help with flooding carb

[bkuhr]

83 Venture, Cylinders #2 and #4 dead and cold to touch, even after ride. Verified good spark. Plugs come out very wet. Suspected very rich flooding cylinder preventing fire. Float fuel levels verified good. Sync perfect. MPG=25-28:(. 1/2 tank strong seafoam run thru. Carbs rebuilt by me but can't confirm I did not do something wrong. Installed skydoc17 needle shim mod.

 

Today confirmed carbs #2 and #4 only, dumping too much fuel.

 

At idle, placed tip of shop towel into throat against main fuel needle for just a second.

Towel tip comes out wet in carbs #2 and #4 and dry in #1 and #3. Thought I could see fuel coming from jet and along needle, and confirmed with above towel method.

 

Now I am 99.9% positive excessive fuel is preventing cylinder #2 and #4 to fire.

 

Fuel float levels are correct, but during operation carbs dumps too much fuel out the main fuel jet, even during idle when main jet should be completely closed off.

 

1. What could cause this?

2. What to inspect?

3. How to repair?

4. How to pretest after repair on the bench?

 

pics not very good but first Pic, tip of towel in throat

second pic tip wet

[Yammer Dan]

Swap plugs to see what happens. A lot of times if you flood a plug with unleaded fuel it will not refire. If you get the dead cylinders firing they may pull something on thru there that the Sea-Foam loosened.

[greg_in_london]

We could run through making sure that you forgot nothing.

 

First - did you replace any out of:

the nozzle o-ring ?

the jet block gasket that you can't but anymore/ was it in good condition ?

the little rubber bubgs at the botton of each jet block ?

 

Next - how long have you run it since you rebuilt the carbs ? Is it possible that any jets have worked loose ?

Could the brass bolt in the end of the nozzle have worked loose ? Or even the screws that hold the jet block.

I've a feeling that it is possible to get two of the jets the wrong way round, but I'm not 100% sure of that.

 

At the end of the day, it doesn't take that long to pull the carbs off. It takes me even less time now that I've bought some very long nosed surgical pliers from Maplins that makes reconnecting the two throttle cables easier.

 

[edit] oh - and have you taken the air box off to verify that the slides are all moving okay when you blip the throttle with the engine running ?

Edited August 7, 2010 by greg_in_london
addition

[bkuhr]

We could run through making sure that you forgot nothing.

 

First - did you replace any out of:

the nozzle o-ring ?

Yes, but I recall putting oring on in wrong order with block gasket and having to go back and fix, maybe I forgot to fix in another carb at the time?

 

the jet block gasket that you can't but anymore/ was it in good condition ?

can still buy, and yes I did replace. Old ones came apart/destroyed on orginal disassembly

 

the little rubber bubgs at the botton of each jet block ?

did not replace, they seemed fine

 

Next - how long have you run it since you rebuilt the carbs ? Is it possible that any jets have worked loose ?

got bike new to me non-running in Oct last year, rebuilt carbs same time, have abour 200 miles on it, runs great on 2 cylinders, but can feel miss at idle and gas milage real low.

 

Could the brass bolt in the end of the nozzle have worked loose ? Or even the screws that hold the jet block.

Anything is possible, guess only way to find out is to pull carbs and seperate rack again

 

I've a feeling that it is possible to get two of the jets the wrong way round, but I'm not 100% sure of that.

Not sure what you mean here???

 

At the end of the day, it doesn't take that long to pull the carbs off. It takes me even less time now that I've bought some very long nosed surgical pliers from Maplins that makes reconnecting the two throttle cables easier.

I agree other than I have farings on, and throttle slider box is under left fairing, hardest to get off with tuner/amp, going to see if I can get slider worked down below faring

 

[edit] oh - and have you taken the air box off to verify that the slides are all moving okay when you blip the throttle with the engine running ?

Sliders all do work together, and verified no vacum leaks with starter fluid all around boots etc...also checked for jasonm's leaking enrichers(choke) with o-scope on coil inputs, did not change rpm at all

 

 

Thanks for input

Brian

[Condor]

Ok, have one question. How can you have a perfect sync when two of the carbs are not firing?? OK two questions. How are you adjusting the idle when it's set by the #2 carb? The #2 carb is the benchmark when syncing.

[bkuhr]

Ok, have one question. How can you have a perfect sync when two of the carbs are not firing?? OK two questions. How are you adjusting the idle when it's set by the #2 carb? The #2 carb is the benchmark when syncing.

 

I'll take pic of sync before I pull carbs tomorrow.

Sync is only measurment of vacum in manifold below the butterflies. Dead cylinders still pull vacum even if they do not fire, barring other problems such as vacum leaks or valves not closing. Proper air/fuel mix typically can only be measured with some type of EGR sensor, such as dedicated test equipment or O2 sensor in cage. If I had EGR tester likely would show very rich in my dead cylinders. I do not have this type of test equipment, and had to figure out some other way to prove to myself I was dumping too much fuel as I suspected with wet plugs and no heat on pipes. I was working on a clear tube individually feeding each carb with equal amounts of fuel in each. My thinking was if a carb was too dumping fuel its fuel level in tube would drop faster that other carbs. Think I proved same thing with the shop towel.

 

I orginally suspected spark issues, but replaced diodes in TCI, replaced coil high tension wires and resistor caps, then verified both pickups signals and coil input signals at the TCI with Osilliscope. 1 final test was with HF spark tester (modified to accept MC plugs). Spark is good. Only thing I did not verify is spark timing, but as it is not adjustable on MC I suspect ok. I may go ahead and put timing light on to verify, as I scribed TDC of all 4 cylinders on stator when I had motor apart, but I read hard to keep oil from spraying out inspection hole.

FYI good resistor caps appear to read 2k-4k ohms. I had 3 that read ~, and replaced all 4.

I also did a mod to get coil rack out from the top with out having to pull farings, for future maintenance of coils if ever needed. I took pics but they did not turn out. If anyone wants, while Im working on carbs I can pull coils again and take pics.

 

Engine running on 2,3,4 cylinders still idles somewhere, then adjusted for for proper idle speed. Likely when I get all 4 cylinders running, idle will be too high and will need to be readjusted. Sync should not change when running on all 4 except for me taking rack apart and putting it back together. This will probably cause changes and require re-sync

 

Would anybody like pics of O-scope traces for pickups and coil inputs. Maybe some of those working on IgniTech solution. I only have 1 channel scope so I can not provide timing between pickup and coil at different rpms(advance), but I thought wave forms were interesting, especially EMF spike on coils

 

Thanks for input, feel free to correct anything I say you feel is incorrect-discussion helps us all learn, and keep suggestions coming

 

Brian

[GeorgeS]

Since you did the carb sync, have you removed and re-installed the carbs.

 

If so, you should re-do the sync.

 

Quesiton: ?? Do you have any slack in the Throttle Pull cable on the left front carb ?? You should have 1/16 to 1/8 in. of slack in the cable after the Sync Job, is completed.

 

Back out the master idle screw to the just contacting position.

 

Then do the same with the Sync Screw on left side. ( set to Just Makeing contact)

 

Now on the Right, back out both and re-set to Just makeing contact.

 

Then re-check the Pull Cable, Slack, makes sure its still there.

 

-----

Then, hook up your Sync Vaccume Gauges, and Redo the Sync process.

 

 

And as above, try a new set of plugs !!

[Condor]

Putting all the technicals aside, and lets get back to basics. You say you have spark, and you have fuel. You should be getting ignition. Change the plugs. Weak plugs will break down under compression. If everything checks out like you say it does then it will run. BTW, although true, a non-igniting cylinder will have manafold vacuum, it won't be any where near the vacuum produced by the draw of hot gases exhausting out of a firing cylinder. When syncing after changing the plugs try backing off all the sync adjustment screws. Start from scratch by setting the idle with the #2 carb without any influence from 1,4, and 3.

[bkuhr]

here are pics

1. Idle

2. sync before doing anything. Note: noticed clear vapor? pulsing in clear tubes of sync tester in only cylinders #2 and #4

3. resync, still vapor pulsing

4, spark tester at #2

5. spark tester at #2

6. removed #2 plug, did not come out soaking wet this time

7. new plug installed in #2, no change to #2 pipe temp

8. modified HF spark tester, tapped end of shaft for screw on terminal to accept MC boot cap, and place screw on terminal on MC plug to accept tester boot

 

Thru entire time #2 and #4 exhaust pipes are still cool to touch, only warmed up to temp of engine casing, engine h20 temp up to mid scale

also loaded up and hard to get over 3000 rpm

 

Any other suggestions before I start pulling carbs?

[bkuhr]

If anyone cares here are scope views of

1. coil pickups

2. ing coil primary inputs

 

All taken from backstab at TCI

[93 venture]

From the picture the plug dont look wet from gas

[bkuhr]

Alright, carbs out...

 

Took #2 carb apart

 

Sprayed carb cleaner into main fuel pickup bottom of removed jet block, small piece of junk came out and sat on wall of port where needle jet port normally resides.

IMO this could cause blockage in main fuel pickup, meaning no gas from this carb, but my problem of flooding from this carb would be an opposite effect not explained by this piece of junk. MAYBE:bang head:, I have confused my self (not hard to do) and my problem is in fact not flooding, as my #2 plug did not come out wet this time.

 

Also noticed needle port jet (with end plug removed)will slide completely up the needle all the way to the slider. I had expected it to stop at some point along the needle taper. Is this normal or do I have worn needle or jet? Did simular test on good working #1 carb, and jet did same, slid all the way up the needle.

 

Alright, HELP, what else do I need to inspect while I have carbs off?

Any way to bench test carbs for fuel flow? Some kind of 'Yankee inginered' bench test rig? I have almost any kind of tool you could think of.

[Condor]

Any way to bench test carbs for fuel flow? Some kind of 'Yankee inginered' bench test rig? I have almost any kind of tool you could think of.

 

You can simulate air flow by blowing compressed air through the venturi.. It won't be exact but it will show if you're getting fuel....make sure you have fuel in the bowl. You can also blow air across the oval opening at the top of the venturi to see if you're getting slide movement from your diaphragm.

[bkuhr]

Took carbs back apart, and found jet in jet block completely plugged in carbs#2&4

Looking at diagrams I believe this paticular jet is called #29 jet, pilot (#42.5) on page B6 in parts manual. Best I could do to clean it out was run .020" stainless lock wire thu jet. When compaired with a good jet, .020 was just barley too big, meaning I reamed out my clogged jets just a little. Unsure at this time what this will do.

 

Anyway, I installed carb assy on bike, without cables, without clamping boots, without aircleaner, only hooked up fuel line. Started right up, idled very smooth, all 4 pipes get hot:). Hand operated throttle, and bogs at about 3000rpm. No resync yet

 

Now need to get everything hooked up correctly.

[blurider 54]

Don't know if tuis will help you or not ,but I had the same problem with my 90 VR,ie running rich,fouling plugs ,dumping fuel out overflows, had me pulling my whats left of my hair out . Then I tried 1st replacing fuel lines as they tend to break down, especially with the ethanol additive in fuel then I replaced the fuel filter, and dumped copious amounts of seafoam through the carbs, HOORAH my bike has never run better mileage went from 20 to 33 mpg,engine idles smoother and no more dumping, Trash in carbs from bad lines is all it was ...try this before you pull out carbs it may be all it is.

[bkuhr]

Got carbs hooked back up properly, startes right up and idles smooth. Boggs at about 3000rpm. Hooked up sync. Was WAYYY off. #1and #2 almost off scale and nothing even close to each other. Unsure sync off due to disassemble/reassemble rack or FINALLY all 4 cylinders running. Probably combo of both. As I brought sync back together idle kept climbing. Finally got sync matched and idle was about 2800. Brought idle back down and verified sync. Pulled sync gauges, plugged vac ports, and ZOOM ZOOM.. I need to replace cracked air cleaner purge line before I take for ride. But sounds better than ever has, and throttle response is better then it has ever been for me. Bog is gone.

 

Little concerened about the little bit of reaming I did to the pilots jets in #2 and #4. Think I will check plugs after about 100 miles looking for too lean. I have skydoc17 needle shims in for leaning carbs. Maybe if some cylinders too lean I can try to put stock spacers back into needed lean carbs.

 

Think I am finally getting there. Its been a chore. Thanks for all the help.