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 Post subject: Cracked carburetor hoses
 Post Posted: Mon Apr 01, 2019 2:43 pm 
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I saw a post the other day, someone changed their carb hoses since they were cracked from the inside. I know mine are too. Will normal fuel hoses do or should I change for some specific hose? It is fuel that goes through right?

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 Post Posted: Mon Apr 01, 2019 6:29 pm 
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if you're referring to they are vacuum hoses. (fuel doesn't pass through them)

The six vacuum hoses.

Four short hose's (one per carb body) access is very awkward to the inner three.

A vacuum hose running from cylinder 2 inlet to the fuel tap. (Mine was cracked causing a rev hang)

A (long) vacuum hose running from cylinder 3 inlet to the pair valve.

Cyl 4 has rubber cap retained by a tiny clip rather than a vacuum hose. Here you would attach one of the hoses of a carb balancing tool or fit a vacuum hose to operate a chain oiler. Providing it's not perished just leave it be. Some folk remove the cap and attach a short vacuum hose which they then plug . - makes it easier to link up the carb balancer next time around.


Type into Ebay silicon vacuum hose. :)

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 Post Posted: Mon Apr 01, 2019 6:38 pm 
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Thanks for the reply! I've commented on the other post. I've decided to try and separate each carb to change all hoses. Is this a bad idea?


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 Post Posted: Mon Apr 01, 2019 7:02 pm 
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Irongamer727 wrote:
Thanks for the reply! I've commented on the other post. I've decided to try and separate each carb to change all hoses. Is this a bad idea?


Separating them would make the job easier... but i didn't fancy it.with all them springs ect ( <-- Read bottled it :angel )

What i did was cut the hoses to length and fed them through using an Allan key stuck in one end (gives you something to hold and makes manipulating the hose easier) while i gently grabbed the other end with a pair of forceps and pulled it on... a smidgen of WD 40 on the receiving carb pipe helps no end.

For what it's worth - I attached the hose to the metal pipe first then slipped it on the plastic pipe last.

Once you've done one the other two get easier :)

Try it first (you've nothing to lose) then if you can't manage it go with splitting them.


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 Post Posted: Tue Apr 02, 2019 8:28 pm 
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Bad day today. Started out good. I got hold of some really good hoses that seemed to fit really nicely. Sadly I had no choice but to split each carb to replace the hoses. I did not replace all of the o rings after splitting since they looked good. I mounted everything back together and lost all sense of where all the sync screws should be. I synced every carb so they were roughly the same. Popped everything back together and the bike now revvs like crazy when I start it sometimes. It can go to 5000 rpm and stay there but it could also go to 1000 rpm and slowly die. As soon as I touch the throttle it dies. Really love when you screw something up that worked completely fine. Ideas?


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 Post Posted: Wed Apr 03, 2019 4:31 pm 
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No idea mate...

First check the simple stuff... like the idle setting, correct choke and throttle cable operation and for manifold vacuum leaks. Take the air box off and check to see if a slider is sticking.

If no joy pull and double check your carb assembly, that the throttle linkages operate smoothly, that the butterflies open and close, that you haven't missed an o ring or pipe fitting.

Too many variables to pin point, something hasn't gone back correctly... you just got to find out what. :eek

Also double check the variable you have changed... the bench sync.

I did mine slightly different to Hoons using one drill bit.

I opened up the idle screw until the drill bit was a 'slight touching sliding fit' under no3's butterfly. Then with the idle screw holding no 3's setting i adjusted the other butterflies using the drill bit and sync screws. When all were the same (double checked all with drill bit) i dropped the idle back down.

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 Post Posted: Wed Apr 03, 2019 5:51 pm 
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I didn't change the idle setting. That means nr 3 should be where it was before right? I adjusted the others so they were pretty much identical to nr 3. Should I just start her up and let her idle at 5000 rpm or should I continuously start and shut her off?


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 Post Posted: Wed Apr 03, 2019 6:25 pm 
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If the idle hasn't been touched 3 should be where it was.

With the air box removed you should be able to see the butterflies - lift each slider and check each butterfly opens and shuts again leaving a tick over sized gap. (With the BIKE OFF use a torch and a helper to open and shut the throttle)

If all seems well it must be a vacuum leak or something else.. presumably the 4 vacuum pipes you fit were a snug fit?

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 Post Posted: Wed Apr 03, 2019 7:00 pm 
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Can I remove the air box and look for leaks? Or will the bike rev like crazy without the box? I want to start her up and spray some starting fluid at the vacuum connectors.


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 Post Posted: Wed Apr 03, 2019 7:45 pm 
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Might not start... but if it does it will be running a lot leaner so don't run it for long.

I've never tried it so not sure.

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 Post Posted: Wed Apr 03, 2019 9:53 pm 
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Progress was made today. Found out that it is indeed the stupid vacuum hoses. Time to pull everything apart, again.


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 Post Posted: Fri Apr 05, 2019 10:07 pm 
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Carbs back apart. Seems more and more unlikely that its these vacuum hoses. My theory is that its these . https://imgur.com/a/y7m8IdD
Think they need to seal pretty good right? Possibly time to replace? What do you guys think?


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 Post Posted: Fri Apr 05, 2019 11:03 pm 
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Unlikely... didn't you say the issue occurred after separating the bodies to replace the vacuum pipes? (You wouldn't have disturbed the diaphragms )

I'm thinking carb inlet rubbers.. how old are yours ?

They tend to age stiffen which makes them susceptible to damage when removed. (Check that the 'sealing lip' hasn't got damaged on removal. (In each throat of the rubber stubs there's a raised ridge (like an Oring) which mates with a recess on the carb/inlet manifold.

Even if they 're not damaged... it'l be difficult to get a good seal if they've gone hard.

(If you decide to replace don't buy second hand)

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 Post Posted: Fri Apr 05, 2019 11:18 pm 
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Mine a 2000. Separating the carbs means this rubber is also removed. It feels really stiff and most likely wont seal very good. Have a hard time thinking its the inlet rubber. It's hard but the carbs sit in there really solid.


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 Post Posted: Fri Apr 05, 2019 11:58 pm 
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Irongamer727 wrote:
Mine a 2000. Separating the carbs means this rubber is also removed. It feels really stiff and most likely wont seal very good. Have a hard time thinking its the inlet rubber. It's hard but the carbs sit in there really solid.



Sorry... thought you meant the diaphragms under the large black caps.

Not 100% certain... but i think that collar forms part of the 'vent' pipe work enabling the diaphragms to move freely. Basically displaced air moves along this circuit as the diaphragm moves up an down. The circuit itself would not cause a vacuum leak as it's the wrong side of the diaphragm.

Image
Image

Hopefully someone who knows for sure will chime in :angel

P.s.
Hard will bolt up solid... but soft and pliable will ensure a good seal.

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 Post Posted: Sat Apr 06, 2019 11:43 am 
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you go. (Last post)

and here



The large diameter hole (in your pic) vents the float chambers and is connected to the sub air cleaner and the smaller diameter hole vents the diaphragm.

:)

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Last edited by Biggabit on Sat Apr 06, 2019 12:13 pm, edited 1 time in total.

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 Post Posted: Sat Apr 06, 2019 12:09 pm 
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Hornet Warrior

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Wow thanks! Shouldn't spend any more time on them then?


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 Post Posted: Sat Apr 06, 2019 12:31 pm 
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Nah.. they're just air vents.

Your issue is else where.

Have you checked for smooth operation of the air slides? Using a finger lift each one and let it drop... they should all feel the same and fall in a similar manner. If one is sticking there could be an issue with the spring not seating properly.


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 Post Posted: Sat Apr 06, 2019 12:39 pm 
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Yes they all move nicely. Didn't touch them at disassembly. I'll spin some wire around each end on the vacuum hoses and see if that fixes something. I'll change the inlet rubber next as you recommended! Again, many thanks :)


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 Post Posted: Sat Apr 06, 2019 6:08 pm 
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I got everything back together and this time I noticed the butterflies were pretty much entirely closed (after bench sync). They were slightly open first time. This have probably been the problem all the time. Thanks for all the help and knowledge


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 Post Posted: Sat Apr 06, 2019 6:36 pm 
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Your welcome - seems like you've got it sorted :)

It was worth doing the vacuum hoses because now you KNOW they're good, and can pretty much rule them out in any future issue.

Regarding the bench sync... it's only a starting point (The bike should start) but highly unlikely to be accurate, due to cylinders, rings and valves not wearing equally. (The cylinders won't all suck the same)

When she's up and running it'd be worth doing 'vacuum sync' at some point, so she can run efficiently as possible.

:)

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 Post Posted: Sat Apr 06, 2019 6:57 pm 
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Already done it! What a difference it made!


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