Idle problems, weak battery

[RonH]

I thought I would throw this out there in case anyone runs into this. I knew my battery was weak, and has been for some time, but since the motorcycle still started I didn't see the need in replacement. The problem I was having was not a big deal but what was happening is each morning after a cold start when I rode out of the driveway the idle would rise to 3,000 RPM and stay at this level forever until I stopped moving for about 7 or 8 seconds, so until I stopped at a stop sign or stoplight ect and sat there at a complete stop for 7 or 8 seconds I had in effect a 3,000RPM cruise control. Even if I rode 5 miles if I didn't stop for 7 seconds the idle would still be 3,000RPM. It has done this every day all summer like clockwork. I replaced the vaccuum cap on the throttle body and it did nothing. It still started, but I could tell the starter was laboring worse than ever. I put a meter across the battery and at open circuit had a normal 12.7v, but during starting the volts dropped to 9.2V. I bought a new YTZ14S battery and with the new battery volts drop to 11.4 during start. A huge improvement. Old battery load test 122CCA, new battery 334CCA. After replacing the battery the idle problem is gone. Sorry for the long winded post, but I'm just happy it fixed something I didn't expect. All I can think is during the 9.2v the PCM was getting confused, resetting or something to that effect.

 

[Checkswrecks]

Sorta.
An injected engine with big cylinders is a heavy combined electric load for the ignition, the injection (with digital ECU), and the starter speed. Electricity will take the easiest path thru the circuits back to the battery, and the starter gives it the fattest wiring to do so.


Right after start, the battery is still drained, the idle speed is not enough to charge it, and electricity is still being drawn by both the injection and ignition, plus now adding the combined load of all the lights.

 

[Cycledude]

Nice to hear a new battery fixed your idle issues !
Mine has always sounded weak but a battery load says the battery is good, I think Yamaha should have built a more powerful starter. Mine only did the fast idle thing once and I think that might have been because I didn't let it idle at all from a cold start that morning, I just took off and 2 miles later at the stop sign it was idling fast, so ever since that happened I always let it warm up a little before taking off.

 

[Checkswrecks]

When replacing the battery, the battery case size comes in a version with higher CCA. That's the one to buy and you'll be surprised at the difference a few CCA make.

 

[RonH]

Correct, the YTZ12S is the factory battery rated at 210cca, the YTZ14S is the same physical size and rated at 230cca. I put in the YTZ14S. I'm still amazed the battery fixed the high idle problem. For 6 straight mornings now I've ridden down the street without being stuck at 3000rpm. I'm still a little miffed, as in voltage checks the old battery dropped to 9.2v then returned to 13.7v immediately after the cold start, and idle would be normal til I rode out the driveway at which time it would rise to 3000rpm. It didn't matter if I let it warm up, or not, always the same thing would happen. The new battery drops to 11.4v then returns to 13.7, but for some reason idles fine and doesn't rise to 3000rpm. Strange, but I won't question the easy fix.

 

[WJBertrand]

I wonder if there's some logic in the charging system/ECU that makes the engine rev up in order to re-charge the battery faster? Once the engine has started you are mostly seeing the charging voltage rather than battery voltage? If the system thinks the battery is still low maybe it is attempting to add more RPM to improve recharging?

 

[Cycledude]

When replacing the battery, the battery case size comes in a version with higher CCA. That's the one to buy and you'll be surprised at the difference a few CCA make.

Yes ive been eyeing that battery for a long time now but haven't bought one yet, maybe next spring, will be interesting to experience the actual results.

 

[Checkswrecks]

My 2012 didn't have hard start problems, but I have always thought using the bigger battery would be a good step for those with the issue and it sure couldn't hurt.

 

[RonH]

Even with the better battery it will never turn over like a GL1800. My goldwing turns over twice as fast with a 8yr old battery than the super tenere with a new battery, even the better one. For sure the super tenere needs all the help it can get in cranking power.

 

[Cycledude]

Even with the better battery it will never turn over like a GL1800. My goldwing turns over twice as fast with a 8yr old battery than the super tenere with a new battery, even the better one. For sure the super tenere needs all the help it can get in cranking power.

I agree Honda put the proper sized starter in the GL1800, Yamaha saved themselves a couple bucks by using a starter that isn't quite big enough. Back in the early 80's I bought a brandnew chevy truck, it always seemed like the battery was weak but it tested great but then one day I crawled under the truck to look around and saw the starter it was about half the size of a normal v8 starter ! So I complained to the dealer, they got me a brandnew normal sized starter and installed it for free ! After that it sounded normal when cranking and started much better.