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Discussion Starter · #1 ·
Got it started. Starts up real nice after i rebuilt the carbs but i have to use the throttle to get her going. Sounds good when started no popping or choking. But it wont idle so after i let off the throttle it dies. Any Suggestions?
 

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I did both of my 450s with kits from 4into1..still learning about hondas and I noticed these have no enrichment knobs or "ticklers" only a choke to help with starting.. both mine still need a bit of throttle to start in the mornings or cold. But after that, during the day.. fires without any issues...
I ATTEMPED to clean them prior to buying the kits.. but the low idle jet is so small (and corroded) I couldn't get a guitar string to pass through to clean it.. once replaced they were "good to go".. untill they needed to be cleaned..I forgot to add fuel filters. The percock filter is "fine" for larger particles.. but not good enough to handle the "fine" stuff..
I do run non-ethenhol fuel,(easier to set low idle) and my new Electronic Ignition has improved top end and getting the low idle dialed in..
Oh, I did install new NGK Iridium plugs also..
 

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Got it started. Starts up real nice after i rebuilt the carbs but i have to use the throttle to get her going. Sounds good when started no popping or choking. But it wont idle so after i let off the throttle it dies. Any Suggestions?
Is this when hot? If so, idle circuit is still dirty.
 

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First things first are you using the idle adjustment knob to find a place where it will idle at around 1200 (after warm up) or is it at all adjustments of the idle knob?

Also you say no choking, do you mean that it starts cold with no choke? If so that would indicate you're running way too rich. It's designed to start cold with choke, idling around 2000-2500. It's warm enough when you can push the knob in without the engine dying (happens after maybe a minute).

If it wont idle at any adjustment the above post is probably your issue
 

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Have the carbs been sync'd yet? Were the mixtures set properly, the turns out reference in the FSM is just a beginning point.
 

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Discussion Starter · #6 ·
bike idles great now. Im onto the sync and mixture screws. Should i set the mixture first then sync? Also i see there are two different methods for the mixture. One for pre 1985 ONE FOR 1985 and above. My bike is a 1985 but my carb is pre i believe. The bike came with the VE carbs but i switched it out with a VB. Which method should i use?
 

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Discussion Starter · #7 · (Edited)
Okay bike was idling great was about to start working on the mixture but the it shut off, plugs are pretty black. I don't have an fsm where does it say to start from on the mixture screws? Also once its warm the rpms seem to bounce back and forth they wont stay consistent.
 

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Ok.. to make sure everyone is on the same page..
Sinc= Physical -mechanical movement / opening (the same)
Balance=air / fuel ratio -idle adjustment screws (manometer)
Someone please correct if I'm wrong..
 

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sync and balance are the same thing. you don't adjust air/fuel with a manometer.
 

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Yeah... we are NOT on the same page..
AFTER valves are properly adjusted and compression check shows proper readings.. carbs are (mechanically) synchronized, cables adjusted so both butterflies open together.. butterfly positions are the same at WOT(both flat-90degrees to airflow)..
Then... with a manometer attached (intake ports) the carbs can be "balanced" by adjusting the air/fuel adjustment screws. The manometer will show what carb is "rich" or "lean" compared to each other..
IMG_6428.jpg
I find it hard to help solve a problem if good communication isn't established.
 

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PM sent for the FSM's
A manometer is measuring vacuum or negative pressure, has nothing to do with air/fuel ratios.
Synchronizing carbs is is adjusting the throttle plates to be open exactly the same amount at idle.
Balancing carbs is to adjust the throttle opening at higher RPM to match, similar but not the same thing.
On the SOHC carbs the linkage is tied together so synchronizing at idle is the same as balancing at higher RPM.
On bikes that have dual throttle cables, linkages can operate independently, balancing is done at 2,000 or higher RPM by adjusting each cable so air flow is matched.
On to mixture setting:
With the engine hot after riding some and parked on the center stand set the idle speed to 1200. Never over 1300.
Pick a carb and adjust for highest idle speed, you may have to re-adjust the idle speed while doing this to keep it low enough. Once that's done go to the other carb and repeat. Repeat on both one more time. Go ride a few miles to cool the engine down and recheck the mixtures one more time. You're done.
Honda list "turns out" in the FSM for mixture. Consider that as a starting point for setting the mixture.
If there are limiter caps on the mixture screws cut the tab off of them or the tab on the float bowl.
 

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I just re read my post.. I didn't mean the manometer "measured" air / fuel.. I meant it would "show" increase or decreased vacuume in the intake when the air/fuel screws are adjusted.. by adjusting the screw..you will lean or enrichen the idle..
Like I said "good communication" helps...
 

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Discussion Starter · #13 ·
i set the mixture screws according to factory spec but i cant adjust because of erratic rpm... same with sync the carbs. every time i turn the sync screw it doesnt even seem to register on my sync guages. The rpm just bounces all over the place.
 

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Ok..,let's start at the beginning..
1-make sure your timing is right
2-adjust valves/chain.. take compression test
3-"bench" sync the carbs (physical movements)
4-factory set carbs
... I've learned the hard way.. no carb adjustment will correct bad timing .. and visa versa
Oh.. did I mention check your charging system? I just discovered a "gremlin" in my wife's 450.... it will go"dead" during idle our of the blue... but ONLY with the headlight ON..
Possible power draw, possible bad / old connection..
You gotta remember .. these components are 40+ years old.. things aren't always what they are supposed to be...
 

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You'll also want to take a look at the sync screw ass'y. There are 2 washers on the screw, one goes above and one below the aluminum link.
201_4644-002.jpg
Also be sure that the carbs are fully inserted into the insulators, they actually bottom out against one another
 
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