Visit here FIRST for starting problems!

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Visit here FIRST for starting problems!

Post by banner001 »

The number of "my bike wont start, plz helps me" posts is too damn high!

Here is a checklist for anyone with starting problems...this should be a place of first reference for anyone with starting problems, if you dont follow these steps dont expect a great deal of help/insight folks.

You need 5 things for an engine to fire:-

1. battery condition
the zxr needs a good battery, so get a multimeter on it. The battery should be putting out over 12.6V, if its lower than 12V your battery is probably dead, if its between 12V and 12.6V get it on a charger and see if it maintains its voltage when left alone for a few days.

2. coils/HT leads
pull the caps off the spark plugs and look inside for signs of corrosion, bad contacts make for poor sparks. Remove the spade connectors from the coils and check the primary winding resistance, it should be ~2.3 - 3.8 ohms. Pull the HT leads out of the coils and check the secondary winding resistances, it should be ~12,000 - 18,000 ohms. If these are out of spec your coil will struggle to produce the large voltage required by the spark plug and you might get miss-fires. check the condition of the HT leads, but its always a good idea to just replace them with fresh 7mm HT lead (they push onto the connector in the coil, and screw into the spark plug cap).

3. spark plugs
Remove all 4 spark plugs and check them for fouling/carbon buildup/detonation/colour etc...there should be a small amount of carbon around the bottom of the metal thread of the spark plug, and the ceramic insulator in the middle should be a light tan brown colour. If your spark plugs are ok you can now try to get a spark, reattach the spade connectors to the coils, reattach to HT leads to the coils and to the spark plug caps, and one-at-a-time push a spark plug into the spark plug cap. whilst holding a part of the rubber/plastic HT lead place part of the metal "screw-thread" part of the spark plug onto the metal frame of the bike (or any piece of grounded metal). making sure not to touch part of the metal the spark plug is touching depress the starter button and check for a spark. it wont be something thats gonna light the room up, but it should be small and blue, and not too bright and it should fire a few times a second...repeat for all 4 spark plugs in their respective HT leads.

4. Compression/Air
Good, your battery is fine, and you have sparks, if you have access to a compression tester test all 4 cylinders for compression, this will also confirm that you are getting AIR into your cylinders. If you dont have a compression tester and you know the bike HAS fired up before you can ASSUME that compression is ok, likewise you are getting air into your cylinders. If the bike has NEVER fired up, do a compression test, or at the very least screw all 4 spark plugs back in and see if you can feel air being either sucked through the carbs (you might have to open the throttle a bit) or feel it being push out the end of the exhaust (again, open the throttle a bit)...but really look at buying/hiring a compression tester, compression should be 100-150psi per cylinder, too low and it can indicate worn rings/poor valve sealing, too high and it can indicate oil in the cylinders/large carbon buildup/foreign bodies in the cylinders.

5. Timing
everything needs to be timed correctly, there's no point in your spark plug firing on the middle of a compression stroke. If you have not touched anything timing related (not changed cam chain, removed camshafts etc.) then there is NO NEED to worry, if you want to check that its timed correctly remove the RHS crank cover, remove all 4 spark plugs and remove the rocker cover. Turn the crank clockwise onto a 'T' mark and check if the cam lobes on cylinder #4 (the RHS cylinder) are pointing away from each other, if not turn the crank 360 degrees and they now should be pointing away from each other. Grab and inspection mirror and look for 2 grooves on the RHS of the toothed gear on the end of each crank. These timing marks should be pointing away from each other and there should be a total of 30 chain links between one and the other (check in the manual if confused)...if everything looks ok, then your timing is fine!

6. valve clearances...
no-one likes to do them, but moriman has made an excellent guide (viewtopic.php?f=55&t=8002)...if your valves are all tight the bike will be a bitch to start, and as the valves tighten over time you are only delaying the inevitable by not doing them. its time consuming and tricky at first, but not difficult once you get the hang of it. if its too much for you at least get some imperial feeler gauges (they come in 0.001" increments, you will need sizes of 0.002" - 0.009" to measure your valves) and check the valve clearances to see if they are within tolerance. If they are not, and you dont fancy doing it yourself, get a garage to pick it up and change the shims for you.

7. Fuel/carbs


Ok, you battery is good, you have good sparks and good compression, there is nothing wrong with your timing and your valves are all within can only be fuel and carburettion...there is nothing else left. Firstly check that your fuel pump works, unclip the fuel pipe on the carbs, place that pipe in a jug and press the starter, the fuel pump should pump fuel, this means that your carbs should always have fuel in them. Next you are going to have to strip and clean (and i mean really clean, and ideally sonicate) your carbs thoroughly (viewtopic.php?f=115&t=14018), making sure that all the passageways are clear (an air compressor works wonders for this, bit of carb cleaner and blast the passageway with 90psi air pressure). Once your carbs are spotlessly clean check the float heights (11mm) and check that your fuel floats are sealing (makes sure your carbs wont flood), check how many turns out (from fully lightly seated) your 4 pilot air screws are (they should be ~2 turns out as standard) and note what size main jets you are running (standard are anything from 88 - 100, if you have an aftermarket air filter and/or free flowing exhaust you will probably need bigger mains).

Now, reassemble your carbs and put them back on the bike, make sure that you have an idle speed adjuster cable fitted to the RHS and make sure that it is screwed in slightly so that it has moved the throttle pulley slightly (this gives a permanent amount of minimum airflow through the main carb body). reassemble everything else back on your bike, check that battery again for >12.6V and hit the starter. you will need to hit the starter intermittently for about 30seconds to fill the float bowls fully before the bike will start, it might splutter a few times whilst doing this.

8. My starter button doesnt do anything/makes clicks
If you hit the starter and nothing happens, try the following, make sure the ignition is on and the kill switch is set to "RUN", turn the ignition on, put the sidestand up and pull in the clutch, see if you get anything. If not it could be a wiring fault, if you get a clicking sound its probably a dead starter relay, this will need replacing but you can "bypass" the starter relay by shorting out the connection with an insulated screwdriver by making a connection between the two big nuts on the starter relay (you might get a few sparks), this will bypass the relay and your bike should fire up - you might need to try this with the sidestand up and the clutch pulled in.

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Once you think the bike is ready to start i find the best way is no choke and no throttle, see if that works. if no start, give it a little throttle whilst starting. if its still dead try a little choke and no throttle, and finally choke and throttle...and see if you can get it to turn over.

Once you get it fired up you will need to ease off the choke (if applied), and keep the revs above 1500rpm using the throttle, now what you need to do is turn the idle speed adjuster cable clockwise until the bike holds at a steady rpm and you dont need to use the throttle to keep it turning over. final idle speed should be 1000-1400rpm, ideally 1200rpm.

You will need to get the carbs balanced to get a nice smooth idle, and you might need to play about with the pilot air screws to get it fueling right, but your bike should now start off the button first time!

If not, double check everything and after ruelling out everything mechanical blame the carburettion...but at least you have managed to isolate the problem.
Last edited by banner001 on Thu Jun 06, 2013 4:31 pm, edited 1 time in total.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
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Joined: Mon May 06, 2013 7:19 pm
My Bike: ZXR 400 L2
Location: Hull

Re: Visit here FIRST for starting problems!

Post by BikerDuck »

Thanks for this, Banner! Hopefully something on this list will make mine work :smt001

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Posts: 45
Joined: Sun Jan 20, 2013 7:22 pm
My Bike: ZX400 G
Location: South Africa - Western Cape

Re: Visit here FIRST for starting problems!

Post by Animammel »

This is one of the best simplified reads with compact filled information. Fantastic

Thank you
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