OK...carb problem...maybe!

[John Schmidt]

I have a bank of six vacuum gauges I use to sync the carbs, they do a good job for me. I recently rebuilt the carbs on the old bike and installed them sans the tank...using an external unit hanging from the handlbars and hooked up directly into the main fuel line using a petcock in line. All went well except for #3 & #5, #3 eventually came around and started showing a deflection so was able to adjust #1, 2, 4, 6 to match #3. Number 5...nothing. Ignition...major spark but swapped plugs anyway just in case which showed no difference. Next, I checked the bowl drain and there's gas in there. So, then I swapped gauge postion in case I had a bum gauge. No change...in the new position the gauge formerly on #1 was dead on arrival and the former #5 gauge worked fine on #1. So now I know it's not a bad gauge nor spark plug, plus no lack of fuel in the bowl. Next I did a compression check on all 6, the readings were all within 5 lbs. of each other so that ruled out a stuck valve. Since I'm using vacuum gauges, even if it might have a plugged jet in that carb, I can't figure out why I don't get a reading. I do get a slight RPM bump when I manually engage the enricher on the right side so that makes me think that carb might have a plugged passage internally...all jets and needles are new. All the carbs got a hot 90 minute bath that was preceeded by a shot of carb cleaner into evey hole/passage before going in. The bike is desmogged and the tubes used on the vacuum gauges have been tested for leaks.

What am I missing here? Even with a plugged jet/passage I would think a vacuum gauge would still get a reading....or will it? I'm stumped. Obviously I'd like to not have to pull the carbs again but I left the tank off purposely just in case. Tonight before I shut down I added almost a full can of Berrymans "vitamin" B-12 to the external tank and ran the bike for a few minutes to let it get into the carbs. I'll let it sit for a day and try again but I'm open to suggestions and/or ideas.

[pancho]

Hey John, try closing down the adjustment screw (sync) screw on #5. It seems you are not building a vacuum,   maybe opened too much.

[Skinhead]

Is the port you have the gauge attached to on 5 open?  Simple things first.

[f-Stop]

Maybe the #5 intake manifold is not sealed properly.  Either at the collar on top or the O-ring on the bottom.  Or...it's possible the seal on the manifold's vacuum joint is bad.

[John Schmidt]

Well...I double checked everything. It's all tight, new o-rings, the vacuum port is open but just for kicks I pulled the gauge tube off while running and had no effect...just like when I pull the plug wire. Not sure what to check next but will probably pull the carbs back off in the next day or so. Turning the sync screw in or out also had no effect except to lower or increase the rpm. I might try using a new plug wire but don't think that's the issue...just not creating a vacuum which I think it should do even if that cylinder isn't firing or getting fuel. Also might pull the diaphragm just to double check for a miniature hole, I did check each one with a flashlight on one side while viewed them from the opposite side...and it was with lights off so was in limited light in the shop, easier to spot a hole. I'm still bugged by the fact that rpm increases when I engage the choke on just the right side. That sounds like slow jet issues, but why won't it at least pull a vacuum? 

[Skinhead]

When you do a cold start on the bike, does that exhaust pipe got hot as quickly as the others?

[Cracker Jack]

John, sounds like the throttle butterfly is not closing against and therefore not responding to the sync. screw. Look for something binding the butterfly and holding it partially open.

I can say with pretty good confidence that the problem is mechanical and not fuel related.

[John Schmidt]

When you do a cold start on the bike, does that exhaust pipe got hot as quickly as the others?

No! Just cranked it up cold, used my temp sensor gun and found #3 & 5 are quite a bit lower temp than the other four cylinders. Strangely enough though, #3 has good gauge deflection. Cracker Jack has an idea I hadn't checked, however before I installed them I used the brass shim that the Redeye kit has to test/adjust the butterfly settings before installation. Sort of a preliminary bench sync and all was well at that point. You open them individually and lay the shim in the opening, then slowly pull the shim out...feeling for a similar tugging resistance on all the butterflies.

Tomorrow I'll pull the top off both those carbs, #5 first, then remove the diaphragm & needle. Hopefully I can see in there good enough to check butterfly operation. It has a definite miss that gives it a mean sounding lope, kinda like an old Oldsmobile I had as a young man with a wild cam and rollers installed. That alone scared away a lot of challengers I'm sure. 

[Jims99]

I agree with f-stop. Maybe oring moved when installing. Maybe try starting fluid or propane to find a leak. You’re right about having vacuum even with no spark. Engaging enriched will help if getting to much air (leak) I don’t think it would be a bad diaphragm, it would have to be really bad to lose that much vacuum. How much lower is the vacuum compared to the others? 

[John Schmidt]

I agree with f-stop. Maybe oring moved when installing. Maybe try starting fluid or propane to find a leak. You’re right about having vacuum even with no spark. Engaging enriched will help if getting to much air (leak) I don’t think it would be a bad diaphragm, it would have to be really bad to lose that much vacuum. How much lower is the vacuum compared to the others?  

No vacuum showing on any gauge...I swapped them around just in case it was a bad gauge. Three different units show no deflection but work fine on other cylinders.

Today I'm going to unbolt the intake runners and lift them up to check the o-rings, but I'm pretty sure they're solidly in place. I used a slight amount of sticky gasket maker stuff to hold them in place while positioning to bolt down. Won't say it can't happen but I feel confident a displaced o-ring isn't the problem.

PS: There's plenty of spark across the board, but when I pull the plug wire from #5 it has no effect on the rpm.

[pancho]

Turning the sync screw in or out also had no effect except to lower or increase the rpm.

?? If you are talking about the sync screw on #5, that shows that #5 is running. Have you verified all exhausts including #5 are hot?

It has a definite miss that gives it a mean sounding lope, kinda like an old Oldsmobile

Your idle mixture screws (pilot screw) may need to be opened up on #3 and #5

[John Schmidt]

Turning the sync screw in or out also had no effect except to lower or increase the rpm.

?? If you are talking about the sync screw on #5, that shows that #5 is running. Have you verified all exhausts including #5 are hot?

It has a definite miss that gives it a mean sounding lope, kinda like an old Oldsmobile

Your idle mixture screws (pilot screw) may need to be opened up on #3 and #5

I have them all set at 2 turns out, I can try opening them further I guess...just never had to before but this isn't the same carbs that were on the bike when I was riding it. Those carbs were moved over to the trike since I had rebuilt them last summer. The trike runs fine. Any suggestions as to how much I should open them up...maybe a half turn!  #3 has good gauge action, it's just #5 that's the troublemaker. Once it has cooled down I'll open up #5 a bit more...maybe in the morning.

[John Schmidt]

A summary of what I did today in search for a cure. After exhausting all other avenues, I went ahead and pulled the carbs again...getting really good at it.   Flipped them over and removed the bowl cover for #3 & 5 and then removed the slow jets in both and the mixture/pilot screws as well. I then shot some carb cleaner in both orifices of those two carbs, let it sit for a bit then blew it out. That produced some real brown coffee looking residue from #5, a bit less on #3, so I did it again which produced less of the brown stuff from #5, but #3 was clear. Did it a 3rd time on #5 and it now ran clear. I replaced the jets and pilots and closed up the bowls. I figured since I had them out I'd go ahead and do the same thing to the other four, all of which blew clear the first time. Due to the stuff that came out of #5 at first and now clear I was in hopes I had cured the problem so put it all back together and started the bike. Well, I guess what I did wasn't in vain but it didn't help the problem...it still exists. Tomorrow I'll try opening the #5 pilot maybe a half turn and see if it improves, they're all now set a 2 full turns out so 2 1/2 turns out isn't exactly out of the question.

As for working conditions, right now they kinda suck...it's hot! And in winter it's cold out there. I really miss my air conditioned & heated shop in Florida, if I ever buy a house up here that will be the first thing I'll do. Since my place opens directly out to my double garage, I crank the a/c down a few degrees and open the door to the garage, meanwhile leaving the big door closed. I then set a large fan in front of the door and blowing into the garage...it brings the temp down enough so I can work fairly comfy out there. I have other things I need to take care of so I need to get this issue solved.

[yrunvs]

After cleaning out the gunk from 3 and 5 fuel orifices did you then clean out the slow jets in those 2 carbs? Although new they most certainly could be plugged by that gunk you got out of the passages. Another words the new jets may have been compromised after their recent installation. 

[John Schmidt]

After cleaning out the gunk from 3 and 5 fuel orifices did you then clean out the slow jets in those 2 carbs? Although new they most certainly could be plugged by that gunk you got out of the passages. Another words the new jets may have been compromised after their recent installation.

Yes!....(in other words  )

UPDATE: This morning, Saturday, I opened up the #5 pilot about 3/4 turn with no effect on performance. No action on the vacuum gauge for that cylinder. I double checked the compression and compared it to the other cyls.--it's the same. The only effect opening the pilot had was to show that cylinder was running rich. I even replaced the plug wire with a known good one even though the current wire shows a nice fat spark when hooked to a plug laying on the motor. I'm at my wits end and about to give up, at this point I have no idea what to do or check next. I just don't understand why with good compression it's not pulling a vacuum, everything is tight and clean. It's getting fuel, has spark at what appears to be the same intensity as the other cylinders. I'm stumped...it doesn't make sense.

Five cyl. running great and adjusted to #3 with no issues, #5 has everything going for it the other 5 do yet it's a dead cylinder.

[Cracker Jack]

John, your problem is mechanical, not fuel or spark related. You should be developing vacuum without any fuel in the carb or no wire going to the plug.
Find the problem which is associated to the butterfly or slider. Bottom line, TOO MUCH AIR GETTING PAST THE CARB.

[John Schmidt]

John, your problem is mechanical, not fuel or spark related. You should be developing vacuum without any fuel in the carb or no wire going to the plug.
Find the problem which is associated to the butterfly or slider. Bottom line, TOO MUCH AIR GETTING PAST THE CARB.

Too much air from somewhere...my thoughts as well but can't figure out from where. Going to pull the cap and double ck. the diaphragm or see if it's stuck.

[Cracker Jack]

I believe something is keeping the butterfly from closing all the way against the sync screw.

[pancho]

Try putting a wire down the vacuum nipple on the intake tube to clear it John, seems like it is plugged up. Adjusting the #5 pilot screw was to get rid of your miss, not make the vacuum gauge work.

[John Schmidt]

Try putting a wire down the vacuum nipple on the intake tube to clear it John, seems like it is plugged up. Adjusting the #5 pilot screw was to get rid of your miss, not make the vacuum gauge work.

Re. #5 pilot, there was no change...still has a miss. I'll go remove that vacuum nipple, easy to get to on #5. Doubt that's an issue but at this point I'll try anything. Just removed the diaphragm and needle to see if it was either stuck or a hole in diaphragm. Again...neither was the case.

[John Schmidt]

I believe something is keeping the butterfly from closing all the way against the sync screw.

How can I check that without pulling the carbs again? Plus, if it didn't close all the way wouldn't that show at the sync screw by not returning to the resting position like the other cylinders?

UPDATE: In trying to clear a possible blockage in the vacuum nipple of the #5 intake, I finally had to remove the runner. I couldn't see or feel anything but it didn't feel like my wire went all the way in...turns out it hadn't. Have no idea what the junk was but took a few minutes to clear it out. I put the runner back in but even with a clear vacuum now, it shows good vacuum but unable to adjust out the miss(which I expected) so I pulled the carbs for the 3rd time and partially disassembled #5. I squirted some carb cleaner in everywhere, let it sit for a bit then blew it out. Tomorrow I'll flip it over and open the bowl...again...and use some more carb cleaner. I don't want to remove that carb from the rest of the ass'y. even though I'd kinda like to cook it in the sonic bath for an hour or so. Have to see if I have an extra set of o-rings for the fuel rails. Got the carb removal down to about 15 min. now even while answering the phone. Kinda sucks, some talents I just as soon not develop. 

[John Schmidt]

Rather than do a half-way job I just pulled #5 carb off the carb bank and disassembled it as though starting over. It's now running in a sonic hot bath of Krud Cutter, thinking another 90 minutes at least. Sure wish there was a way to bench flow test these things, I'm getting tired of r&r these carbs...only to find there's still something amiss. My life is rather dull but this isn't my idea of excitement as a method needed to liven it up!  

UPDATE: Got it...finally! Had already found the "no vacuum" issue source but that still didn't correct the #5 problem. Got it back together after a second bath for 90 minutes, installed the carb bank and all associated parts including the vacuum gauges, said a prayer and hit the starter. YEEHAW...it has often been said the 3rd time is a charm, this must be proof, I was able to bring all five into the #3 reading. When it first cranked it was running rough and barely turning over, but then I noticed both #1 & #5 gauges were way off #3. As I slowly adjusted them the motor smoothed out and rpm picked up to the point I had to back off the idle adjustment knob. When I pulled the carb out of the hot tank, I noticed there was a collection of crud floating on the top of the fresh fluid so apparently there was still something in the carb body that was affecting the operation. Now on to other things, thankfully.  

[Jims99]

What a pain. Glad you finally got it cleared up. Suggestion from these guys are great (even if not the right  one). Usually something simple that may slip your mind (me all the time) I’ve been working on a set for a Yamaha, 4 times off, ultrasonic bath, new parts, still can’t get it right. Maybe 5th times a charm for me. Lol. Can’t wait to see your trike when you make a trip down.

[Skinhead]

The vacuum is created by the downward travel of the piston reducing pressure in the intake, it would have nothing to do with the jets which meter fuel flow based on vacuum.  If you are not building vacuum, I would look at the valves, is one bent, burned, of cracked.  Perhaps a borescope for camera through the spark plug hole would shed some light.  Is the problem cylinder even firing?

If all checks out, I would remove the vacuum pet on that cylinder and insure it isn't clogged.

[John Schmidt]

The vacuum is created by the downward travel of the piston reducing pressure in the intake, it would have nothing to do with the jets which meter fuel flow based on vacuum.  If you are not building vacuum, I would look at the valves, is one bent, burned, of cracked.  Perhaps a borescope for camera through the spark plug hole would shed some light.  Is the problem cylinder even firing?

If all checks out, I would remove the vacuum pet on that cylinder and insure it isn't clogged.

Vacuum issue cleared up...see a couple posts back.

[pancho]

Rather than do a half-way job I just pulled #5 carb off the carb bank and disassembled it as though starting over. It's now running in a sonic hot bath of Krud Cutter, thinking another 90 minutes at least.

John, wondering if you had any problems on the alloy surfaces from the Krud Cutter? What was the total time in the tank, and at what temperature?

[John Schmidt]

Rather than do a half-way job I just pulled #5 carb off the carb bank and disassembled it as though starting over. It's now running in a sonic hot bath of Krud Cutter, thinking another 90 minutes at least.

John, wondering if you had any problems on the alloy surfaces from the Krud Cutter? What was the total time in the tank, and at what temperature?

No problems at all, this particular version of Krud Kutter is made for such a task. See label in the picture below. I don't dilute it, comes in a white gallon plastic jug but you need to look specifically for the gray label since KK has various versions available. I ran the carbs for 90 minutes with the peak temp of 80 deg. which doesn't seem like much, but I guarantee you won't pick it up with bare hands. My sonic cleaner will hold two carb bodies but usually only put one in at a time. That lets me hang a SS spice basket in with it that holds all the small parts.

[pancho]

Thanks John, that is the stuff I need. I haven't used my ultrasonic cleaner for carbs since the corrosion problems some people were having in their cleaners a couple of years ago,, do you think that might be 80 degrees C?

[John Schmidt]

Yup, sure is, never gave it a thought so had to go have a look. Guess that equals about 176 F, no wonder it's so hot!    Maybe setting it on 50 would work just as good, that would be around 122 F.

[Bagger John - #3785]

Off-topic a little, but my Tourer's digital water-temp gauge runs at a consistent 80 degrees when putting down the freeway.

Yes, I bought the Celsius version by mistake. 

I've actually gotten used to it. A reading of 99C immediately starts flashing and tells me that the radiator fan had better be coming on soon else I need to stop and shut the bike off. Easier to read from a distance than three digits.