Sporadic Start Failure ( NOT "hard-start" issue....)

sandro1973

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Jan 26, 2018
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Portugal
Hi guys,


I ran this question on a local ( portuguese ) FB Group, some folks told it also happens ramdomly to them....no apparent reason that anyone knows, even with new less than 1 year old bikes.

Really simple to explain..... Key ON, fuel pump builds pressure, ignition button, bike seems more sluggish than usual to get started ( more revolutions on starter motor ), then the engines starts and dies almost immediately.....Key OFF to kill the lights, Key ON, starts immediately....

This has happened a 2 or 3 times, with no apparent reason. Bike runs fine, has a Yuasa 14S, had 12,74v this morning, on idle it's stable at 14,30v, so everything works fine......recently it had 4 new plugs, valves checked and adjusted ( all 8 were tight ), new camchain, FI throttle bodies cleaned and synched...never ran better, feels and sounds like a new bike, much less rattle and engine noise than before ( though it'll never be a quiet one...this also had happened before all this maintenance.

Have you had this happen to your bike ? Any idea why ?
 

Thetractorman

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Mar 20, 2018
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I've a 2013 and it's happened sporadically over the 6 years I've owned it. Original battery when I got it, upgraded to 14s,a little improvement. Upgraded to a lithium a few months ago, no further issues! Fires first time every time.
I can't can't offer you a diagnosis, many have mentioned it over the years, but the lithium is definitely my answer.

Sent from my SM-G991B using Tapatalk
 

Boris

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I've a 2013 and it's happened sporadically over the 6 years I've owned it. Original battery when I got it, upgraded to 14s,a little improvement. Upgraded to a lithium a few months ago, no further issues! Fires first time every time.
I can't can't offer you a diagnosis, many have mentioned it over the years, but the lithium is definitely my answer.

Sent from my SM-G991B using Tapatalk
I upgraded to a 14s at the beginning of this riding season, also now starts and stays started 1st time every time. Was also having similar lazy starting issues on a battery that was at least 5 years old.
 

Squibb

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A lot of work appears to have been undertaken recently. Was the problem evident beforehand? Have you checked for codes?

My initial reaction was poor fuel pressure, but it may be a sensor connection., given the recent service work.

It could even be the caps on the TB have perished; this results in leaning out the mixture initially, an uneven idle from cold which often settles once the bike warms up.
 

sandro1973

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A lot of work appears to have been undertaken recently. Was the problem evident beforehand? Have you checked for codes?

My initial reaction was poor fuel pressure, but it may be a sensor connection., given the recent service work.

It could even be the caps on the TB have perished; this results in leaning out the mixture initially, an uneven idle from cold which often settles once the bike warms up.
I bought the bike with 45.000 miles ( 2015 ES model ), it never had the valves checked and i was noticing ( even with my very recent experience with it ) some rattle / whine that sounded like cam-chain slack when riding, lack of power in the first 3 gears up until 3.000 rpm and sometimes, RPM dropping on warmup....so i took it to the dealer and have it all done.....even a compression check was made, no funny stuff in the oil, so i now know the engine is in good running condition and all the small issues mentioned above, including the lack of power in the 1st three gears, are non-existing now.

It actually feels like a new bike now. Never had error codes. Even burns less fuel......accelerates much better with less vibration....still a noisy engine, but less noisy. I also have a sump-guard, which i suppose will add up some of the noise.

The bike has started fine since this more rigorous maintenance, this particular "issue" seems to happen without no apparent reason, randomly. And it also happened a couple of times before it.

Being this a huge engine, i've even thought it could be from the engine / crankshaft being in a particular position at some startups, making it a bit harder sometimes.

Capturar.JPG
 

sandro1973

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Jan 26, 2018
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I've a 2013 and it's happened sporadically over the 6 years I've owned it. Original battery when I got it, upgraded to 14s,a little improvement. Upgraded to a lithium a few months ago, no further issues! Fires first time every time.
I can't can't offer you a diagnosis, many have mentioned it over the years, but the lithium is definitely my answer.

Sent from my SM-G991B using Tapatalk
Never had a lithium battery on any bike, but i know someone who has one on his Teneré...and he's done 115.000 miles on his, so he trusts it.

I've read they have a much better starting power, but give no signs of going bad, are more temperature sensitive and are more prone to catch on fire. I need to read a bit more into this before making that option.
 

WJBertrand

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The LiFePO4 chemistry is very fire resistant. There are other lithium ion and lithium polymer batteries more likely to fail that way, and are responsible for the reputation, but most vehicle batteries are the LiFePO4 type. I’m running one almost 3 years now and 30,000 miles or so with no issues at all.


Sent from my iPhone using Tapatalk Pro
 

Thetractorman

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Yes I'd read those things too, and they're more expensive than a Yuasa.
It was the fact that I was having trouble sourcing a Yuasa that gave me the final push into the purchase.
So far absolutely no regrets.

Sent from my SM-G991B using Tapatalk
 

~TABASCO~

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Obviously this is just an "idea".......

If this bike was in front of me right now, the first thing I would probably look at and inspect carefully is the decompression springs and mechanism. Make sure this all looks and works properly. If one of the springs has come loose or has slipped off its possible only one weight is working and only partially decompressing the cylinder.
I only say this because I have seen the decompression assembly get hung up before. You have to double check it (several times) before putting the whole bike back together. I normally check this on the bench with the cam out. Then again right before I install it, and the last time after its installed.

Once again, this is like a doctor checking out there patient over the phone. Its just an idea :) If this all started after you got your bike back from service I would check this out. Also, If I was this deep I would double check the valve clearances AGAIN after they were adjusted, make sure they in spec and proper. Ive seen people with the very best intentions adjust they're valves. They got the math conversion a little wrong and actually installed the wrong shims. This happens ! Quickly double check those valves again and write down all the numbers so we can take a look.

This is where I would start.
 

sandro1973

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Obviously this is just an "idea".......

If this bike was in front of me right now, the first thing I would probably look at and inspect carefully is the decompression springs and mechanism. Make sure this all looks and works properly. If one of the springs has come loose or has slipped off its possible only one weight is working and only partially decompressing the cylinder.
I only say this because I have seen the decompression assembly get hung up before. You have to double check it (several times) before putting the whole bike back together. I normally check this on the bench with the cam out. Then again right before I install it, and the last time after its installed.

Once again, this is like a doctor checking out there patient over the phone. Its just an idea :) If this all started after you got your bike back from service I would check this out. Also, If I was this deep I would double check the valve clearances AGAIN after they were adjusted, make sure they in spec and proper. Ive seen people with the very best intentions adjust they're valves. They got the math conversion a little wrong and actually installed the wrong shims. This happens ! Quickly double check those valves again and write down all the numbers so we can take a look.

This is where I would start.
Thanks TABASCO , just to clear it up, the maintenance was done by professionals ( with proven credits and i know others that went to the same place with great feedback ), and the bike indeed is SO much better now. I'd never even try do adjust valves....kudos to those who have the ability to do it.... :)

This also happened before all this work was done and several other guys with the same bike report the same random issue. If it keeps going and turns into a regular thing, then i'll worry, so far, from my short experience, the only thing i can associate with this issue, is a slower and longer cranking of the starter motor.

This morning as soon as i heard it cranking, i had a immediate feeling the bike wouldn't start, like if the battery was on its last legs, which it doesn't seem to be. Cranked strong and just fine 3 seconds later.
 

sandro1973

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Starting the bike after 8 hours being stopped....open garage at work, sunny day...cranked quicker than usual than a cold overnight morning-start, normal voltage drop while cranking...worlds apart from this morning...go figure....

 

sandro1973

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I think this is what your bike does. This is mine:


Hi Stefan, exactly just like that, thanks for the video ;) ....the only difference is that today it had a harder time to move the starter motor, like when the battery is about to die on you, more sluggish and took more turns to get it going ( not usual neither )
 
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sandro1973

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Today, early morning cold start....no issues at all....it only happens randomly and i won't be wasting more time trying to figure it out, the bike runs great and usually starts just fine.

Maybe it's when the crankshaft is in a particular position, making it harder to turn sometimes....if that makes any sense.....whatever it is...there's no way of telling.


 

Squibb

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Today, early morning cold start....no issues at all....it only happens randomly and i won't be wasting more time trying to figure it out, the bike runs great and usually starts just fine.

Maybe it's when the crankshaft is in a particular position, making it harder to turn sometimes....if that makes any sense.....whatever it is...there's no way of telling.
Can we take it that no codes are registered currently?

I see your battery voltage dips down to 11volts, maybe less in the moment, when you hit the starter, which could be where the problem lies. Can I suggest you have the battery tested for CCA capacity. IIRC, the 14S should produce 230CCA. That & checking the terminals are tight/snug would eliminate the battery as the source of the issue.

Then we come back to the decompressor system, that has been mentioned already by @TABASCO. The 11.0:1 compression ratio is reduced to a pressure of 84-108 psi when cranking & rises to around 180-200 psi once running. Clearly if one, or maybe even both decompressors aren't functioning correctly, the starter/battery will have a far tougher job on a cold start.
 
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