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Unread 02-02-2013, 12:55 PM   #1
Scurv
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Tired, Nutted, 258, Weber 34

Been workin on this for a couple months. Went to pick up the harley with a trailer and she started bucking on the highway and the only way to keep her going was to mash the pedal thru the floor. Puffin some white smoke when it bucks only. I figured the carb had a clogged jet so I tore it apart, cleaned it. Been runnin 40 idles and 145/147 mains for a few years now with no problem. Felt like it needed more fuel for a while now so I switched the mains to 147/150. Float is set 10.1mm from top edge to gasket based on a Solex 34/34 document I found in spanish. Changed the filter, tore apart my holley fpr and put a new psi gauge on it, and replaced pump, new IM, distributor, plugs, wires, msd coil, clutch, slave, and master. Timing is good at 8. Advance to 12 no change. Ported vac. 3 vac lines. Starts right up on hi idle cam, warms up, revs like a race car and sounds awesome at 500 idle, put it into gear and and release the clutch and it still bucks like a nun in missionary. WTF! NO POWER. No air leaks. No cat. Pump filled a half a cup in 10 sec. Accelerator pump squirts awesome. 1.5 turns on idle screw. Maybe 2 on IA screw but that's goofy now because of the bigger mains. RIngs are tired. Dry/Wet compression on cyl 1-6: 90/120, 120/170, 120/130, 115/120, 115/120. Not burning oil, radiator full, no sheen with couple bubbles. Nothing in the oil or on dipstick. Any input would be greatly appreciated.

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Unread 02-02-2013, 01:13 PM   #2
Scurv
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italian http://www.scribd.com/doc/7097992/DE...-SOLEX-34-TEIE

compression test was done with the motor cold.
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Unread 02-02-2013, 07:11 PM   #3
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bump

bump
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Unread 02-02-2013, 09:16 PM   #4
140mower
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Kind of going out on a limb here, but any chance the timing chain has skipped a tooth? I've hit this problem in the past and was much as you described. Have you tried hooking a vacuum gauge to it and taking it for a drive? Just a couple ideas, I'm sure someone else will contribute soon.

Don
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Unread 02-03-2013, 07:53 AM   #5
Scurv
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i replaced the chain aout 20k miles ago. i did notice when installing the new dizzy that when at tdc the rotor would either be a tad behind or in front of the #1 marking on the base. (that's my 8 deg of timing?) as far as hooking up psi guage and running it...a loss of vac would show??
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Unread 02-03-2013, 12:40 PM   #6
140mower
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At 20k the timing chain should be good, but stranger things have been known to happen. A vacuum gauge will (in the right hands, not necessarily mine however) show everything from the obvious vacuum leaks to late valve timing, ignition timing, even a burnt valve will show up. They are kind of old school but there isn't much a vacuum gauge won't tell you.
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Unread 02-04-2013, 05:27 PM   #7
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found this website. http://www.secondchancegarage.com/public/186.cfm
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Unread 02-24-2013, 08:59 AM   #8
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Still playin with this thing and now back to the carb. It has been running pretty good for a few years and suddenly started to buck..sooo...what am I missing? Yesterday I went ahead and replaced good seals on the accelerator pump and power valve. Sprayed 3 different cans of cleaners through all the passages. Removed air corrector jets and emulsion tubes. In the process of removing these AC jets....which are pressed in by the way. I (fill in the blank) them so I have to wait a week before the new ones come
in. In the mean time I hope there is something little that I have done to fix it. 7I've spent lots of time reading about Webers in general and can't seem to find much info on the actual fuel level in the bottom of the float bowl. Previous level seemed to work OK....maybe a tad lean. The secondary side has a 40 idle and 145 main so I was thinkin something in the circuit was clogged or the float needed raised. Something I was doing wrong was ensuring that the little spring loaded ball on the end of the needle was not depressed when measureing float height. I was a little low so we'll see. The fuel in the bowl seems pretty low sitting right at if not below the main jets and 1/4 inch or so below the air corrector passages? Does anyone have an idea where it should be on a progressive weber. The bell housing leak has turned out to be the front oil seal on the tranny and not the slave. I really don't like using stop leaks because at some point you have to replace all the rubber when it fails. In this case am am willing to accept any recommendations on an additive. Good thing my little beater truck stopped leaking PS fluid and coolant...lol
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Unread 02-24-2013, 09:28 AM   #9
lrandrews838
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I had a similar experience with my yj which caused me to chase down every possible carburetor and ignition issue I could think of. It turned out to be a soft fuel line at the frame rail collapsing while the engine was under a load. Usually between 2nd and 3rd gear. 25 y/o fuel lines and a little ethanol are not a good mix. Replaced all of my soft fuel lines with marine grade ethanol resistant lines. Solved my problem.
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Unread 02-24-2013, 09:39 AM   #10
jsawduste
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Webers are sensitive to Fuel Pressure. Although you mention rebuild the FPR I would still wonder what the actual FP is.

Since it ran good for a long time with the 40`s and 145/147`s any jetting changes are masking the problems. Go back to your 40 and 145/147`s as a baseline.

Standard rules of engagement. Vacuum leaks, FP, float level, float buoyancy, needle/seat.
Check the timing with a timing light. You will find out quick whether it is a timing issue.
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Unread 02-24-2013, 09:42 AM   #11
jsawduste
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Quote:
Originally Posted by lrandrews838 View Post
It turned out to be a soft fuel line at the frame rail collapsing while the engine was under a load. 25 y/o fuel lines and a little ethanol are not a good mix. Replaced all of my soft fuel lines with marine grade ethanol resistant lines. Solved my problem.
Ethanol is the devils curse. Soon there will be a myriad of folks having issues with ethanol laced fuels. You will too, if it has not happened it will.
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Unread 02-24-2013, 09:55 AM   #12
Old4X
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Ethonol laced fuel is not gasoline. Stoic A/F ratio is markedly different. FI engines can kinda/sorta compensate, but not carburetors. You may need to totally re-tune your engine, fuel system and ignition to work with the fuel you are buying.
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Unread 02-24-2013, 10:09 AM   #13
Scurv
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Dam your right. Winter blend here in Illinois. My fuel should be decent...sample never separated. Added a can a seafoam to half a tank and will fill up with premium. The regulator shows a bouncey 3.5 while reving but I did notice that the pressure seemed to drop off a bit that concerned me. When I clamped to overflow it rose to 6+ and flooded the carb. Will crawl under it in a bit.
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Unread 02-24-2013, 10:33 AM   #14
lrandrews838
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My fuel lines had weaken and when under a load cavitation would occur causing the line to collapse and starve the carb bowl which resulted in my yj "bucking". By the time I would shut down the engine and then pull the top cover off my carb the fuel level had returned to normal. I was stumped for a month until an older gentleman in my community, who is known for carb work, test drove my yj and diagnosed my problem. This may not be the problem but it is a cheap and simple fix.
.
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Unread 02-24-2013, 10:40 AM   #15
Old4X
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Think about it, pump fuel has as much alcohol as wine. Ever notice how different a glass of wine is compared to a glass of grape juice?
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