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1981 CM400T
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85 Posts
Discussion Starter · #1 ·
my first problem post here so, help needed :)
I guess I'm having some air leaks through carb boots,
will inspect once more this weekend,,,they dont seem bad at all,anyway, i'm going to replace them 100%, not sure how old is the rubber
the info on VB31D carbs are pretty scarce here, guess it's due to being euro standard,
so I was wondering if anyone knows which boots would fit these carbs?
I was going to order these ones but not sure if they fit
https://www.ebay.com/itm/80-81-HOND...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
Is there any reference Honda Genuine Number to relate to when searching for these?

Also, one off-topic,
i start the bike with full choke (pulled), starts on first,and after warming up a bit, barely idling, the revvs dont go any higher, i have to leave it open/on full (the choke) and it's the only way to start riding, if I start closing it (way down) when idling (supposingly warmed enough), the bike shuts down..
only after few km of riding I can start closing it slowly..is that normal? Guess not...the weather is pretty bad and subzero but i dont know if it has some effect on it..
PO says he cleaned the carbs, but not sure if fully synced/balanced..
I will start with carb boots change + new spark plugs change + airbox clean and mixture adjusting or should I start with checking something else first at this point?
I'm pretty new at these oldies but goldies bikes :)
thanks for help folks
t
 

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24,208 Posts
The insulators you listed should be fine.
To clarify terms: choke off= choke plate open= cable/knob pushed in. Choke on= choke plate closed some or fully= cable/knob pulled out. Confused yet? LOL
Cold weather requires more choke for a longer time until the engine is fully up to temperature which takes longer because it's so cold. Also the carbs can freeze up with higher rpm's, literally iced over, and really low temps.
It wouldn't surprise me to see a 5 minute, or more, idle warm up at zero C (32F).
 

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Registered
1981 CM400T
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85 Posts
Discussion Starter · #3 ·
Got the choke thing :) i meant "Choke on= choke plate closed some or fully= cable/knob pulled out. " so that's clear

5min of warming up,really?didn't know that,,,will wait for higher temp to evaluate the whole deal..
But i guess new boots are a must if leaking,,,,
One more thing,i was going to take out the airbox and clean it,and the manual says first to take out the rare wheel,and so on..really have to?
 

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9,796 Posts
The rear wheel and fender need to be removed to slide the air box back out the frame. Even then, it's a tight squeeze.
 

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Registered
1981 CM400T
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85 Posts
Discussion Starter · #5 ·
Thanks :/ i'll pass on that one then..will just clean it and put a new air filter in..
 
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