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post #1 of (permalink) Old 04-22-2000, 06:29 PM
**DONOTDELETE**
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Sorry - another BBD Question

If I haven't offended too may Jeep owners maybe I can get an answer to this question. Here it is:
How do you check the Vacuum Piston Gap adjustment on a BBD carb? The adjustment calls for .035". With the accelerator pump mechanism in the way, you can't see what the gap is. If the adjestment screw is turned clockwise it richens the air/fuel mix, counterclockwise leans it. The Jeep manual says it is a critical adjustment so I want to get it right.
Also, what's the initial setting of the 2 mixture screws?

I hope someone can help

Ralph...

Carpe Diem - to make every day count!
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post #2 of (permalink) Old 04-22-2000, 08:05 PM
sas87yj
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Re: Sorry - another BBD Question

canada
i've never adjusted the vacuum piston gap but there is a picture and directions-specs in my chiltons. i messed with my carb until i could do no more. bought a rebuilt carter by holly and it just purrs. [img]/wwwthreads_images/icons/smile.gif[/img]
have you seen this site?
http://www.off-road.com/jeep/tech/258bbd/Major.htm
i turned in my two mixture screws until the engine wanted to die and then backed out 1/2 turn or so. i havn't seen any specs on these but have used this method on other carbs.
what engine do you have? i didn't look at your profile.
you also might want to re-route your air pulse system if you have the 4.2 litre.
there is a neat write-up i can get up if you need.
see ya
usa steve

post #3 of (permalink) Old 04-23-2000, 07:51 AM
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Re: Sorry - another BBD Question

Steve, thanks for the reply. The engine is a 4.2 and I just had the carb rebuilt. However, after getting it back, I've had to do several things to it. The mechanic forgot to reattach the WOT switch, the stepper motor was not fully pushed in and the timing was very retarded. Also, when I took the plate off the top of the carb to check the accelerator pump adjustment, I noticed the small spring that contacts the metering pins was just dangling down. After putting this right I tried to check the vacuum piston adjustment. It almost looks like I'll have to remove the accelerator pump mechanism to check it properly.

I'd be interested in getting information to re-route the air pulse system on the 4.2 litre. So far, I've not addressed this area.

Thanks - Ralph...

Carpe Diem - to make every day count!
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post #4 of (permalink) Old 04-23-2000, 06:25 PM
sas87yj
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Re: Sorry - another BBD Question

ralph
sounds like they hacked your carb rebuild job.[img]/wwwthreads_images/icons/frown.gif[/img]
my carb was only 2 years old (a rebuild) when i bought in jan.
i did two idle pick-up tube cleanings.[img]/wwwthreads_images/icons/tongue.gif[/img]
found dirt in the bowl.[img]/wwwthreads_images/icons/mad.gif[/img]
this new rebuild is working great so far.
check out:
http://www.off-road.com/~lhsoo/yj-faq/yj-faq.htm
the whole site is very informative.
see "idle/stalling" under "engine" catagory for the pulse-air re-route.
i did this to mine as they were letting exhaust into the air canister and into the carb.
later
steve

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