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Across Value Clearance - won't start

Discussion in 'Technical and Troubleshooting Torque' started by grunterr, Sep 1, 2012.

  1. Across Valve Clearance - won't start

    Hi All,
    Just did valves on my suzuki across (4 cylinder, dual throat carbs). Have put everything back together and am having trouble starting it. I only adjusted the clearances on the inlet valves and did all of them (5 were just out of spec) so they are even and all at the loose end of the spec. ie .27 where limits are .17 to .27mm

    The battery is fine as i have tried one from a ninja 250 as well. There is fuel in the tank, kill switch etc all ok. ( i did run out of fuel just before this service though so had to fill up from some new petrol in a jerry can. Fuel is pumped into the carbs which im about to clean.

    It has fired shortly when spraying brake clean into the air box but dies straight away.

    I have checked for a spark and put new plugs in.

    Just after any suggestions while i try to work this out.

  2. If you are getting spark, and it fires when brake clean is squirted into the airbox, it suggests that it would be a fuel delivery issue (ie fuel tap off, fuel hose not connected etc), given that the brake clean can apparently make it's way through the carb and be ignited.
  3. yeh that's what i was thinking by cleaning the carb as in something was stuck in there.. however it didnt make any different... there was a bunch of red - maybe rusty type stuff in the carbs that i havent seen previously...

    the fuel tap is on reserve, there is a fuel pump that primes & fills the float bowl in the carb- i know it's filling it because i had to drain it to clean the carbs. Also if i take the hose off then it will spray out fuel...
    when the fuel tap is off you can clearly hear the fuel pump attempting to pump the fuel so there is definitely fuel going to the carbs its just a matter of what is happening from there...

    also there one wire that i cannot find a home for.. i will try to attach a picture so if anyone with an across has any idea where it goes to can they let me know?? - i dont think this should be a problem with it starting as it looks as though all the important stuff is plugged in.. WIRES ARE BLACK, LIGHT BLUE & LIGHT GREEN - i cannot make sense of the wiring diagram in the service manual - too small & pixilated.

    another thing.. by having all the valves on the loose end will this effect compression or something like that? when i turn the engine over with a wrench it feels the same as it did before so i'm assuming everything is ok there would it be worth me trying to see if it will start with the old shims where it is very tight?? (a fair amount of work....)

    thanks for your suggestion llewellyn.. if anyone has anything else to add i'd be glad to hear it. If i can try something out or give more info i'll do so..

  4. Few variables there, think i will keep outa
    This one.
    Could be fuel - or vacuum leak etc.
    Could be your clearances - but u sound like
    You have done it before.
    Note if the clearances are to tight it wont start
    Cos valves wont close properly.

    To hard to late
    Battery / turnover speed good ??
  5. thanks phil, the clearances are on the larger/looser end. this means (thinking aloud) the valve will be open for less time/far than on the tighter end..

    I believe the clearance i have is at the upper limit possibly above it by a small amount - .279 - thus the valves may not be opening enough either duration/timing/wide enough - however compression is not lost (as it is when valves don't close at the other end of the spectrum)

    My question here will be - how likely is it that this is the cause - otherwise i think i may look into a vacuum leak first as it seemed like the throttle (more air) killed the bike straight away when it did fire up for a very short time on brake clean (only propellant i had..)

    so basically are my valves not opening far/long enough to let the air/fuel mix into my engine? (possibly/is this logical)

    i have some pondering/testing to do in the morning..
  6. Is the engine getting any oxygen?
  7. I would assume it's getting air.. have tried with/without air filter/box.....

    Anyway.. i have tried a compression test and it seems to show between 30-60 PSI for each cylinder which is way too low... then i add some oil i have tried varying amounts from 2ml to 10ml and this boosts the reading up to anywhere around 180-210 PSI.. can someone tell me how to interpret this? As from what i have read this indicates piston/rings and not a valve problem...

    A mech has come out and looked at the bike when i wasn't here.. so i and him only got half a story... and he basically said a valve must be bent.. by why does adding oil change the compression so much then??? - does the oil allow the valve to be sealed better too?

    any input is appreciated. i will most likely be trying to get him out again next week unless someone has any helpful info..
  8. took off the head with the help of a friend.. tested all the valves for leakage by pouring kero in the intake/exhaust ports.. small leakage/weeping on one valve only some small drops.. and not across all cylinders....

    put the head back on and checked timing/cam chain as tension was not done up correctly the first time.. it was too tight.. made this all correct and still no compression...

    will be giving the mech a call in the morning to get any ideas from him... not expecting a lot...

    any ideas? or suggestions to try?
  9. Is the compression low on all cylinders?

    The compression should be around 180psi across all the cylinders (excuse the pun). It's normal to vary by 5-10psi but not as much as you suggested.

    Has the bike overheated recently. If so possibly a cracked head, or block, or even a blown head gasket. A tell tale sign of that would be white creamy stuff in the coolant, or possibly water in the oil.

    And since you said you had the bike on reserve, it could simply be sediment from the fuel take getting pulled through and clogging the jets. Fill it up with fresh fuel and put the tap to on. Clean the jets, and see if that works.

    I hope any of this is helpful. Sorry to hear about the issues!
  10. yes compression is low 'across' the board (i have not tested this compression tester on any other bike/car and it is cheap so it may be faulty.. however it seems too easy to turn over by hand/starter motor... there is a new head gasket in as i took the head off a few days ago. It has fresh fuel, i also tried some 'start ya bastard' today with no luck. It does not seem to be firing even...

    Can anyone with an across confirm the spark plug leads for cylinder 1 & 4 come from the left side ignition coil and 2 & 3 come from the ignition coil on the right side? (just want to eliminate another possibility...
  11. That sounds about right. But FYI you can actually download the full workshop manual here:

    Might be helpful.
  12. U gotta go back to basics
    Engine needs

    Start with spark no spark and your going nowhere
    Pullva plug and earth it and turn over.
    It cud be just an electrical prob.

    Compession readings sound weird but i would
    Sort the spark first
  13. Are you sure you have the valve timing correct?
  14. Hi guys thanks for your responses, i had a reply typed up but lost it. i will get back to this in a day or so.

  15. The compression numbers have increased because the oil in the cylinders provides a total piston-ring seal.

    You have worn rings/ bores.
  16. Sounds like you don't have compression. Did you double check your valve clearance? You should recheck the clearances once everything is back together and the engine has been rotated (manual or by starter) several times to make sure everything is seated correctly.

    Also if using aerosol to start it up didn't help then it is either compression or no spark. From your compression test, it does lean towards low compression, however check you have good spark first.

    Spark plug leads are correct left (when sitting on the bike) are 1&4 while right coil is 2&3.
  17. what a hassle. bike shop checked timing & clearances which all checked out OK. then they cranked and cranked and cranked flattening their battery while trying to spraying oil into the cylinders & aerostart, until finally it started up and blew smoke for half an hour.

    turns out it must've been a sticky valve so the heat would have helped loosen it up, or some oil get into it to free it up......

    all good in the end.