Topic: 73 cb 750 gas coming out the carb inlet? Fixed video

[izaleth]

You can also look at autozone to see if they have one in the loaner tools??

i have confirmed the intake valve on number 4 isnt seating, im guessing its somehow bent or the seat is damaged looks like ill need to rebuild the head unfortunately

[Tracksnblades1]

You can also look at autozone to see if they have one in the loaner tools??

i have confirmed the intake valve on number 4 isnt seating, im guessing its somehow bent or the seat is damaged looks like ill need to rebuild the head unfortunately

Sorry to hear it was the valve. I’ve tried running the lash really loose on the affected valve so the cam can “ slam the seat”. It rarely works unless it wasn’t ridden after improperly lashed..  given its not bent.

[PeWe]

I run lash 0.10mm on both IN and EX on my stock CB750 K2.
Honda manual say 0.05/0.08mm.

Too easy to get not fully closing valves.
I bet that 0.05mm less IN lift will not reduce the power that much or any.

[izaleth]

I run lash 0.10mm on both IN and EX on my stock CB750 K2.
Honda manual say 0.05/0.08mm.

Too easy to get not fully closing valves.
I bet that 0.05mm less IN lift will not reduce the power that much or any.

full top dead the valve isnt touching the rocker at all, my feeler gauges dont really work with the inspection ports which kind do you use?

i did a compression test and had 0 compression and everything came out the intake, used some oil and it goes right in the cylinder through the intake

would a not fully closing valve be due to improper lash like the rocker is still making contact? i know for sure mine isnt contacting it when top dead on the stroke it has a bit of wiggle room so to say

[izaleth]

You can also look at autozone to see if they have one in the loaner tools??

i have confirmed the intake valve on number 4 isnt seating, im guessing its somehow bent or the seat is damaged looks like ill need to rebuild the head unfortunately

Sorry to hear it was the valve. I’ve tried running the lash really loose on the affected valve so the cam can “ slam the seat”. It rarely works unless it wasn’t ridden after improperly lashed..  given its not bent.

it cant hurt it much more than it currently is right? worth i shot i guess, set the lash loose and turn it over? how does that work?

[Tracksnblades1]

You can also look at autozone to see if they have one in the loaner tools??

i have confirmed the intake valve on number 4 isnt seating, im guessing its somehow bent or the seat is damaged looks like ill need to rebuild the head unfortunately

Sorry to hear it was the valve. I’ve tried running the lash really loose on the affected valve so the cam can “ slam the seat”. It rarely works unless it wasn’t ridden after improperly lashed..  given its not bent.

it cant hurt it much more than it currently is right? worth i shot i guess, set the lash loose and turn it over? how does that work?

It usually doesn’t work.. the cam has gentle take up ramps to start to lift and to set the valve back gently on its seat.
Most cams get busyand get things going around .050 lift.  Some set it at .050 and let it jump the nose at a fast Idle. I’ve tried it at several settings before on several after the owners set the .002 lash to tight. That can be its own debate on how much slack do you take up while setting the lash.  Some in the old days have pressured the cylinder removed the spring, chucked a drill on the valve and spun it while holding up with greater success. Both are just a long shot if it’s been rode any distance under a load……your going to pull it, and you know the saying “while your there” and the snowball starts growing…😜

[Don R]

 You could have a little rust on the valve face, it could wear off. Fix the leaks, do the 3,000 mile tune-up  and run it

[izaleth]

You can also look at autozone to see if they have one in the loaner tools??

i have confirmed the intake valve on number 4 isnt seating, im guessing its somehow bent or the seat is damaged looks like ill need to rebuild the head unfortunately

Sorry to hear it was the valve. I’ve tried running the lash really loose on the affected valve so the cam can “ slam the seat”. It rarely works unless it wasn’t ridden after improperly lashed..  given its not bent.

it cant hurt it much more than it currently is right? worth i shot i guess, set the lash loose and turn it over? how does that work?

It usually doesn’t work.. the cam has gentle take up ramps to start to lift and to set the valve back gently on its seat.
Most cams get busyand get things going around .050 lift.  Some set it at .050 and let it jump the nose at a fast Idle. I’ve tried it at several settings before on several after the owners set the .002 lash to tight. That can be its own debate on how much slack do you take up while setting the lash.  Some in the old days have pressured the cylinder removed the spring, chucked a drill on the valve and spun it while holding up with greater success. Both are just a long shot if it’s been rode any distance under a load……your going to pull it, and you know the saying “while your there” and the snowball starts growing…😜

yeah to be honest if im taking the head off im going to get it properly machined and cleaned up, and yeah lol, if im taking the head off might as well get the bottom end rebuild kit and do the pistons and rings while im there

[izaleth]

You could have a little rust on the valve face, it could wear off. Fix the leaks, do the 3,000 mile tune-up  and run it

my only problem with that is im worried about having it backfire as its the intake thats stuck open, i will say after inspecting it, it doesn't look bent so its possible its corrosion as you have said. im just not sure what i should do at this point, afraid to run it, but i know that could be all it needs

[Tracksnblades1]

Yep it’s a snowball 😜

[izaleth]

Yep it’s a snowball 😜

yeah, i might get a proper leak down tester and try the valve tap trick first see if i can bring it back, its likely its corrosion so ill give it a shot

[Tracksnblades1]

Yep it’s a snowball 😜

yeah, i might get a proper leak down tester and try the valve tap trick first see if i can bring it back, its likely its corrosion so ill give it a shot

There’s these but a .002 & .003 aren’t to hard to bend to the angle you need.

I like the narrow ones Sears used to sell under the Craftsman name…

[izaleth]

You can also look at autozone to see if they have one in the loaner tools??

they dont have a leakdown i looked, ill ask a few more places monday

[izaleth]

Yep it’s a snowball 😜

yeah, i might get a proper leak down tester and try the valve tap trick first see if i can bring it back, its likely its corrosion so ill give it a shot

There’s these but a .002 & .003 aren’t to hard to bend to the angle you need.

I like the narrow ones Sears used to sell under the Craftsman name…

so the valve lash should be around .005? thought i saw .05 somewhere

[ekpent]

The book says .02 intake and .03 for exhaust.

[izaleth]

The book says .02 intake and .03 for exhaust.

i need to buy a book thanks!
kinda strapped for cash with all the parts and tool purchases...

[seanbarney41]

.02 and .03 INCHES!  Of course Honda lists specs in milimeters.  Lets not get ourselves confused.  Folks from all over the world posting here.  Only us backwards Americans still even using inches.

Don't be afraid to run it.  If anything gets worse, at least you know it has to come apart.

[izaleth]

.02 and .03 INCHES!  Of course Honda lists specs in milimeters.  Lets not get ourselves confused.  Folks from all over the world posting here.  Only us backwards Americans still even using inches.

Don't be afraid to run it.  If anything gets worse, at least you know it has to come apart.

thanks will do!
ill go ahead and try the tap method to get any gunk loose might fill it at TDC with a mix of Marvels and acetone to break anything up and try another compression test

[Tracksnblades1]

.02 and .03 INCHES!  Of course Honda lists specs in milimeters.  Lets not get ourselves confused.  Folks from all over the world posting here.  Only us backwards Americans still even using inches.

Don't be afraid to run it.  If anything gets worse, at least you know it has to come apart.

thanks will do!
ill go ahead and try the tap method to get any gunk loose might fill it at TDC with a mix of Marvels and acetone to break anything up and try another compression test

I’m not sure about the .02 and .03 or where that came from.

If I’m reading the manual correctly it’s .002 intake and .003 inches. Some over here express that 2 thousands and 3 thousands.  .02 and .03 inches would be expressed as 20 and 30 thousands respectively…

See Honda’s recommendations below.

[ekpent]

.02 and .03 INCHES!  Of course Honda lists specs in milimeters.  Lets not get ourselves confused.  Folks from all over the world posting here.  Only us backwards Americans still even using inches.

Don't be afraid to run it.  If anything gets worse, at least you know it has to come apart.

thanks will do!
ill go ahead and try the tap method to get any gunk loose might fill it at TDC with a mix of Marvels and acetone to break anything up and try another compression test

I’m not sure about the .02 and .03 or where that came from.

If I’m reading the manual correctly it’s .002 intake and .003 inches. Some over here express that 2 thousands and 3 thousands.  .02 and .03 inches would be expressed as 20 and 30 thousands respectively…

See Honda’s recommendations below.

Your right and sorry to cause confusion on my lack of zero's.

[bryanj]

Easy done, and regularly

[PeWe]

Millimeter or inches is the normal confusing thing.
Honda manual cover often both.
Bearing and piston-bore clearances have lots of zeros when inch is the unit.

Quick to check via Google
"mm vs inch" to find calculators.
Or use the calculator 1"=25.4mm

I do same with
Nm vs ft lbs
PSI vs BAR
F vs C

[izaleth]

.02 and .03 INCHES!  Of course Honda lists specs in milimeters.  Lets not get ourselves confused.  Folks from all over the world posting here.  Only us backwards Americans still even using inches.

Don't be afraid to run it.  If anything gets worse, at least you know it has to come apart.

thanks will do!
ill go ahead and try the tap method to get any gunk loose might fill it at TDC with a mix of Marvels and acetone to break anything up and try another compression test

I’m not sure about the .02 and .03 or where that came from.

If I’m reading the manual correctly it’s .002 intake and .003 inches. Some over here express that 2 thousands and 3 thousands.  .02 and .03 inches would be expressed as 20 and 30 thousands respectively…

See Honda’s recommendations below.

thankyou!
appreciate all the help!