Irreparably Lean: I'll try anything!!

[Science.Dan]

I'm so desperate to get rid of the ______ _____ _____ popping!! I've checked, rechecked, and triple checked just about everything but I'm still running lean! I'm at my wits end and almost ready to give up, but I refuse to let this beat me. I will try anything and will probably retry everything. Your suggestions and support are most welcome.

For those of you who have been following my thread, Air Filters and Lean Mixture, this is a continuation of that thread.

A quick recap of the problem/symptoms:

• Major popcorn sounds on deceleration or when the throttle is closed while the engine is revving at high RPMs
• Lack of power for first quarter throttle
• White spark plugs after driving around below first quarter throttle. Almost tan plugs after driving on the highway
• Low 30s mpg when driving around town but 50+ mpg on the highway.
• Engine revs +2-3000 rpms when a paper towel is stuffed into air box. Adjusting idle screw to 1000 rpms produces a beautiful idling sound with very responsive throttle and no popping. However, the engine will die if driven around past 1/4 throttle...

The most obvious culprit is the pilot jets... but before you all start screaming solutions at once, please read what I've done so far.

This has actually been a problem for at least a year now. Some of you may remember my thread, New Rider/Old Bike/Soon to Be Ether Junkie - Choke Cable. The choke cable was crimped causing the choke valve to rust open. In addition, or maybe related, my gas tanks were completely rusted. Needless to say the carbs and engine were flooded with rusty gas. This is how I unknowingly bought the bike. When I replaced the choke cable and was finally able to close the enrichment circuit, the bike has run lean ever since.

A quick recap of tests and attempted solutions:

• Acid etched both gas tanks and lined with POR15 to remove and prevent rusting
• Replaced all fuel lines and gas filter (Auto zone brand/not OEM)
• Rebuilt Carbs: Completely disassembled carbs and dipped into Berryman's Chem dip for at least 24 hours - each carb separately. Cleaned varnish and rust particulate with metal brushes and guitar wire. Sprayed all ports with compressed air in a can. Replaced all o rings and gaskets with Honda gasket kit. (Pilot screws were left in carbs for cleaning because one couldn't be removed at first, Pilot Screws and Jet Needles. Past owner was a real jerk apparently)
• Second Carb cleaning: professionally tapped out broken pilot screw and redipped in chem dip. Returned float level and pilot screws to factory settings.
• Built manometer and synced carbs
• Adjust screws to +1 from factory setting (~4 turns)
• Replaced Spark plugs and gapped to spec
• Tested all plugs for spark
• Added Berryman's B12 over 3 gas tanks
• Tested for air leaks with can of ether and repaired: Found some minor leaks around rubber boots above carbs and the airbox. Removed rubber boots from air connecting tube (a.k.a. the snorkel). It was very dirty with failing sealant. It was unknown if the the sealant was from past owner or factory. Cleaned away and replaced with only a little bit of oil. No one seemed to know if sealant was necessary in the thread: Rubber Boots and Sealant?. Also cleaned similar grime/oil/dirt/sealant from elbow and rubber boot where the crank case breather hose passes through air box. Also found same stuff on rubber boot where air connecting tube meets the air box. No sign of air leaks after cleaning when testing with a can of ether at idle. Still wondering if the sealant is necessary to prevent leaks at higher rpms.
• Replaced copper gasket at exhaust port and tightened to spec torque
• Cleaned OEM air filter and reoiled using 90wt gear oil as per shop manual
• Replaced air filter with UNI foam filter and oiled with uni foam oil
• Replaced spark plugs once again. (Broke one and decided to replace them all: Reusing Used Spark Plugs)
• Cleaned carbs for third time: Removed carbs and all jets, needles, plugs, screws and diaphragms but left carbs connected (synced). Dipped in 80/20 pine sol/water for two days. Checked every 12 hours or so to spray all circuits from all ends with 80 psi of air and then sprayed with acetone. No real signs of varnish or clogs (good spray of acetone from exit points). Passed guitar string where possible. Rinsed with hot water before returned to pin sol bath. Repeated 3 or 4 times. Polished jet needle (which was pretty worn on one side) with brasso until smooth. Polished float seats with brasso. Rebuilt carbs and returned float level and pilot screws to factory settings.
• Checked for leaks with can of ether
• +1 turn of pilot screws from factory settings (~4 turns total)
• Checked fuel pump flow rate: 117 cc in 13 seconds (~540 cc per minute) Spec is 614 cc per min +/- 10%... which puts me right on the low end
• Readjusted raised float levels to be rich (adjusted from 7.5mm spec to 6.5mm)
• Lightly sanded plastic carb slide with 1000+ grit paper (I dunno... getting desperate)
• Rechecked for leaks with ether
• Replaced stock 40 pilot jets with size 42s
• Rechecked for leaks with ether
• 1/3 can of Berryman's b12 in 2.5 gallons of gas in fuel tank.

That's pretty much a chronological account of everything I've done up until now. Nothing has worked so far. There were only minor, short-lived improvements. Increasing the jet sizes seemed to make the biggest improvement in power, but the popping still persists like crazy. I'll end this post here and edit the symptoms and add attempted solutions here as I notice/perform them. This way new readers will be more or less up to date by the first post.

Thank you in advance for everyone's input no matter how big or how small. I'll try anything!!

[u37cn13]

Wow! That's alot of work! Stupid question...did you tighten the pilot screws and then unscrew about 4 turns? or did you just unscrew one turn?

[Science.Dan]

Originally Posted by u37cn13

Wow! That's alot of work! Stupid question...did you tighten the pilot screws and then unscrew about 4 turns? or did you just unscrew one turn?

No such thing as a stupid question in this thread. The pilot screws have been removed and reinserted with the second and third carb cleanings. The screw was fitted with the spring, the washer, and a new o ring in that order so that the o ring was closest to the needle tip of screw and first to enter the hole.

Each time they were first adjusted to the factory setting of 2.75 turns from seated (not tight) and then adjusted to +1 turn (3.75 turns total). I have since turned it out to +4 turns from seated but have yet to brave anything past that limit.

[MotorDonkey]

Have you done a cylinder pressure leak-down test yet? Maybe a burned valve? Are your valves adjusted correctly? Did you seal the airbox joint at the intake tube? Any cracks in the rubber on ANY boots? Are you CERTAIN there are no rust particles lodged in any of the carb ports?

[Mentat Ix]

I'm usually wrong when I chime in on these things, but... adjust the floats to run the bowl levels a little higher? That should richen it up a bit...

Ah, dang it. Just re-read, and saw you already did that. Sorry.

[orlenz]

I see that you checked for leaks with ether, also checked the intake manifold boots?

I dont see that you changed the main jets, thats about all I can think of that you havnt already done.

[verdeva]

I think your best clue is what happens with the paper towel. It sounds like you are running rich at idle to compensate for the mid range band. Mid range is controlled by the slider needles.

I had a similar situation with my Sabre. I found that I had crud in the needle holder, even though I had pine sol soaked and cleaned my carbs numerous times. I have seen pictures that some carbs allow this holder to be tapped out with a driver from the bowl side, but I am not sure if our carbs can remove this part. What fixed my cab was deep cleaning with carb spray. I used golf tee's to plug this hole where the needle slider fits and soaked the spray from the bowl side. After 30 min, I hit this with lots of compressed air. I actually saw some crud come out! I repeated this soaking two more times. When you get the carb reassembled, make sure that the slider pistons move very freely with the same suction in each side. I hope this helps. - Dave

[rockyroad217]

Mine was running lean and bogging down undriveably(if that's a word). I rebuilt the carb 3 times and never could get it fixed. Thankfully my bike has one carb instead of 2 like yours and I bit the bullet and bought a brand new carb and no problems since. It ran like brand new after that. My plugs were also turning a grayish white.

[mr hammond]

reply from other thread....."No no I'm glad you chimed in. Do you know what jets they replaced and to what size??"

...im pretty sure that they r stock

[Science.Dan]

Originally Posted by MotorDonkey

Have you done a cylinder pressure leak-down test yet? Maybe a burned valve? Are your valves adjusted correctly? Did you seal the airbox joint at the intake tube? Any cracks in the rubber on ANY boots? Are you CERTAIN there are no rust particles lodged in any of the carb ports?

I have not done a cylinder pressure leak-down test yet. I also need to do a compression check too. I have been thinking about doing these tests as I have oil leaking around the cylinder head (maybe this should go in my symptoms list). I understand this would cause a loss in power, but how would a leaky valve or piston rings explain only a loss in the first quarter throttle and white spark plugs? How does this lean out the mixture? Can anyone tell me how to arrange the piston so that it is at Top Dead Center? My manual just says put piston at TDC and nothing more.

I have self-adjusting valves, but I have not wanted to pull the engine and so I haven't checked them yet. It seems I might have to do this if I'm going to solve this mystery.

I cleaned all the joints on both sides of all rubber boots including the one between the air tube and air box. The rubber was not dry or cracked. I stretched them all looking for imperfections. If you mean seal as in added a bit of oil and clamped down the clean boots with OEM clamps, then yes. If you are asking if I added sealant, the answer is no. I would gladly go buy some sealant if someone would tell me what is supposed to used. I tried gasket sealant but that just made a mess and I cleaned it up. It appears that there was some type of sealant between boot joints that are rarely disturbed (i.e. between airbox and boot leading to air tube, between air tube and boots leading to carbs, and boot for breather tube that passes through air box).

I'm as certain my carbs are clean as anyone who has cleaned their carbs 3 separate times as I have detailed above. However, I bought a can of spray carb cleaner with nastier solvents than just acetone (i.e. xylene). I will try a fourth time probably this weekend and let loose all of **** on that pilot jet circuit!!