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Carbs and Fuel System
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post #1 of 29 (permalink) Old 12-11-2012, 01:44 PM Thread Starter
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What else is there?

Well, it's cold out, looks like the clouds are pregnant with snow and I'm about the hook the ol' girl up to the trickle charger and cover it up for the season. But maybe I'll cast one last line and see what happens... I bought this 89 with 14,000 miles on it in October. Since then I have put hours and hours into it, but still can't get it to start without great acrobatics. To get it to start I have to give the big black idle speed knob a turn or two in (more on this later) then perform several sessions of holding the throttle all the way open and cranking with no choke. After that I can let go of the throttle and crank it. It will start for a second or two then die. Repeat as needed for 5 minutes or so until it starts. Cannot start with any choke at all. When it starts, it's running only on the back cyl. Now, if I let it warm up a while, then take it off the center stand and put it on the kickstand, after a minute or so the front cyl. will start sputtering and then kick in eventually. Once warm will be racing around 2,500 to 3,000 rpm so I have to back off the idle knob down to 1,100, (which is why I have to turn it back up to start later). Starts fine warm. So I'm having a very hard cold start, probably greatly exacerbated by trying to start on only one jug. So here's what I've done...

1. Had carbs out 3 times, am no longer afraid of them, they are clean as a whistle. All jets are factory size and clear; jet needles are factory size with no shims, all diaphragms look ok, have had mixture screws out, choke plungers out, coasting enricher plungers out and blew air through the holes . Have run two tanks of a strong seafoam mix through them. Couldn't get the floats out because a screw stripped for one side and on the other I couldn't get the little holding pin out to remove the float and look at the needle... so I haven't put eyes on either float needle, BUT the floats move freely, and if I tilt the carb where they close by gravity and then try to blow into the hose where the gas flows in, I can't, it seems to be a perfect seal. Tilt it back upright and I can blow through fine.

2. Have measured the gas that comes out of the carbs from each drain, seems approximately the same amount from each carb, and the level seems correct when using the clear hose on the drain nipple to measure.

3. On the bike I've used all new clamps and spraying carb cleaner on the boots no longer affects idle so I think I'm air tight. Factory intake is in place with K&N filters in the ears. Carbs are synced (at normal operating temp), with both vac lines securely capped. Mixture screws 2 1/2 turns out.

4. Fresh air system removed and reeds securely capped, big hose to surge tank securely capped and carb vent hose cut at 45 degrees and not bottomed out in right ear.

5. New AGM battery and NGK iridiums - performed coil mod - getting apx 12.3 volts to the coils with ignition on. All spark plugs showing blue spark when cranked against the engine. Ran in the dark garage and see no sparks jumping to ground from the plug wires while running.

6. I discovered previously that gas was seeping through the petcock vacuum hose and ordered a rebuild kit, only to fine that the PO had already removed the guts from the petcock, so it was no longer vac operated. I left it like that but replaced the gasket material to stop the leaking. If I drain the carbs then come to the bike the next morning, and let some gas in for a moment then close the petcock again, I get the same results, so it doesnít look like a bad float needle flooding out the cyl.

7. Left goats belly in place but debaffled mufflers.


The bike runs great out on the road once warmed up except for a lot of popping in the exhaust. Basically it's the hard starting that's got me. I don't want to be the last guy in the parking lot at night cranking away praying it will start before the battery gives out. I can't think of anything else to check. It seems to have symptoms of being rich (any choke kills it), but why would that be? If anything, with the K&Ns and factory jets I'd expect it to be on the lean side. Anytime Iíve pulled the plugs they were damp at least. I've looked into the surge tank with a flashlight and I don't see any obstructions. Anything I'm overlooking?
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post #2 of 29 (permalink) Old 12-11-2012, 01:57 PM
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I would think having a non vacuum operated petcock on an engine that is supposed to have one could be a bad thing. Maybe I'm wrong... but I would purchase a good OEM petcock and try that.

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post #3 of 29 (permalink) Old 12-11-2012, 02:04 PM
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So I'm having a very hard cold start, probably greatly exacerbated by trying to start on only one jug.

No question about it.

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Starts fine warm.
= two jugs

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The bike runs great out on the road once warmed up except for a lot of popping in the exhaust.
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Last edited by WilliamTech; 12-11-2012 at 02:08 PM.
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post #4 of 29 (permalink) Old 12-11-2012, 02:05 PM
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I would think having a non vacuum operated petcock on an engine that is supposed to have one could be a bad thing. Maybe I'm wrong... but I would purchase a good OEM petcock and try that.
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Last edited by WilliamTech; 12-11-2012 at 02:09 PM.
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post #5 of 29 (permalink) Old 12-11-2012, 02:36 PM
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"4. Fresh air system removed and reeds securely capped, big hose to surge tank securely capped and carb vent hose cut at 45 degrees and not bottomed out in right ear."

Maybe you just forgot to mention the vacuum nipple on the right side carb that used to go to the valve under the seat to control the reed valve airflow, but .....that nipple on the carb should be capped with a rubber cover.

I was going to say it sounds like a carb balancing issue or in improper choke cable adjustment. make sure you have that vacuum nipple plugged on the right side.
my cable adjustment was just a tad too short (1/2 turn on the handlebar adjustment) and it would not start easily either. Adjust your choke cable so that the enrichener valve is all the way IN on the carb end. pulling the choke cable will move it out.

how do the plugs look? I bet that after trying to start it, they are wet.

Hope you get it figured out.
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post #6 of 29 (permalink) Old 12-11-2012, 02:40 PM
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Carbs are synced (at normal operating temp), with both vac lines securely capped.
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make sure you have that vacuum nipple plugged on the right side.
already capped
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post #7 of 29 (permalink) Old 12-11-2012, 02:44 PM
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already capped
I missed that part...thanks!

Ok........ so check your chassis grounds and check your choke cable adjustment.

let us know what you find out.
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post #8 of 29 (permalink) Old 12-11-2012, 03:20 PM
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I would be interested to find out if there is fuel being drawn in through the vacuum port on the petcock since the guts were removed. If its no longer vacuum operated, you shouldn't need the connection and could remove the house and cap both ends.



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post #9 of 29 (permalink) Old 12-11-2012, 04:08 PM
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I would be interested to find out if there is fuel being drawn in through the vacuum port on the petcock since the guts were removed. If its no longer vacuum operated, you shouldn't need the connection and could remove the house and cap both ends.
those are the lines that we were just talking about....he has them both capped, so I would assume there is no vacuum applied to the petcock.

I also am assuming the petcock nipple is capped or fuel would spill out since the guts were removed from the petcock vacuum mechanism.
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post #10 of 29 (permalink) Old 12-11-2012, 07:17 PM
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Quote:
Originally Posted by kc2dgq View Post
those are the lines that we were just talking about....he has them both capped, so I would assume there is no vacuum applied to the petcock.

I also am assuming the petcock nipple is capped or fuel would spill out since the guts were removed from the petcock vacuum mechanism.
I didn't get that from his post... must have missed it. Only other thing that comes to mind would be a timing issue.



Mods
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HD Electra Glide Fairing
Earshave/Coastered/CA emissions - gone...
R/R relocated
Nightster seat
Tombstone taillight
Drag specialties turn signals relocated
Sportster progressive shocks... Dropped rear 1 1/2"
Progressive Fork Springs dropped front 1"
NGK plug wires and iridium plugs
Coil Relay Mod
Paint
ACCT to MCCT
Honda Rebel luggage rack
VN800 Handlebars & controls
Screamin Eagle mufflers
F&S Engine Guard & Kury highway pegs
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