Got the bike all assembled today, fueled it up, and tried starting it up. Pushing on the starter I could gear it trying to come to life when suddenly BANG!!!! A backfire so loud my ears were ringing 30 minutes later.

Look down after the backfire and what do I see but FIRE! After frantically putting out the flames I searched for the cause.

Turns out the vent hide coming from the top T of my carbs was cracked. So when I had the petcock on prime to fill the carbs gas was dropping out onto the engine. Not sure exactly how it ignited though.

After an extensive search for damage from the 10 second blaze turning up nothing. I cut a new line, clamped it up, reassembled the bike and tried again. This time no gas leaking and the engine fired up in the first few seconds of hitting the starter.

So here I am after a change of pants and a shower, sharing the tale with you. Thoughts?

Sent from my Nexus 4 using Tapatalk 2

  ... dont do it again!!

.. glad you are ok!   

Possibly vapour igniting from finding its way into your starter motor armature and flashing back to the fuel. Thats about the only way it could happen with a cold engine, but amazing odds to get the vapour ratio right..

Lucky / Unlucky at the same time. glad you didnt get any fuel on you and it was only the bike that got a little burnt.

Im missing some arm hair but nothing serious. I was assuming sparks from the starter motor igniting any vapors that got underneath the cover, but wasn't sure.

No pictures of your bike on fire? The last member who burnt his bike had the courtesy to post pictures of it burning.
(What, too soon?)

Probably some gas down in the starter motor area. You burnt it off so you're good to go now.

Quote from: adidasguy on June 04, 2013, 09:22:04 PM
No pictures of your bike on fire? The last member who burnt his bike had the courtesy to post pictures of it burning.
(What, too soon?)

Probably some gas down in the starter motor area. You burnt it off so you're good to go now.

You know...You're right. Who the hell do I think I am....?

Quote from: PatheticPuma on June 04, 2013, 09:23:22 PM

Quote from: adidasguy on June 04, 2013, 09:22:04 PM
No pictures of your bike on fire? The last member who burnt his bike had the courtesy to post pictures of it burning.
(What, too soon?)

Probably some gas down in the starter motor area. You burnt it off so you're good to go now.

You know...You're right. Who the hell do I think I am....?

Ayrton Senna? 

.. and yeah .. what were you thinking .. no handy phone camera or mini cam/vlog rig running .. just in case something spectacular happened!! .. tut tut tut!! 

(yes i saved xune's photo becuase it was worthy of epicness)

Not that is a bike on fire! Not sure if I would have snapped a pic or ran to the lake with a bucket!

HELP!!

Okay. So I thought my fuel leak came from the vent "T" on my carbs. I added the missing vent hose and thought it had stopped the leak. But today when I got the bike started up I started getting fuel drips. Basically when the fuel is flowing, it is leaking. ON and RES are fine as long as the bike is off, and PRI will leak regardless.

Any and all help is appreciated.

If there are any GS experts in the Grand Rapids, MI area willing to give me a hand and drink a couple beers, just say the word.

So when fuel flowing, it spills everywhere.

Carbs over flowing into the airbox? What does the inside of the airbox look like? Wet with gas?

Airbox drain hose missing?

Carb drain screw not screwed in? (Been there - done that!)

Float bowl leaking?


Dry it.
Baby powder it.
Put on PRIME.
Where is gas coming from?

Quote from: adidasguy on June 05, 2013, 04:10:46 PM
So when fuel flowing, it spills everywhere.

Carbs over flowing into the airbox? What does the inside of the airbox look like? Wet with gas?

Airbox drain hose missing?

Carb drain screw not screwed in? (Been there - done that!)

Float bowl leaking?


Dry it.
Baby powder it.
Put on PRIME.
Where is gas coming from?

The airbox is dry, and i tried the the drain screws. The gas seems to be dripping from directly above the bottom T on the carbs. Its just a small steady drip, about 1 every 2 seconds.

If coming from the bottom T, probably a bad seal on the T (o-ring?). If coming from the upper T, which is the vent, one or both float needles is leaking.

Quote from: Paulcet on June 05, 2013, 04:39:10 PM
If coming from the bottom T, probably a bad seal on the T (o-ring?). If coming from the upper T, which is the vent, one or both float needles is leaking.

Hmmm, I wonder why they would have started leaking. I assumed it is something I did during the teardown, but i never got around to even touching the carbs. There was no leak before the disassembly.

Also, apart from simply cleaning out the bowls/jets, I know NOTHING about carbs. How would I fix leaking needles?

The needles can be finicky during float assy install.  I have had a set of brand new needles/seats leak when I tried to install them with carbs mounted on the bike.  It took 2 or 3 tries.  I should have taken the carbs off to install new needles.

Or, your needles could be worn out.  They are to be replaced with the seats as a set.  If you think the needles and seats are good, you could have a bad seat o-ring.  You can replace them by removing the seats.

Would sitting untouched for the winter cause the seals to have problems?

I will have to check out the carb thread...

Sent from my Nexus 4 using Tapatalk 2

Yes, I think so.  When I bought my bike from Dgyver, it hadn't been ridden much.  Shortly there after, one of the float needle seats had a bad o-ring.

I have a spare set of carbs. I will put them on tomorrow and see if the leak still exists.

Sent from my Nexus 4 using Tapatalk 2

Had a similar leaking problem after a tip over.  Turns out the float needle had dislodged.  Cleaned carbs while I was at it, put in new O rings and no more leak.  BTW, please pass the marshmallows.

Maybe I missed something, but float needles don't cause fuel to leak from the T connection.  If it's leaking from there, then you have a bad gas seal on one or both sides of the T, or the T itself is cracked.  You have to split the carbs and replace the seals and possibly the T as well.  I had to do this on my carbs, and a set of carbs I rebuilt and resold.  It's common for those seals to dry out and crack when you rotate the T around while installing the carbs.  Also, don't use a metal worm screw hose clamp for your fuel lines, because they put too much pressure and break the T.  The PO of my bike had done this. 

Fix the leak first, and then move on to checking the float height and adjusting your float needles.  If the float needles are leaking, you might get gas overflowing into the airbox, not dripping from the carb T.