Re: Running under load issue-anything common or obvioius

cgwood13 · Post by **cgwood13** » Sun Oct 21, 2018 1:38 am

Hi all, I have enjoyed being a group member and reading you post for several years. Finally bought a really nice 72 Z on Friday. It had been sitting for awhile, and then recently just idled around a dealer lot, onto the auction block, on and off my trailer, and such.
It starts and runs perfectly at idle, no smoke, clearly has compression and firing both cylinders correctly. It won't rev out under load. I am competent to figure it out and will begin going through all of the checks but am really hoping there is something common you all know from experience that I should check first.
Thank you. Curtis Wood

Don B Laughton · Post by **Don B Laughton** » Sun Oct 21, 2018 3:01 am

Check ignition timing and advance (mechanical advance can lock up). Check condition of wires from coil to spark plug caps. Check for a foiled plug. Good luck.

Sent from my iPhone

On Oct 21, 2018, at 8:26 AM, cgwood13@... [2cylinderhondas] wrote:

Hi all, I have enjoyed being a group member and reading you post for several years. Finally bought a really nice 72 Z on Friday. It had been sitting for awhile, and then recently just idled around a dealer lot, onto the auction block, on and off my trailer, and such.
It starts and runs perfectly at idle, no smoke, clearly has compression and firing both cylinders correctly. It won't rev out under load. I am competent to figure it out and will begin going through all of the checks but am really hoping there is something common you all know from experience that I should check first.
Thank you. Curtis Wood

art Remai · Post by **art Remai** » Sun Oct 21, 2018 3:40 am

Fuel starvation? Maybe take the carb apart and clean or rebuild it. Today s fuels can gum it up fast.

Sent from my iPhone

On Oct 21, 2018, at 10:01 AM, Don B Laughton dontranspac@... [2cylinderhondas] wrote:

Check ignition timing and advance (mechanical advance can lock up). Check condition of wires from coil to spark plug caps. Check for a foiled plug. Good luck.

Sent from my iPhone
On Oct 21, 2018, at 8:26 AM, cgwood13@... [2cylinderhondas] wrote:

Hi all, I have enjoyed being a group member and reading you post for several years. Finally bought a really nice 72 Z on Friday. It had been sitting for awhile, and then recently just idled around a dealer lot, onto the auction block, on and off my trailer, and such.
It starts and runs perfectly at idle, no smoke, clearly has compression and firing both cylinders correctly. It won't rev out under load. I am competent to figure it out and will begin going through all of the checks but am really hoping there is something common you all know from experience that I should check first.
Thank you. Curtis Wood

Paige Hunt · Post by **Paige Hunt** » Sun Oct 21, 2018 3:46 am

When this happened to me, it was a faulty fuel pump. The damn thing was shiny and new, just defective. I replaced it with a regular style, as I've never been a fan of the old style clicker type. just make sure the pressure is low, and volume is high to avoid flooding.
ererveI'veSent from Yahoo Mail on Android

On Sun, Oct 21, 2018 at 11:38 pm, cgwood13@... [2cylinderhondas] wrote:

Hi all, I have enjoyed being a group member and reading you post for several years. Finally bought a really nice 72 Z on Friday. It had been sitting for awhile, and then recently just idled around a dealer lot, onto the auction block, on and off my trailer, and such.
It starts and runs perfectly at idle, no smoke, clearly has compression and firing both cylinders correctly. It won't rev out under load. I am competent to figure it out and will begin going through all of the checks but am really hoping there is something common you all know from experience that I should check first.
Thank you. Curtis Wood
#ygrps-yiv-1391464129

Curtis Wood · Post by **Curtis Wood** » Sun Oct 21, 2018 9:11 am

Thanks all. I have checked valve timing, lash, compression, ignition and ignition advance. All is good.
Really just feels like the throttle is only part open and because there is no coughing or spitting I doubt fuel pressure is a problem.
Is there a way to confirm the slide is lifting and pulling the needle jet up? Based on experience with SUs on British cars that seems likely.
Carb is next. Again thanks.

Sent from my iPhone

On Oct 21, 2018, at 12:40 PM, art Remai artremai@... [2cylinderhondas] wrote:

Fuel starvation? Maybe take the carb apart and clean or rebuild it.. Today s fuels can gum it up fast.

Sent from my iPhone
On Oct 21, 2018, at 10:01 AM, Don B Laughton dontranspac@... [2cylinderhondas] wrote:

Check ignition timing and advance (mechanical advance can lock up).. Check condition of wires from coil to spark plug caps. Check for a foiled plug. Good luck.

Sent from my iPhone
On Oct 21, 2018, at 8:26 AM, cgwood13@... [2cylinderhondas] wrote:

Hi all, I have enjoyed being a group member and reading you post for several years. Finally bought a really nice 72 Z on Friday. It had been sitting for awhile, and then recently just idled around a dealer lot, onto the auction block, on and off my trailer, and such.
It starts and runs perfectly at idle, no smoke, clearly has compression and firing both cylinders correctly. It won't rev out under load. I am competent to figure it out and will begin going through all of the checks but am really hoping there is something common you all know from experience that I should check first.
Thank you. Curtis Wood

Don B Laughton · Post by **Don B Laughton** » Sun Oct 21, 2018 9:56 am

Early carburetors have a vacuum piston with a rubber diaphragm. These diaphragms are known to tear. If your carburetor has a stamped steel top, you have a rubber diaphragm. Carbs with aluminum tops have a steel piston. Remove air cleaner to carb bellows and with a mirror watch to see if piston rises with engine speed. Steel pistons can get gummed up. Good luck

Sent from my iPhone

On Oct 21, 2018, at 4:11 PM, Curtis Wood cgwood13@... [2cylinderhondas] wrote:

Thanks all. I have checked valve timing, lash, compression, ignition and ignition advance. All is good.
Really just feels like the throttle is only part open and because there is no coughing or spitting I doubt fuel pressure is a problem.
Is there a way to confirm the slide is lifting and pulling the needle jet up? Based on experience with SUs on British cars that seems likely.
Carb is next. Again thanks.

Sent from my iPhone
On Oct 21, 2018, at 12:40 PM, art Remai artremai@... [2cylinderhondas] wrote:

Fuel starvation? Maybe take the carb apart and clean or rebuild it... Today s fuels can gum it up fast.

Sent from my iPhone
On Oct 21, 2018, at 10:01 AM, Don B Laughton dontranspac@yahoo..com [2cylinderhondas] wrote:

Check ignition timing and advance (mechanical advance can lock up)... Check condition of wires from coil to spark plug caps. Check for a foiled plug. Good luck.

Sent from my iPhone
On Oct 21, 2018, at 8:26 AM, cgwood13@... [2cylinderhondas] wrote:

Hi all, I have enjoyed being a group member and reading you post for several years. Finally bought a really nice 72 Z on Friday. It had been sitting for awhile, and then recently just idled around a dealer lot, onto the auction block, on and off my trailer, and such.
It starts and runs perfectly at idle, no smoke, clearly has compression and firing both cylinders correctly. It won't rev out under load. I am competent to figure it out and will begin going through all of the checks but am really hoping there is something common you all know from experience that I should check first.
Thank you. Curtis Wood

Curtis Wood · Post by **Curtis Wood** » Sun Oct 21, 2018 11:24 am

Got it !! Thanks everyone. Not positive it was the carb piston but I removed the piston top cover, cleaned everything with fine emory cloth, then reassembled like an SU torqueing the cover bolts a little at a time while sliding the piston up and down. Fired it up and it runs like a top!

Fun first drive under the belt

Curtis
--------------------------------------------

On Sun, 10/21/18, Don B Laughton dontranspac@... [2cylinderhondas] wrote:

Subject: Re: [2cylinderhondas] Running under load issue-anything common or obvioius
To: 2cylinderhondas@yahoogroups.com
Date: Sunday, October 21, 2018, 6:56 PM

Early carburetors have a vacuum piston with a
rubber diaphragm. These diaphragms are known to tear. If
your carburetor has a stamped steel top, you have a rubber
diaphragm. Carbs with aluminum tops have a steel piston.
Remove air cleaner to carb bellows and with a mirror watch
to see if piston rises with engine speed. Steel pistons can
get gummed up. Good luck

Sent from my
iPhone
On Oct 21, 2018,
at 4:11 PM, Curtis Wood cgwood13@...
[2cylinderhondas]
wrote:

Thanks all. I have checked valve timing, lash,
compression, ignition and ignition advance. All is
good.
Really just
feels like the throttle is only part open and because there
is no coughing or spitting I doubt fuel pressure is a
problem.
Is there a
way to confirm the slide is lifting and pulling the needle
jet up? Based on experience with SUs on British cars that
seems likely.
Carb
is next. Again thanks.

Sent from my
iPhone
On Oct 21, 2018,
at 12:40 PM, art Remai artremai@...
[2cylinderhondas]
wrote:

Fuel starvation? Maybe take the carb apart and
clean or rebuild it.... Today s fuels can gum it up
fast.

Sent from my
iPhone
On Oct 21, 2018,
at 10:01 AM, Don B Laughton dontranspac@...
[2cylinderhondas]
wrote:

Check ignition timing and advance (mechanical
advance can lock up).... Check condition of wires from coil
to spark plug caps. Check for a foiled plug. Good luck.

Sent from my
iPhone
On Oct 21, 2018,
at 8:26 AM, cgwood13@...
[2cylinderhondas]
wrote:

Hi all, I have enjoyed being a group
member and reading you post for several years. Finally
bought a really nice 72 Z on Friday. It had been sitting
for awhile, and then recently just idled around a dealer
lot, onto the auction block, on and off my trailer, and
such.
It starts and runs perfectly at
idle, no smoke, clearly has compression and firing both
cylinders correctly. It won't rev out under load. I
am competent to figure it out and will begin going through
all of the checks but am really hoping there is something
common you all know from experience that I should check
first.
Thank you.
Curtis Wood

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