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Bike taking ages to warm up??

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Tomcatalex, Jan 14, 2008.

  1. My bike taking ages to warm up, even on a hot summers day? Stalls with choke on, but warms up ok when choke off and throttle to around 2k, down side you have to sit on the bike with hand on throttle for 10 mins minimum

    Anyone got ideas?

  2. It's an early '80s, low tech, CV carbed 250. That's what they were like from new :grin: .
  3. I wouldn't warm it up for more than 5 minutes. Best to just get on it and ride it very gently than to idle it warm.
  4. Regardless of the age ^^^ its not right.
    You should be able to ride without dramas after starting although a short warm up while you're putting on your gear is the accepted practice.
    If you have to sit there and rev your bike for 10 mins something needs attention. A small amount of choke is acceptable for a period of time but you should still be able to ride.
  5. What happens if you try to ride off? Will it run OK once moving?

    There normally is no need to warm up an engine - just ride it gently (1/3 throttle and no more than half revs) for a minute or so.

    If it won't idle before this time that should not affect the way it rides, well, not all that much. :)

    It sounds like the idle mixture could be badly "out".


    Trevor G
  6. ^^^ What Trevor said. Sounds like your carbs need a tune. Oh, also is your bike water cooled? Perhaps the thermostat is stuck open (think thats definitely a long shot though). Best of luck :cool:
  7. Air cooled,
    Yea it is ridable after say 3 mins of revving, but if you come to a stop within 10 mins the thing will stall.
    It didnt do this before, i tryed carb spray, cleaned the filter, put premium changed plags to a cooler type, got rid of the knocking sound, but seemed to stall less with the hot plugs,
    still confused,
    another thing while riding the bike for more than an hour the base idle kicks up to 2500 rpm, cold idle is round 1000 rpm, if i turn the idle screw at cold to a higher rpm, will it go even higher when running warm???
  8. OK, rideable but temperamental after 3 mins doesn't sound too bad. However, the idle speed doesn't sound right.

    First off, check your manual (you have got a manual, right?) for the correct grade plugs and make sure whatever it says is what's in there. Mucking about with plug grades shouldn't be necessary on a stock engine (except, maybe, a highly strung two-stroke) so go with the manufacturer's recommendation.

    The variation in idle speed is not normal. Could be quite a number of reasons, from a badly routed throttle cable, to an air leak somewhere between the carbs and the head. Could be something as simple as the carbs being out of balance. Difficult to diagnose at long range though.
  9. It didn't do this before what happened?

    1) Do you have enough throttle freeplay? When you first move the throttle is there some slack movement before the throttle slides open and the engine speeds up? You can feel when this is happening.

    You should have at least 5mm free play.

    2) Use standard/recommended spark plugs only - they have nothing to do with idle speed but can burn nice holes in the top of the pistons if you are riding on the freeway with hotter plugs than you should be.

    3) There are idle mixture controls on the carbs - these should be set for a smooth idle when hot, after you reset the hot idle speed to the correct rpm. The idle mixture screws are either on the side or the underneath of the carbs, and the heads of the screws will be flush with the body of the carb.


    This should only be attended to after you solve the lean running and check the following.

    There is a problem with some Suzukis where the clips which hold the jet needle in the throttle break and the needle does not lift with the slide. That shouldn't affect the idle, though.

    Check for loose mounting clips from the carbs to the inlet rubbers.

    I believe you have a vacuum operated fuel tap. Remove the vacuum line from the inlet manifold and carefully:

    a) check that no fuel leaks out

    b) clean the end

    c) suck on this line and then hold the tip of the line against your tongue to seal it. If the vacuum diaphragm is OK the vacuum will hold indefinitely (unless you have holes in your tongue - ouch!).

    d) If the diaphragm tap has failed you will have to run it on prime all the time...is that what happened?

    e) Check that the tops of all the carbs are firmly screwed down.

    When did you last have the valves adjusted? These multicylinder OHC engines need valve adjustments somewhere between 10 and 20,000 km. Tight valves will make idling and starting difficult and smooth idling impossible.

    Does this engine have points ignition or electronic ignition? If points, then they are probably way out of adjustment.

    Ask questions if you need more help


    Trevor G
  10. Trevor G

    It didn't do this before what happened? Changed plugs to cooler ones, manual recomends the ones I put in, but had hotter ones when i got the bike

    1) Do you have enough throttle freeplay? yea

    2) Use standard/recommended spark plugs only - both types are recomended but the hotter if plugs apt to get wet) when i put the coooler plugs in engine knocking stopped

    There are idle mixture controls on the carbs - do both carbs need to be set, or just the one?

    I believe you have a vacuum operated fuel tap. Remove the vacuum line from the inlet manifold and carefully: doesnt need to run on prime, goes ok on on or res

    When did you last have the valves adjusted? how do you do this ??

    Does this engine have points ignition or electronic ignition? electronic ignitions

    Thanks Tom

  11. I don't think changing the plugs to a colder (as recommended) type can alter the idling. If that was the case as soon as you refitted the original plugs it would run correctly again.

    EXCEPT: very occasionally, if there is engine wear or other badly set things such as valve clearances, cold plugs will not run correctly, if at all, until the engine is really hot = very warmed up. Usually, though, they will backfire and misbehave so badly that you cannot even get it to warm up, when this is the problem.

    That does not sound quite right. What are the two grades of plugs recommended? Which ones did you think were "hotter"?

    Both. I thought this was a four?

    If you don't have a manual and don't know how to do it you definitely need to have a shop check them for you.

    All the best

    Trevor G
  12. has this all of a sudden started happening? does it blow black smoke ( rich fuel ) when you give it a rev ? if so , maybee check choke cables to all carbs making sure they are not siezed or popped out of any connecting joints.
  13. the user manual says

    If the standard spark plug is unsuitable for your usage, that is apt to get wet change as shown below
    NGK D8EA if standard plug is unsuitable replace with this plug.
    NGK D9EA Standard

    The motor was knocking, but started easy and got warm quick with D8EA, When i did an oil change I put D9EA, knocking stopped, but takes longer to warm up.
    Also changed oil to thicker 20w50 but this is also ok in the manual says 10w40 standard or 20w50 in warmer climates

    Cleaned the carbs with spray carb cleaner, because when taking off on full throttle , the bike hesitates before accelerating, what could cause this?
  14. Umm...using full throttle?? ;-)

    Ideally we should open the throttle gradually rather than "jerk" it.

    An engine can only accelerate at a certain rate - even with vacuum carbs, which are designed to only open as much as the engine revs allow, you might notice some hesitation while cracking the throttle at low engine speed.

    Some people like to be able to jerk it open anyway, so increasing the fuel height by maybe 1mm can help. This is done by bending the tang on the carb floats, which means pulling the carbs off and apart. It's a big job for a novice, but hey, we all start somewhere!


    Trevor G

    PS I think your valve clearances might need checking...it's easy enough if you have a manual and some patience, plus a good feeler gauge.

    Get a manual or a printout of the section and I'll be able to give you enough clues to get you by...