my ropes.

Valves checked and in spec.
No leaky intake manifolds.
Floats perfectly set with wet method.
Mixture orings and throttle shaft seals new.
No passage blockages.
All jets in their proper spots.
Everything spotless.
Cleaned the rusty gas tank, using fresh clean gas and new filter.
Usable cylinder compression


My mixture screws have to be set at 4+ turns out to get it to even idle/rev right. I can't get some of my carbs to go rich at all. I play a game of sync colortune sync colortune and never really get anywhere.

I don't know why this thing won't run right at this point. It still acts like it's not getting enough fuel through the pilot circuit. I get the bog/surge at 4.5k as the mains kick in.


Any other last minute hail mary's before I admit defeat?

 

Are you doing a vacuum sync? Or are you using the color tune plug? If you are doing the vacuum sync are you doing all four at the same time? I found that while doing the color tune spark plug I had a slight air leak on one of the vacuum plugs. It was not detectable even with propane but as soon as I replaced them all everything fell into place. Just a thought.

 

I'm doing a sync with a homemade 4-port atf manometer, and checking mixture with a colortune. I leave the manometer hooked up while I adjust the mixtures just to keep an eye on it. I hadn't thought about it leaking slightly at the vacuum plugs, I suppose I could clamp down my tubing while i'm checking it.

I still feel like something else is going on though.

 

Try that. I was pulling my hair out for a while to. I was fine with the manometer, I bought one from Len. I didn't trust the home made one. My problem came when I disconnected the manometer and then did the colortune. The old plugs for the vacuum tubes on the carb seemed to be all right. I checked them with propane with no changes in revs to indicate a leak. But every time I did the color tune I couldn't get the number 3 or was it 4 cabs set right. And I had to start all over. I ran down to the auto parts store found some replacements, problem solved.

 

Well, that wasn't the issue. Tried colortuning without the manometer, tried clamping the hoses down to prevent leaks... same result.

I took my carbs to a XS11 friend of mine for him to go through. He said they looked spotless, and that I did set the floats right. He doesn't think the carbs are my issue.


So if I have compression (125psi each), have properly cleaned and adjusted carbs, in spec valves, no air leaks, new air filter, clean fuel, new plugs, and at the very least HAVE spark... what could my problem be?

I've looked at my TCI module, which seems to have been replaced at some point, and it is the proper module and looks to be in good shape. Colortuning has told me I at least have some spark. Only visual question is that one of my pickups looks like the wiring has been repaired using liquid electrical tape right where it enters the plastic. Not sure if an intermittent connection there would manifest my symptoms or not, but I can't imagine it would.

 

Do you have the YICS blocked?

Have you unscrewed the plug caps from the wires, lopped off 1/4" or so and re-attached? Checked INSIDE the plug caps to be sure you don't have a loose resistor core?

Honestly though? It sounds like you weren't all that thorough on the cleaning of the PILOT circuit passages (you know, the ones with the worn out tiny o-rings and missing washers?)

If 4 1/2 turns won't get you too rich, either you've got a massive vacuum leak somewhere or your carbs aren't truly clean. If your YICS isn't blocked properly, it could be contributing to misleading you.

You can chase the ignition until you turn blue in the face, if the problem is still in the carbs (you can't "see" the passages I'm referring to) all you're doing is wasting your time.

And THIS has carbs written all over it, sorry:

You can't argue with physics; the machine will win.

 

One last question or two:

Did you replace the throttle shaft seals?

Did you dip or submerge the carbs in any sort of cleaner/solvent?

There is one other possibility...

 

YICS was clean and blocked when sync'ing.

Not yet, i'll try that.

I replaced the mixture o-rings and washers, and blasted the pilot passages with carb cleaner. The flow seemed evenly distributed.

Many carb take-offs ago, when I replaced the throttle shaft seals, I stripped each carb body down completely and boiled them for 30 minutes in lemon juice, then blasted them with carb cleaner and compressed air. No rubber was left in them at that point.

I also ohm'd my pickups and coils, and they're all within specs. My voltage did drop below 10v when cranking so I'm going to try to track that down as well. I have already replaced the stock fuse box so my instinct is connectors or ignition switch.

 

2 and 4 resistor cores were backed way out, and 2 popped off the wire with a light tug. 1 and 4 didn't have screw in resistors, they seemed to be clipped in. 2 and 4 were stamped denso, 1 and 4 were stamped NGK.

I chopped 1/4" off and tightened the loose resistor cores, and things did actually seem a bit more stable. Ran out of daylight to sync and colortune, so i'll report back tomorrow night after I do.

I did notice that when i tried to hold the rpm's around 2500-3000 the motor would stumble and the tach would studder by a couple hundred rpm, but considering the motor isn't sync'd that might not be an indication of anything, OR it could mean spark is dropping out. I dunno yet.

What was your other possibility, just in case this fails to fix the issue as so many other "solutions" have before it lol.

 

Pull your top hats off the carbs. Pull out needles and Diaphragms. If they have adjustments. Try lowering the clip down to rich en the needle mixture thus opening more fuel sooner. If it gets worse try raising it to lean out. You should only have the mixture screws open to no more than 3.5 turns. Then it is usually time to bring in larger pilot jets. This can all be done with carbs on bike.

 

Sync'd and tuned. Didn't go so well.

I would sync it with the YICS blocked, then put it back together and cyl 1 would be way high with YICS unblocked. I'd adjust it back down then check it again with yics blocked and then 4 would be super high. Played that game for awhile and finally decided on syncing unblocked, as it seemed smoother. I am using the Chacal YICS port blocker btw, with fresh seals.

The only way, once again, to get it to idle well was to richen things up. This time I was able to get them all to read rich though, which was an improvement... but all the carbs are set to between 5-5.5 turns out.

I remember when cleaning/checking the carbs for the first time that the needles seemed to be in various positions, so i set them all as low as they'd go in the holder. As far as I know the clip that holds them in didn't have various positions, there was just about 2mm of play I could adjust them in. I'll set them all the way up (rich) but I don't really think that's going to affect my pilot fueling which is the issue here.

 

Is your air intake totally stock? Stock box, filter, etc.? Did you replace your vacuum caps with new or just try to clamp them?

 

Albeit it a pain its an interesting thread good luck mate Gaz

 

Totally stock airbox. New filter. New vaccum caps. I've spray checked and propane tested for leaks.

Just checked the needles, they were all firmly seated in the up position, so that's not the issue.

If my lemon juice boil and blasts of carb cleaner and air weren't good enough, short of completely tearing down the carbs AGAIN and this time soaking them for a few days in carb dip to try to clean the pilot passages, I don't know what to do. Any other ideas?

 

Hold on a sec.

You were talking "rich/lean" in relation to SYNC.

Adjusting the mixtures comes after you're in sync. What sort of manometer are you using?

Confirming; float levels accurately "wet" set?

Set all 4 mixture screws at 3 turns out and leave them.

Go back and do the running vacuum sync with YICS blocked.

THEN you can worry about rich/lean. You don't sync the carbs via the mixture screws, but you can screw up a good sync that way.

 

Thats how I have been doing It. I sync, adjust mixture, sync, adjust mixture. The motor is too unstable until i richen it up to 5 turns out on all 4 carbs is why I was talking about it that way.

Floats have been confirmed wet set. Using a 4 port homemade atf manometer.

 

This may be a stupid question, but when you say 5 turns out, are you counting full 360 degree revolutions of the screwdriver? The reason I ask is if you are making half turns...2.5 full 360 turns is 5 half turns out...

 

Yup, i'm counting full turns. Plus regardless the bike doesnt run right, so even if i wasnt something is wrong

 

Ok, have you verified that the pilot fuel and and air jets are of the correct size and placement? They are backwards in the Haynes manual.

 

Yep all my jets and needles are stock size and in the correct placement per the chitchat on this forum. I've been goIng strictly off yall's writeups, not a haynes/chilton manual.

 

Hmmm.

"The motor is too unstable until i richen it up to 5 turns out on all 4 carbs "

Your pilot circuits aren't truly clean and/or you didn't replace the little o-rings on the pilot mixture screws; or your float levels are still off.

One other question: have you done a compression test on this motor yet?

 

+1 to the above assessment, your pilot mixture is lean for a reason, 5 turns out is beyond adjustment anyway-basically just completely screwed out at that point.

Maybe you need new carb bodies-if you've done everything right and its all clean in there-something is letting in air somehow.

You might try dropping your idle downward (around 800) and just bump up your enrichment circuit a little, to proper RPM's to see if that lets it run better. If so then you aren't getting enough fuel-if this does nothing to smooth it out then you have a big air leak somewhere.

 

Like I said before, mixture orings replaced, float levels checked by two different people, compression is 125psi on all cylinders.

I'm not sure how there could be something THAT wrong that I'd just need to scrap these carbs and start over... that sounds ridiculous. I also don't see how I could have a big enough air leak not to be detectable by propane or starter fluid testing. It seems to me that the problem is evenly distributed among the carbs, since they ALL have to be set to 5 turns out. Deductively, that indicates to me that either the pilot passages are evenly coated and in need of cleaning, one is badly coated and holding the rest back via sync, or my low compression is insufficient to pull enough fuel through the pilot circuits. Please tell me if any of that deduction is ill founded.

I guess the only thing I can do at this point is tear them back down and do a real carb dip. Anyone have some suggestions to make dame sure I get those pilot passages clean? I've read "the house of clean" and many other threads talking about cleaning, I just mean any other tips or tricks that might not have been mentioned. I want to get this right this time.

 

Well, after a full disassemble, cleaning, and a full 24 hour soak of the bodies in berryman's carb dip, I still have the issue. I blasted the pilot circuits with carb cleaner and air, all seemed to flow well.

On reassembly I did notice I had two main air jets in one carb, and two pilot air jets in another while pulling off the table... so I'm not sure if they were in the carbs that way, or if they got mixed up on the table.

Seems like 1 2 and 3 didn't have to be set much richer than 3 turns (didn't count), but 4 had to come way out. I was able to get all of them in the sweet spot, and had a really good sync. I will say this is the best they've run, but I still have my bog/surge at 4k rpm.


I wish I had someone else around with a known working set of carbs i could borrow just to see if that's really the issue
I just can't imagine how they wouldn't be clean at this point...

 

somewhere back there you said.
"Just checked the needles, they were all firmly seated in the up position, so that's not the issue."
there is no up position, their spring loaded to come down all the way.
if a motor bogs stumbles and chugs but works itself out and keeps going it's usually rich, if it just cuts out and quits at that throttle opening
it's lean

 

I guess what I should have saod is that they werent firmly seated all the way into the holder. They are now and have been the last few tear downs.

It has little power below 4k, increasing throttle beyond ablut 1/4 has no effect until 4k, when it stumbles then gets full power and takes off. On decel once you hit 4k it drops back into no power again. Also, not sure if its new or has been doing it the whole time but opening the choke tends to kill it instead of raise the revs.

 

Any other ideas? Any of you experts willing to let me ship you these things to look at, clean, test on bike to see if it's my motor, anything?

I'm hesitant to take the bike to a local shop... since they probably know even less than I do.

 

Cover 1/2 of your air filter with masking tape to seal off 1/2 (top or bottom doesn't matter) and see if your lean idle pilot circuit/adjustability changes... if so, there can be no doubt that you have "encumbered" pilot circuits (or an air leak) somehow.

At least you may get a definitive data point you can trust...

Also, your darn plugs are NEW right?

p.s. did I read back there that you mixed up air circuit jets? The ones under the diaphrams?

 

I suppose I can try it. There's NO way I'm going to get those pilot passages any cleaner though... I've cleaned them on maybe 5 separate occasions. Lemon juice boil, carb dip (don't worry, no rubber was involved), carb cleaner blasts, and compressed air.

Plugs are brand new.

They were at some point... but they're all in the proper (not Haynes) location, and i'm still having the issue.

 

Only After the tape test (to see if reducing air flow richens the idle mixture...)


Then let's ensure you have the proper sized jet needles (reference Len's catalogue for sizes or other reliable source you have) and that you have them properly seated with the springs functioning OK (set into the slide pistons properly with the nylon nuts)

 

This is conflicting "bog/stutter/shudder then SURGE" is rich low/middle -- but you're reporting 4+ turns out at idle --- so you need to tape test or figure out that low end

However, "bog/stutter/shudder then SURGE..." is rich ...Now middle issues can be the result of worn (one one side) needles -- Also, over time, the needle can rub the emmulsion tube (the spring tends to load it to one side) -- and can cause the top of the main fuel emmulsion hole to be oblong instead of circular which can richen the mixture too