Weak after new battery!

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Paul W

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I put in a new battery and now 2006 is very weak. Where do I start looking for my problem? Maybe a coil ground? I thought plug wires at first, but they seem good
Thanks
 
All your grounds, disassemble them and get the leads shiny-clean. Rt side of the engine near the oil filler for the main one.
 
Did you by chance check the battery voltage before putting it in the bike?
 
I didnt check voltage before but left it on trickle charger for a while before starting it. it has 14.3 running right now. ---when I unplug one coil - it does not affect RPM but that coil has 14.3V and it seems to have spark
 
---when I unplug one coil - it does not affect RPM but that coil has 14.3V and it seems to have spark

An engine needs three things to run, a spark, fuel and compression.
Assuming your spark is good then it must be down to one of the other two.
 
Considering you’re claiming loss of power after the battery install I would check everything you did to remove the old battery and install the new battery. When you unplug the one coil, If it’s not idling different, how about sound? You should hear the difference for sure. Might be something really simple just getting overlooked.
 
What is 'weak?' More descriptive explanation needed. You should have an altered idle & rpm's would be affected if you disconnect a coil. Slower to rev & uneven sound.
 
What is 'weak?' More descriptive explanation needed. You should have an altered idle & rpm's would be affected if you disconnect a coil. Slower to rev & uneven sound.
yep all that - doesnt want to idle and struggles to rev -- definately missing
 
johnny utah says:
Hey guys, I've been lurking around here for some time since I bought my dad's 89 Vmax 1200 last year. I have a odd question (and I apologize if its been asked somewhere else).

So I put in a new battery this afternoon (UB 12180) after seeing many recommendations throughout the forum. After getting it installed, I let the choke out (as I normally do when I start it for the first time each day) with the choke out the engine was sputtering and fighting but with the clutch all the way in and a small pull of throttle it was fine. However when I pull the choke out to let it warm up the RPMs drop and ultimately stall.

I left the choke in and set the idle screw a little higher and let it run for a few minutes grabbed my helmet and took it around the block. The first thing I noticed was it had really poor acceleration. Went through all the gear and it was just sluggish. I double checked the coil plugins and all the other connections under the seat where I was working.

All I touched was the battery box and fuses, Just got the carbs synced in December by my local shop guy with a Vmax of his own. Any ideas for me? Has this happened to anyone else?
Easiest way is to feel for a cold exhaust pipe. A less-painful alternative: Spraying a spritz of water on the pipes by the cyl heads will quickly reveal which pipe gets hot, and which doesn't.

Fire-medic says:
My diagnosis is that the two are unrelated. You may have a plugged pilot jet, which is the jet controlling idle and low-speed operation. However, the fact that you say during a run around the block it was way-down on power, is something else. A plugged pilot jet or jets will affect low-speed/idle operation only, once you get into the middle of the rev band the other jets take over metering gas, and there should be no loss of power, assuming they aren't blocked.

Try removing your gas filter, and blowing through it. A plugged gas filter may flow enough to allow the bike to run, but not to run at-speed.

In the vicinity of the rear coils, above the battery box, there are a couple of leads for the primary circuits. You will see two 2-wire nylon plug-ins, one pair is white, one pair is yellow (male/female). Check that those are tight, not corroded, and that you don't have a bare wire grounding-out someplace, as that would cost you a cylinder's normal operation.

You also might want to check that in moving the ignition coils pair above the battery, that you didn't pull loose the high-tension spark plug leads out of the 'nose' of the ignition coils. The ribbed black plastic barrel on the nose of the ignition coil and through-which the spark plug high-tension lead comes, is a screw-on cylindrical nut holding the high-tension spark plug lead into the coil. If you unscrew this, you can remove the spark plug wire from the ignition coil. Then you can inspect the wire end for corrosion and ensure that it's inserted fully into the ignition coil body. The end that usually is prone to developing corrosion over time, is the spark plug boot end of the spark plug wire. The common thing to do if you find green electrical corrosion on the spark plug wire after unscrewing the spark plug cap from the spark plug wire (yes, the spark plug cap unscrews from the wire) is to cut-back the spark plug wire a fraction of an inch, until you see clean, uncorroded wire. Then you simply screw-on the spark plug cap, and replace the cap on the spark plug. I like to use a bit of dielectric grease on any electrical connections, it helps to prevent any water intrusion, and helps keep the contacts from corroding.

https://www.vmaxforum.net/threads/issues-after-installing-new-battery.47924/#post-477510

In the front, the right coil fires the left plug, and vice-versa. The 2-wire plug for the right coil will be in the vicinity of the ignition switch; the 2-wire plug for the left coil by the CDI box connectors.
 
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