Hot start detonation (starter kickback)?

[Bad Karma]

So,

I've had this recurring problem since I got the bike but it only happens with with a hot start and not all the time either.

When I start the bike I get a detonation witch kicks back on the starter. Usually happens at gas stations when the bike hasn't cooled off that much. It starts fine after this happens. I've searched this forum on google and the search function but haven't found any other cases with Buells at least.

I have found the same issue in other Harley forums but the general theory is that "it happens". Not much of a definitive answer to damage done or not.

I never find any metal in the oil. I just hope I'm not loosing starter teeth. Or putting excess wear on the starter and batt.

Has anyone else experienced this? Is it a problem or just something that happens on high compression motors in a hot start condition?

 

[Bad Karma]

Really not one of you guys have had this happen. Makes me wonder if air/fuel is off a bit.

 

[Squattybodyjr]

mine started do the same thing last fall and the bike is all stock.

 

[Xb12armyguy]

Mine kicks back alot but always starts

 

[JOEL9]

Try this:

1. key off
2. twist throttle to wide open & hold open
3. key on, do not start bike
4. still holding throttle open, the check engine light will come on then go out and then start to blink.
5. check engine light will blink about 4 times, when it stops, close the throttle & key off.
6. start bike normally

this procedure will fire the spark plugs for a few seconds, burning off any excess fuel. you may hear a little burp from the exhaust. i've tried it a few time and it seems to work on my bike, '08 xb9sx.

 

[JOEL9]

Found the thread where i heard of this:

http://www.buellxb.com/Buell-XB-For...for-cleaning-the-combustion-chambers-of-buell

 

[bguinn]

I have the same problem. I will try this the next time I fill up or just stop for a leg stretch. It makes sense and sounds like the cause. The bike runs like crap for a few seconds, until I rev it to clear it out.

Thanks for the info.

 

[Bad Karma]

OK I've been away for a while. But thanks for the replys.

It may be due to a quick bump before I fully depress the starter switch. I'll pay closer attention.

@Joel9 Learned something new there.

If it's not just me bumping the switch I'll give this a shot.

I didn't think it was a big deal, just sounds like crap and a little embarrassing.

Gets everyone looking at you like you hit the starter while the engine was running

 

[Squattybodyjr]

I thought that it be that i was bumping the starter too, but i make sure that i hold and press and hold til it starts and mine still does it.

 

[crxtasy169]

I have the same exact problem on my 09 lightning.

 

[Bad Karma]

No clue yet. I'm 100% pos that it's not me letting go of the button momentarily. I did have the primary open over the weekend and no starter teeth are missing and no grind marks. Yay!!

So I chalk it up to the weird ass antics of a Buell and not to worry about it.

 

[jriffe108]

Yep, my 2008 XB12 does it. It did it when all stock, and does it now. Here in south Texas, when summer riding, you pull into fuel station, switch off bike, fan runs, pump fuel, key on, fan still running, ignition hot, fan kicks off, bump starter, chug, chug, chug, spit, release starter, bump starter again, engine fires, extremely low idle, barely running, wait a 3 seconds, clears itself and idles fine.

Sounds like crap, and is embarrassing. At first, I assumed I had a leaky injector, which was loading up a cylinder, causing the hard start, and subsequent low idle in an attempt to burn off the remaining fuel. But, it appears to be a hot fuel issue, while off and pumping fuel, the fuel line absorbs heat from the engine which cause the fuel in the line to boil, releasing vapor bubbles which are detonating upon impact with the hot piston as soon as the injector fires upon restart.

I conducted an experiment in my garage where I removed the lower airbox, ran bike to operating temp, 320 degrees F, turned off, let rest for 4 minutes, average refuel time, then restart with berp, spit, snort, symptoms.

Warmed bike up again to 320-340 F, then uses a cool tube to remove heat from fuel line only, restart as normal after 4 minutes.

If a constant circulation fuel system, with return fuel line was used with fuel reg on rail, this problem wouldn't exist. Just my two cents. I try to refuel in the evening or allow the bike to rest a little longer now to avoid the condition. Will try insulating the fuel line this winter to see if it helps next summer. An additional ducted fan near the fuel line may help or some vents to allow heat to dissipate quicker in the area may help but the fuel line sits right over the valley of heat from both front and rear cylinders, with the stock fan only drawing air over the rear jug from the scoops or perpendicular side of rear jug, leaving a low pressure zone (vacuum) right where the fuel line runs.

 

[okey]

My 09 Xb12ss has done this on several occasions. Especially after a fuel up i do the normal wait till light goes out the hold the starter .Sometimes i will get the "huff" of the pistons moving then "crack" . Sounds like a tooth sheared off the starter but bike fires runs a little uneven then after a couple of seconds runs fine and normal. Spoke to the tech on its first service and he basically said its a large capacity twin trait but harleys and buells were the more likely v twins to do it . He has a buell also and said not to be too worried . I dont feel easy about it though.