CBR400 carbs being cleaned...

i am having the carbs cleaned & re-balanced on my bike next week.
While they are being stripped/cleaned.. should there be any parts i MUST replace?
seals?
gaskets?

want to get any parts needed for the chap before hand.

Does your cbr400 have carbs with those plastic or metal caps over them, roughly like this:-



If so a very common cause of poor running is the diaphragms get splits/cracks so they don't react at the same speed as each other.

Also the piston sliders that the diaphragms active wear and thus drag funny.

I'm considering getting one of those ultrasonic cleaners, got a set of carbs from my GT380 to do.

Yeah they work pretty well, but size depends on price as always. I have a little tiny one, but it's not really big enough to fit anything serious in it.

HighlyJetted wrote: I have a little tiny one, but it's not really big enough.

That's why Minimouse doesn't want to share her camper.....

Never seen the inside of my carbs... But I think it does have a diaphram x4

[quote="Logi"]

HighlyJetted wrote: I have a little tiny one, but it's not really big enough.

That's why Minimouse doesn't want to share her camper..... [/quote

Its flipping well worth coming on this site JUST for you humour Logi. Though I am very surprised you haven't picked up on LP talking about her DIAPHRAGMS .

Blame the iPhone auto spelling!

leopard_pagan wrote:Blame the iPhone auto spelling!

Blame the I-Phone ? Don't be silly ! It's the silly "I-Cant Spell " Old Phoney that wrote it.

Actually LP English and spelling were my best subjects at school -- but that was 48 years ago. When I wrote it out it LOOKED correct to me so I have checked it out in my Giant Collins English Dictionary and it is correctly spelt.

Its just my "cant send pictures" lessons that I am hopeless at !!

English is my 2nd language, didnt pay too much attention in school!

Mr honda is now £75 more happy! for a carb gasket/o-rings etc set x 4.

Diaphragms (?) for my bike are discontinued & no old stock but my bike is 21/22 yrs old now & a Grey Import.
but apparently Evo Stick "serious glue" is what my bike shop use to repair rubber inlets/Diaphragms etc.. its stays flexible & is petrol proof. does take 24hrs to set..

On the contraception side you can use a condom to fix the diaphragm


My school was so good it was approved....

I've bought them from these guys I think:-

http://www.nrp-carbs.co.uk/honda_carburettor_diaphragms.htm

The properties of the rubber define how the main needle lifts from the main jet in the carb, thus how it controls the fuelling.

Make the rubber weaker or tougher with a repair and you'll have a cylinder that doesn't respond the same as the rest.

Looked at nrp, cbr400 out of stock.
Condoms eh? Lol

I wouldn't meet your troubles half way!

You might have 4 good condition diaphragms.

Why are you cleaning the carbs?

Yes I certainly concur there HJ. The Triumhph 2000 and others in the range used twin Strombergs and they were infamous for diaphragms splitting .
What you say about the different properties of using a repaired one and a new one can make a noticeable difference.

The Lotus Elan on the poor mans version ran Twin Strombergs instead of Twin DCOE 40's and I couldnt get a pair of new ones so just fitted a cheap aftermarket one and it didnt run right. Just couldnt work it out so stripped them both out and you could tell the difference between the two compound s of rubber or neoprene or what ever they were made of.
Fitting two the same and she ran sweetly.

And that was all back before you were even born !!
Blimey that's scarey.

I learnt about the ways of the engine from my dad who is a carb era sort of bloke. But in my served time, just as I started to learn by myself in my teens, carbs were on their way out. So my entire repairing cars life has been with EFi. But occasionally I'll take something apart that uses the old crude venturi carb technique.

Carbs are normally a case of just strip them down, clean everything up, replace any worn bits like sliders, needles, diaphragms etc.... then put them back together. Set the float heights good, make sure the jets are all clear and correct.

I'll get something with multi carbs running, but I'm no old school carb tuner. Balancing and tuning multi carb setups is somewhat of an art. I wouldn't be surprised what I call "my poor attempt" is better than many peoples "thats perfect", but I realise you meet wise old blokes who know how to massage them into near perfection.

Single carb setups are well within my experience ability, but I just haven't had enough experience with multi carb setups to get them to near perfect. I've got one of those balancer tube kit things with the balls that move with pressure difference. But there's more to carbs than having the tools.

It's like plastering, I've got a trowel and some other gear - but I'm no plasterer

Morning Matt. Thanks for your lovely reply.
Yes I know EXACTLY what you mean about plastering or rendering-- its like that Silver Hi-Jet paint-- it keeps falling off. It is I am told because the mixture is not wet enough and I haven't made the walls wet enough. So I just leave it to someone else who is an expert and do something else I am good at to pay them for their work.

Carb Balancing Tools ? Mine was a piece of hose pipe that you stuck in your ear and I balanced them by listening to the sound of the induction noise. Pretty crude but I got pretty good at it.
Then along came Gunsons with their Clear bodied Spark plug called Sparktune so that you could actually see the colour of the combusted mixture in the cylinder when the engine was running.

Then they came out with Carbalancer- which had a moving cursor on top ( like on a radio dial ) and it relied on the amount of air being inducted over a flap which then moved the cursor.
Of course you would set one carb and then check that and of course it had changed because you had altered the other one so there you were going back and forth like a "Fiddlers Elbow" till you got an equal reading.

Talking of "Elbow " when I was at Winterbourne I had the privilege of meeting them when they stayed on the Saturday night before they were the Closing Act at the Iow Bestival on the Sunday night. They put a beautiful comment about Winterbourne in the Visitors book ( I have a photo
on my camera of it ) just before leaving to perform the Closing Act of the Festival.
Anyway as usual I digress. I much preferred the old SU carbs to Strommies
and with single venturi fixed jet carbs there wasn't much you could do.
You definitely needed a Crypton Tuner (as it was a matter of having access to hundreds of different jets AND a good knowledge of the particular carb ) which was way out of the small mans league.

I had a start on your Spoiler yesterday and the bolts just fell out so great start. Hhhmmm ! It is stuck on with double sided sponge sticky tape.
So I thought Yep Matts suggestion of the cheese wire is the answer to a Maidens Prayer. So I knocked up a couple of comfortable wooden handles for my " Mobile Bear Trap" hands and drilled a couple of holes, inserted some 08 welding wire and hey presto --- my cheese cutter. All to no avail.

I think its a hair dryer job on the metal or my Hot Air Welding gun for our roofing. Ve haff vays of getting you off. I will not be beaten. It's not in my nature to be beaten and I am a damn poor loser,

Right on the subject of Roberts prop for his 07 Piaggio I got him finally to measure the distance between cap centres and it came out at 320mm for the van whereas for the 5 pickup props I have they are 340mm.

He wants me to send the Newish one I have despite my trying to explain that with that extra 20mm under fully loaded conditions could damage the back of the gear-box tail section or punch out the metal seal in the splined end or damage the UJ's.

I have got 3 vans for breaking but -- they arent at my yard coz I have had to move them out because of Wednesdays impending visit by the Planning Department . The ONLY way I can tell if they are any good is if I take them off and try them -- which means visiting 3 different locations.

I am not happy about sending the longer propshaft to him.
Have you had any experience of this HJ or what is your gut reaction ?

I would be grateful for your thoughts on this matter,

Logi wrote:On the contraception side you can use a condom to fix the diaphragm


My school was so good it was approved....

As usual Logi you have always got the funniest answer. Thanks for that.

long story, £300 later... the bike isnt running right at low speeds under 20mph/filtering (in any gear/RPM/hot or cold); it jerks as if your playing silly buggers with the throttle open/shut/open/shut etc. it feels drive related but already replaced cush drives, clutch basket, carb/head rubbers/chain.
put Forte carb/fuel cleaner thru.. nowt.
balanced carbs.. nowt but was never happy with that job
so now its clean carbs & replace bits stage!

Get your tank and seat off and have a look!

It won't fix itself

Carburettors are DEVILS WORK!!!
i have booked the bike to be picked up by a mobile bike mechanic £35 an hr
i have already bought the replaceable parts for him, he may find something else in there... dunno yet..

carb gaskets now in.. bike booked for collection this sat...
i did get an email back from nrp-carbs.co.uk they just got stock of my bikes diaphragms.. £33 + VAT each... so at least *IF* mine are fooked... i'm not up poops creek with no loo roll!.

Just about to go to bed but you popped into my mind

How did all this carb antics go in the end?

What was the state of them?

cleaned, new seals in etc...
rebalanced... idle was set too high (2K) when i got the bike back, turned it down to 1.5K

BUT... my choke cable is bolloxed.. which i knew before hand.. i have no choke to start the bike properly with now.
the idle cable is also bolloxed & waiting for a good 2nd hand one to come in then change them both.

the carbs need re-balancing because shes not happy low revs/idle as i found last night. mechanic i used doesnt get that my bike revs high, 1/2 choke on mine sees 4-5K RPMs easy.. & is very normal. my red line starts at 14,500rpm.. blow up at 16,000rpm!
compared to a month ago the bike is running 1,000 times better.. now i know the issue..

Ya know when ya have one of those   moments....
My choke cable has been so damn hard to pull out i near on put a foot against the bike to pull the sod out!

so.. waited for new idle cable to arrive & fit the new choke cable at same time...
gets to where i need to be with the choke cable.. to see the slide bar (bank of 4 carbs) is being fouled by a breather pipe... that *I* moved when i changed the rocker cover gasket months ago!... FFS...
will be taking it for a good run in a few days to see if new idle cable (doubt it) & free-ed up choke will improve the niggly idle it now has.. already mentioned to mechanic that he might have it back to fine tune the carbs..