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1991 F2 Rescue - Carbs

  #21  
Old 12-30-2017, 10:43 PM
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So, progress is being made, but the saga continues. We've cleaned the carbs another time, replaced the a/f needles/screws, replaced a leaky float valve, and fixed an intermittent spark issue that kept popping up.

Now, with the a/f screws 2 turns out, the bike starts and stays running, as long as we keep the choke on. With the choke on, it will warm up and rev up to 3k on it's own, but we can't get it to idle without the choke. Once the choke is off, the bike will die. Put the choke back on and it fires right up.

From what I understand, this can be either:
1. The a/f ratio is off (too lean) or
2. The idle circuit needs more attention. (pilot/idle jets have been pulled and cleaned thoroughly)

I've read that prior to the carb sync we need to get the bike to idle without the choke? If that's the case, I'll keep chasing the idle issue, otherwise I'll give the sync a go.
 
  #22  
Old 12-31-2017, 03:44 AM
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Hi, can you take the rpm up to about 5000 rpm with the throttle ,then knock off the choke and keep the rpm high with the throttle?
 
  #23  
Old 01-01-2018, 12:33 PM
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Originally Posted by CaBaRet View Post
Hi, can you take the rpm up to about 5000 rpm with the throttle ,then knock off the choke and keep the rpm high with the throttle?
Yes, but it starts to load up and I have to play with the throttle to keep it running.
 
  #24  
Old 01-01-2018, 01:42 PM
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When you took the carbs off to clean them ,did you leave all 4 joined together and did you bench sync them before you put them on (butterflies all moving in unison)
 
  #25  
Old 01-01-2018, 01:53 PM
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Originally Posted by CaBaRet View Post
When you took the carbs off to clean them ,did you leave all 4 joined together and did you bench sync them before you put them on (butterflies all moving in unison)
I took them all apart and soaked them individually, and did a bench sync before putting them back on. I have a sync tool, but have been told that i need to get it to idle off of choke before syncing the carbs. (If that's wrong, I'll warm it up and sync them...)
 
  #26  
Old 01-01-2018, 02:09 PM
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As number 2 carb is the base for the others to be set to, jut take a look at the other butterflies operation in relation to that one
 
  #27  
Old 01-01-2018, 02:22 PM
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Originally Posted by CaBaRet View Post
As number 2 carb is the base for the others to be set to, jut take a look at the other butterflies operation in relation to that one
They were close after the bench sync, should be close enough for it to idle. I'll go take a look.

Is it true that the on-bike sync can't be performed with the choke on?
 
  #28  
Old 01-01-2018, 02:30 PM
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The engine will need to be running at about 3000rpm to get the sync right, the choke could be used initially to achieve that but then you stand a chance of stalling the engine with a rich mixture, if you can get those butterflies all working at the same time you will be half way there
 
  #29  
Old 01-01-2018, 02:41 PM
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Originally Posted by CaBaRet View Post
The engine will need to be running at about 3000rpm to get the sync right, the choke could be used initially to achieve that but then you stand a chance of stalling the engine with a rich mixture, if you can get those butterflies all working at the same time you will be half way there
Thanks for the prompt responses. I'll give the sync a shot using the choke to see what happens.
 
  #30  
Old 01-11-2018, 05:37 PM
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So, I haven't had time to sync the carbs, will get to that this weekend.

Decided to pull the carbs and give them another cleaning since I'm a sucker, and now I'm second guessing the jetting. Pilots are the stock 38s, but there are Factory Pro 128s in 1&4, and 130s in 2&3. I've got a set of stock 135s, and what appears to be a set of DynoJet 126s. The bike is stock (from what I can tell) except for full Two Brothers Exhaust.

Keeping in mind that this bike is targeted for track-only and ridden at basically sea level (Florida), any suggestions on which jets to go with for starters?
 

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