Honda VTX Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
68 Posts
Discussion Starter #1
I asked it on the FB page already but post the question here too:

2003 VTX1800C. Cobra longshots with DB-killers. Total desmog with block-off plates. Opend up airfilterhousing with K&N. PCIII with dual cilinder dyno run (each cilinder has its own map) 35000km. 2 weeks ago changed the spark plugs because I thought they were to blame.
Since a couple of weeks she starts to decel pop on me. Did some hill side riding lately and downhill she pops like crazy. This weekend back in the hills again and she still pops.

Except for a batwing and hard bags, nothing changed on the bike. I always use new gaskets when I put on exhaust.

Any suggestions?

Hans

Verstuurd vanaf mijn SM-G960F met Tapatalk
 

·
Registered
Joined
·
11,946 Posts
Check the torque on the exhaust bolts at cylinder head. Verify no air leak in pipes. Check vacuum hose, FPR. You can change A/F at PC3 for closed throttle.

My 1300 becomes a popcorn popper above 3500 feet. It is contained by my extra baffle. In 2007 I was riding near an 1800 that had decel explosions......
 

·
Registered
Joined
·
7,726 Posts
Aftermarket exhaust flanges are thinner than stock, and in the torqueing process, I've found it doesn't take much to bend them. I have a PC3 also, and a 2-0-0 setting is better to richen the system and helps to reduce decel popping. I found better results from just replacing the exhaust gaskets and making sure my flanges were true'd in a bench vise.
 
  • Like
Reactions: Blast

·
Registered
Joined
·
2,667 Posts
Some decell popping is the nature of this particular engine (1800). Most is masked by stock exhaust and highlighted by aftermarket systems. Eliminating the 'secondary air' crap, and getting a true seal at the exhaust port is the best you can do without a 'programmer'. Having someone to help hold the header square in the port as the flange nuts are torqued is a huge help. And, as Ranger wrote; flat flanges and OEM crush gaskets are a must.
 
  • Like
Reactions: rangers4u

·
Registered
Joined
·
1,901 Posts
How is the PCIII connected? Not with Vampire clips I presume since they cut the wiring.
Disconnect or put a zero map in the PCIII and see what happens.
 

·
Registered
Joined
·
7,726 Posts
Solder the connections, or just do away with it altogether. Many have done that, and are just as satisfied as having the programmer.
 
  • Like
Reactions: Blast

·
Registered
Joined
·
68 Posts
Discussion Starter #7
All connections are solsered. Like I said. Bike ran fine for years and starts to pop recenly

Verstuurd vanaf mijn SM-G960F met Tapatalk
 

·
Registered
Joined
·
2,667 Posts
Brackets move slightly over time. Things shift. It's a motorbike. With bike 'cold' apply 100psi forced air to each cylinder on its exhaust stroke. Block header outlet. Leak check ex flanges with soapy water.
 

·
Registered
Joined
·
1,901 Posts
Malfunction of PCIII still possible. Also check and clean electrical connectors under seat, left side cover, coils, plug wires and redo ground fix.
 

·
Registered
Joined
·
1,909 Posts
Check the welds on your pipes. Any cracks will allow fresh air to easily enter the exhaust system on the reverse pulses. As mentioned the PCIII calibrations can start to drift, as mine did, and the decel popping returns. If your PCIII is a USB unit you can try adjusting the map. Richen the zero throttle position column to 30 starting at 1500 rpm up to red line.
 
1 - 10 of 10 Posts
Top