• NC29 carb problems

Posted: **Sun Sep 04, 2011 5:02 am**

Hi

I wonder if someone can help with some advice & info.

I am in the process of rebuilding/renovating a N reg nc29 RRR. Most of the work is done but having big problems with the carbs.

Bike hadn't run for 10 years and so I knew carbs would need really good clean, removed and stripped to clean but No3 airmix screw was siezed and in getting out left needle in carb body.
Got another set of carbs of fleabay but found No4 choke siezed & main fuel feed snapped so stripped both sets & built 1 good set.
Refitted and got running - really badly - wouldn't rev @ all.
I've sent carbs to be ultrasonically cleaned, hopefully this will help, but main point and question.

Differences between 2 sets of carbs are diaphram springs, RRR uses a very loose spring - unknown set a far tighter one.
Needles, RRR are not adjustable - just have 1 washer under, unknown ones have circlip which is fitted on second grove from top with 1 washer under.
Trumpets, RRR has equal length trumpets, unknown has two centre trumpets longer than outside ones.

Jets, I cannot see any markings on any of the jets to identify size but I believe RRR uses standard 105 jets as this bike is virtually unmolested.

Did earlier versions of NC29 come with adjustable needles or would you say as I suspect it is fitted with a dynojet or equivilant kit ?

Are there any differences between versions of NC carbs which would mean I can't mix & match carb bodies ?

Does anyone know where I can get jets ? -

I must admit although I can see how the carbs are built I know very little of "the dark art" of carb adjustment - I'd like to use the (if they are) dynojet springs & needles as they allow adjustment but am concerned that without knowing what size jets I have I may be drastically overfueling, I believe RRL's came with 110 or 115 jets as standard !

Please help with whatever info you can.

THanks

SPal

Posted: **Sun Sep 04, 2011 9:37 am**

SPal wrote:Hi

I wonder if someone can help with some advice & info.

I am in the process of rebuilding/renovating a N reg nc29 RRR. Most of the work is done but having big problems with the carbs.

Bike hadn't run for 10 years and so I knew carbs would need really good clean, removed and stripped to clean but No3 airmix screw was siezed and in getting out left needle in carb body.
Got another set of carbs of fleabay but found No4 choke siezed & main fuel feed snapped so stripped both sets & built 1 good set.
Refitted and got running - really badly - wouldn't rev @ all.
I've sent carbs to be ultrasonically cleaned, hopefully this will help, but main point and question.

Differences between 2 sets of carbs are diaphram springs, RRR uses a very loose spring - unknown set a far tighter one.
Needles, RRR are not adjustable - just have 1 washer under, unknown ones have circlip which is fitted on second grove from top with 1 washer under.
Trumpets, RRR has equal length trumpets, unknown has two centre trumpets longer than outside ones.

Jets, I cannot see any markings on any of the jets to identify size but I believe RRR uses standard 105 jets as this bike is virtually unmolested.

Did earlier versions of NC29 come with adjustable needles or would you say as I suspect it is fitted with a dynojet or equivilant kit ? I would suspect that the earlier carbs have been fitted with dynojet needles yes

Are there any differences between versions of NC carbs which would mean I can't mix & match carb bodies ? As far as I am aware the two types of carbs are quite different so unsure what can be used from each carb

Does anyone know where I can get jets ? - You can order them from Graeme France on here or Rick Oliver or go through the likes or Lings Honda etc

I must admit although I can see how the carbs are built I know very little of "the dark art" of carb adjustment - I'd like to use the (if they are) dynojet springs & needles as they allow adjustment but am concerned that without knowing what size jets I have I may be drastically overfueling, I believe RRL's came with 110 or 115 jets as standard ! L & N models used 108 main jets as standard and R models 105

Please help with whatever info you can.

THanks

SPal

Posted: **Mon Sep 05, 2011 6:31 pm**

Hi Kakama,

Thanks for the info, when yuo say carbs are quiet different, in what way? - They appear the same, fit on the same rail and mate up to all the RRR carbs inlets (fuel, air ) etc, trumpets fit as do inlet rubbers so physically they look the same.

I was wondering if stuff like emulsication tubes may be different, the RRR jets, pistons, floats all fit, but knowing my luck there'd be some reason that it fuelled differently to the later bodies and all this work was a waste of time.

Does anyone know if its the same dynojet kit throughout the NC29 range, cause f it is i'd probably go with rebuilding the carbs using it.

Has anyone got any info on fitting dynojet kit ( where the washer should go on the needle etc etc) only thing i think i'd need to buy would be the correct dynojet main jet ( can you get these seperatly to the complete kit ?)

THanks

SPal

Posted: **Mon Sep 05, 2011 9:01 pm**

There are several parts that are different. These two pages should show the different part numbers between the VP01A-A & VP01A-B carbs

http://www.cmsnl.com/honda-cbr400rrl-nc ... t/E17.html

http://www.cmsnl.com/honda-cbr400rrr-nc ... t/E17.html

Dynojet kit only fits the earlier carbs I think.

Here is the instructions for the dynojet kit:

Posted: **Tue Sep 06, 2011 1:15 am**

HI Yakama,

Thanks for these, hopefully the guy doing the Ultrasonic cleaning can remove the siezed airscrew needle, then I can go back to using the original RRR carbs.

I'm not overly bothered about using the dynojet kit atm as the bikes standard inc silencer.

THanks for yuor help.

SPal

Posted: **Thu Sep 08, 2011 4:15 pm**

Hi Yakama,

Had a proper look @ the dynojet instructions today ( couldn't get pic when logged on @ work )

Dynojet shrouds (that fit between needle & plastic bit with spring in it) wern't fitted to carbs when they arrived, but were supplied, I thought they were included in error but obviously not.

Do you know what they do ?

Also obvious that I had small washers under needle washer not above as pics show.

Carbs are still @ cleaners, but think i'll rebuild with dynojet kit (now i've got instructions), only thing i need to check out is if pistons have been drilled out or not.

Does anyone know what size drill was included in the dynojet kit.

cheers

SPal

Posted: **Thu Sep 08, 2011 4:24 pm**

Hi All,

Don't know why I didn;t try this first but spoke to PDQ in windsor. ( Dynojet dealer)

Needles are the same across the whole NC29 year span.
Jets should be either 112 or 116 - as mine is standard I need 112's
Drill is available for a huge £ 0.98p

So plan is that when carbs back from cleaners, check jet sizes ( which are available seperatly) - if needbe change - check drilled pistons fitted (using drill as feeler gauge) then rebuild and pray - lol

SPal

Posted: **Thu Sep 08, 2011 5:01 pm**

I'm sure the needl4es arent the same for the whole NC29 year span see here as they have different part numbers:

http://www.cmsnl.com/honda-cbr400rrr-nc ... E17-1.html

[urlhttp://www.cmsnl.com/honda-cbr400rrl-nc29-100- ... E17-1.html][/url]

i.e RRL = 16012MV4000
while RRR = 16012MV4780

Posted: **Thu Sep 08, 2011 6:33 pm**

Hi Yakahama

Sorry, OEM needles may be different i was talking about the dynojet needle.

must b more accurate with posts in future.

SPal

Posted: **Sat Sep 10, 2011 12:18 am**

Hi All,

Well did a bit more checking out, jets i've got are 116's - i need 112's which i've located @ approx £3 each.

Checked out the dynojet instructions yakahama supplied (thanks again) and found that four brass spacers (which were sent to me with the carbs, but not fitted) go above the needle.

Built up 1 set of diaphrams with standard OEM needles and 1 set with the dynojet needles, but with the brass spacers fitted the plastic needle retainers dont go fully down. Is this right?

Built up 1 of the old carbs with the dynojetted piston and the piston appears to go up fully, ie bottom of piston above carb appature so looks like it should be ok.

Anyone else had this? - i'm going to dynojet dealer next week to get jets & drill to open up piston holes so will double check.

Carried out repairs to two of the trumpets which were dented tonight and polished - now just waiting for carbs to come back.

Gonna b a long week. lol

SPal

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