tink tink sound on back off when hot on a 2 rattle

[shelpi]

ok you 2 smoke Guru's what are all the possible causes for a slight metalic tink tink sound on back off, ie timeing, air leak? did do before rebuild so took liberties to check all but its doing it again the culprit is a suzuki t250 with 350 pots and carbs, could air leak threw the topsof cabs do it? plug reading good and goes hard and starts great hot and cold

[Montynut]

Do you have the bike set up to idle? If so try backing the idle off to just a dead throttle therefore no air entering the engine with throttle closed. I always have 250 and larger MXers set as dead throttle

[shelpi]

Do you have the bike set up to idle? If so try backing the idle off to just a dead throttle therefore no air entering the engine with throttle closed. I always have 250 and larger MXers set as dead throttle

yer me to, but oddly enough not on this one cheers will give it a go

[bazza]

Did you check compression? What type of fuel (eg 98 octain?)

[VMX60]

Check all the ex/pipe mounting springs are not touching the pipe or the thread has not pulled the pipe up to the barrel if using the std fittings if it was their before this motor Maybe 

[shelpi]

Did you check compression? What type of fuel (eg 98 octain?)

yep 98 octane with 1% 2stroke oil in it

[shelpi]

Check all the ex/pipe mounting springs are not touching the pipe or the thread has not pulled the pipe up to the barrel if using the std fittings if it was their before this motor Maybe 

have looked and will look closer for mecanical clash, cant see any, but sounds like left cylinder only

[evo550]

Do you have the bike set up to idle? If so try backing the idle off to just a dead throttle therefore no air entering the engine with throttle closed. I always have 250 and larger MXers set as dead throttle

2t engines will always draw air into the engine through the carb no matter what the idle setting, the slide cutaway doesn't seal the throat entirely. The problem with no idle is no fuel which means no lube. Not much of an issue with MXers but old 2t air cooled roadies it's a diff story.
No idle on big bore mxers is mainly to prevent overshooting of corners 

[bazza]

yep 98 octane with 1% 2stroke oil in it
Is that 32:1 ?   What brand of oil?

[shelpi]

yep 98 octane with 1% 2stroke oil in it
Is that 32:1 ?   What brand of oil?

Nah still running the posi drive oil pump system which also feeds the main bearing, the oil recommended by trev Otto is castrol 2t

[shelpi]

Do you have the bike set up to idle? If so try backing the idle off to just a dead throttle therefore no air entering the engine with throttle closed. I always have 250 and larger MXers set as dead throttle

2t engines will always draw air into the engine through the carb no matter what the idle setting, the slide cutaway doesn't seal the throat entirely. The problem with no idle is no fuel which means no lube. Not much of an issue with MXers but old 2t air cooled roadies it's a diff story.
No idle on big bore mxers is mainly to prevent overshooting of corners 

its now a Motocross sidecar, so what do ya think, try back the idle of?

[Montynut]

Do you have the bike set up to idle? If so try backing the idle off to just a dead throttle therefore no air entering the engine with throttle closed. I always have 250 and larger MXers set as dead throttle

2t engines will always draw air into the engine through the carb no matter what the idle setting, the slide cutaway doesn't seal the throat entirely. The problem with no idle is no fuel which means no lube. Not much of an issue with MXers but old 2t air cooled roadies it's a diff story.
No idle on big bore mxers is mainly to prevent overshooting of corners 

Actually the engine side of the slide does cut off virtually all air if allowed to hit bottom and some fuel always enters through the idle circuit due to the vacuum on the engine side of the carbie via the air screw. But you are correct with most road bikes having an idle set but I don't think it is for the reasons you describe. Most TZ road racers (well they did back in the day) are set up with dead throttles. Over-run siezures are possible but not common under normal operating conditions.
Yes I realise that the main reason for the dead throttle on larger bore MXers or anything for that matter (most top trials riders in the non stop era used dead trottles) is to stop 'push' in corners.

[shelpi]

Do you have the bike set up to idle? If so try backing the idle off to just a dead throttle therefore no air entering the engine with throttle closed. I always have 250 and larger MXers set as dead throttle

2t engines will always draw air into the engine through the carb no matter what the idle setting, the slide cutaway doesn't seal the throat entirely. The problem with no idle is no fuel which means no lube. Not much of an issue with MXers but old 2t air cooled roadies it's a diff story.
No idle on big bore mxers is mainly to prevent overshooting of corners 

Actually the engine side of the slide does cut off virtually all air if allowed to hit bottom and some fuel always enters through the idle circuit due to the vacuum on the engine side of the carbie via the air screw. But you are correct with most road bikes having an idle set but I don't think it is for the reasons you describe. Most TZ road racers (well they did back in the day) are set up with dead throttles. Over-run siezures are possible but not common under normal operating conditions.
Yes I realise that the main reason for the dead throttle on larger bore MXers or anything for that matter (most top trials riders in the non stop era used dead trottles) is to stop 'push' in corners.

cool dead throttle gets a go. cheers thanks fellas and would be interested to hear if anyone else has incounted this problem.

[GMC]

Soft springs on one chamber allowing it to vibrate on and off the spigot can make a rattly noise

[shelpi]

Bingo  backed off the idle and its gone  as soon as I throttled it up to old setting it came back no throttle gone, and 2ndarry effect may need to turn the idle air scews in a twig
Thanx Montynut and Evo550