Vacuum Guage Carb Synchronization

[Harryc]

My Tourer is new to me (June 2016 purchase) and it is displaying some symptoms that 'might' indicate it needs a carb sync...erratic idle and some sputtering at low speeds off idle, particularly at decel.  It has 24k miles on it. I don't think it's a vacuum leak. I installed a Pingle and replaced all of the vacuum caps with Honda OEM ones, and I checked the vacuum lines to the cut-off valves...looked good although I trimmed off the ends for good measure. I also checked and tightened all carb boots and intake clamps and bolts. If it leaks it would be an intake o-ring but I don't see any evidence of leakage. Anyway, my question is on the sync device. Everyone I have asked recommends the Bon S digisync, but I am not a rich man and $175 means a lot to me. I have some vacuum gauges that I have used on other bikes with success. Any reason I can't just use those? A pic of the gauges I have is linked here. I also have another 2 gauge set that is identical. So I do have a total of 6 gauges. I am aware that I might be looking at carb rebuilds and cleaning, but that is a last resort.
https://www.amazon.com/dp/B004MSJ7E6/ref=pe_385040_30332190_TE_3p_dp_1

[Gavin_Sons]

My Tourer is new to me (June 2016 purchase) and it is displaying some symptoms that 'might' indicate it needs a carb sync...erratic idle and some sputtering at low speeds off idle, particularly at decel.  It has 24k miles on it. I don't think it's a vacuum leak. I installed a Pingle and replaced all of the vacuum caps with Honda OEM ones, and I checked the vacuum lines to the cut-off valves...looked good although I trimmed off the ends for good measure. I also checked and tightened all carb boots and intake clamps and bolts. If it leaks it would be an intake o-ring but I don't see any evidence of leakage. Anyway, my question is on the sync device. Everyone I have asked recommends the Bon S digisync, but I am not a rich man and $175 means a lot to me. I have some vacuum gauges that I have used on other bikes with success. Any reason I can't just use those? A pic of the gauges I have is linked here. I also have another 2 gauge set that is identical. So I do have a total of 6 gauges. I am aware that I might be looking at carb rebuilds and cleaning, but that is a last resort.
https://www.amazon.com/dp/B004MSJ7E6/ref=pe_385040_30332190_TE_3p_dp_1

I still use gauges. A comparrison was done after I synced carbs with my gauges to the digisync and all were within 2 points of perfect.

[Harryc]

@Gavin_Sons , that is good news. Not sure what 2 points on a digisync relates to, but if it is inHG, I think the Honda spec is within 1.6inHG related to each other.  I suppose that might be doable with vacuum gauges as long as they are calibrated. So I guess this was really my question. Vacuum gauges are not going to be as precise as a digisync, but are they 'good enough'? You said yes...anyone else? Someone might answer 'they're not bad if that's all you have', and I'd have to accept that answer.

[98valk]

symptoms do not indicate carb sync.

check plugs, plug wire connections to plug and coils.

most likely it needs a can of B12 with a nice ride.
https://www.berrymanproducts.com/products/gasoline/b-12-chemtool-carburetor-fuel-system-and-injector-cleaner/

[Harryc]

symptoms do not indicate carb sync.

check plugs, plug wire connections to plug and coils.

most likely it needs a can of B12 with a nice ride.
https://www.berrymanproducts.com/products/gasoline/b-12-chemtool-carburetor-fuel-system-and-injector-cleaner/

Thanks. Plugs are brand new, and wires look new and are tightly connected. I have used Seafoam (a couple of tankfuls) but I can certainly try the Berrymans.

[98valk]

if u blip the throttle what do the RPMs do? stay up and then go down? then vacuum leak.
have u tightened the intake manifold bolts, 1/2 turn? maybe more?
could be manifold o-rings, tightening bolts could fix problem.

[Harryc]

if u blip the throttle what do the RPMs do? stay up and then go down? then vacuum leak.

Basically yes. It is worse when the engine is hot if that makes any sense. I can be idling at 900rpm after a half hour ride, but if I go for a 2 hour ride at highway speeds and stop at a light it will be steady @ 1200rpm. That's why I said it is erratic. I'll tighten those bolts.

[pancho]

I was going to suggest that you bite the bullet and pull the carbs and go through them and clean or replace the slow jets, but after the last comment it sounds as if you might have vacuum leaks. Check all hoses and caps for the condition and check the screws on all the clamps for loose ones.

Don't get too carried away on the tightness of the intake to head bolts,, they have been known to snap off.

[Harryc]

Check all hoses and caps for the condition and check the screws on all the clamps for loose ones.
Don't get too carried away on the tightness of the intake to head bolts,, they have been known to snap off.

Thanks. As I said the caps are brand new, I have a pingle so no vacuum line for the petcock, and the hoses for the cut-off valves seem good at the intake manifold end, but I have not pulled the airbox to replace them. I can do that as well. The clamps have all been checked for tightness. I'll check the intake bolts.

Edit: So the Honda tech manual says 6.5 ft lbs of torque for the intake manifold bolts. I just checked them all with an in lb torque wrench set to 78 in lbs, an they were all 12 at least that tight...and as I said earlier there is zero staining around the intakes. I'd have expected to at least see some seepage if they were leaking, but maybe I am wrong.

[jim@98valkyrie.com]

Harry, has a desmog been done on your ride? Even this is designed to reduce vacuum leaks, if something was overlooked, it could produce a vacuum leak. My bike sat idle for 2 years to a knee issue I needed to heal from. She took many cans of B-12 to finally come around and get cleaned out. The gas that was in the tank looked more like an IPA that something that powers the ride....

Long before BonS' Digisync came along, I picked up a Morgan carbtune. I have used it exactly once. Haven't needed another one yet. Bon checked my carbs with his Digisync at IZ this summer, it was spot on. Here is a link to their website:
http://www.carbtune.com/
Another idea is to host a wrenching party. Invite some riding buddies and everyone works on the bikes that need it.

[Harryc]

Thanks Jim, some good ideas there. The bike is totally stock (including exhaust) except for the pingle, and it behaved the same before that. No desmog done to it. Everyone around here swears by Berryman B12 so I am going to try that next. Seafoam was my preferred brew, but maybe it is not up to the task this time. I ran (2) tank fulls with 1/2 bottle of Seafoam each tank with no improvement. You guys are my only riding buddies with Valks...I'll host if you'll come.

[jim@98valkyrie.com]

Thanks Jim, some good ideas there. The bike is totally stock (including exhaust) except for the pingle, and it behaved the same before that. No desmog done to it. Everyone around here swears by Berryman B12 so I am going to try that next. Seafoam was my preferred brew, but maybe it is not up to the task this time. I ran (2) tank fulls with 1/2 bottle of Seafoam each tank with no improvement. You guys are my only riding buddies with Valks...I'll host if you'll come.

Seafoam was my brew too, but I have used B-12 with some better success. It took me at least 10 cans and 15-20 tanks to get the cars squared away. I was very close to pulling the whole set. Check out this page and see how the gel plug can form. I ended up opening the pilot screw 1/2 turn and I believe it helped to dissolve the gunk that was in there.
It's here:
https://sites.google.com/site/valkparts/
under the "Pilot Screw SOW Kit"

[Harryc]

10 cans...guess I better get a case. Thanks for the link. Obviously this bike did set up some. 20k miles in 19 years, so it's not hard to do the math. Also I just went out (with my glasses on this time ) and took another look at the intakes. I do have some staining at the #6 rear left intake at the very corner in the back. O-rings are going to be done as well.  (On order from Red-Eye)

[Itinifni]

I was experiencing a similar issue when I first got my Valk, rising idle speed once fully warmed up. After running through basic maintenance (all fluids, plugs, valve adjust, carb sync, etc.) the problem persisted. Finally resolved by replacing the O rings between the manifolds and heads (easy job). They looked fair but were probably original.

To your original question regarding syncing with mechanical gauges, yes, you can do it. From what I hear the Digi-Sync is most accurate and easy to use but like you, I didn't want to spend the cash for a tool I'd use infrequently. I settled for the Motion Pro manometer, not as easy to use as the mercury manometer I used to use but not bad. If I had six gauges available I would have used them and put the cash towards something more fun for the bike.

If you go ahead with your gauges I suggest you T them all together to a single, stable vacuum source. A Mityvac would be ideal so you can check the calibration across the full range of the gauges. If you don't have a Mityvac you could use manifold vacuum on a car as a rough check of calibration. The key is to identify any gauge that is a significant outlier.

Good luck,
Matt

[Hook#3287]

Harry, that bike is too good looking to not run right.

Seafoam is good but Berrymans is better.

Do a couple of bottles and if it don't get better, might be time to go through the carbs, maybe do a de-smog.

Cool meeting and riding with ya this weekend.

[Harryc]

@Itinifni , thanks for the information. Between the o-rings and the Berryman B12 I am hopeful it will help. @Hook#3287 , great meeting and riding with you also and thanks for the compliment on the bike. I am pretty persistent and patient, so I know it will all fall into place eventually. My last bike, a Honda Shadow 1100 ACE sat up unused and not ridden for 16 years and by the time I sold it, it was running like a top. For the ACE I came up with a permanent fix for a known guide plug oil leak problem that had been until then mostly unsolved. I hope to give back to this community the same way in the future. I am planning on having a long term relationship with my Valk (great machine in all ways), so I'll be around for a bit.  By the way, I think I mentioned Greylock Mtn in NW Mass to you. Well I took a ride up to the summit yesterday with a buddy. Word of advice...do not take a motorcycle up that high on a windy day in mid- October in NW Mass. Man was it cold. LOL

[WintrSol]

@Gavin_Sons , that is good news. Not sure what 2 points on a digisync relates to, but if it is inHG, I think the Honda spec is within 1.6inHG related to each other.  I suppose that might be doable with vacuum gauges as long as they are calibrated. So I guess this was really my question. Vacuum gauges are not going to be as precise as a digisync, but are they 'good enough'? You said yes...anyone else? Someone might answer 'they're not bad if that's all you have', and I'd have to accept that answer.

The gauges don't have to be calibrated, per se, as long as they can be adjusted to match each other while connected to a common vacuum source, like a MityVac pump. Just adjust them as closely as possible to, say, 10", then watch them move from 5" to 20", noting any deviations, so you can compare them throughout the normal range. Before I got my DigiSync, I used gauges matched this way, with good results.

[Harryc]

@WintrSol, good advice, thanks.

[Hook#3287]

@Itinifni , thanks for the information. Between the o-rings and the Berryman B12 I am hopeful it will help. @Hook#3287 , great meeting and riding with you also and thanks for the compliment on the bike. I am pretty persistent and patient, so I know it will all fall into place eventually. My last bike, a Honda Shadow 1100 ACE sat up unused and not ridden for 16 years and by the time I sold it, it was running like a top. For the ACE I came up with a permanent fix for a known guide plug oil leak problem that had been until then mostly unsolved. I hope to give back to this community the same way in the future. I am planning on having a long term relationship with my Valk (great machine in all ways), so I'll be around for a bit.  By the way, I think I mentioned Greylock Mtn in NW Mass to you. Well I took a ride up to the summit yesterday with a buddy. Word of advice...do not take a motorcycle up that high on a windy day in mid- October in NW Mass. Man was it cold. LOL

 Yeah, yesterday would've been my choice for Mount Greylock. More like a week day in July or August or a weekend day, early before the civilians get there.

I usually get there about once a year. 

One year got up there and there was a bunch of hang gliders. That was cool, but I didn't see any this year, wondering if the state shut them down.

[signart]

No need to calibrate gauges, you only need one. The gauge doesn't even have to be accurate. You just sync the carbs so they all read the same as what the gauge you are using reads. Mine is a quality gauge however. Fish aquarium doodads, one for each carb, set to #3.

[Harryc]

No need to calibrate gauges, you only need one. The gauge doesn't even have to be accurate. You just sync the carbs so they all read the same as what the gauge you are using reads. Mine is a quality gauge however. Fish aquarium doodads, one for each carb, set to #3.

Thanks. Necessity is the mother of invention for sure...Fish aquarium doodads and all.

[Ramie]

Stealth desmog is easy to do, I did the full desmog on my standard as I took out the carb bank and cleaned all the carbs.  I used some of this on the intake O-rings to keep them in place when installing the intakes.
http://www.oreillyauto.com/site/c/detail/PERN/80062/N2362.oap?ck=Search_gasket+makers+%26+sealers_-1_-1&keyword=gasket+makers+%26+sealers

[signart]

No need to calibrate gauges, you only need one. The gauge doesn't even have to be accurate. You just sync the carbs so they all read the same as what the gauge you are using reads. Mine is a quality gauge however. Fish aquarium doodads, one for each carb, set to #3.

Thanks. Necessity is the mother of invention for sure...Fish aquarium doodads and all.

The single brass adjuster valve above #5 and below gauge controls needle bounce, if needed

[Harryc]

Stealth desmog is easy to do, I did the full desmog on my standard as I took out the carb bank and cleaned all the carbs.  I used some of this on the intake O-rings to keep them in place when installing the intakes.
http://www.oreillyauto.com/site/c/detail/PERN/80062/N2362.oap?ck=Search_gasket+makers+%26+sealers_-1_-1&keyword=gasket+makers+%26+sealers

Thanks Ramie. If it ends up I have to go into the carbs I will keep that in mind. I have a lifetime supply of Hondabond around here from previous bike projects so I am good on the gasket maker.

[Willow]

... Regarding syncing with mechanical gauges, yes, you can do it. From what I hear the Digi-Sync is most accurate and easy to use but like you, I didn't want to spend the cash for a tool I'd use infrequently. ...

For what it's worth, yes,if you're really good with gauges you can probably do a good job without the Digi-Sync.  I'm not that good.  After having my Interstate synced with Digi-Sync I experienced about a ten percent improvement in fuel mileage.  With gasoline at $2 per gallon t=you can do the math to figure out how long it would take you to get to where the Digi-Sync didn't cost you anything. At one time it would have taken me less than a year.  At today's age it looks like I'm within two. 

[Fazer]

Surprised there is no one in your vicinity with a DigiSync.  Maybe someone will chime in.

[Harryc]

I was experiencing a similar issue when I first got my Valk, rising idle speed once fully warmed up. After running through basic maintenance (all fluids, plugs, valve adjust, carb sync, etc.) the problem persisted. Finally resolved by replacing the O rings between the manifolds and heads (easy job). They looked fair but were probably original.

So I replaced the O rings today, and while it looked like 5 out of 6 were marginally leaking at some point and they probably needed replacing anyway, that was not the problem. It's strange, if I set the idle to @500rpm the throttle returns normally, but if I set it to 900rpm and rev it, it hangs before it drops. It still increases while warm. So the journey continues. I am going to try backing the A/F mix screws out a half turn and running some Berrymans through for a half hour or so, then I'll put them back where they were and run a few tankfuls through. Can't hurt. I think over the winter I am going to do a desmog and pull the carbs and clean them if this does not work, then I'll do a carb synchronization.

[98valk]

I was experiencing a similar issue when I first got my Valk, rising idle speed once fully warmed up. After running through basic maintenance (all fluids, plugs, valve adjust, carb sync, etc.) the problem persisted. Finally resolved by replacing the O rings between the manifolds and heads (easy job). They looked fair but were probably original.

So I replaced the O rings today, and while it looked like 5 out of 6 were marginally leaking at some point and they probably needed replacing anyway, that was not the problem. It's strange, if I set the idle to @500rpm the throttle returns normally, but if I set it to 900rpm and rev it, it hangs before it drops. It still increases while warm. So the journey continues. I am going to try backing the A/F mix screws out a half turn and running some Berrymans through for a half hour or so, then I'll put them back where they were and run a few tankfuls through. Can't hurt. I think over the winter I am going to do a desmog and pull the carbs and clean them if this does not work, then I'll do a carb synchronization.

hanging up is always a vacuum leak. or throttle cables hanging up? preventing carb return springs from closing throttle blades?
are you setting idle at 500 or 900 after engine is at operating temp? has to be done when fully warmed up.

[Harryc]

...hanging up is always a vacuum leak. or throttle cables hanging up? preventing carb return springs from closing throttle blades? are you setting idle at 500 or 900 after engine is at operating temp? has to be done when fully warmed up.

Yes, any adjustments to idle are being made at operating temp. The only place left for vacuum leaks I have not checked (or replaced) are at the pair valves as far as I know. I checked the pair valve lines at the intake and they looked fine, but I sliced off a half inch of each line and reconnected them anyway. The way I look at it if I am going to replace the pair valve vacuum lines I need to pull the airbox, therefor I might as well do a desmog. Make sense? I have not lubed throttle cables but I can try that. The fact that 'heat' makes the idle rise makes me think that is not the issue.

[Harryc]

I decided I was being lazy in not continuing to trace my problem, so I pulled the airbox today and replaced the pair valve to intake vacuum lines, even though the old ones looked new and didn't leak. The only thing I found, and it could be a big thing, is the airbox boot on the number 1 cylinder was spun around and not seating right. Evidently some 'mechanic' in the past took off the airbox, most likely to rebuild the carbs and didn't put that one boot back on right. It was literally turned 45 degrees from it's proper position. If you've ever seen one you know there is a cutout on the inside bottom for air intake...it was nowhere near where it is supposed to be. Inside the #1 carb throat it was really dusty and grimy. So I sprayed carb cleaner around to clean things up the best I could. I put the bike back together and added Berrymans at half a can to a full tank. I ran it for a half hour or so and the idle is staying down. I'll keep monitoring it and keep running Berrymans, but so far so good. A one or 2 hour trip will tell the tale. Used bikes are fun ...

[The emperor has no clothes]

I decided I was being lazy in not continuing to trace my problem, so I pulled the airbox today and replaced the pair valve to intake vacuum lines, even though the old ones looked new and didn't leak. The only thing I found, and it could be a big thing, is the airbox boot on the number 1 cylinder was spun around and not seating right. Evidently some 'mechanic' in the past took off the airbox, most likely to rebuild the carbs and didn't put that one boot back on right. It was literally turned 45 degrees from it's proper position. If you've ever seen one you know there is a cutout on the inside bottom for air intake...it was nowhere near where it is supposed to be. Inside the #1 carb throat it was really dusty and grimy. So I sprayed carb cleaner around to clean things up the best I could. I put the bike back together and added Berrymans at half a can to a full tank. I ran it for a half hour or so and the idle is staying down. I'll keep monitoring it and keep running Berrymans, but so far so good. A one or 2 hour trip will tell the tale. Used bikes are fun ...

Harry, it sounds like you found the problem. I think it was a big thing.  It was good riding with you. 

[98valk]

I decided I was being lazy in not continuing to trace my problem, so I pulled the airbox today and replaced the pair valve to intake vacuum lines, even though the old ones looked new and didn't leak. The only thing I found, and it could be a big thing, is the airbox boot on the number 1 cylinder was spun around and not seating right. Evidently some 'mechanic' in the past took off the airbox, most likely to rebuild the carbs and didn't put that one boot back on right. It was literally turned 45 degrees from it's proper position. If you've ever seen one you know there is a cutout on the inside bottom for air intake...it was nowhere near where it is supposed to be. Inside the #1 carb throat it was really dusty and grimy. So I sprayed carb cleaner around to clean things up the best I could. I put the bike back together and added Berrymans at half a can to a full tank. I ran it for a half hour or so and the idle is staying down. I'll keep monitoring it and keep running Berrymans, but so far so good. A one or 2 hour trip will tell the tale. Used bikes are fun ...

if u replaced the vacuum lines and it runs better then that was the problem. the intake tube u mentioned is upstream of the carb and wouldn't affect the operation of the engine. it just was letting unfiltered air in.

[Harryc]

Harry, it sounds like you found the problem. I think it was a big thing.  It was good riding with you. 

It was great meeting and riding with you and Brenda Rob. I hope to do it again someday soon.

[Harryc]

if u replaced the vacuum lines and it runs better then that was the problem. the intake tube u mentioned is upstream of the carb and wouldn't affect the operation of the engine. it just was letting unfiltered air in.

Jeez Jim, I hope so. LOL

[Harryc]

So today I calibrated the vacuum gauges to a fixed vacuum source and then checked the carb sync. All (6) carbs were dead on in relation to #3. So my question is, if all the carbs are sync'd the same in inHG level, that means I do not have a vacuum leak....right? Just trying to plan the next logical step here. My idle is still all over the place. Bike warms up....idle goes up. I just want the bike to idle at 900rpm after warming up 5 minutes or so and stay there all day. That's how it's supposed to work I am guessing. That's how my Honda cars work anyway. I was going to do a desmog this winter anyway, so that's neither here nor there, but I think the next step is a carb rebuild. Agreed? By the way, I've run through 6 tanks of Berrymans B12 with no change so far. I thought I found a vacuum leak in an earlier post talking about replacing the vacuum hoses, but that did not pan out.

[WintrSol]

If the intake tube to a CV carb is not seating on the carb properly, it WILL affect the mixture, causing it to be somewhat leaner, as the air input stream will have a slightly higher pressure because it is bypassing the air filter. It can also cause turbulence, which can upset the flow into the air jets, which will cause an irregular fuel spray. Now that you have that intake set, test - it may, or may not, be the cause of your issues.

[Harryc]

Now that you have that intake set, test - it may, or may not, be the cause of your issues.

Thanks. I've ridden maybe 800 to 1000 miles since I had the airbox off and reset everything including replacing the o-rings on the intake tubes, and the issue is the same. Before I take the carbs apart I am going to try one more thing since this seems like an odd issue that we can't seem to pinpoint. I am going to replace the Engine Coolant Temperature Sensor. I normally don't like throwing parts at a problem, but this one has me stumped and there are no internal diagnostic codes on a '97 Honda Motorcycle. This issue described at this link is not identical to mine but it's very close.  - http://www.goldwingowners.com/forums/18-engine-work/54410-gl1500-surging-problem-one-solution.html

[pancho]

Harryc, you can just remove the lead from the ECT sensor and go for a ride,, it will keep the timing from changing,, see if the problem is gone. In our bikes, the ECT circuit is used by the ECU to advance the timing which does effect engine RPM.

[Ricky-D]

If you still have an erratic idle after synchronizing the carburetors I'd suggest to get some silicone spray and generously wash down all the carburetor linkage, take off the chrome covers to do it and work the throttle also while doing it. That's what I think may be the problem. The linkage is non-compliant.

***

[Harryc]

Harryc, you can just remove the lead from the ECT sensor and go for a ride,, it will keep the timing from changing,, see if the problem is gone. In our bikes, the ECT circuit is used by the ECU to advance the timing which does effect engine RPM.

Thanks for the idea. Do you know if that connector is reachable without removing the radiator?