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Discussion Starter · #1 ·
when bike currently doesn't idle? :D
thanks. I usually don't have that problem but that is where I will be at come this evening. this is a particular challenge! I have my pop hold the throttle steady but he never holds it steady enough and keeping it running while tuning in that manner doesn't give the results, just yet.

who has a quick cheat? I rarely get that stuck to which it won't idle at all.....tonight is reconfirming timing, cleaning out carb jets and reconfirming float heights.
 

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idle has to be set before balancing. No idle is probably dirty carbs, idle circuit to be precise. Do the idle adjust screws do nothing or is the RPMs too high when they are used?
 

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FWIW .. I would start with timing / points.. my wife's 450 wouldn't hold a idle well.. even after carb rebuilds.. installed a E.I. And I can bring the idle so low you would think it is gonna die.. but nope.. smooth and steady..
New iridium NGKs also went in..
 

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Also, double-check the float levels. You can verify open-throttle sync with a third hand holding it up to about 3k rpm, and if one is stronger, use its adjusted to reduce flow volume. Then ease the throttle down to about 1k rpm; if still holding the throttle at that point, turn the idle screws until it starts to rev above that point. If it won't lower to ~1k rpm without trying to quit, you have a mixture problem, which could be air leaking around the throttle or rubber boots, or a blocked pilot circuit. A good fan to keep the engine from getting too hot is recommended, I think.

Rob's suggestion about timing should be done with a light - if you are still using the stock advancer, the springs could be letting the timing bounce around too much.
 

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Had trouble with the idle on my 400 A found the air cut valves bad. After writing to L D R I changed the valves and its fine now.

Just a thought.

Bill
 

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Had trouble with the idle on my 400 A found the air cut valves bad. After writing to L D R I changed the valves and its fine now.

Just a thought.

Bill
CB450 DOHC have no air cut valves - not incorporated till CB500 twin (same part as GoldWing 1000, which also share the same points as CB450/500T).
 

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In answer to your question, you can bench sync slide carbs by adjusting the slide heights so a small gauge (I use zip ties but 1/8 drill bits work) just fits under the slide.

That gets it close enough to run assuming no other issues. Once it's running, there are other methods to fine tune it.

Sent from my SM-G930V using Tapatalk
 

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In answer to your question, you can bench sync slide carbs by adjusting the slide heights so a small gauge (I use zip ties but 1/8 drill bits work) just fits under the slide.

That gets it close enough to run assuming no other issues. Once it's running, there are other methods to fine tune it.

Sent from my SM-G930V using Tapatalk
450 slides are not connected to the throttle cable - slides don't move unless the bike is running.
 

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You REALLY don't want any "quick cheats" on these bike, it will plague you with problems. Do everything correctly by the FSM and you will have a reliable bike for years.
You need to fix the idle problem before you can sync the carbs. They get synced at idle and then again at 3000 RPM.
Not idling can be weak battery, dirty carbs, fouled plugs, valves out of adjustment, points out of adjustment.
I am assuming you are referring to a 450K. By the FSM, you put your thumbs over the exhaust outlet and adjust the carbs until the pressure feels even. Dumbest thing I have ever run across. I thought long and hard before I decided to drill vacuum ports in my head, best decision I ever made. Properly synced carbs with a manometer and it was like a totally different bike, easier starting, more power.
 

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I have thought about this also.. (vacuume ports).. but drilling and tapping the heads (on the bike) scares the crap out of me.

I aquired a second set of intake boots I'm gonna drill and epoxy some small threaded tubes so I can get this bike "dialed in".. when I used a simple homemade manometer (tube with motor oil) .. I was amazed to see how much of a difference in vacuume a SMALL ADJUSTMENT on the idle screw made.. plus, I SWEAR the motor vibration at mid and higher RPMs smoothed out..
 

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Discussion Starter · #12 ·
thanks, all. No worries. It's just annoying that a bike that was well-stored and un-ridden somehow needs adjustments when I rode it fine toward the end of the season. My wife always says to take it easy cuz I always get it going anyways. However, it's the process leading to the end result that is basically really tedious over the years. will report back in due time. and yes, the ports seems like a good idea. It's funny because Honda did some great engineering stuff while also doing some boneheaded choices at the same time; Cheap stock coils anyone?:p
 

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How was it "well stored"?
 

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I have thought about this also.. (vacuume ports).. but drilling and tapping the heads (on the bike) scares the crap out of me.

I aquired a second set of intake boots I'm gonna drill and epoxy some small threaded tubes so I can get this bike "dialed in".. when I used a simple homemade manometer (tube with motor oil) .. I was amazed to see how much of a difference in vacuume a SMALL ADJUSTMENT on the idle screw made.. plus, I SWEAR the motor vibration at mid and higher RPMs smoothed out..
You should know the metal flange extends a short way into the boot, maybe 4-5mm, so drilling is a challenge, if you want to be close to the flange. I did this, and had to be really careful to keep the drill from jumping into the rubber-only area. The rest should work well, if you get a good seal.
 

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Did you drill and tap with the head installed?
Yes, I stuck a rag in the intake to keep shavings from going into the cylinder.
 

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Back in the day we used vacuum gauges to set carbs on cars. If you dont have a manometer and had ports drilled for testing could you say block off # two and set #1 with the vac gauge, then block off #one and set # two? Just wondering.

Bill
 

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Home-made manometers are fairly simple to make with some tubing, some clear pipes, and a reservoir for some light, colored oil. As long as the vacuum isn't too different, this type is the most accurate. But, dual gauges sets are fairly cheap on eBay, and all you need do is connect both to the same vacuum source and calibrate them to each other, before testing the engine. Trying to use a single gauge to sample both would require some kind of vacuum switch, so you can flip from one to the other while the engine runs, and the engine runs smoothly enough that the vacuum doesn't bounce around a lot.
 

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Back in the day we used vacuum gauges to set carbs on cars. If you dont have a manometer and had ports drilled for testing could you say block off # two and set #1 with the vac gauge, then block off #one and set # two? Just wondering.

Bill
Using just one gauge? Yes just make sure to recheck both sides after adjustment, kind of a pain to do.

One thing a lot of people forget before balancing with multiple gauges is to verify calibration.
 
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