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Hesitation, bucking, loss of power ‘72 dual carbs [SOLVED]
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SlowRhode
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PostPosted: Thu Jun 24, 2021 10:20 pm    Post subject: Hesitation, bucking, loss of power ‘72 dual carbs [SOLVED] Reply with quote

Only seems to happen when warm (after running for 15 minutes or so)

In 3rd/4th gear I get a sudden drop in power, barley able to climb hills. At highway speeds it will drop to 45-50 MPH.

I’m running dual solex 40/44 eis carburetors & electric fuel pump. Running a pentronix ignition in lieu of points.

I just pulled the engine to replace the clutch and this has started occurring since then (earlier this week).

So far I have:
Replaced the fuel filters (a little dirty but didn’t seem overtly bad)
Replaced the coil
Pulled carbs and cleaned them (little dirty in the bowls)
Rechecked all my connections

Am I missing something major here? I’m thinking next step is to drain the fuel tank and check the sock?

Any help would be super appreciated! Pretty stumped!


Last edited by SlowRhode on Sun Jun 27, 2021 12:03 pm; edited 1 time in total
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Wildthings
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PostPosted: Fri Jun 25, 2021 1:36 am    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs Reply with quote

If your fuel tank venting properly?

Set your timing to 28° BTDC @ 3800+ rpms, hoses off and plugged.
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SlowRhode
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PostPosted: Fri Jun 25, 2021 3:21 am    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs Reply with quote

Wildthings wrote:
If your fuel tank venting properly?

Set your timing to 28° BTDC @ 3800+ rpms, hoses off and plugged.


Tried driving without gas cap and no change. I will attempt to reset my timing to those specs but I did try altering timing a few times with no luck.
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SlowRhode
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PostPosted: Fri Jun 25, 2021 10:56 am    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs Reply with quote

Can pertronix ignitor go bad in a way that it starts to fail when engine is warm?

Ordered a replacement (and replacement distributor as well) but I really hate throwing parts at a problem.
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busdaddy
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PostPosted: Fri Jun 25, 2021 11:14 am    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs Reply with quote

SlowRhode wrote:
Can pertronix ignitor go bad in a way that it starts to fail when engine is warm?

Ordered a replacement (and replacement distributor as well) but I really hate throwing parts at a problem.

Yes, it usually starts as a miss on the highway, much like fuel starvation.
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timvw7476
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PostPosted: Fri Jun 25, 2021 11:30 am    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs Reply with quote

SlowRhode wrote:
Can pertronix ignitor go bad in a way that it starts to fail when engine is warm?

Ordered a replacement (and replacement distributor as well) but I really hate throwing parts at a problem.


Rockauto will deliver WVE brand points & condenser for $12.84.
I have no experience with WVE points & condenser, but I would use them
as a substitute for the Pertronix ignitor to troubleshoot. Cheapest diagnostic path I know of. That's assuming your ignition coil will tolerate points, maybe you have a proprietary Pertronix coil as well & no old points style to substitute?
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SlowRhode
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PostPosted: Fri Jun 25, 2021 11:55 am    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs Reply with quote

timvw7476 wrote:
SlowRhode wrote:
Can pertronix ignitor go bad in a way that it starts to fail when engine is warm?

Ordered a replacement (and replacement distributor as well) but I really hate throwing parts at a problem.


Rockauto will deliver WVE brand points & condenser for $12.84.
I have no experience with WVE points & condenser, but I would use them
as a substitute for the Pertronix ignitor to troubleshoot. Cheapest diagnostic path I know of. That's assuming your ignition coil will tolerate points, maybe you have a proprietary Pertronix coil as well & no old points style to substitute?


I actually was able to buy points and a new pertronix off of Amazon and it’s arriving tomorrow. I had the same thought about helping diagnosing 👍
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airschooled
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PostPosted: Fri Jun 25, 2021 12:03 pm    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs Reply with quote

All hail Lord Bezos.
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SlowRhode
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PostPosted: Sun Jun 27, 2021 12:06 pm    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs [SOLVED] Reply with quote

So pulled the carburetors again while waiting for our lord and savior Jeffrey Bezos to deliver my parts.


Drivers side carb needle valve was coming apart. I peened back the edge a little to keep the spring/internal needle inserted. Runs 100% while I wait for a new needle valve.

Thanks everyone for your help!
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69BahamaYellow
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PostPosted: Sun Jun 27, 2021 7:43 pm    Post subject: Re: Hesitation, bucking, loss of power ‘72 dual carbs [SOLVED] Reply with quote

Thanks for sharing the needle valve was bad in one of your carbs. So many things can cause the problem you described in your original post and unfortunately not everyone shares what the ultimate fix turned out to be so others can learn from it.

I consider myself a pretty advanced mechanic, and I always learn something new on this forum
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