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  Topic Review (Newest First)
10-07-2019 05:51 PM
Hans&Feet
Quote:
Originally Posted by Harkon View Post
Sorry, my bad brother. I had my mind on the petcock diaphragm and did not read your post closely enough. My apologies.
No apologies needed!
LoL ....
ACO diaphragm vs petcock diaphragm!

SeaSteve Post #7- AND still got the "One-Shot" backfire... But now it was a muffled PHUMF sound I could live with.
Mine has this at random times.

Harkon your post #8 was informative! Thank You!
10-07-2019 05:00 PM
Harkon
Quote:
Originally Posted by Hans&Feet View Post
Looks like manifold vacuum on one side and air on the other side. Valve closes air to low speed jet, richer mixture does NOT ignite.
Also if someone wold have a defective ACO diaphragm then to investigate if JBM Industries would make one for a VTX.
I am using a JBM Industries slide valve diaphragm.
http://jbmindustries.com/aboutus.html
Or get in touch with me...

OEM ACO hose plugged, quiet at 50 > 35 MPH decel, pops at 80>60 MPH decel, pops at 20 MPH decel in 1st gear(this was the loudest).
My first half dozen 50 MPH decels were quiet, wind noise may have masked some pops.

At 3500 feet or higher my X is a pop-corn popper. Constrained some by baffling, not explosions nor gunshots..
Sorry, my bad brother. I had my mind on the petcock diaphragm and did not read your post closely enough. My apologies.
10-07-2019 04:10 PM
Hans&Feet
Quote:
Originally Posted by Harkon View Post
I think a rubber tire tube will dissolve with gas, possibly contaminating the carb. Just a heads up. You'll want to use something fuel safe for this IMO.
Looks like manifold vacuum on one side and air on the other side. Valve closes air to low speed jet, richer mixture does NOT ignite.
Also if someone wold have a defective ACO diaphragm then to investigate if JBM Industries would make one for a VTX.
I am using a JBM Industries slide valve diaphragm.
http://jbmindustries.com/aboutus.html
Or get in touch with me...

OEM ACO hose plugged, quiet at 50 > 35 MPH decel, pops at 80>60 MPH decel, pops at 20 MPH decel in 1st gear(this was the loudest).
My first half dozen 50 MPH decels were quiet, wind noise may have masked some pops.

At 3500 feet or higher my X is a pop-corn popper. Constrained some by baffling, not explosions nor gunshots..
10-07-2019 01:35 PM
Harkon
Quote:
Originally Posted by Hans&Feet View Post
Check the Air Cutoff valve diaphragm.

Expensive little sucker.. Cover, spring and diaphragm/valve
Fill it with RTV??? Rubber tire tube to make a new diaphragm??

14 VALVE SET, AIR CUT 16048-MZ8-H00 In Stock $84.02 $65.02

Look up MR VTX Carb 101 for carb teardown pix.
I think a rubber tire tube will dissolve with gas, possibly contaminating the carb. Just a heads up. You'll want to use something fuel safe for this IMO.
10-07-2019 11:40 AM
PoggiPJ
Quote:
Originally Posted by Hans&Feet View Post
Check the Air Cutoff valve diaphragm.

Expensive little sucker.. Cover, spring and diaphragm/valve
Fill it with RTV??? Rubber tire tube to make a new diaphragm??

14 VALVE SET, AIR CUT 16048-MZ8-H00 In Stock $84.02 $65.02

Look up MR VTX Carb 101 for carb teardown pix.
Hello Hans! It has been a long time. I decided to purchase the entire petcock, because for a little bit more it would also include a new filter screen, and also since the front of the valve is riveted, I couldn't check the condition of the plastic diverter and so didn't want to chance that it was damaged.
10-07-2019 11:37 AM
PoggiPJ
Quote:
Originally Posted by MrAnudo View Post

The petcock assembly replacement is interesting - and look pretty easy. Where did you get yours?
I picked up mine at PartsFish, for $116. So far I've ridden it about 98 miles, with just one, solitary POP.
10-06-2019 12:16 AM
MrAnudo Just ordered - will give it a go - thank you!

Update: replaced the ACO and still same exact symptoms. Hesitates on initial throttle roll on. Backfires on decel. Like a firecracker

To date:

1. Desmog - no change
2. Replaced all vacuum hoses - no change
3. Reseated exhaust - no change
4. All new plugs - no change. And the ones I took out looked great
5. Sea foam - no change
6. Replaced ACO - no change



Does it matter that I’m at altitude in Denver?
10-05-2019 11:40 PM
Hans&Feet Check the Air Cutoff valve diaphragm.

Expensive little sucker.. Cover, spring and diaphragm/valve
Fill it with RTV??? Rubber tire tube to make a new diaphragm??

14 VALVE SET, AIR CUT 16048-MZ8-H00 In Stock $84.02 $65.02

Look up MR VTX Carb 101 for carb teardown pix.
10-05-2019 11:26 PM
MrAnudo How timely - I was literally going to post the same question. I have tried just about everything on my 1300c.

Background - I recently took off stock pipes, replaced with V&H. New crush gaskets (twice removed since they're cheap and new ones placed) - did the washers under the acorn too. No change at all. I've tried monster baffles and then replaced with quiet baffles. Literally no change - so pressure made no difference. I've monkeyed back and forth with the AF mix - I can make it pop more... but not less.

Just did the pair valve removal. But STILL no luck. Still backfires on decelerations. Also - I am experiencing what is uneven acceleration when first twisting the throttle - a little hesitation. Had you experienced the same?

The petcock assembly replacement is interesting - and look pretty easy. Where did you get yours?
09-26-2019 09:01 PM
PoggiPJ SOLUTION: Two years later, I finally had some extra time to work on my VTX. Combination of two things, although I think it was principally #2. I do still detect an occassional low, rumbing backfire, similar to what I can hear on my 2017 Indian Roadmaster.

#1, I pulled out the carb just enough to not require disconnecting the water hoses. Dropped the float chamber, opened and cleaned the fuel pump and vacuum diaphragms, both the main and idle jets. Blew out all the fuel pathways with compressed air. Cleaned out all varnish.

#2, I also found that the petcock diaphram had ruptured, resulting in drawing fuel into the vacuum line. I replaced the entire petcock assembly for about $112. In my uneducated, layperson opinion, This is what most likely was causing extra fuel getting into my system and going KAPOW in my pipes almost every time I decelerated.
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