HarleyTechTalk

The new 23.5 121 CVO uses an updated trans top cover vent that acts as a really nice CCV.  I have verified that it is retrofittable.  A better explanation of how it works can be found HERE.
The new cover only uses 4 of the 6 original bolts but does use the nice rubber band style of gasket.  PN is 29400448 and retails for around $90 and  comes with a gasket but no hose.
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Great info Joe.     

Very interesting.  Thanks!

I'm not experienced with the M8 engines...

Based on that video, it looks like this new CCV replaces the older breather valve assemblies in the heads.... correct?

It looks like it would reduce (possibly significantly) the oil mist ingested into the intake, thus reducing the carbon build up on the pistons..

So on a retro fit to an older M8, could you block the breather bolts and use this system as the only CCV?

Quote from: hattitude on December 04, 2023, 09:22:56 AMI'm not experienced with the M8 engines...

Based on that video, it looks like this new CCV replaces the older breather valve assemblies in the heads.... correct?

It looks like it would reduce (possibly significantly) the oil mist ingested into the intake, thus reducing the carbon build up on the pistons..

So on a retro fit to an older M8, could you block the breather bolts and use this system as the only CCV?

Yes that is possible.  I used 3/8-16 set screws to block off the head breathers as there is plenty of room behind most all breather bolts.  On the setup pictured above I just used a hose and small UNI filter ran above the throttlebody like the A1 vent is ran but you could drill and tap for a nipple on the back of most any A/C setup to have the fumes still go into the air cleaner. 

Feuling made their own video about the differences in the heads of the 121 motor and the normal M8 motor.

https://harleytechtalk.com/htt/index.php/topic,120375.msg1450330.html#msg1450330

Quote from: joe_lyons on December 04, 2023, 09:34:12 AM

Quote from: hattitude on December 04, 2023, 09:22:56 AMI'm not experienced with the M8 engines...

Based on that video, it looks like this new CCV replaces the older breather valve assemblies in the heads.... correct?

It looks like it would reduce (possibly significantly) the oil mist ingested into the intake, thus reducing the carbon build up on the pistons..

So on a retro fit to an older M8, could you block the breather bolts and use this system as the only CCV?

Yes that is possible.  I used 3/8-16 set screws to block off the head breathers as there is plenty of room behind most all breather bolts.  On the setup pictured above I just used a hose and small UNI filter ran above the throttlebody like the A1 vent is ran but you could drill and tap for a nipple on the back of most any A/C setup to have the fumes still go into the air cleaner. 

Why does the air leaving the engine need to be filtered?

Quote from: hrdtail78 on December 04, 2023, 10:02:25 AM

Quote from: joe_lyons on December 04, 2023, 09:34:12 AM

Quote from: hattitude on December 04, 2023, 09:22:56 AMI'm not experienced with the M8 engines...

Based on that video, it looks like this new CCV replaces the older breather valve assemblies in the heads.... correct?

It looks like it would reduce (possibly significantly) the oil mist ingested into the intake, thus reducing the carbon build up on the pistons..

So on a retro fit to an older M8, could you block the breather bolts and use this system as the only CCV?

Yes that is possible.  I used 3/8-16 set screws to block off the head breathers as there is plenty of room behind most all breather bolts.  On the setup pictured above I just used a hose and small UNI filter ran above the throttlebody like the A1 vent is ran but you could drill and tap for a nipple on the back of most any A/C setup to have the fumes still go into the air cleaner. 

Why does the air leaving the engine need to be filtered?

To catch any residual that possibly makes it up the hose.

So is it possable to make one of these out of the stock cover? Anybody try this yet?

I used this and this. Drilled a hole in the top cover for the grommet, and then poked a couple small holes in the gasket for airflow. Will post a pic later.

You are the man, I know someone out there is thinking all the time. I'm a retired deisel mechanic and i've been working on "Potty mouth" ever since I was a kid. Retired and on a fixed income and i love these motorcycles,but man the price on some of this stuff is unbelievable! So i'm always looking for a way to get it done. I really apreciate the help I get from this site! Bunch of knoledgable guys here.Hope to see the pictures soon. Thanks!  

Quote from: roadkingdresser on December 05, 2023, 02:52:58 AMSo is it possable to make one of these out of the stock cover? Anybody try this yet?

A lot of people have done this trick of tapping into the top cover for crank case venting.  The size of the additional vent determines if you can delete the original CCV or not.  Then there is the debate on when is too much or too little CCV good/bad.

"A lot of people have done this trick of tapping into the top cover for crank case venting"
"So on a retro fit to an older M8, could you block the breather bolts and use this system as the only CCV?"
" I used 3/8-16 set screws to block off the head breathers"


Doesn't the engine still need to breathe? (don't know why my question is highlighted, but it did)

Here's a pic. When I get done testing, I'll throw a hose on it. and route it properly.You cannot view this attachment.
You cannot view this attachment.

Is the Toyota PCV valve a one way valve letting pressure out only 

Yes

Quote from: rigidthumper on December 07, 2023, 04:48:04 PMYes

Ok. Good work . 

On the 121 VVT the hose goes back up to the air intake manifold after the air filter before the Throttle body.  There are no breathers in the Heads of the 121 VVT.

Quote from: FLSTFIDave on December 08, 2023, 05:17:36 AMOn the 121 VVT the hose goes back up to the air intake manifold after the air filter before the Throttle body.  There are no breathers in the Heads of the 121 VVT.

I was referring to the post about retrofitting a older M8 and blocking off the head breathers. Trask (maker of trans cover vent for older models) advises against blocking them off.

Quote from: Deye76 on December 08, 2023, 06:04:27 AM

Quote from: FLSTFIDave on December 08, 2023, 05:17:36 AMOn the 121 VVT the hose goes back up to the air intake manifold after the air filter before the Throttle body.  There are no breathers in the Heads of the 121 VVT.

I was referring to the post about retrofitting a older M8 and blocking off the head breathers. Trask (maker of trans cover vent for older models) advises against blocking them off.

That is interesting, that they advise against blocking them off.  Harley has blocked them off for the VVT.

Quote from: FLSTFIDave on December 09, 2023, 04:34:32 AM

Quote from: Deye76 on December 08, 2023, 06:04:27 AM

Quote from: FLSTFIDave on December 08, 2023, 05:17:36 AMOn the 121 VVT the hose goes back up to the air intake manifold after the air filter before the Throttle body.  There are no breathers in the Heads of the 121 VVT.

I was referring to the post about retrofitting a older M8 and blocking off the head breathers. Trask (maker of trans cover vent for older models) advises against blocking them off.

That is interesting, that they advise against blocking them off.  Harley has blocked them off for the VVT.

I was referring to the post about retrofitting a OLDER M8 and blocking off the head breathers. Trask (maker of trans cover vent for older models) advises against blocking them off.

Quote from: Deye76 on December 08, 2023, 06:04:27 AM

Quote from: FLSTFIDave on December 08, 2023, 05:17:36 AMOn the 121 VVT the hose goes back up to the air intake manifold after the air filter before the Throttle body.  There are no breathers in the Heads of the 121 VVT.

I was referring to the post about retrofitting a older M8 and blocking off the head breathers. Trask (maker of trans cover vent for older models) advises against blocking them off.

Harley evidently found that the CCV that they were using were inadequate and designed a new version.  The Trask CCV I believe does not have the capability of flowing what the new harley unit does and so in conjunction with their CCV setup and stock setup creates enough venting.  If you want to run both the new CCV and the old CCV that definitely wouldn't hurt but the a/c setup that the customer had on this bike is prone to making a mess so I eliminated that.

"The Trask CCV I believe does not have the capability of flowing what the new harley unit does"

Hmm, wonder what the difference is? Isn't it just a barb and a hose?

Quote from: Deye76 on December 09, 2023, 04:09:56 PM"The Trask CCV I believe does not have the capability of flowing what the new harley unit does"

Hmm, wonder what the difference is? Isn't it just a barb and a hose?

No it has a valve. 

From the Trask website:  "The Trask Performance CheckM8 vented transmission top cover fixes most of these issues by using a one-way Boyesen valve to bleed off excess crankcase pressure whilst keeping oil/air mist in the cam chest".