Author Topic: Engine won't start after spraying carb cleaner  (Read 1812 times)

Offline sashkar2000

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Engine won't start after spraying carb cleaner
« on: July 22, 2013, 01:01:54 PM »
I acquired a 2002 bike with 8K miles that was sitting for 3.5 years, I replaced the fuel lines, cleaned the carbs and the bike started ok and i rode it for 30 minutes.

A week later it didn't start and I diagnosed it due to rust in the fuel tank clogging up the carbs. I replaced the tank, cleaned the carbs again, looked inside the manifolds and noticed gunk on the valve stems.

At this point I made a terrible judgment call that I really, really regret. I sprayed carb cleaner inside the manifest to dissolve the gunk. And in an attempt to do a better cleaning job, I turned the engine over by rotating the wheel while in gear.

After about 20 minutes I attempted to start the engine and after 10 minutes of cranking it began coughing out smoke out of exhaust and backfiring. I thought it was cleaning itself out so I continued cranking. Then a massive backfire explosion happened in the intake manifolds and smoke went thru the carbs and came out from below the seat.

After some more cranking I took off the air box so I had direct access to the carbs. I sprayed a bit of starter fluid into the left carb while cranking. To my immense disappointment white smoke came out not just from the exhaust but from the air port of the 2nd carb.

I suspect in the best case I have deposits on the intake valves but could the backfire have burnt them as well? I plan to order a compression tool to see how bad things are but i'm afraid an engine rebuild may be required which is way beyond my abilities and sounds like a really expensive job for a shop.

I would appreciate any suggestions, though I should have consulted you guys before i fked things up. Please don't be too harsh, i'm already really devastated over it.


Offline Kerry

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Re: Engine won't start after spraying carb cleaner
« Reply #1 on: July 22, 2013, 02:04:20 PM »
An engine rebuild?  Whoa ... calm down.  I doubt very much that you could have done any kind of permanent damage to the engine with carb cleaner and/or starter fluid.

Just curious; how do your plugs look now?
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Offline sashkar2000

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Re: Engine won't start after spraying carb cleaner
« Reply #2 on: July 22, 2013, 03:15:57 PM »
Spark plugs were soaked and a blackened from being flooded but otherwise looked fine.

It's not just the carb cleaner that's in there but also the gunk that was previously on top of the valve stem got dissolved and flowed inside the cylinders. I tried to flush it out with seafoam by removing the spark plugs and running the starter but it didn't help.

how else to explain exhaust fumes coming out of the carb other than an intake valve seal issue?


Offline 78530i

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Re: Engine won't start after spraying carb cleaner
« Reply #3 on: July 22, 2013, 04:53:12 PM »
The only connection between the 2 sides is the crossover in the exhaust (that I can think of). Am I wrong?

Offline Kerry

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Re: Engine won't start after spraying carb cleaner
« Reply #4 on: July 22, 2013, 04:58:38 PM »
how else to explain exhaust fumes coming out of the carb other than an intake valve seal issue?

One possibility would be a timing issue, where the plug fires while the intake valve is still open.  Or the cylinder is hot enough to fire the incoming fuel without a spark.  (Not that carb cleaner / starter fluid would cause either of those to happen, either.  Well, maybe starter fluid ... since it's so volatile?)
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Offline sashkar2000

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Re: Engine won't start after spraying carb cleaner
« Reply #5 on: July 22, 2013, 07:13:15 PM »
hmm, would a massive backfire possibly screw up timing?

If there is something stuck to the intake valves, what are some options to get it off? I tried  flushing it out by spraying seafoam and running with sparkplugs disconnected, and then with spark plugs removed so the liquid was coming out. It was bringing up some particules with it. maybe i didn't run that long enough.

Offline fetor56

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Re: Engine won't start after spraying carb cleaner
« Reply #6 on: July 22, 2013, 07:35:33 PM »
Try push starting.....not particularly technical but often effective.
« Last Edit: July 22, 2013, 08:15:54 PM by fetor56 »

Offline Blueknyt

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Re: Engine won't start after spraying carb cleaner
« Reply #7 on: July 22, 2013, 11:07:10 PM »
you sprayed carb cleaner into the carbs?  :mad: :sad:  there goes those Diaphrams :technical:
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Re: Engine won't start after spraying carb cleaner
« Reply #8 on: July 22, 2013, 11:15:29 PM »
you sprayed carb cleaner into the carbs?  :mad: :sad:  there goes those Diaphrams :technical:

... wait... what? ... only for disassembled carbs? ..  :icon_question:

... carb cleaner ... makes sense .. spray carbs!! ... not so much though?! .. i dont use the stuff so 'newbie surprise time!' .. learn something new everyday eh!  :thumb:

i should say .. while i am jacking this topic .. i know my own limits and patience... for carb problems ive only ever gone to a carb guy ... may cost me more .. but if they frag it then they get to fix the frag! .. if i frag the job ... then i still have to pay them to fix it!  :icon_neutral:
« Last Edit: July 22, 2013, 11:17:48 PM by Janx101 »

Offline Blueknyt

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Re: Engine won't start after spraying carb cleaner
« Reply #9 on: July 23, 2013, 12:43:55 AM »
yeah, you don't want carb cleaner spray or dip on those diaphrams, they will distort and break down. ive learned that one the hard way.   the use of starting fluid  down the carb throats is not encouraged either. 
Accelerate like your being chased, Corner like you mean it, Brake as if you life depends on it.
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Re: Engine won't start after spraying carb cleaner
« Reply #10 on: July 23, 2013, 02:46:35 AM »
Start simple. It may need a valve adjustment. Tight exhaust valves can cause backfiring through the carbs, as the exhaust isn't fully released. So, the new air/fuel mixture ends up pre-igniting.
I'd check the valve clearances, and while you're in there, you can check the top end for gunk and whatnot.
Chemicals can only do so much. Nothing beats a good hand job (hehe).
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Offline sashkar2000

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Re: Engine won't start after spraying carb cleaner
« Reply #11 on: July 23, 2013, 11:15:35 AM »
Looks like I'll be opening up the engine for the 1st time. I'll check valve clearance and timing but I also suspect the intake valve is not sealing properly so may have to take off the head.

Anyone know what all the tools are needed to get to the valves and how to check them?

Offline The Buddha

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Re: Engine won't start after spraying carb cleaner
« Reply #12 on: July 23, 2013, 11:45:26 AM »
OK I would really suggest you post where you're located and find a twinner near by who you would bribe with beer/pizza Wine/cheese $$ etc etc to come and help you.

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Offline sashkar2000

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Re: Engine won't start after spraying carb cleaner
« Reply #13 on: July 23, 2013, 12:14:58 PM »
I'm in Staten Island. Any twinners here willing to lend a hand? Beer, dinner, and eternal gratitude is on me.

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Re: Engine won't start after spraying carb cleaner
« Reply #14 on: July 23, 2013, 01:16:46 PM »
IIRC, it's just Allen wrenches to get the heads off. You'll need a socket wrench to pull the right side cover and spin the engine to check the clearances. And a feeler gauge that can measure .03-.08 mm. You can pick one up for $5-10 at an auto store. You may want to consider replacing the head gasket, too, if it looks worn out.

Here's the page from the wiki: http://wiki.gstwins.com/index.php?n=Maintenance.CheckValves

It's not too difficult if you're mechanically inclined, but it would probably be better to have someone there who's done it before if for no other reason than the peace of mind that no harm is being done.
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Offline Blueknyt

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Re: Engine won't start after spraying carb cleaner
« Reply #15 on: July 23, 2013, 06:31:21 PM »
how did we go from "......bike started ok and i rode it for 30 minutes." to opening the engine?   :nono:  THink carefully   :cookoo:   start simple....check carbs again after a new set of properly gapped NEW sparkplugs.  kinda rare for something to change that drasticly inside the engine.   even valve clearences  dont change that quickly unless something is very wrong and you would have noticed it in that 30min of riding.
Accelerate like your being chased, Corner like you mean it, Brake as if you life depends on it.
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Offline sashkar2000

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Re: Engine won't start after spraying carb cleaner
« Reply #16 on: July 24, 2013, 01:52:02 AM »
Performed a compression test today. Both cylinders registered under 10psi. Just to double check I tried the finger instead of spark plug test and i could definitely overpower the pressure from pushing my finger out.

I think it's the massive backfire due to the gunk i put into the cylinders which caused valves to burn. or it could be something else, i won't know till i open her up.

i've ordered most of the tools. still need a valve spring compressor. anyone know of a cheap one online?


Offline The Buddha

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Re: Engine won't start after spraying carb cleaner
« Reply #17 on: July 24, 2013, 03:16:58 PM »
Performed a compression test today. Both cylinders registered under 10psi. Just to double check I tried the finger instead of spark plug test and i could definitely overpower the pressure from pushing my finger out.

I think it's the massive backfire due to the gunk i put into the cylinders which caused valves to burn. or it could be something else, i won't know till i open her up.

i've ordered most of the tools. still need a valve spring compressor. anyone know of a cheap one online?

You hold the throttle open during compression test ?
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Offline sashkar2000

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Re: Engine won't start after spraying carb cleaner
« Reply #18 on: July 24, 2013, 04:01:02 PM »
I had the carbs out during the compression test.


Offline AlexT

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Re: Engine won't start after spraying carb cleaner
« Reply #19 on: July 24, 2013, 11:19:18 PM »
Whoa sashkar, I'm in Staten Island too. I wish I could offer my help but I am not very knowledgeable when it comes to these sorts of things. I just do a lot of googling and ask the friendly people on this board.

However, I recently (and still) have an exhaust valve issue when my bike overheated which required me to attempt to take off the cylinder head on my own. I never actually got the head off but maybe if you read through that thread a bit, you can learn from my mistakes which mainly included stripping/rounding every dang bolt on the bike.

PS. I had the carbs out when I did a compression test. Should make no difference.