Flat spot at 3500 RPM's

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Re: Flat spot at 3500 RPM's

#16

Post by Rat »

A little MMO in the gas tank can temporarily make the slides work better ....

Possible diagnosis ....

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Re: Flat spot at 3500 RPM's

#17

Post by Track T 2411 »

Thanks, all, for the advice. Sounds like the carbs will be coming off sometime soon...
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
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'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
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Re: Flat spot at 3500 RPM's

#18

Post by Track T 2411 »

Did a plug chop, but it was inconclusive. While I was out of town, the kid took her out for an 80 mile run around, and the plugs yet again ended up black and sooty (except #3 again). Pulled the carbs, the started with whiskerfish's vacuum test. I'm not sure if maybe my shop vac just doesn't have enough power, but could only get #3 slide to move, and only twice out of numerous attempts. All the others were non - responsive. Turned the rack upside down and did a vacuum test on the fuel line, and it held 20 PSI for several minutes, so I think the float needles are good. Pulled the carb tops and polished up the slides extra thoroughly, then pulled the bowls and reset the floats (which were close, but not great). Weather permitting, they'll go back on tomorrow, and we'll see what we have...
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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Re: Flat spot at 3500 RPM's

#19

Post by Whiskerfish »

While they are still off try the shop vac thing again now that they are cleaner. Make sure you are opening the throttle while holding the hose on the runner. If they are working right it is easy to detect. Also you can usually hear a slight click as the slide bottoms out when you close the throttle.
I use regular hot soap and water and a small piece of worn scotch brite to clean inside the brass liner of the cap. Then after I blow it dry I do a test of the smoothness in my hands.
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Re: Flat spot at 3500 RPM's

#20

Post by Track T 2411 »

Thanks for the tips, again, whiskerfish! The slides were definitely sticking. They got a soapy water bath and a scotch-brite scrub this morning, followed by a brake cleaner rinse. Once installed, they popped up and down like grease on a hot griddle! Got the carbs installed and the bike ready to ride just in time for a torrential downpour to put a damper on things! GRRRRR! We're now sitting on the porch watching the radar...
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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Re: Flat spot at 3500 RPM's

#21

Post by sparkyrasmus »

I've been following this. Hope the ideas work out well, Keep us informed!
Goldwings don't accelerate, they gain inertia.

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Re: Flat spot at 3500 RPM's

#22

Post by Track T 2411 »

Shagged a quick ride in between showers. NO FLAT SPOT! WHOOP, WHOOP! Gonna revisit the idle and sync, and take her for a real ride!
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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Re: Flat spot at 3500 RPM's

#23

Post by Whiskerfish »

Awesome!!!
"Agreement is not a requirement for Respect" CDR Michael Smith USN (Ret) 2017
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!

Psst. oh and by the way CHANGE YOUR BELTS!!!!
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Re: Flat spot at 3500 RPM's

#24

Post by Track T 2411 »

Well, between my step-son and I, we've logged about 300 mostly highway miles with varied results. The flat spot is still noticeable at times, and sometimes almost as bad as when we started. I can't make it happen in the driveway. It doesn't happen (or is hardly noticeable) with a full tank; half a tank or less, rough roads, and/or lots of curves, it becomes more obvious. It doesn't seem to change much if I switch to reserve, either.
Possibilities I'm pondering include partially clogged fuel lines inside the tank (it was professionally cleaned and lined several years ago), too small a diameter fuel lines (new, 1/4 inch, IIRC, along with a flushable fuel filter), a questionable fuel pump, or some combination thereof.
One more thing to throw in the mix... The compression hasn't changed at all. She's still running right around 90 PSI for all four cylinders. The plugs look better, but still have a fluffy carbon build-up around the outside and gray/ white electrodes. I was expecting (hoping) for some signs of improvement, but maybe it's to soon...
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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Re: Flat spot at 3500 RPM's

#25

Post by Track T 2411 »

Jugs one and three...
15371136872422063422777.jpg
15371136872422063422777.jpg (66.7 KiB) Viewed 353 times
Jugs two and four...
1537113824392-1458762990.jpg
1537113824392-1458762990.jpg (65.08 KiB) Viewed 353 times
Jugs two and four...

These plugs have about 200 miles on them. Carbs are at factory settings, and have been synced. Would the low compression be a contributing factor to this? Should I be concerned about it yet, or just keep riding it? I really don't want to make things worse...
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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Re: Flat spot at 3500 RPM's

#26

Post by robin1731 »

pm sent
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Re: Flat spot at 3500 RPM's

#27

Post by OCR »

Plugs appear to be indicating lean burn and #4 is not firing at all or at least long enough to wash off any residue at low rpm.
You need to do "plug chops" to find exactly where this is occurring so that it can be fixed.
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Re: Flat spot at 3500 RPM's

#28

Post by Track T 2411 »

OCR wrote:Plugs appear to be indicating lean burn and #4 is not firing at all or at least long enough to wash off any residue at low rpm.
You need to do "plug chops" to find exactly where this is occurring so that it can be fixed.
Thanks for the response. I've done three chops, and all were inconclusive. I haven't gotten any noticeable sooty build-up on any rides less than 10 miles of mostly highway. When I pull any plug wire, there's a noticeable change, although it's not as significant on #4. Reading Randakk's tips, factory settings on these is typically lean to begin with, and I've been running a K&N air filter, which I've read can also cause a lean condition. The quandary is 'black sooty' typically means rich, yet the electrodes read lean.
Right now the cylinders are soaking to see if the rings will loosen up. I'm going to pull the carbs (again), as well as order a stock air filter. If the compression didn't show any change, a leak - down test will be on the to - do list...
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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Track T 2411
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Re: Flat spot at 3500 RPM's

#29

Post by Track T 2411 »

So I just read back through this thread to get an idea where I left off messing with these carbs and just rode the bike. Now that I'm going through them yet again, there are more pieces to the puzzle.
A. One of the carb tops was damaged at some point after the last rebuild. Makes me wonder if any were leaking before.
B. The air cut valve diaphragm was installed improperly, likely making it inoperable, but in what position, who knows.
C. The jet towers show significant corrosion. I pretty much ignored this issue, thinking that the o-rings would still seal properly. Upon disassembly, I found several of the jet o-rings to be deformed or damaged.
20210612_131204.jpg
20210612_131204.jpg (150.68 KiB) Viewed 285 times
20210612_130719.jpg
20210612_130719.jpg (103.19 KiB) Viewed 285 times
This is probably the worst one. If you look closely at the inside you can see a darker ring where the o-ring sits when installed. The area looks quite porous...
Can these be saved?
"I have no special talent. I am only passionately curious." - Albert Einstein

"He that is good with a hammer tends to think everything is a nail" - Abraham Maslow

"If you can't take the time to do it right the first time, how are you ever going to find the time to do it over?" -Unknown

Current Rides:
'Grumpy' - '81 Standard, now fully dressed.
'Layla' - '81 Standard w/dealer installed fairing and Hondaline bags.
'Scarlett' '76 'Survivor' nekkid as a j-bird!

Under Construction:
The 'Jalopy' '78-'79 Mash-up
'Quikie' '81 gl1100I back on the lift, project with the step-son!

In The Shed:
'81 gl1100I barn find aka "Josie, the farmer's daughter." (almost comatose build)
'77 gl1000, roller parts bike.
'82 gl1100I, 'Old Crusty' titled roller parts bike (free!)
'82 gl1100I, My first 'Wing, and an expensive lesson!
New2U Bike? Read Me.
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Re: Flat spot at 3500 RPM's

#30

Post by flyin900 »

That is definitely an issue with the corrosion on there that will not seal correctly. Is it causing your issue; well only fixing that and trying the repair will tell the tale.
I would look for a replacement set of carbs, or individual units if you can find a cost effective set available. As the guy who repairs cooling fins on cylinders :-D I would try to rebuild those towers with an epoxy that is gas proof, if another set isn't available.
I will be time consuming and tedious work, which is right in my wheelhouse as a challenge. :orange
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1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
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1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
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