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Author Topic: Working on a 350F for a friend, won't rev over 4k  (Read 1129 times)

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Offline xtravbx

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Working on a 350F for a friend, won't rev over 4k
« on: March 02, 2016, 03:34:12 PM »
My guess is this is carb related. It kick starts just fine, requires choke to start. Idles fairly okay when playing with choke.

Has a hard time climbing the revs, wants to die when you give it too much throttle. Biggest issue is, even if you get WOT and its running alright, it still will not climb over 4k. When you shut down the throttle after attempting to rev it higher, it usually will die.

Using the stock airbox, but the PO cut the muffler(s) off, so its 4 straight pipes that are cut off under the motor.

My guess is the chopped exhaust isn't helping, and possibly the carbs need attention.

Could it be anything else? Ignition related? It appears to be firing on all 4 just fine.

I just adjusted the valves, BTW. Intake was fine, exhaust was tight. Otherwise okay.

Thanks all.
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Offline HondaMan

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #1 on: March 02, 2016, 04:13:07 PM »
Usually when I see this on the Baby Fours, it is a bad coil.
;)
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Offline carnivorous chicken

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #2 on: March 02, 2016, 05:51:51 PM »
Might as well check your spark advance too.
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Offline Gene

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #3 on: March 02, 2016, 05:54:15 PM »
Check your points. 
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Offline scottly

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #4 on: March 02, 2016, 06:14:16 PM »
Quote from: xtravbx on March 02, 2016, 03:34:12 PM
My guess is this is carb related.
That would be my guess as well. Pull the spark plugs and see what they look like.
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Offline gtmdriver

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #5 on: March 03, 2016, 01:01:45 AM »
Mine had a similar problem when I bought it and the fuel tap was completely clogged with rusty sludge.
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Offline xtravbx

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #6 on: March 03, 2016, 08:12:17 AM »
Thanks all. Don't see it as a fuel issue, since I pulled the tank and ran a clean line right to the carbs.

I'll download the manual for it to check spark advance etc.

Also, will a coil from my 550 work?
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Offline flybox1

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #7 on: March 03, 2016, 09:57:52 AM »
Quote from: scottly on March 02, 2016, 06:14:16 PM
Quote from: xtravbx on March 02, 2016, 03:34:12 PM
My guess is this is carb related.
That would be my guess as well. Pull the spark plugs and see what they look like.
+1
Nothing has been mentioned about a last carb cleaning, sync, or any of the 3000mi tuneup components except for valve adjustment.
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Offline a_king

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #8 on: March 03, 2016, 10:50:18 AM »
is the spark advance mechanism behind the points free?
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Offline chewbacca5000

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #9 on: March 03, 2016, 11:26:54 AM »
That don't really run right without a muffler to provide a little back pressure.  Have you check the plugs?  Are you getting spark on all 4.  Those floats need to be set perfectly too.  Man I can't wait to ride my 400f this summer.
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Offline HondaMan

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Re: Working on a 350F for a friend, won't rev over 4k
« Reply #10 on: March 03, 2016, 11:44:26 AM »
Quote from: xtravbx on March 03, 2016, 08:12:17 AM
Also, will a coil from my 550 work?

Yes, it is the same coil.
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See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com
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