SuzukiSavage.com - Engine dies above half throttle

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Engine dies above half throttle
07/05/09 at 06:57:07

I have rebuilt an old Savage that I was originally going to use for spares - I decided to put it back on the road instead. It starts easily. It idles with no problem. It runs well and pulls hard - up to about half throttle. If the throttle is opened to more than half the engine immediately dies - there may be a splutter or two if the throttle is kept wide open but the only way to resume running is to reduce throttle to below half. It then runs fine. I have checked that the main jet is clear and I have tried increasing the main jet size - makes no difference.

There is no obvious problem with the air intake on the filter side.

It exhibits the same behaviour with both normal and "prime" settings of the fuel tap.

My instinct is that this is a carb problem but I haven't ruled out electrical. It seems likely that it is either too liitle or too much fuel (or too little/too much air). It also seems likley to be main jet related as it runs so well at lower throttle openings. Any suggestions would be very welcome.

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Engine dies above half throttle Reply #1 - 07/05/09 at 09:03:11 If I thought it was electrical Id put a timing light on it & see if the plug stops firing when the engine goes to crap. That would not fix the problem, I know, but it might help you find it. Im l4eaning toward the carb, but eliminating the electrical option would make me feel better if it was my problem.
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SV og LS Full Member Offline Kawasaki ZZR 1200 Posts: 236	Re: Engine dies above half throttle Reply #2 - 07/05/09 at 09:17:27 It's not main jet size. It won't shut down altogether even if there was a 125 installed provided nothing's blocked. I'd check fuel delivery first - as a quick check yank the fuel hose off the carb and check how the fuel flows out in PRI. You don't have any aftermarket filters which might slow down the fuel flow?
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Serowbot YaBB Moderator ModSquad Online OK.... so what's the speed of dark? Posts: 28634 Tucson Az Gender:	Re: Engine dies above half throttle Reply #3 - 07/05/09 at 10:12:36 Check that the needle-jet slide is not sticking,... while you're in there you might as well clean all the fuel passages in the carb. Don't just use carb cleaner, find a very fine wire to run up and down the passages. .009 to .011" Guitar strings work great.
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Engine dies above half throttle Reply #4 - 07/05/09 at 10:13:45 I dont know if its possible for the twist grip & kill switch to get together, but if you reach down on the carb itself to throttle it up, if that makes a difference, then youll have it found.
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Serowbot YaBB Moderator ModSquad Online OK.... so what's the speed of dark? Posts: 28634 Tucson Az Gender:	Re: Engine dies above half throttle Reply #5 - 07/05/09 at 10:34:41 Keep in mind that as throttle increases, the carb circuits work cumulatively. Pilot and needle circuits don't stop when the main opens. And without the needle-jet slide working, the main is essentially blocked.
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Engine dies above half throttle Reply #6 - 07/05/09 at 10:41:38 So a stuck slide will do this?
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DrT YaBB Newbies Offline I love YaBB 1G - SP1! Posts: 40	Re: Engine dies above half throttle Reply #7 - 07/05/09 at 10:42:59 OK - I have checked the "prime" setting and the fuel flows fine. I have run it without the air filter - seems slightly better but no major difference. I have checked the electrics and the regulator is working OK. I am starting to wonder if the coil is breaking down under load or the CDI is malfunctioning.
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Yonuh Adisi FSO Serious Thumper Offline Savage Jedi (Knight) Posts: 3622 Pilot Valley NV, aka Tatooine Gender:	Re: Engine dies above half throttle Reply #8 - 07/05/09 at 11:08:07 Remove the top of the carb and check to be sure the spring didn't get bunched up or the diaphragm ain't damaged.
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bill67 Serious Thumper Offline old tired Posts: 8517 genoa city wisconsin Gender:	Re: Engine dies above half throttle Reply #9 - 07/05/09 at 11:29:38 I would run some Sea Foam in it could be carb slide in sticking.
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Serowbot YaBB Moderator ModSquad Online OK.... so what's the speed of dark? Posts: 28634 Tucson Az Gender:	Re: Engine dies above half throttle Reply #10 - 07/05/09 at 12:06:04 justin_o_guy2 wrote on 07/05/09 at 10:41:38: So a stuck slide will do this? It can,... the main jet screws into the bottom of the needle jet, so if the needle is stuck down, it will block some fuel flow.
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justin_o_guy2

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What happened?

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East Texas, 1/2 dallas/la.

Re: Engine dies above half throttle
Reply #11 - 07/05/09 at 12:11:34

Not trying to start anything, cuz I am no kinda carb guy. They are as magical as transistors to me. So, that said.

If the slide has lifted enough to clear the main of the metering rod, would it still make it die? Is making it to 1/2 throttle enough to make a stuck slide less likely the culprit? If it was up to 1/2 throttle & rolled off just as it started to act up, would it go to idle slowly due to the slide hanging?

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Serowbot

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OK.... so what's the
speed of dark?

Posts: 28634
Tucson Az
Gender: male

Re: Engine dies above half throttle
Reply #12 - 07/05/09 at 12:35:58

Wow!,... I can't think that one out...
Now that I'm thinking about it too much, I can't figure how the vacuum opens the slide.... Seems like it would pull it closed, if drawing from below, and that's what the function of the spring is. So, it must pull from the top?...
I swear it all made sense yesterday.....
My head hurts... Huh

Main thing is,... clean everything in the carb. Oh,.. and check that the washer under the main jet is in place. That being missing would put the main further up into the needle. Might cause trouble too.

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DrT YaBB Newbies Offline I love YaBB 1G - SP1! Posts: 40	Re: Engine dies above half throttle Reply #13 - 07/05/09 at 14:11:54 OK its NOT the carb! I remembered that I had another carb in my spares box so I tried that - same problem. Then I tried a different plug - same problem. I am now 99% certain that its the coil. I have a replecement on its way (good old ebay) so I'll try that next.
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