Hot starts - MVAgusta.net
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post #1 of 13 (permalink) Old 10-23-2019, 08:06 AM Thread Starter
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Hot starts

Bike: 2015 dragster rr
Miles 6300

So my bike is due for a sprag and map update, but I'm beginning to suspect that there may be an electrical issue when I attempt to hot start the bike, so I thought I'd probe the collective mind here to get some opinions.

The issue is the slow crank at hot starts, which i know is part of the sprag problem, but beyond that the battery dies very quickly when I attempt the hot starts. Before I start throwing money at the problem I started running some tests when I noticed something interesting.
First I tested the stator (hot and cold). Resistence on the 3 yellow wires is in spec, no short to ground, and volts ac are also within spec.
Next the reg/rec with a diode test, and again all within spec.
Lastly the lithium battery. It sits freshly charged at about 13.1, when doing load test with a volt meter cold it doesnt drop much below 11 volts, and when idling it sits around 14 volts (if I remember correctly). When steady revving the bike it charges up to about 14.5.
Now the interesting part is when the bike warms up and the fan kicks on it drops back down into the low 13's and even while revving cant go beyond 13.8. The hotter the bike gets, the lower that voltage gets. Now when I shut the bike off after this it rests around 12.7 volts. This isnt enough juice to hot start the bike again without killing the battery.
Keep in mind all of my test show that the charging components are passing tests even when they are warm.
So what do we think: is a cell in the battery failing when warm?
Is the reg rec to blame?
Or does this simply fall within the category of sprag failure?

Thanks all!
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post #2 of 13 (permalink) Old 10-23-2019, 09:33 AM
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I would say that service loads on your bike are greater than the system can overcome to provide sufficient charge to your battery.

If a cell has failed, or is failing on your battery, it becomes a large resistive load.

This could account for your findings as the REG/RECT circuit appears to provide the required 14.5vdc cold.

ME, I'd go back to a quality AGM battery.

On the sprag note, the sprag repair also includes an ECU update to change the starting profile in the ECU.

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post #3 of 13 (permalink) Old 10-23-2019, 10:31 AM Thread Starter
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I'm beginning to think that about the battery as well, as it's pretty hit and miss in terms of voltage.
Not to mention the PO didnt exactly maintain the bike well.
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post #4 of 13 (permalink) Old 10-23-2019, 10:31 AM Thread Starter
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Would you suggest replacing any other components?
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post #5 of 13 (permalink) Old 10-23-2019, 10:42 AM
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Quote:
Originally Posted by Dangydave View Post
Would you suggest replacing any other components?

Nope. I would replace the battery.

Read this first: https://www.motorcycle.com/products/...s-vs-realities

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post #6 of 13 (permalink) Old 10-23-2019, 11:23 AM Thread Starter
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This article implies lithium is better! So agm it lithium?!?!!? Ahhhh too many choices
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post #7 of 13 (permalink) Old 10-23-2019, 11:29 AM
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Quote:
Originally Posted by Dangydave View Post
This article implies lithium is better! So agm it lithium?!?!!? Ahhhh too many choices

Lithium is better IF:

1. Your charging system will support the higher charging voltage (By your testing, yours will not.)
2. The lithium battery you choose has a dedicated and good Battery Management System.
3. Your maintenance charger is designed for Lithium Batteries.

You need to be able to read that article objectively and apply what you read to your situation.

From what you have described, your battery has failed because the charging system cannot keep up with house loades and provide acceptable charging voltage to the Lithium Battery.

Therefore; in your case, lithium is NOT better.
esq'z me and Teeps like this.

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post #8 of 13 (permalink) Old 10-23-2019, 11:51 AM Thread Starter
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First off: thank you for being so helpful.
I guess I'm confused because so many people run li batteries on this bike and dont seem to have the same problem, ie the voltage drop when warm
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post #9 of 13 (permalink) Old 10-23-2019, 12:24 PM
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Quote:
Originally Posted by Dangydave View Post
First off: thank you for being so helpful.
I guess I'm confused because so many people run li batteries on this bike and dont seem to have the same problem, ie the voltage drop when warm
Well, you have to play the cards you are dealt.

Your battery may be faulty, theirs may not. It happens.

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'07 Ducati Monster S4Rs, '07 Ducati Monster 695
2010 Harley Davidson Ultra-Classic Electra-glide CVO FLHTCUSEBLK
'63 Honda C100A Cub
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post #10 of 13 (permalink) Old 10-23-2019, 06:56 PM Thread Starter
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Pulled the battery, turns out it wasnt lithium, and on top of that had a bad cell! Fixed that problem
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