Author Topic: Bike just won't idle....?!!!! 350f  (Read 1668 times)

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Offline schwebel

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Bike just won't idle....?!!!! 350f
« on: September 13, 2008, 02:58:32 AM »
 So this week I got all my boxes of new parts for my 73 350f. I installed them in my project bike. I put in a new air filter, new points and condensors. Carb rebuild kits (with all new jets) and I dipped the carb bodies. I set the carbs to factory specs, 21mm float height and 7/8 out on the air screws. The needles are on the third clip. New plugs and also new gas. I set the the dwell/gap, timing (as best I could without a good consistant idle), and the valves.

The bike is all stock except for the exhaust, it has 4 into 2, the mufflers are from a cb500-4 aftermarket and the baffels that were in the headers were cut out. Riding the bike there is a little flat spot at around 3-4k, so im thinking I need to raise the needles a notch? It seems to have a small fuel shortage issue with the petcock being slow (new one on the way). After about 5 mins of riding the bowls are a little low,the power weakens until I let it sit for a minute then the bowls fill back up, but that shouldn't affect idling? Do I increase float height or decrease float height for more fuel...?!?. The bike just won't idle down to 1100rpm-1200rpm. It will idle at 1800-2000rpm. It just dies out when the rpms get low. Also the bike seems to want choke whenever starting, if it is shut off for more than a minute it needs choke to start back. Any ideas?,...suggestions...?








 

KingCustomCycles.com

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Re: Bike just won't idle....?!!!! 350f
« Reply #1 on: September 13, 2008, 03:29:41 AM »
I am certain you have an intake leak around your rubber carb boots.  This can be cracks, improperly rotated or seated boots, distorted clamps, etc... your symptoms describe an intake leak exactly.

Offline Johnie

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Re: Bike just won't idle....?!!!! 350f
« Reply #2 on: September 13, 2008, 10:50:49 AM »
Let me add one more idea for you.  In looking at your 1st paragraph you did everything you needed but did you do the last step, carb sync?
« Last Edit: September 13, 2008, 11:08:48 AM by Johnie »
1970 CB750K0 - Candy Ruby Red
1973 CB750K3 - Candy Bacchus Olive or Sunflake Orange
1970 Chevy Chevelle SS396 - Cortez Silver
1976 GL1000 Sulphur Yellow

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KingCustomCycles.com

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Re: Bike just won't idle....?!!!! 350f
« Reply #3 on: September 13, 2008, 02:14:07 PM »
Let me add one more idea for you.  In looking at your 1st paragraph you did everything you needed but did you do the last step, carb sync?

I haven't done a valve job or carb synch beyond a static bench set-up in years and have never had one not idle for those reasons.

Offline hs2k007

  • 1972 Honda CB350F
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Re: Bike just won't idle....?!!!! 350f
« Reply #4 on: September 13, 2008, 02:18:31 PM »
mine would not idle and I adjusted the set screw on the right side of the engine that contacted the carb arm lever.  Now it idles fine.

Offline MRieck

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Re: Bike just won't idle....?!!!! 350f
« Reply #5 on: September 13, 2008, 02:52:00 PM »
I am certain you have an intake leak around your rubber carb boots.  This can be cracks, improperly rotated or seated boots, distorted clamps, etc... your symptoms describe an intake leak exactly.
I'd look for vacuum leaks too.
Owner of the "Million Dollar CB"

Offline speedy gonzalais

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Re: Bike just won't idle....?!!!! 350f
« Reply #6 on: September 13, 2008, 02:58:56 PM »
id listen to the vacum leak suggestions ive seen so many bikes not idle due to extra air leaking in somewhere
82' C90
87' yamaha T80
79' CB125T/CD200 project
82' CB650z
80s kawasaki ae50/150cc project
92' Suzuki GSXR600
80' CB250N

KingCustomCycles.com

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Re: Bike just won't idle....?!!!! 350f
« Reply #7 on: September 13, 2008, 04:12:25 PM »
I am certain you have an intake leak around your rubber carb boots.  This can be cracks, improperly rotated or seated boots, distorted clamps, etc... your symptoms describe an intake leak exactly.
I'd look for vacuum leaks too.
A vacuum leak is an intake leak. 

Offline schwebel

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Re: Bike just won't idle....?!!!! 350f
« Reply #8 on: September 13, 2008, 04:49:15 PM »
Update:  Well it does seem to be some sort of vacuum/air leak. I sprayed carb cleaner all around the boots and the idle jumped up. I think the middle two are cracked and I found a small piece missing from the "pre-airbox" part. Also some of the clamps are kind of bent out of whack, I might try some new hose clamps as well. I'm going to take it all apart and inspect it tomorrow. Luckily I have some spares from a parts bike. Hopefully that solves my problem, I really wanna make this bike my daily rider. I am going to do a carb sync as well, as soon as I get my sync tool in the mail. Thanks for all the quick replies and help so far  ;)

Offline bender01

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Re: Bike just won't idle....?!!!! 350f
« Reply #9 on: September 13, 2008, 08:23:31 PM »
Good luck getting it as your daily rider. I rode mine 5 days this week. They arent powerful but go fine in traffic. Very rewarding to get it going. You will tune and tune  and then some one here will post going 106 mph on there 350f and the tuning will start again..!!! Im still tuning. ;D It seems your well on the way.
« Last Edit: September 13, 2008, 08:29:45 PM by bender01 »
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http://www.bikepics.com/members/bender01/
So, the strategy is to lie to people you are asking for help?

I think I'll be busy going for a ride.

Good luck!
Two Tired Quote !

Offline speedy gonzalais

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Re: Bike just won't idle....?!!!! 350f
« Reply #10 on: September 14, 2008, 02:42:45 AM »
i had cracked boots on my 650 i wrapped electrical tape round the outside and plumbing tape round the inside this fix worked fine while i was waiting for the new ones to arrive
82' C90
87' yamaha T80
79' CB125T/CD200 project
82' CB650z
80s kawasaki ae50/150cc project
92' Suzuki GSXR600
80' CB250N

KingCustomCycles.com

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Re: Bike just won't idle....?!!!! 350f
« Reply #11 on: September 14, 2008, 04:24:39 AM »
I sealed mine with used bandaids I had soaked in honey....WTF?   ;)