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Dental Rider
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Discussion Starter #1
I recently bought the bike that hadn't been started in over 2yrs. I already cleaned out all the rust and jelly fuel out of the carbs, lines, line switch, pump, tank, new fuel filter, cleaned tank filters, and fresh oil/filter.

With a brand new battery, full choke, she turns over and idles for maybe a second and dies. I've tried starting it with the throttle cranked open and it won't even idle. Now the thing is I didn't change the plugs because I was "told" it had new plugs before it sat. Granted that was a long time ago.

The fuel mixture screws are backed out 2.5 turns, which seems reasonable. I adjusted the floats to spec using the height method rather than the service fuel method. I have a feeling it could be the floats are adjusted to high. But since I haven't layed eyes on the plugs maybe they're completely fouled to hell. The previous owner did tell me he had tried to get it running for a while so who knows what these so called "new plugs" went through.

For the experience carb guys, what would be your plan of attack?
 

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itch808 said:
I recently bought the bike that hadn't been started in over 2yrs. I already cleaned out all the rust and jelly fuel out of the carbs, lines, line switch, pump, tank, new fuel filter, cleaned tank filters, and fresh oil/filter.

With a brand new battery, full choke, she turns over and idles for maybe a second and dies. I've tried starting it with the throttle cranked open and it won't even idle. Now the thing is I didn't change the plugs because I was "told" it had new plugs before it sat. Granted that was a long time ago.

The fuel mixture screws are backed out 2.5 turns, which seems reasonable. I adjusted the floats to spec using the height method rather than the service fuel method. I have a feeling it could be the floats are adjusted to high. But since I haven't layed eyes on the plugs maybe they're completely fouled to hell. The previous owner did tell me he had tried to get it running for a while so who knows what these so called "new plugs" went through.

For the experience carb guys, what would be your plan of attack?
New plugs will not hurt but me thinks that you have other issues. Is the pump working properly. Are the carbs really clean and are you getting clean fuel. You may want to bypass the fuel tank and pump by using fuel bottle hooked up to carbs. Also a carb syncronizing could help but is not a main problem now.
 

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Dental Rider
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Discussion Starter #4
DonRR said:
Pull the plugs and replace them then give it a try.Do you smell fuel from the exhaust when you are turning it over? Sounds flooded to me.
I smell fuel and get the occasional backfire when cranking it with the throttle closed. Probably is flooded, but when I try cranking it with the throttle open it won't even turn over.

Veefer97 said:
New plugs will not hurt but me thinks that you have other issues. Is the pump working properly. Are the carbs really clean and are you getting clean fuel. You may want to bypass the fuel tank and pump by using fuel bottle hooked up to carbs. Also a carb syncronizing could help but is not a main problem now.
Pump is definitely working, I tested it outside the bike directly to a battery and ran it a bit to flush out all the gunk that built up in it. Fresh fuel was just put in yesterday as I completed flushed the tank and gave it a POR-15 treatment. Carbs are super clean, I cleaned all the jets and needles, passages, etc. Haven't gotten around to syncronizing the carbs yet but I figured it would idle well enough without having done it yet.

Gonna eat some lunch for now and then change the plugs.
 

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run some seafoam through the first tank....do as the other guy said and check the plugs, you can check for spark by pulling them out and hooking to the plug wire, and ground it out and the top of the cylinder head
 

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Dental Rider
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Discussion Starter #6
Wow, ok just got back from the garage. Turns out it WAS the plugs. They were covered in carbon and had a little oil on them. New plugs, gapped, BAM...she fires right up!

Ok now the rest of the story. Fully warmed up, choke off, it will idle a bit but after up to ~1min it will just die out. Also noticed that when revving it @ idle there's a bit of hesitation from idle to 3k rpm. From 3k+ though, response seems great. It just seems to bog at the low end.

Does this sound like a carb sync issue, air/fuel mixture screw, or a float issue? I recorded a quick clip and will post it up on youtube soon to see if it helps. Sorry, I'm a bit of a carb newbie as this is the first carbureted vehicle I've ever worked on.
 

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Dental Rider
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Discussion Starter #7

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my *guess* would be some of the low end jets may be running a little lean... either still stopped up or needing a good sync - but i'm no expert lol
 

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pull those carbs off and disassemble them right down to the smallest pilot jet and reclean everything,sounds like its only running on 3 cyls
 

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Mine sync was way off and the bike ran poorly at low end (slow to rev up). After sync it ran great at all RPM. Made 99.2 hp on the dyno (98 zx6) with a slipon and jetted properly. Do a search on how to make your own sync tool. All you need is some hose, a board and water. Do 2 carbs at a time (1&2 and 3&4) and then sync 2&3 together.
 

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Dental Rider
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Discussion Starter #11
Hmm, I'll see if a sync helps it. I swear those carbs have got to be clean. I had taken out every jet and blasted them and the passages like crazy. Then I did it again! I guess if the sync doesn't work I'll pop the carbs out again for yet another cleaning...

I'm sure the fueling could use a little work since the bike isn't quite stock. Dynojet stage 1 jet kit, K&N air filter, and a full Akrapovic 4-1 exhaust system.
 

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Dental Rider
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Discussion Starter #12
*UPDATE* Since someone mentioned it maybe running lean I tried unscrewing the mixture screw another 1/2 turn out changing it from 2.5 to 3 turns. It could be my imagination but it seemed to make the idle less likely to die out, but now it seems a bit more lopey at idle. Another thing I forgot to mention is that when I blip the throttle, the revs hang. I'll blip it a little and it goes to 3k-pause-2.5k-pause-2k-pause-idle.
 

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itch808 said:
*UPDATE* Since someone mentioned it maybe running lean I tried unscrewing the mixture screw another 1/2 turn out changing it from 2.5 to 3 turns. It could be my imagination but it seemed to make the idle less likely to die out, but now it seems a bit more lopey at idle. Another thing I forgot to mention is that when I blip the throttle, the revs hang. I'll blip it a little and it goes to 3k-pause-2.5k-pause-2k-pause-idle.
Hanging throtle is usually a sign of a vacuum leak. While the engine is running try spraying WD40 on intake boots and see if idle changes. Lopey idle can be caused by out of sync carbs and also by anyhing else that can go wrong with a carb
 

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Dental Rider
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Discussion Starter #14
Veefer97 said:
Hanging throtle is usually a sign of a vacuum leak. While the engine is running try spraying WD40 on intake boots and see if idle changes. Lopey idle can be caused by out of sync carbs and also by anyhing else that can go wrong with a carb
I just ordered a Morgan Carbtune sync tool, so I will sync the carbs and check the intake boots at the same time when it arrives. I'll post back later with the results!! Hopefully it will be good news....
 

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+1 on the vacuum leak, lean on high vacuum...hanging revs, check all the vacuum hoses, boots. I chase VL with an unlit propane torch, when I hit the sweet spot the idle will bump. The loopy idle may be the lean cylinder misfiring.
 

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Discussion Starter #16
BTW just an update in case anyone else ever has similar problems...

I found a couple small cracks in the boots right around the ports for plugging in a carb sync tool. Sealed them up...much better but not perfect.

Also oddly found a small crack/slow leak in one of the fuel lines, replaced...it got better.

Then I synced the carbs and readjusted the idle...really close to perfect.

I messed around with the idle mixture screws going both ways and found that 2.75 turns helped a bit with the hanging revs (dynojet jet kit came with the bike).

Rode it around a bit and then bam, all of a sudden the idle went up to 2k. Turned the idle back down and she runs smooth like butter! So I guess there was something really small clogging one of the jets even though I cleaned everything as best I could. Riding probably dislodged it.

Anyway, she runs excellent now! :banana
 
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