Author Topic: Engine dies with throttle input.  (Read 101 times)

Offline Triaviator

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Engine dies with throttle input.
« on: June 14, 2018, 03:19:34 AM »
I just completed a carb rebuild, but now I'm having issues.  After starting the bike with full choke in neutral it idles normally at ~5k rpm.  A small throttle input in neutral will increase rpms to ~6k, but more than a little throttle and the bike decreases rpms all the way to zero and shuts down.  If I release the throttle before it shuts down, it will idle back at 5k rpm.  It's like it becomes fuel starved or something.  Did I mess something up in the carbs? Please help, thanks!

Offline Watcher

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Re: Engine dies with throttle input.
« Reply #1 on: June 14, 2018, 10:50:40 AM »
I really should bite my tongue and wait for someone more knowledgeable than me to chime in, but I think it could be either the mixture screws are off or the idle is set incorrectly, or a combination of both.
May also be a vacuum leak somewhere mucking everything up.  Sounds like it's running way lean.

Will it idle off choke?  Have you tried giving it time to warm up?
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Offline mr72

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Re: Engine dies with throttle input.
« Reply #2 on: June 14, 2018, 02:51:54 PM »
My bet is the slides don't come up. Could be the diaphragms are damaged, torn, etc., needles/slides installed incorrectly so they can't move or are restricted from moving freely, or severe vacuum leak such that there's no vacuum at the top of the diaphragm.

Try running it with the airbox off so you can look into the carbs. When you open the throttle, do the slides come up?

I'd start there, get back to us :)

Offline user11235813

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Re: Engine dies with throttle input.
« Reply #3 on: June 14, 2018, 11:42:51 PM »
I had that problem recently, it drove me completely batty, it gradually got worse. Sometimes I could get it to go away for a while by giving it a lot of throttle. After months of pulling the carbs apart and putting it back together I gave up and took it in to the Suzuki mechanics by which time it was almost unridable, they discovered that  the problem turned out to be that the press fit part of the carb that guides the slide, was loose. They did a pathetic job on the bike which meant I had to dismantle it again to fix their crap work, but at least now I knew what the problem was. Bought a new set of carbs and it's been perfect.

You can see there are two punch marks on that press fit part, I could see that the mechanics put a couple more punch marks on it, but they could not guarantee it wouldn't come loose again.




« Last Edit: June 14, 2018, 11:52:31 PM by user11235813 »

Offline Triaviator

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Re: Engine dies with throttle input.
« Reply #4 on: June 16, 2018, 03:17:20 PM »
So I ran the bike with the airbox off, sure enough as I gave it juice, the slides didn't come up.  They move freely when I push them up, so bad diaphragms?

Offline J_Walker

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Re: Engine dies with throttle input.
« Reply #5 on: June 16, 2018, 03:57:45 PM »
are the vent hoses from the white caps routed correctly?

did you remove these white caps?
-Walker

Offline mr72

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Re: Engine dies with throttle input.
« Reply #6 on: June 16, 2018, 04:58:58 PM »
So I ran the bike with the airbox off, sure enough as I gave it juice, the slides didn't come up.  They move freely when I push them up, so bad diaphragms?

Could be, but more likely just a very bad vacuum leak. Start tracing every vacuum hose, cap, etc. and make sure they are all in good shape. But also likely you will wind up pulling the carbs again and when you do, you might make sure you didn't lose an o-ring or two when working on it. Easy to do.