Author Topic: 74 cb750 dies out  (Read 1480 times)

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Loudiggs

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74 cb750 dies out
« on: July 16, 2007, 06:51:08 PM »
I rebuilt carbs and replaced an old after market air filter with 4 pods. There was very high rpm's but have been able to bring it dom, but once engaged in 1st gear and attempt to open throttle the bike dies. However, if I keep the choke on the bike will run but runs poorly. Any help? Thanks

Stevien1

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Re: 74 cb750 dies out
« Reply #1 on: July 16, 2007, 06:53:55 PM »
You need to tune the carbs to compensate for the increase air flow.  Raising the needles a notch and playing around with the air screw might be all you need.  If not, you'll need to re-jet the carbs.

Offline Gordon

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Re: 74 cb750 dies out
« Reply #2 on: July 16, 2007, 10:48:57 PM »
Take a deep breath, type "pods" in the search field, and dig in! :)

johnny-from-bel

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Re: 74 cb750 dies out
« Reply #3 on: July 16, 2007, 11:04:31 PM »
With the pods it is now running way to lean. If raising the needles is not enough you may need to rejet.

Offline TwoTired

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Re: 74 cb750 dies out
« Reply #4 on: July 16, 2007, 11:31:39 PM »
Unless you are making the engine rev to a higher RPM or have made mechanical changes to the engine, the airflow through the engine is exactly the same as before.

Pods often change the air pressure in the carb throats such that the existing metering devices don't provide as much fuel as when using the stock air filter.

When you add choke now, it simulates the restriction of the stock air filter amd make the jets flow more fuel.

To increase the roll-on throttle response, you will have to turn the Air screws in some.  If your air screws are hollow tipped, their adjustment range is limited.  Once you get down to 1/2 turn out from seated, closing them further will be of little benefit.  You will have to then increase the size of the slow jet and find a new Air screw setting that keeps the idle rich enough for throttle reponse, but doesn't foul spark plugs.

You may also find the midrange throttle settings effected by the loss of throat pressure differential.  Raising the needles a notch clip should help that.

Finally, wide open throttle may need to be richened, also.  And, a step or two larger main jet may be required, depending on how the spark plug deposits look.

Cheers,

I wonder how many times this topic has been discussed in this forum?
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline dusterdude

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Re: 74 cb750 dies out
« Reply #5 on: July 17, 2007, 09:23:26 AM »
i dont think i want to know.
mark
1972 k1 750
1949 fl panhead
1 1/2 gl1100 goldwings
1998 cbr600 f3

johnny-from-bel

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Re: 74 cb750 dies out
« Reply #6 on: July 17, 2007, 10:57:21 AM »
i dont think i want to know.

Since we all know the answers. It gets shorter every time

Offline kuyarico

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Re: 74 cb750 dies out
« Reply #7 on: July 17, 2007, 11:06:57 AM »

I wonder how many times this topic has been discussed in this forum?


2nd one today I think.  :D