Adding a Vacuum Manifold - Page 3 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #21 of 24 (permalink) Old 02-24-2020, 02:45 PM
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Quote:
Originally Posted by Jason Pittenger View Post
I am referring to the reed valves that sit on the sides of the engine, that dump extra air into the exhaust during decel to burn off unburned fuel. I believe those operate using manifold vacuum. These are typically removed with an ear shave, and a plate is put in place where the reed valves used to sit. As I understand it, putting these plates in place stop the popping on decel.

When I did my ear shave last year, I left that system in place, because I like the popping on decel. I didn't notice any issues with the enriching diaphragms in my carb. It ran more or less the same as before the ear shave. Only more intake noise and slightly improved MPG. I did notice that running the idle screw slightly richer than optimal, got rid of the popping.



For the Tuxedo mod, I've got the cover off (needed to remove it anyways, to remove the cam chains). It will be modified off the bike, in a different building, in a different city and county [IMG class=inlineimg]/forum/images/VN750_2015/smilies/tango_face_grin.png[/IMG]. I actually didn't realize that people try to do this mod on bike. That doesn't sound like a good plan, for the reasons you outlined.

Yep, there’s a video on YouTube of some guy cutting the engine while on the bike. With a drummer like tool nonetheless. Even I a novice to mechanic work said “are you f—kin nuts?” When I saw this.

https://youtu.be/AJs9peopqZg
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post #22 of 24 (permalink) Old 02-24-2020, 05:40 PM
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Mine still popped with the reed valves removed and capped.

Once the seafoam got in there, it stopped popping. That's why I thought coast enrichers were stuck closed.

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post #23 of 24 (permalink) Old 02-24-2020, 06:01 PM
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Quote:
Originally Posted by Jason Pittenger View Post
I am referring to the reed valves that sit on the sides of the engine, that dump extra air into the exhaust during decel to burn off unburned fuel.
Those are part of the EGR system, its for emissions not operation and has nothing to do with the popping. The coasting enrichment valves in the carbs are that function.

Quote:
I did notice that running the idle screw slightly richer than optimal, got rid of the popping.
Thats doing the same thing as the CE valves in the carbs, except running that rich at idle can foul your plugs with any significant idle time.

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2006 Honda Rebel Diesel
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post #24 of 24 (permalink) Old 03-03-2020, 08:44 AM Thread Starter
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I finally took a picture of my carburetor & verified where the vacuum port gets its source of vacuum. You can see in this picture, the hole drilled that is going out to the right side of the picture. The picture got rotated when it was uploaded. When was the right side of the picture, is now the top of the picture. The hole I am referring to, is the larger hole. Not the small tiny hole. That hole, links to the vacuum port on the outside of the carburetor. It looks like it is in fact true engine vacuum. It is down stream of the throttle plate, and it is not blocked by the throttle plate when it's closed (ported vacuum). So this should give me a good spot for a map sensor.

I'm still not sure if linking the two carburetor vacuum ports will cause any running issues or not. Worst-case, I can tee off of one of the ports.

I also have no idea how the petcock stays open at Full Throttle. Maybe there is still some vacuum at Full Throttle? Maybe it doesn't take much for the petcock to be open? I don't know.
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'89 VN750 Bought stock 4/12/18 @ 17805.9 miles $800. Wrecked once. 27454.5+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB. 110/90 Front Tire. Pick-up coil mod. Shindengen MOSFET FH020AA r/r. USB Outlet + Voltmeter. Repainted Metallic Blue w/ new tank bages. Ear Shave (wo/ coasters) 40/140 NO shims 45MPG. MCCT conversion.

Planned modifications:
Custom LED turn signals. Windshield. Highway Pegs. (Possible) ignition adv. Tuxedo Mod. Ignition coil mod.

Last edited by Jason Pittenger; 03-03-2020 at 08:47 AM.
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