Honda MC question
 

Hi there,

I know this isn't the motorcycle group, but I am looking for some general
info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5 spd
trannie.

I have searched the net up and down to no avail. I think my only option will
be to break down and try and find a manual at a decent price. So far no luck
on EBay.... There is a Clymer one, but I wouuld prefer an actual Honda
manual.

So what I am looking for is

A) Advice on how to tune up the carbs on this bike OR

B) Link to a website that shows diagrams and a step by step procedure on how
to do this.

The current symptoms include:

1. Brown smoke coming from the exhaust, indicating that the bike is
overfuelling and running very rich.
2. Intermittently runs on one cylinder, indicating overfueling and fouling
of one cylinder.
3. Gas occasional pours out of the overflow of both carbs, indicating a
problem with the floats or the fuel shut off valve.

Thanks for your input.

t

--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx...-cars/200608/1

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651b17842c12b@uwe...
>
> I know this isn't the motorcycle group, but I am looking for some general
> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
> spd
> trannie.

news://rec.motorcycles.tech

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651b17842c12b@uwe...
>
> I know this isn't the motorcycle group, but I am looking for some general
> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
> spd
> trannie.

news://rec.motorcycles.tech

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651b17842c12b@uwe...
>
> I know this isn't the motorcycle group, but I am looking for some general
> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
> spd
> trannie.

news://rec.motorcycles.tech

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651b17842c12b@uwe...
>
> I know this isn't the motorcycle group, but I am looking for some general
> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
> spd
> trannie.

news://rec.motorcycles.tech

Re: Honda MC question
 

Don't know if you have actually visited news://rec.motorcycles.tech, but it
SUCKS.

A helpful link, PLEASE.

t

Seth wrote:
>> I know this isn't the motorcycle group, but I am looking for some general
>> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
>> spd
>> trannie.
>
>news://rec.motorcycles.tech

--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx...-cars/200608/1

Re: Honda MC question
 

Don't know if you have actually visited news://rec.motorcycles.tech, but it
SUCKS.

A helpful link, PLEASE.

t

Seth wrote:
>> I know this isn't the motorcycle group, but I am looking for some general
>> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
>> spd
>> trannie.
>
>news://rec.motorcycles.tech

--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx...-cars/200608/1

Re: Honda MC question
 

Don't know if you have actually visited news://rec.motorcycles.tech, but it
SUCKS.

A helpful link, PLEASE.

t

Seth wrote:
>> I know this isn't the motorcycle group, but I am looking for some general
>> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
>> spd
>> trannie.
>
>news://rec.motorcycles.tech

--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx...-cars/200608/1

Re: Honda MC question
 

Don't know if you have actually visited news://rec.motorcycles.tech, but it
SUCKS.

A helpful link, PLEASE.

t

Seth wrote:
>> I know this isn't the motorcycle group, but I am looking for some general
>> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5
>> spd
>> trannie.
>
>news://rec.motorcycles.tech

--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx...-cars/200608/1

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651c4b7afeccc@uwe...
> Don't know if you have actually visited news://rec.motorcycles.tech, but
> it
> SUCKS.
>
> A helpful link, PLEASE.

Yeah, I read it often. There was a discussion just last week regarding
tuning carbs.

Don't like my link, don't follow it, but the data you seek is there.

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651c4b7afeccc@uwe...
> Don't know if you have actually visited news://rec.motorcycles.tech, but
> it
> SUCKS.
>
> A helpful link, PLEASE.

Yeah, I read it often. There was a discussion just last week regarding
tuning carbs.

Don't like my link, don't follow it, but the data you seek is there.

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651c4b7afeccc@uwe...
> Don't know if you have actually visited news://rec.motorcycles.tech, but
> it
> SUCKS.
>
> A helpful link, PLEASE.

Yeah, I read it often. There was a discussion just last week regarding
tuning carbs.

Don't like my link, don't follow it, but the data you seek is there.

Re: Honda MC question
 

"loewent via CarKB.com" <u10197@uwe> wrote in message
news:651c4b7afeccc@uwe...
> Don't know if you have actually visited news://rec.motorcycles.tech, but
> it
> SUCKS.
>
> A helpful link, PLEASE.

Yeah, I read it often. There was a discussion just last week regarding
tuning carbs.

Don't like my link, don't follow it, but the data you seek is there.

Re: Honda MC question
 

loewent via CarKB.com wrote:
> Hi there,
>
> I know this isn't the motorcycle group, but I am looking for some general
> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5 spd
> trannie.
>
> I have searched the net up and down to no avail. I think my only option will
> be to break down and try and find a manual at a decent price. So far no luck
> on EBay.... There is a Clymer one, but I wouuld prefer an actual Honda
> manual.
>
> So what I am looking for is
>
> A) Advice on how to tune up the carbs on this bike OR
>
> B) Link to a website that shows diagrams and a step by step procedure on how
> to do this.
>
> The current symptoms include:
>
> 1. Brown smoke coming from the exhaust, indicating that the bike is
> overfuelling and running very rich.
> 2. Intermittently runs on one cylinder, indicating overfueling and fouling
> of one cylinder.
> 3. Gas occasional pours out of the overflow of both carbs, indicating a
> problem with the floats or the fuel shut off valve.
>
> Thanks for your input.
>
> t
>
well, your symptoms certainly /do/ point towards float problems and/or
needle valve leakage. you need to strip and clean to see what's up.
needle valve failure/leakage is very common on older high mileage carbs.

regarding subsequent adjustment, i can't say because i've not stripped
those particular carbs, however you can balance between chokes/idle
circuits with an old pen and a glass bead. pens usually have a slightly
conical center [aids mold removal during manufacture] and therefore a
glass bead trapped therein will rise according to airflow from bottom to
top, if you see what i mean. that and a rubber tube and a pin [to
prevent accidental bead ingestion] and you can now balance relative
airflows between carbs. it doesn't give you a setting for what the
actual flow rate /should/ be, but it allows you to balance them
perfectly and costs almost nothing to make. or you can buy the tool
that does the same job!

Re: Honda MC question
 

loewent via CarKB.com wrote:
> Hi there,
>
> I know this isn't the motorcycle group, but I am looking for some general
> info on how to tune the carbs on my 79 Honda CM400 Twin. 395CC engine, 5 spd
> trannie.
>
> I have searched the net up and down to no avail. I think my only option will
> be to break down and try and find a manual at a decent price. So far no luck
> on EBay.... There is a Clymer one, but I wouuld prefer an actual Honda
> manual.
>
> So what I am looking for is
>
> A) Advice on how to tune up the carbs on this bike OR
>
> B) Link to a website that shows diagrams and a step by step procedure on how
> to do this.
>
> The current symptoms include:
>
> 1. Brown smoke coming from the exhaust, indicating that the bike is
> overfuelling and running very rich.
> 2. Intermittently runs on one cylinder, indicating overfueling and fouling
> of one cylinder.
> 3. Gas occasional pours out of the overflow of both carbs, indicating a
> problem with the floats or the fuel shut off valve.
>
> Thanks for your input.
>
> t
>
well, your symptoms certainly /do/ point towards float problems and/or
needle valve leakage. you need to strip and clean to see what's up.
needle valve failure/leakage is very common on older high mileage carbs.

regarding subsequent adjustment, i can't say because i've not stripped
those particular carbs, however you can balance between chokes/idle
circuits with an old pen and a glass bead. pens usually have a slightly
conical center [aids mold removal during manufacture] and therefore a
glass bead trapped therein will rise according to airflow from bottom to
top, if you see what i mean. that and a rubber tube and a pin [to
prevent accidental bead ingestion] and you can now balance relative
airflows between carbs. it doesn't give you a setting for what the
actual flow rate /should/ be, but it allows you to balance them
perfectly and costs almost nothing to make. or you can buy the tool
that does the same job!