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Been playing with carbs :D

Discussion in 'FZR250.com - Archives' started by TBone, Nov 27, 2005.

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  1. TBone

    TBone New Member

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    I have been experimenting / servicing carbys on FZR250s lately.. what I find is this:

    These carbs are the most tunable little things... there are a lot of ways one can change the air/fuel moxture... but this is aloso the couse of problems... they have a nimber of plastic parts which get worn out fairly quickly (both bikes have over 40,000km on the clock) the sliders, niddles and jets all are fairly worn out on these bikes... I mean the bike I worked on yesterday had groves in the sliders going good 1mm in!! and niddles with steps!!

    I would be seriously recomending a good fuel filter (perhaps one out of a car) and a mojor clean and tune on the carbs... also fuel pumps on these bikes DO make a difference!! and a fenominal one... though I would recomend using a bike fuel pump rather than the aftermarket pulse pumps as they are in the ON position when the bike is not running and the fuel has to be turned off manualy... there is a solution that I have worked out.. a fuel swich fom a LPG sustem... it will turn of the fuel for you automaticaly so it is a good idea especialy if your fuel tap is not working...

    A lot of these bikes are running rich... which gives them a real good power especialy up high in the rev range... but down low it can mean they get boged down and actualy flood... there is a point at which the carbs get so worn out that they run supper rich.. but I have found that lowering the niddles sort of restores the balnce.. Ok you DO lose some HP a the top but you gain all the revs and power down low... I was riding the FZR at 3K-6k and it actualy felt good and responsive!

    Any how I thought I would share my Carb expiriance with you guys...
     
    TBone, Nov 27, 2005
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  2. FZR Dude

    FZR Dude New Member

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    As you explain (and I have stated many times) check those emulsion tubes while you are in there cleaning the carbs.

    Emulsion Tubes = Needle Jets = the part that the needle slides up and down in.

    I'll check with a buddy over on the Brotherhood who has an in over at Factory Pro. I'll see if they can dig anything up on the 250's. We had a really good group buy for the Hood members. 15 members took part in the buy.
     
    FZR Dude, Nov 27, 2005
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  3. ACE

    ACE Active Member

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    What emulsion tubes do the 250 3ln1,s have. Mine seems too not have any. Im in oz is that y
     
    ACE, Nov 27, 2005
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  4. FZR Dude

    FZR Dude New Member

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    This part is in the carbs and can only be accessed by disassembling the carbs. This part is prone to wear on all motorcycles that have carbs.
     
    FZR Dude, Nov 27, 2005
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  5. TBone

    TBone New Member

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    oodly I have found the sliders (which are plastic) and the housing in which they slide (plastic again) to have worn out more than the needles and needle jets... there seams to be some sort of snow ball effect I think.. once some dirt goes in there b/w the two it scraches up the plastic cousing more rubbish to build up etc...

    As I understand needles and needle jets are easly accesable as they are simply a MIKUNI part...
     
    TBone, Nov 27, 2005
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  6. FZR Dude

    FZR Dude New Member

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    Well I hope so, as Factory Pro does not make anything for the FZR250.
     
    FZR Dude, Nov 30, 2005
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  7. super_poopra

    super_poopra New Member

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    What should we be looking for with emulsion tubes? How well the needle fits inside of it? At what point do they require replacing?
     
    super_poopra, Dec 27, 2005
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  8. TBone

    TBone New Member

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    replace your needles when they have teeth...

    Basicaly when you can feel/see that they are not smooth and the end has steps rather than smooth cone...

    With the jets just replace when changin the needles...

    I have odered (through a third party) a heap of spare parts for the carbes from Yamaha Japan... one thing I did not include were the jets and needles as I belive they can be obtained here in Australia directly from a carby specialist...
     
    TBone, Dec 27, 2005
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  9. ACE

    ACE Active Member

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    Im a dick I fought you ment tubes that on some bikes go from the head to the intake for the emissions <!-- s:oops: --><img src="{SMILIES_PATH}/icon_redface.gif" alt=":oops:" title="Embarassed" /><!-- s:oops: -->
     
    ACE, Dec 27, 2005
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  10. TiMBuS

    TiMBuS New Member

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    TBone.. PLEASE say that you ordered airboxes and rubber boots!!
     
    TiMBuS, Dec 27, 2005
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  11. TBone

    TBone New Member

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    no on the air boxes but new rubber boots <!-- s:D --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt=":D" title="Very Happy" /><!-- s:D -->
     
    TBone, Dec 28, 2005
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  12. koma

    koma New Member

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    Nice work on the 'overnight parts from Ja-Pan' <!-- s:D --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt=":D" title="Very Happy" /><!-- s:D -->
     
    koma, Dec 28, 2005
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  13. TBone

    TBone New Member

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    I wish they were over nite... it is some bloke in japan with whom I have never coresponded with B4... som eone else sort of konws him and has asked him b4 to check out some prices... I do hope some thing comes out of this...
     
    TBone, Dec 28, 2005
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  14. FiZzR

    FiZzR New Member

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    Interesting - I think my carb's got a few problems. Like you said, once it's revving it goes fine, but at the bottom end it has a few probs, often cuts out when idling unless I keep the throttle on slightly.

    It's also got another problem at the moment - it won't start. When it's been sitting for a while it seems to flood, even with the fuel tap off.

    I haven't ridden it for about 3 weeks, went to start it the other day and it just cranks over but doesn't fire. Backfired a few times but that's it. comes close to starting but won't quite kick over.

    I've had the problem before, took it to a mech who replace sparkies, changed oil and fuel and charged like a wounded bull for his trouble.

    What should I do - empty the float bowls, check the sparks and change the oil? Apparently, according to the mech, I should be riding it more often. He said that the fuel leaks down into the cylinders (presumably because the rings are a bit worn?)

    Any advice appreciated. Otherwise, looks like I'll be shelling out for the mech again. I think I could get it going again myself, I have tools and a bit of know how, but I don't really have a garage...
     
    FiZzR, Dec 28, 2005
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  15. TBone

    TBone New Member

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    Clasic FZR problems.. especialy amplified by not riding or short changing of gears (also ideling for longer periods)

    Change your spark plugs!! if the oil has been in the bike for longer than 4-6 months or 5000km CHANGE it (especialy if you have a foulty fuel tap)

    Re tune the carbs to run leaner (drop the needles if you have an aftermarket fuel pump) and turn down the idle mixture screws (3 turns is standard but on some bikes less is better)

    I'm working on a electric fuel swich that will cut the fuel off when the bike is off for all the people with fuel tap issues... I wil sell it for $55 as a kit or $75 installed I'm hoping to have the kit avalable soon...

    I'm also hoping to buy NEW original fuel pump for the FZR250 3LN-3... I'll test it for preasure and fuel delivery as all the fuel pumps I have fitted (aftermarket) are causing the bikes to run to rich... So I hope I will be able to find a more suitable pump or modify the ones I have been using...
     
    TBone, Dec 28, 2005
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  16. TiMBuS

    TiMBuS New Member

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    Raise your idle speed a bit, it's a good temporary fix. I learned while looking at the throttle mechanism on the carbs that the idle speed screw just holds the throttle slightly open.. So technically it's just holding the throttle open for you, which means less bogging down. Plus even those without tools or a garage can raise the idle speed...

    TBone! I fixed my fuel tap! I just bent the metal a little bit.. But I still want that 'kit,' which I guess for me is just two wire splicers and the actual switch, seeing as you already ran wires down the bike. Tell us when you've gotten a hold of the merchandise ey?
     
    TiMBuS, Dec 28, 2005
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  17. FiZzR

    FiZzR New Member

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    It had a change of plugs and oil at the end of August, hasn't done more than a few hundred kms in that time....will check the plugs and will change out the oil.

    Faulty fuel tap: not sure if this is an issue I'm having...maybe a slight leak I guess, would this explain the problem of fuel leaking into the cylinders?

    I don't have a fuel pump, as it's gravity feed...but I think the carbs could probably do with some adjustment. Anyone know of a reasonably priced bike mech in Sydney who has a clue about FZRs?

    Are you saying that the 3LN-3 comes standard with a fuel pump? I thought they were all gravity feed only...
     
    FiZzR, Dec 29, 2005
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  18. TBone

    TBone New Member

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    the importers throw them out... they do not want warrenty problems... after the bike has been sitting for number of years in Japan the fuel pumps get all stuffed up with jelly (the japonise fuel has so many addetives it can actualy go hard as a rock within fiew years)

    you can buy a new pump off the importes but they ask some thing like $250?? for it... also when thebike has a fuel pump and is setup good and proper it has as much power as a CBR250RR without the fuel pump it actualy has more power and sell better... but it runs rich which fiew years down the line couses some problems...
     
    TBone, Dec 29, 2005
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  19. TiMBuS

    TiMBuS New Member

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    Well there's no way that the fuel can get pushed through any other way, unless your floats were so high that the amount of petrol in the carbs gave enough pressure to seep past the needles. But if that was the case your bike would be running rich... *scrolls down* Oh wait, you say it is. No pump + running rich, you'll probably need to lower the floats, or change your air filter.
     
    TiMBuS, Dec 29, 2005
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  20. FiZzR

    FiZzR New Member

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    Well, got the Fizzer going again. Very simple really: changed teh spark plugs. Took one out and found it was black, so swapped them all for new ones and it kicked over first time. I was suprised they were so bad, as they've only been in for about 4 months, and it has hardly been run in that time. Hope this doesn't mean I'm burning oil = rings on way out...

    What other things could black spark plugs signify?

    Thinking maybe it's time to get rid of the Fizzer...been considering an upgrade anyway now that I'm on my open licence.
     
    FiZzR, Jan 3, 2006
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