really high idle on 87 dt 140

[mike8353]

hey, Im having an idle issue, had the carbs off and when I put them back on the idle rpm goes straight up to around 4000 and dosnt come back down.
If I put it straight into gear before the revs get too high it runs really well and putts along at under 1000 rpm nicely, but as soon as I put it back to idle the revs run away again.
Ive had the silencer off and checked that the throttle butterflies are closing and they are, and its hitting the stop on the likage.
I havnt checked the timing yet but suspect that may be the issue. Am I right in thinking that the throttle valve sensor controls timing at idle?
I had the tvs hooked up at first but then disconnected it completely and it made no difference whatsoever.
Its frustrating because I took the carbs off for a different issue and it was idling fine before that.
How do I tell if the tvs is faulty?
Any advice would be great.
Thanks

 

[Inducted]

Re: really high idle on 87 dt 140

I'm not familiar with that engine BUT it probably has a mechanical timer base. The timer base moves and at idle it will move in order to advance the timing which will increase the rpms... Your rpms are to high at idle because one of your adjustment settings is incorrect. If you don't have a manual try to watch what happens when you shift from in gear to neutral some thing is probably set to high and restricting the timer base from moving. Good luck!!!

 

[99yam40]

Re: really high idle on 87 dt 140

If you read the other thread you posted this same thing on you will understand what affects the timing and what to check. Hopefully you have the service manual for your motor and can follow it's procedures on adjusting or at least testing the TVS

 

[mike8353]

Re: really high idle on 87 dt 140

Thanks guys. No I dont have a manual but one on the way so Ill have a look at the process in there.
It just seems pretty amazing to me that the revs can get that high through only a timing change when the throttle butterfly is closed unless there is an air leak or something, Anyway Ill see where that gets me.
Cheers

 

[99yam40]

Re: really high idle on 87 dt 140

You can check the timing with a timing light just like on an auto motor while waiting on the manual to see what it is doing