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Suzuki Across fuel issues

Discussion in 'Suzuki 250cc In-line 4's' started by xtan, Apr 6, 2011.

  1. xtan

    xtan New Member Premium Member

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    Hi everyone,

    I'm been intensively searching the internet for help on my fuel issues, people always seem to have similar issues but never posted how they actually fixed them (if they did).
    1990 Suzuki Across GSX250F, stock as far as i know. (With the SPES suzuki power up exhaust system)

    Been getting 135km out of a tank of BP98 octane, been driving conservatively for most of tank.
    I'm getting a big flat spot between 8-10k rpm. (drop in power)

    I have:

    Replaced throttle slide holders and then moved needles from #3 to #2 (leaner setting, which felt even worse so i quickly put it back on #3)
    Replaced all Spark plugs (Old spark plugs just seemed a little oily and dirty)
    Sprayed carby cleaner in fuel line of carby whilst engine running and intake side.
    Ran 1 and a half tanks with carby cleaner (Add in fuel type fluid)
    Now got 4 stroke fuel additive in my fuel tank.

    I don't know where to turn to now, after doing all those things response feels slightly better low down.

    Another thing: My 3rd throttle slider (black cylinder tube) Has a small chip on top and bottom about 6mm semi circle cut on the same vertical axis. I don't know if they affects anything, but i sometimes feel on 3/4 throttle my power feels flat.

    My final test is fuel filter but i don't even think the across has one, all i can find on manuals is there is a small filter just at the fuel cock, but needs a new gasket if i remove it or will defintely leak.

    Any help at all is much appreciated!
     
  2. kiffsta

    kiffsta Senior Member

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    Hey Xtan,

    check your main jets and see what size they are (its printed on the side of the jet), I have a 98 Across and the main jets should be size 90, I have fitted 92.5's on the outside cylinders and 95's on the inner 2, as such the bike goes harder, but my fuel consumption is similar to yours, maybe your jets are worn ?

    My across has a fuel filter, the  filter  is line between the petcock and the fuel pump. I should have a spare slide if want to replace the broken one, PM me if you want it.

    Chris
     
  3. xtan

    xtan New Member Premium Member

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    I've only opened the carbys from the top, i have never taken it apart so i wouldn't be able to see the part number (I was considering that re-jetting kit from ebay a while back). I've looked it up and i should be getting at least 150km before reserve tank.. I realised power drops after 9k rpm.. all the way till redline.

    I ordered a new airfilter from suzuki, will be in on Friday he claims. My current one seems pretty dusty even after blowing compressed air!

    Could you tell me where the fuel filter is?
    Is it directly behind the petcock? Do i need to remove fairing to see it?

    Cheers heaps for your help!
     
  4. Phil

    Phil Senior Member Contributing Member

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    Hey Xtan
    The fuel filter on the gsx250f Across is located above the petcock, use a torch to have a look as they are tiny. Fitting a new air filter is advisable as the engine needs to breath.
    Next I would dismantle bottom of carbs, armed with a good carb cleaner and compressed air you may well find sediment which falls to the bottom, check float level whilst you are at it.
    Take care and check all gaskets are in good condition. Also check diaphragms for any sign of deterioration. If all of the above checks are good have a serious look at your jets, they can cause problems. Hope this helps        Cheers  Phil
     
  5. Phil

    Phil Senior Member Contributing Member

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    Hey xtan
    Rereading your report re loosing power over 7000rpm says to me you are running rich, possibly and new main jets will overcome this problem, possibly. Certainly worth a look at and these won't set you back the earth. Hope this helps    Cheers  Phil
     
  6. xtan

    xtan New Member Premium Member

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    Thanks for the info Phil,

    I'm hoping the air filter is the pain because power downlow seems great, i mean the power around 7000rpm feels decent, does it get better on normal across's? (Never ridden another across so don't know how fast/smooth they meant to feel).
    I'm aware it's running rich (Can smell slight unburnt fuel on idle) but when i put the needle on #2 (leaner by 1 setting) it seemed to run poorly.

    To dismantle the bottom of the carbs, do i need to remove the whole carb assembly? (remove air filter box> Remove the exhaust cylinder side> and then remove tops of carby and work my way down?)
    I'm not well mechanically minded with carbs yet, i am still learning!

    I don't know the history of the bike (It has 45,000km), so i don't know when the valves and all those small components in the head was like adjusted properly. Would this make a difference in power?
    I'm going to do a compression test on weekend to help narrow down issue.

    I've been constantly reading the service manual/owners manual to understand how to replace the fuel filter and it says it's just 2 bolts that come down but i will need to replace gasket as it will leak. Can i use a universal gasket or must i buy the whole fuel tap with gasket. I called up my local suzuki and he said they only sell the fuel tap as a whole unit with gasket for $95.

    Off topic, my choke sometimes works and doesn't work, as in i could have it on and it won't start and ill give it a couple of revs and it will be sweet and once it's on, i will put choke on to test if it works but nothing happens, then 4-6 seconds later it revs higher to like 4k rpm. I sprayed carby cleaner on the lines that go into the carbs, thought it would help lube choke cable but i guess not. Could this possibly affect performance?
    Does anyone know what idle rpm is supposed to be with full choke on?
    Can i just unscrew the choke out of carb (if this is possible) and spray some wd40 or carb cleaner on it and put it back in?

    All the feedback received is really useful guys, thanks heaps!

    James.
     
  7. xtan

    xtan New Member Premium Member

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    Just added new air filter and there was no difference in performance.

    I really don't know where to look for now, i am unsure how to dismantle the entire carburetor. It doesn't seem hard but once i open something and gaskets are needed, i won't know what each gasket is called etc and i'll be stuck with more problems.

    Is buying that ebay kit for rejetting the carbs easy to install?
    Will i be able to install it with little problems?
     
  8. kiffsta

    kiffsta Senior Member

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    Hey Xtan

    How are you air fuel mixture screws, Phil and I have just fixed up my 91 Acrosss which had similar issues to yours, we just fitted new main jets, new pilot jets and the bugger was all over ther shop, wouldnt hold an idle, wouldnt rev past 6000 rpm, in the end we screwed the air fuel mixture screws all the way in ( well until we felt resistance) and backed them out 2 turns, then I had to go another full turn to get it right, the air \ fuel mix screws are the 4 flat head screws in on the carby body accessible from the top of the carby near the 4 black hoses (used for balancing), the rule of thumb I have heard is 2 turns out, but I kept playing with half turns till we got it right. 

    I had to take mine to 3 and it now revs to 18k. Sounds like your in a  jam,  might be worth a go. The only caveat is that you now need to get your carby's balanced as they will be out.

    Chris
     
  9. xtan

    xtan New Member Premium Member

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    I have read about this before, but my idle and reving until 7k rpm feels great, i don't have issues there. Idle is fine at 1.5k rpm and it holds nicely (i think, sounds a little like aftermarket cams in a car like it's about to stall but i thought that was normal for a bike).

    I know that once i move those screws i might have even more problems, i asked other forums and they have told me carby synchonizers or balances are only used for idling properly, i just assumed that it wouldn't affect any performance in the upper rpm.

    I guess next thing to look into is rejetting, the problem with my fairings is that it's missing alot of bolts and i struggle to put it all back together in the end :(
    I've already replaced a handful of bolts with hex heads but i'm missing the inside metal pieces that the screws thread onto. Not sure where to buy them.

    I'm from Perth, anyone here from there?
     
  10. kiffsta

    kiffsta Senior Member

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    Hey Xtan, I belive the across should idle at 1600 rpm, I dont agree with the comment that carby balancers are are only used for ideling,the across has 4 cylinders and the air fuel mix needs to be the same across all 4 carby's for them to work in harmony, when they are out or not in sync they exhibit symptoms as you describe. A set of 4 after market main jets for me was $30, a set of 4 pilot jets from Suzuki was $80, the only way to fit them is to remove the carbys from the bike and remove the float bowls to access the jets, Maybe a better option is ask a mechanic to have a look and use a syncroniser to verify they are fine, that might save you some $$$ in the long run. You dont have to remove the body work to get the carbys out, there are 4 circular clips that hold the carby's on, a phillips head screw driver is needed to loossen the collar then they pop off.

    Alas I'm in Brisbane

    Chris
     
  11. xtan

    xtan New Member Premium Member

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    Chris,
    Would you say it's worth me buying the Sigma rejetting kit from Ebay? It comes with everything needed to rejet? (including pilot jets?)
    It seems easy, but don't i have to remove the airbox side too?

    I posted on perthstreetbikes.com for a carby balancer and i was offered to buy one at $80.
    Worth investing in ?

    Cheers again,
    James
     
  12. kiffsta

    kiffsta Senior Member

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    Hey James

    I bought that Sigma kit and it was about $90 delivered, in essense, they give you a cut away diagram , 6 main jets and a drill bit, not what I would considor a complete rebuild kit. The Across has size 90 main jets, the kit includes 2 x 92.5's and 2 x 90's and 2 x 97.5's , there was a noteable difference when I installed them, but I could have ordered them in OZ from the Mikuni distributor for cheaper. You will have to take the carby's out of the bike to fit the jets.

    I saw your posts on PSB, my preference with a balancer is the mercury type, rather than a gauge. It all comes down to knowing how to use it, I think before shelling out more cash on jets and tools, find a local mechanic , he should be able to set your carby's for under $100  ( most bike shops charge between $80 - $100 per hour), I was going to replace a set of Across carby's on ym red one as they wouldnt work, in the end i adjusted the air fuel mixture and they came good, now I need to get a mechanic just to tweak it and it will be sweet.

    Cheers
    Chris
     
  13. xtan

    xtan New Member Premium Member

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    I heard synchronize and balance are they the same or two complete different things that need to be done to carburetors?

    What is difference between them and how do they work?

    Thanks
     
  14. Phil

    Phil Senior Member Contributing Member

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    Hey xtan  Just finished re reading your posting on the Forum re your fuel issues and I detect a sense of exacerbation creeping in, understandable. What I want to do is walk you through some of the steps you need to take and lets get this bike running to her full potential. When dismantling the various parts on the bike and not 100% sure where everything goes, tag  them. Get some plastic bags and a marking pen and even use your camera, anything that helps you remember where they go. OK, lets begin
    1) Remove top box (glove box) 4 bolts and a couple of wires for the interior light.
    2) Un bolt the air box, 2 bolts that secure to the frame. Then loosen the rubber holders that  secure the air box to the carbs (philips head). Before lifting the air box out disconnect the fuel line from the carb. As a precaution take the key out of the ignition so that you don't turn the fuel pump on. Remove the air box but remember that under the box is a pipe that goes down under the bike to remove oil from the air box.
    3) The carbs are easy enough to get off. Loosen the 4 retainers that hold the carbs to the rubber mounts. Now grab a 14mm open end er and carefully undo the 2 choke cables, if you can wrap these in selo or foil just to keep them together as they are spring loaded and can part too easily( just another precaution). Grab a 10mm and undo the throttle cable, check how it comes off, it's a bit awkward. Once you have done this your are ready to remove the carbs. Grab the metal bracket that secures the 2 carbs and pull back, carbs should be free.
    4) Drain your carbs of excess fuel and you are ready to start dismantling the bowls. I do one side at a time, that way I don't mix parts up. 4 screws and the bowl is off. You are now looking at your float, pull the small chrome holding bar across and the float is ready for removal. My tip is to use a good carb cleaner in the bowl and if available  compressed air to clean away all residue. Repeat this procedure on the other carb and you are one step closer getting her going.
    5) whilst you have the carbs out do the upper again and check the following; diaphrams must be checked for tears and cleaned. Check size of main jets and pilot also as various sizes are available. Check spring loading on jet needles and clean everything with carb cleaner.
    James, hope this helps you a little, having just done this twice in a week it's fresh in my mind. Also screw your air/fuel mixture screws in and count how many turns it took, very important to remember this so it can be reset accordingly.
    Can't think of too much more, all the best
                                                              Cheers Phil
     
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  15. kiffsta

    kiffsta Senior Member

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    below is a picture of a set of across carbs with the bowls off ,the needle and seat removed and the jets, this will at least help you locate the jets. The main jets come out with a large flat bladed screwdriver, the pilot jets need a smaller blade screw driver to go down hole to the jet.

    Chris
     

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  16. xtan

    xtan New Member Premium Member

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    Phil,
    Can i actually remove the carbs without remove the fairings?
    My trunk hasn't been working since i've had the bike and i've always tried to follow the wires but didn't how how to remove the rear fairings, i do know how to remove the front but it was a big pain trying every bolt to fit. Where are those two screws that bolt the airbox to frame? From removing the trunk i only see 4 screws to remove the top airbox cap to gain access to air filter.
    This is a really helpful write up thanks, i'm going to need to do it in a few days when i receive some good condition carbys as i'm going to do a straight swap.

    Chris,
    This might be a silly question but i can't workout when angle i'm looking at the carbys on that picture,
    is that from the side cause i'm rather confused. That metal part at bottom makes me think that's intake side but then the exhaust side has 4 ports :S

    So this is bird's eye view.. Top being intake side and bottom being exhaust side?

    Cheers guys.
     
  17. kiffsta

    kiffsta Senior Member

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    hey Xtan

    The photo is from below the carbs wiyh the bowls off. Where the black writing is on the photo above is the side the air box bolts on, the 4 round sections at the bottom of the page is where they slide into into the engine.

    You dont have to remove the fairings to get the carbies off, just undo the 2 screws at the front of the storage compartment and the 2 on the side  fairing and 2 the  2 inside the storage compartment of it will flip up 90 degrees , then you can undo the fuel line into the carby, and the 2 screws holding the air box in, then have access to the carbies for removal.

    Hope this helps.

    Chris
     
  18. xtan

    xtan New Member Premium Member

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    Chris,

    I have removed the tops already plenty of times to clean the carbys, so i do know how to open the trunk very well now. I just don't know which two screws you are talking about that hold the air box down. How do i remove the airbox off the carbys or must i move the engine side aswell and then the carbys will come up along with airbox?
     
  19. xtan

    xtan New Member Premium Member

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    Changed over carbys, now I crank and doesn't start,
    Cranking is good but not starting, I put a 30ml of fuel into each carby still no luck.
    Any ideas?

    I drained/cleaned new carbies while out of bike.
     
  20. Phil

    Phil Senior Member Contributing Member

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    Hey xtan  The Suzuki Across has an electric fuel pump, so hook up fuel line to carbs and let the pump do it's job. Add 30ml to each carb is not a criteria, that's what the pump is there for.
    You did not mention wether these carbs were new or second hand. If new they should be pre set, second hand is anyone's guess. Keep us posted   
                                                                          Cheers  Phil   
     

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