xt 550

[xt550]

hi i have just got an xt 550 as a non starter. anyway got the bike going without too much trouble but it will not tick over without the tickover being set to say 1200 rpm if i try to slow it down it just dies,then when i ride the bike it pulls really well up to about 4500 rpm then just dosent want to know. i have cleaned the cartb out it has a new float,spark plug is ok. any ideas

thanks Dave

took the carb of today just to check put it back on andd now the bike will not start petrol is getting through and i have a spark ?

[YamaHead]

Could it be that your timing is a bit off?

Once I changed out the electrics on mine.......it has YET to give me ANY grief!

[xt550]

Could it be that your timing is a bit off?

Once I changed out the electrics on mine.......it has YET to give me ANY grief!

will give it a try

thanks

Dave

[yoda]

I think you have dirt in your fuel and its causing fuel starvation.

You need to thoughly strip down the fuel system including the tank and clean the components. Refill with fresh fuel and try again.

[YamaHead]

I think you have dirt in your fuel and its causing fuel starvation.

You need to thoughly strip down the fuel system including the tank and clean the components. Refill with fresh fuel and try again.

Also good sound advice.

[Bruce]

What happens at 4.5k rpm?

Check your plug colour, it'll tell you a lot.

Various checks you can do starting with easiest...

1. Check the carb inlet mainifold rubbers are not leaking through cracks etc. Easiest way to do this is with the engine idling, spray easy start around the intakes. If you notice a rpm change, you have a leak.

2. Check your filters are not dirty, and the guaze has not corroded restricting airflow.

3. Check your idle mixture pilot screw is not set too rich / lean. Should be roughly 2.5 turns out. Note, this does not adjust fuel flow, but airflow so tightening the screw will richen the mixture. Check the vent in front hasn't corroded closed a bit.

4. Use a clear plastic Tygon tube (battery overflow tube works well enough) attached to the float drain nipple and bend it back up against the float bowel. Open the drain screw and petrol tank cock. Measure the difference in fuel height from the bottom of the meniscus to the top of the float bowl. The fuel level should be within spec 5 - 8mm (check against manual for that figure tho)

If you are still having problems, you'll need to strip the carb further.

5. Check and clean all jets and atomisers. DONT forget the mini guaze filter that sits in front of the needle and seat either.

6. Check against the manual that the primary cd slide closes to the correct point and is not compensating for the pilot jet ( idling issues)

7. Check secondary carb is actuated at the correct point. Roughly once 8 - 10 mm of the cd slide has been raised in the primary carb.

8. Check the fuel pipes between the carbs for integrity / leaks

9. Check all diaphrams and the free and vacuum movement of the secondary carb

10. Check the needles for wear and that they are correctly positioned with the retaining C-clip.

Mechanical.

Check that the valves are indeed within tolerance and that the decompression cable free play is not set too tight and then check that your cam chain tensioner has not reached it's furthest limmit introducing a mechanical timing error. If you get the chance to drop the motor check also the cam timing marks.

Timing. Use a strobe and check against the manual that the timing is advancing corrrectly.

After this you are pretty much into the electronic side. Check all cable connectors are making firm contact. Use contact cleaner and then use a multimeter to check against the manual the various resistance tolerances, but honestly, when you get to this point, it's often best to trial fit a part be it coil, stator etc from a donor bike to find the error.

Goodluck.

Edit

Tufty wrote:

You can't directly check your CDI without a known good one to check it against. It's a process of elimination, where if everything else fails, your CDI is probably shot.

The 550 ignition system, being CDI and not TCI, is very simple. You don't need the reg/erct, battery, lighting circuit, etc. All you have is the generator, cdi, coil, plug, ignition switch and kill switch, the rest is entirely separate. Forget the battery circuit for the moment, it's utterly irrelevant.

You'll need a multimeter, and an electrical schema wouldn't go too far amiss either - here's one in italian - http://digilander.libero.it/XT_550/I...co%20XT550.jpg

First thing to do is to check the kill switch. All sorts of crap can get in there, they can block up and fail. It works by earthing the CDI, so the easiest way to test it is simply to disconnect it entirely. Check for continuity between the kill switch contact (where the black and white wire runs in) on the socket and the frame. continuity when in "off" position, none when in "run".

Now the ignition switch (key). Check for continuity on the black and white wire running in and running to earth. Again, only continuity when it's off / lock / park

Now check the wire feeding the kill switch / ignition switch from the CDI. There should be continuity between both ends (obviously), and *no* continuity from either end to earth. This is the black-and-white wire from the CDI.

All good? Time to check the "hot" side of the coil. remove the sparkplug, and reattach it to the plug cap. check for continuity between the centre electrode and earth (should be) and the outer electrode and earth (shouldn't be, as long as the plug is away from the motor. Common failure here is HT lead disconnect from plug cap, shot contacts in the cap itself, shot cap, bad connect from coil to HT lead, bad connect between coil and earth.

Test resistance of hot side of coil (resistance between orange lead into coil and plug electrode) against spec.

Test resistance of cool side of coil (orange to black) against spec.

all still good? Test continuity between orange from CDI to orange in to coil. should be good, with no continuity to earth.

Now check the generator. continuity between red and brown from generator, and resistances good. No continuity between red or brown and earth.

you can't really check the advance detector without a strobe, so plug and unplug repeatedly. contact cleaner if you have any. it's the 3-way connector from the generator with white/red, white/green and green wires.

If that all still checks out, it could well be your CDI that's shot. double-check the earths (black wires) on the CDI to be sure, and all earth connections to the frame, but that's about all you can check.

You can use a non-yam CDI to check, the easiest one to use is a C50/70/90 CDI (and has the benefit of being cheap as chips). This has no advance, so you connect to either the white/red or white/green pulser and the green, plus the red and brown. If you connect the wrong pulser your ignition will be too advanced, and it will throw you off when you kick it over. if you connect it to the right one, the bike should run, but you will only get about 3.5-4K RPM tops. This is all a last resort, though.

FWIW, my money is on something being earthed that shouldn't, or a bad connection on your HT lead.

Simon

[Beefy]

Did you ever sort this out I'm having the same problem with the fuel 4500revs and it holds back

Thanks

Beefy