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Help Suzuki Across Fuel Line Air Lock

Discussion in 'Suzuki 250cc In-line 4's' started by Jethalter, Feb 17, 2019.

  1. Jethalter

    Jethalter Active Member Premium Member

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    Nothing special about the solution, its just simple green orange concentrate, as its very cheap (2.5L for $15).
    The mix i'm talking about is just how much concentrate vs water mix.
    Make it too strong and ultrasonic clean the carb too long and it has the possibility to turn black, tho im yet to hit that point.
     
  2. Jethalter

    Jethalter Active Member Premium Member

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    So this morning was the first proper cold test i was able to do (12+ hours not running overnight), turn the tap to on, key to on, prime ticks for a few seconds, 3/4 choke. Started right up. But the choke has to be turned off completely after about 5-10 seconds otherwise it will stall and with no choke on cold engine the idle rpm is low @ 1000rpm, however warm engine is 1600rpm.
    Still has a hint of rich fuel in it, the idle mixture screws are set correctly, the sweet point is 2 turns out from seated, around 1 1/4 starts stalling and nearly 3 turns stalls also.
    The pilot jets are #30, main jets #90
    The only other options im thinking of is rubber intake boots(tho these look fine), or possible valve clearances. I still need to do a compression test sometime also.
    On a good note no fuel is leaking :)
     
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  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Good work there Mr Jet. I agree that you should check the compression next. Fuel screws are usually a bit more sensitive than that and lack of sensitivity is a symptom of low compression.
     
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  4. Jethalter

    Jethalter Active Member Premium Member

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    What's the easiest way on the across to take the valve cover off to check valve clearances ???
    Is it easier to just take the engine out ???

    I did a compression test hot, and across all four was only getting readings of 60-75psi (throttle WOT), which doesn't make sense. The bike rides ok (granted its not a powerhouse), it doesn't blow any smoke, and for an engine thats meant to be 170-240psi, it seems odd that all four are 60-75psi.

    I also tested my parts bike motor, that has no carbs on it so always WOT, similar psi readings.

    I'm going to hook up my comp tester to a regulated 100psi air just to make sure its working correctly.

    However the only thing i can think of is valve clearances.
     
  5. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Try doing a wet compression test, add a teaspoon of oil to each cylinder and turn it over a few time's, then do another compression test
    If the compression come's up then it's probably worn piston ring's.
    If there's no difference then it's either intake or exhaust valve's or both, you might get away with adjusting the valve clearance's, but the valve's may need reseating too (valve grind), worst case it need's new valve's, seat's recut and may as well throw in some stem seal's while you are at it.

    Could also be worth cleaning out the combustion chamber's with some Threebond Super Engine Conditioner (petrol type)
    Repco have it behind the counter
    It get's sprayed into each cylinder and will help to loosen any carbon and oil etc
    When you start it up it'll blow a bit of smoke if it was bad, then will eventually come clean.
    If the ring's are gummed up and sticking in the piston's it will help to clean out the ring groove's too, and might give you back some compression.
     
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  6. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    WOT does not mean much with CV carbs. Remove the carbs and try again.
     
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  7. Jethalter

    Jethalter Active Member Premium Member

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    Soon as i read that i think i slapped myself a little.
    Anyway i did WOT Comp Test again, this time with the slides of the carbs removed (easier than taking them out).
    The result was 70psi on each cylinder, literally to that exact point, not 1 psi difference either way.
    Double checked my gauge with my air compressor regulator, spot on 100 psi.

    Something certainly isnt right.
     
  8. Andych

    Andych Well-Known Member Premium Member

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    Sounds like Radiator out and cam cover off for Valve clearance check... or... if you have the kit, do a leak-down test first.
     
  9. Jethalter

    Jethalter Active Member Premium Member

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    Wet Test - Cold - 105-100-105-135
    Dry Test - Cold - 70 - 70 - 70 - 70

    Next step im going to check valve clearances, if its out, set it correctly and retest and see.

    If its motor rebuild tbh i don't know if i could be bothered.
     
  10. Jethalter

    Jethalter Active Member Premium Member

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    My parts bike motor tests the same readings.
    I have another bare motor that i'll have to test and see. But not very hopeful.
     
  11. Jethalter

    Jethalter Active Member Premium Member

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    Anyone wanna sell me a cheap gs500 motor complete :p
    Tested the spare motor, thats cactus too :-(
    I can get head & base gaskets cheap, but rings are the exxy part if i go genuine. There is cheap chinese ones available but i dont like that thought.
     
  12. Andych

    Andych Well-Known Member Premium Member

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    @Murdo has used rings from Ali-Express without any issues.. I would trust his judgement over pretty much most peoples on anything mechanical..
    Besides... where do you think your "genuine" rings will be made these days? They wont be made in Japan..
    Have you checked valve clearances yet? I just find it very strange that at least 2 of the engines have identical compression figures. Is your compression tester a screw in item or does it just have the cone rubber tip you have to push down on to get a seal?
    Maybe invest in a leak down tester before doing anything else.. could be $30 well spent.
    https://www.ebay.com.au/itm/4X-Cyli...305292?hash=item46914abdcc:g:q3oAAOSw0NVbpIqY
     
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  13. Jethalter

    Jethalter Active Member Premium Member

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    Valve clearances is on my to do list today. So i will know by the end of the day.
    Compression tester is a screw in one.
    The price of the leak down tester i will get regardless. Probably the cheapest one i've seen ever.
    If thats the case i might try them if i need too. They are cheap enough that i dont mind under $100 to do it all. Much more than that is going to be more than i paid for the bike.
     
  14. Andych

    Andych Well-Known Member Premium Member

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    Check the valve clearances on the spare engine first.. that way you may have some alternative sized shims for the engine in the bike..
     
  15. Jethalter

    Jethalter Active Member Premium Member

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    The two water pipes coming from the head have so much corrosion over the years that its stopping the valve cover coming off. I've cleaned as much as possible off but she's still locked solid.
    Not sure at this point how its going to come off.
     
  16. Andych

    Andych Well-Known Member Premium Member

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    Somebody else had this as well but on a different model.
    I believe some heat assisted it all to come apart.
    Maybe somebody else can find the thread for you.


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  17. Jethalter

    Jethalter Active Member Premium Member

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    will a gsf400 engine fit ???
     
  18. Jethalter

    Jethalter Active Member Premium Member

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    Whelp, i'm committed now.

    I bit the bullet and brought a gsf400 vc engine to fit in instead. The back mounts look the same so if that bolts up the rest is no issues. The front mounts i can fabricate to suit. The sprocket is easy changed to suit the 520 pitch. I know other bits i might have issues with, say carb angles etc.. but im not worried about them, i can work around that.

    Should make an interesting ride or one big disaster.

    The original motor i will sort out at some stage, however with everything going on at the moment, i dont have the time or room to build it yet. My benches are already having other motor/bike stuff in the process of building on them.
     
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    Last edited: Mar 19, 2019
  19. Andych

    Andych Well-Known Member Premium Member

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    The important things are ensuring the sprockets line up perfectly and then the intake.
    These engines won’t run properly unless the intake is perfect.


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  20. Jethalter

    Jethalter Active Member Premium Member

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    Sprocket shouldn't be an issue it should line up, however can machine up an offset one if one isnt available.
    The intake i have a couple of ideas for, since my helmet wont fit in the boot anyway, the boot base can be modified is one option, the other option is using a different set of intake rubbers but would prefer option one over option two.
    Since i have no airbox i will have to run pods and rejet to suit.
     

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