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Hesitation at WOT

2678 Views 8 Replies 6 Participants Last post by  V8GRUMPY
Hey guys. I finished my fuel pump job and a number of other things on the Boss a few days ago. I also changed the distributor cap and rotor. I took it out for a ride and I found that it had a little hesitation when I rolled on the throttle from around 40 mph and then it smoothed out up to about 85 or 90 and I got another hesitation. It never did this before. What is different on my bike is this:

Cap and Rotor
Carter P4070 fuel pump
new fuel lines
5/16 from the petcock to the switch/pump, 5/16 from switch/pump to fuel filter, 3/8 from fuel filter to Carter pump, 3/8 from Carter pump to carbuerator.

I wanted to put 3/8 lines throughout, but the reserve switch/pump was fitted for 5/16 and so was the pingel petcock. So I kept the 5/16 up until I could switch it to 3/8.

The bike starts good and idles good and performs perfectly up until I ask it to do what it is best at.

Any ideas what may be the problem here?

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Hoss , maybe you should change you fuel filter . You never know , that might be your problem .
As I said on the other site, make sure you didn't inadvertently move the HEI unit to change the timing. Try the old fuel pump again and if all is well The Carter is the problem. The fuel filter is a possibility but too coincidental to happen exactly when you changed ****. I'll bet my cookies that if you put the stock fuel pump back on the problem will be resolved.

I did put a new fuel filter on.


Changing the fuel pump back would be a good idea to try, but my stock fuel pump don't work no more. That is why I changed to the Carter.

I haven't read the other site yet to hear what else you thought, but I will check it now. The distributor seems to be in their pretty tight. I don't think that it moved. I checked it before I put the tank back on.

If I end up timing it, where are the timing marks??

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Fuel pump


My bet is fuel pressure. The last couple of Carter's I got produced better than 8 psi. That is more than enough to overrride the needle and seat in the carb and create a "too rich" condition.

I always install a pressure regulator set to 4 to 4 1/2 lbs when I install a rotary vane fuel pump.
fuel lines

I think you should have all 3/8 lines....just my 2 cents.
Neither Tim or I are running regulators with our carters and we haven't had any problem. Tim also tried his nitrous yesterday and the thing ran great.

Just a thought..........check your tank vent & also to see if your cap vent is working. Mine starting acting like it was vapor locking last nite, but I noticed that the tank had a lot of vacuum when I opened the cap.....

If the tank is sealed it may be starving....easy fix :)

Hoss , Tim has a good point . Are you sure your new gas cap is vented ? If not I'll bet that could be your problem.

Easy to tell, just ride aroound for about 10 minutes and stop. Turn off the engine and put your ear by the cap as you loosen it........and vaccum indicates poor vent.

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