Two Stroke help needed :(

[Racey Rider]

I should be on my way to Taupo about now to race tomorrow...
Be here I am with oily fingers making a mess of the keyboard.

Why won't my 150 stop reving???

Every time I start it, it sits at 6000rpm and won't idle.
The throttle cable is not jammed. (Carb slide is closed)
Reeds look ok.
Carb internals look fine.
No leaks can be seen on the intake track.

I can only presume a seal is leaking sucking air in somewhere.



Any other ideas??

Racey.

[cowpoos]

something stopping the needle closing off the jet in the carb or sunthing...its obviously constantly fueling...just pull the whole carb apart and clean it...and also chech the throttle cables working 100%....

[Motu]

Check that the slide is closing with the engine running,vacuum can stick it to the bore....maybe stretch the spring a tad.Squirt around with CRC checking for an inlet leak....take the mag cover off and squirt the left main.

[Racey Rider]

Thanks.
I can see the carb slide/needle is closed while the engine is running.

Could be the seal behind the rotor, but I can't check that with motor running, as it needs that Magneto in place to make it run.

Might be a shop job now. But just checking with ya's to see if I forgot someything simple.
Will use the crc check for leaks where I can.
Cheers.

For Poos:
Thanks.
I can see the carb slide/needle is closed while the engine is running.

Could be the seal behind the rotor, but I can't check that with motor running, as it needs that Magneto in place to make it run.

Might be a shop job now. But just checking with ya's to see if I forgot someything simple.
Will use the crc check for leaks where I can.
Cheers.

[limbimtimwim]

Ultra lean? But usually it races off once the engine is warm, not straight away.

[Karitane pete]

Ultra lean? But usually it races off once the engine is warm, not straight away.

Yep you got an air leak, pull the choke and see if the rev's drop.
Two stroke outboards do this when running on the hose, a flick of choke brings them down.

[DEATH_INC.]

You do realise the carb won't need to be open bugger all to make it rev heaps unloaded? Double/ quadruple check that its shutting all the way, you should be able to kill it even with an air leak if it'll shut enough (it'll go too lean to run) wind the idle out all the way and try again....

[Racey Rider]

Could it be something electrical???

I have replaced that old motor with a new one (only 350km on it), and it is still not idling. Have installed with the new motor it's new carb, new intake rubber, tried the new Boost bottle (between carb and motor), But the bike is fluctuating between 4000 & 5000 rpm. No kinks in the throttle cable. Slide is shutting down in the carb. Used the new motors Magneto system.

This new motor was running/idling perfectly yesterday before I changed it into the race bike. A bit rich still if anything. The only change I made was to move the carb needle clip from the lowest groove to the middle groove. as they setup these bikes to run rich. (yes I will try putting it back in the lowest groove).

Time to get the BIG hammer out and HIT things I think!

[Motu]

So what's the same??

[Racey Rider]

Well, there's a few little electrical things under the fuel tank.
One of them could be a coil or something??

Spark plug cap is the same.
Exhaust is the same, but shouldn't cause this problem.

I have spares,, so will change one at a time and see what happens.

[stanko]

The only thing that can make the motor rev is if ther is too much air gettin in. maybe the throttle slide isnt as closed as you think. disconnect the throttle cable from the slide and see if it idles slower. does it speed up slow down if you turn the handle bars let to right . did you adjust the carb in any way on the new engine. are you using the slide from the old carb or the new one. Remember without the extra air it cant rev, its getting in somewhere. Is there a vacume operated fuel tap on this bike , ? is it connected ? that would give it a few revs.

[Racey Rider]

The solution I found was to remove the 'straight through' muffler that I had on it from my 'B' model bike, and put on the 'A' model muffler which is longer and has a blocker in mid muffler. This produced more back pressure, and caused the new motor to idle as expected.

Now that I have more time, I will but the old motor back in the other frame and do more testing on it to see if it still wants to rev at idle.
One day I'll spilt the caseings I guess and teach myself how to get it back together after a reseal.

Thanks for the help.
Racey.