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Fuel filter for Sachs Express aka FY150-3 & related matters

Discussion in 'Technical and Troubleshooting Torque' started by rr9999, Nov 2, 2011.

  1. Several months ago I let the fuel in the tank run low & had to turn the fuel cock into the reserve position. As luck would have it debris was sucked into the carby and the engine started running rough & finally stopped working 90km from home. After some assistance from a motorcycle shop and further running repairs, as I carry a comprehensive tool kit, I was able to encourage the Sachs to limp home. Over the next couple of months I stripped & cleaned the carby several times until I finally found the source of the problem which was a dirty fuel bowl inlet valve. Now after a few extra tuning steps the Sachs is running better than ever.

    To try to ensure that this problem does not occur again, besides not running with an almost empty fuel tank, I have installed an in-line fuel filter in the fuel line just after the fuel tap. You may wish to consider the same modification. In-line fuel filters are obtainable from Ebay. If you are not familiar with working on engines you may wish to leave the mod to a mechanic. Leaking fuel is best avoided.

    For those of a mechanical bent, below is a description of the best technique I have found for quickly accessing the carby for cleaning. This technique works for me as I have made several mods to the configuration of my Sachs. First I have removed all plastic fairings & the skirt at the bottom of the fuel tank. This makes the bike easier to work on. Second I have relocated the VIN compliance plate from near the carby to the rear bike frame just under the seat. This makes more room for accessing the carby. The technique below may not fully work if the above mods have not been made.

    Make sure the engine is fully cold before starting
    Turn off the fuel tap
    Remove the seat
    Disconnect the fuel line from the fuel tap. Use a rag to stop any fuel from spilling
    Disconnect the fuel gauge wire plug under the fuel tank
    Remove the fuel tank
    Loosen the clamp that attaches the air cleaner box to the carby
    Remove the 2 air cleaner box holding bolts at the top of the box
    Jiggle (is that a technical term?) the air cleaner box until the air cleaner box frees itself from the carby
    Undo the 2 nuts attaching the carby to the engine
    Jiggle (their we go again) the carby until you can move it outside the bike frame. It is a tight fit & you might not be able to do this if you have not made the bike mods I described above
    Remove the cable operating the carby fuel pump. This is harder than it sounds
    Unscrew the carby slide cap & withdraw the slide
    Now the carby body is free from the bike.

    Reinstall in the reverse order.

    There is lots of info on the Internet re cleaning carbys.

    Whilst researching a solution to my problem on the Internet, I came a across a reference which stated that engines similar to the Sachs with lots of bits attached to reduce pollution often have the carby set to run a lean fuel/air mixture. So after I had the engine working again, I gave the engine fuel/air mixture a small tweak. The low speed mixture screw is located on the right hand side of the carby at the front bottom edge of the fuel bowl. It is the screw in a vertical orientation that screws up into the front of the fuel bowl. I had to find a small screw driver & cut off most of its handle to get an implement with which I could easily adjust that screw. With the engine at full working temperature, I first adjusted the engine revs to about 1750rpm (details on page 11 of the user manual that came with the bike) and then unscrewed the fuel mixture screw a quarter turn at a time until the engine started running rough & then turned the screw back in 2 quarter turns or so until the engine ran smoothly again. I went through those 2 steps above until the engine was running smoothly & then turned the idle revs down to 1500rpm. I now find that starting a hot engine is much easier. Over time you may wish to keep an eye on the spark plug to ensure that it does not soot up indicating a too rich fuel mixture. But at the end of the day a slightly rich fuel mixture is better for the engine than a slightly lean fuel mixture.

    So to finish. Don't run out of fuel as I did & you may wish to consider installing an in-line fuel filter.

    Safe riding to all.
  2. Gidday Martyd,

    Re removing plastics (side fairings + skirt under tank). I removed them a while ago, so I can't remember the specifics. I think the fairings are mostly held by plugs into rubber gromets & the skirt under the fuel tank I think (don't hold me to it) may have had a few screws to remove. I prefer the look of the bike without those bits & it makes the bike easier to work on. With the side fairings gone, I did have to make a waterproof inlet into the air filter box. Bits came from plumbing section at Bunnings. Pls see image.

    Seat removal requires 2 bolts to be undone. Easy.

    Re fuel filter, I used a $1.89 vehicle filter from Auto Cheap, but once I am happy that all is working well, I will get a more specific bike filter. Sorry I have no recommendadtions re the best filter. A search on Ebay will display many different types. By the by, Clark Rubber is a good place to buy fuel standard rubber hose if you need any.

    Re instrument cluster removal. Sorry I haven't removed it. When I had the first problem with the fuel guage, the dealer did remove the cluster without removing the head light, so it can be done. I just haven't researched how to do it.

    Sorry I couldn't help more. Good luck with any mods you make.

    Safe riding.

    Attached Files:

  3. rr9999, you have posted a fantastic bunch of info for a bike that doesn't have much service information available. I have an 2010 Express with only 500kms on it - I recently bought it second hand and have had trouble getting it to run smoothly. The previous owner said they played with the fuel/air mix screw so it is not set at the factory setting anymore, but I suspect there might be more at play anyway.

    My question to you is: would you be able to do me a HUGE favour and tell me how many turns you have the air/fuel mix screw turned out from stop? (If you don't have this information available, could you go to the bike and find out for me??? PLEEEEEEEASE???) This information is not readily available and the dealers I've called have also not had it either. I've played with it myself and think it should be about 3 1/4 turns out but as I said there are other issues with the bike which are making it hard to get a good feel. And I would like to get this right to make diagnostics better for the other problems.

    Thanks again for your posts.
  4. Greetings Apate,

    My low speed fuel mixture screw is 2 1/4 turns out from stop. From memory another 1/2 turn out & the motor started to run a little rough. Your 'mileage' may vary.

    It's a little hard to think what else could be wrong with only 500KMs on the clock. It's a fairly simple motor. Without undertaking a full investigation eg. tappet clearance check, spark plug clearance check, carby clean etc., I can only suggest you go thru the carby tuning procedure of setting the hot motor idle speed at approx. 1750 rpm & adjusting the fuel mixture screw until you find the highest increase in rpms. Set idle speed back to 1750 rpm & try to adjust the fuel mixture screw again. Repeat as necessary.

    Good luck and safe riding.
  5. rr9999, you are a champion. That is exactly the information I was looking for.

    The reason I am not able to adjust it properly myself in the first place is because my bike has a strange high idle (3.5k+ rpm) and if I adjust the fuel mix/idle screw such to reduce the revs, at about 3k rpm the bike stalls and won't start up again unless I wind out the idle screw.

    I thought it must be a stuck throttle cable or maybe the needle in the carby not sitting right because at 1/4 throttle to full throttle the engine is smooth and linear, but I've pulled the carby apart and checked everything I thought it could be, cleaned it etc but the problem still exists. I've adjusted the throttle cable and regreased it - to no avail.

    As you say, its a very basic engine so I'm reluctant to take it to the mechanics because I'm sure in time I will be able to work it out. But in the meantime setting the fuel/air mix screw to the same as a similar bike can only help to diagnose the underlying problem.

    Next step for me is (as you say) checking the valve clearance and timing - I've already checked the spark plug gap and even changed the plug - and most probably getting the carby off again for round 2...

    For all the other readers of this post, I recommend rr9999's suggestion of installing an in-line fuel filter immediately after the fuel petcock. The design of the fuel system on the Sachs Express 150 isn't great for keeping 'gunk' from getting in the carburettor. Plus, for most people this would be a very easy modification (unplugging one hose and placing the fuel filter in between the hose and the petcock).

    Lastly, I confirm that rr9999's suggested method for removing the air filter and carby is 100% accurate, and works fine (with some "jiggling"!) WITHOUT the need to remove the side plastic fairings or relocating the VIN tag - however you WILL need to remove the plastic skirt from below the fuel tank which is simply undoing the four screws holding it on.

    Thanks again to rr9999!
  6. Hi martyd, I did get it all sorted. Long story though:

    After hours and hours (and more hours) dismantling and rebuilding the carb, and reseting the air/fuel mix screw numerous times I was able to get the bike working better than before, but every time I pulled the clutch and coasted (pulling up at lights, roundabouts) the bike would stall on me. OK so this only happened after 15mins of riding when the engine was at it's full operating temp, but it was annoying because I had to carry a screwdriver with me when riding and dial the idle screw up when this happened.

    I took it to the local mechanics (Nortside Motorcycles at Artarmon, Sydney - great bunch of blokes) and they spent over a week on it trying to diagnose the problem. Late on Friday night they said they had fixed the issue only to show up to the workshop on Monday morning with a pool of fuel lying under my bike! Turns out the needle from the throttle was breaking down and not sealing properly (cheap crappy metal) which was causing all the air/fuel mix and idle settings to be wrong in the first place.

    To cut this short, the mechanics replaced the entire carby with one from a Yamaha YZ450 (which is a close match) and I've never had a problem since. They charged me $275 for the part and nothing for the labour (very generous) so I'm pleased. For me I suppose the moral was cheap bike = cheap quality parts.

    Now onto your problem: I'm no mechanic but it doesn't sound like a carby problem. Certainly not the same as mine - my issue was entirely with idling/low throttle because at full throttle my bike was OK. When was the last time you filled up with fuel? Sounds like you may have gotten some gunk in the fuel which is clogging up the carby bowl and when you let it sit the gunk sinks to the bottom? If this is the case then follow the instructions above to remove the carby and there are three bolts holding the bowl on the bottom of the carby, take it off and clean it. If you go down this path it will take you 2 hours from go to whoa - but look up carby cleaning on youtube first.

    A lesson I learned is to NOT TOUCH the air/fuel mix screw. If the bike was working fine before then it's definitely not the air/fuel mix screw that needs adjusting - it's something else. And trying to adjust that particular screw is a dark art that many people practice, but only a few people can master.

    You can check your spark plug - very very easy, just look on youtube for videos; and the valve clearance is also pretty easy but you'll need a gapping measurement tool. From memory (check the owner's manual - available online if you don't have it you can google it) I think the clearance needed to be 0.03mm so no gapping tool from supercheap auto / repco is suitable because the only ones I could find started at 0.05mm thick. I ended up buying one from eBay and it cost something like $2 delivered - but it took 4 weeks for postage.

    Hope this helps. Good luck!
  7. Hi apate,

    sorry to bring up an old thread firstly but our situations seem similar.

    I was riding on the highway going about 90ks on my 07 sachs 150 when i felt a couple short splutters. I pulled over and as i did it stalled (first and only time its done that so far). I thought it must have been too hot, as id been almost full throttle for 15 minutes. (lol).
    But then i noticed fuel dripping from the bike, up towards the bottom of the fuel tank area. I saw that the fuel tap was wet.

    Apate you stated you were in the workshop monday morning with a fuel puddle under your bike? Where was the fuel leaking from, the carby?

    Mines not coming from the carby, i cant see where it is though. I have noticed someone has already done the inline fuel filter mod though, so that could be a hint they havent secured the fuel lines properly. Arrgh. I smell fuel every time i ride!
  8. Hi Jase1,

    My sachs was leaking fuel from the carby - so unrelated issue. However I would have thought that your problem should be an easy one to diagnose and fix. If fuel is leaking at or before the fuel tap it's probably a loose hose clamp. Just check all the connections and see where the fuel is coming from and tighten up all clamps between the fuel tank and the carby.

    The odd thing is that it also sounded like your bike stalled because no fuel was getting to the engine. So maybe your fuel line is clogged or the in-line fuel filter was installed in the wrong direction (you can check this because on the side of the filter there will be an arrow and this arrow should point towards the carby).

    I would undo all the hoses between the fuel tank and carby (not a difficult job - just fiddly) and check they are not blocked, then reinstall making sure all hose clamps/seals are tight. This should sort out any problem you have.

    Good luck!
  9. fixed the leak, but hasnt fixed my stalling problem unfortunately. I cant work out if its running rich or lean. After roughly 5 seconds of full throttle itll bog down but if i back off and cruise sorta slowly itll be ok but if i pull over soon after full throttle it will always stall and not start back up without full choke. It's doing my head in!