Welcome to the DoItYourself Forums!

To post questions, help other DIYers and reduce advertising (like the one on your left), join our DIY community. It's free!

Vanguard V-Twin Running Problems

candhp's Avatar
Visiting Guest

Posts: n/a

08-20-05, 08:52 AM   #1  
Vanguard V-Twin Running Problems

Anyone out there who might be familiar with a Vanguard V-Twin 30-HP...or similar...to help me diagnose poor engine running problem? Have tried a good many things already, with no resolve. Only seems to happen after heat-up and under load. This engine is new since March '05.



Sponsored Links
puey61's Avatar

Join Date: Apr 2004
Posts: 3,224

08-20-05, 08:56 AM   #2  
Weak/failed-all-together ignition coil (one of the two). Insufficient valve clearances. You didn't provide any detailed symptoms so it will be difficult to diagnose. The two I mentioned are the first two areas i'd check.

candhp's Avatar
Visiting Guest

Posts: n/a

08-20-05, 09:25 AM   #3  
Sorry...more info on engine symptoms:

Engine sounds "flat"; full throttle sometimes results in engine loss (wants to cut off); only seems to occur after engine heats up and/or under load since cold start sounds/runs fine. Even extended run time (no load) appears ok!

What's been changed to address: New spark plugs, fuel filter, changed engine fuel (110 octane now vs 100 before), new valve springs, carb cleaned (wasn't dirty) and adjusted; valve lash gap set...diode wire was apparently checked and said to be OK.

Haven't Done: Compression test, starter, fuel pump, ignition coil (think this is a maganatron?). Someone just told me to change the fuel pump?

"Certified" dealer has checked twice now and thinks I'm crazy, but others have told me "something's wrong with that engine...doesn't sound right (and they are using the same engine also)".


cheese's Avatar
Forum Topic Moderator

Join Date: Jul 2001
Posts: 16,567

08-21-05, 12:24 AM   #4  
When it starts messing up, try popping one of the plug wires off and see if it changes. If so, then put it back on and pop the other one off and try again. If it stays the same with one of the wires on or off, then the coil that causes no change is bad, or the diode wire you mentioned is bad. If the engine changes with either wire off, then you probably have a valve or carburetor problem.

"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

Search this Thread