Club 80-90 Forums

Hi All

My air cool T25 has very high/fast idle. I've replaced the elbows on the servo side of things as they were perished. I've adjusted the chokes so they are working properly. I've replaced the throttle butterfly bushings and set the butterflys to a correct 0.065mm as per the manual.I've set the mixture screws on each cab to the guidline 2.5 turns out But it still revs very high on idle. If you loosen the distributer you can rotate this through about an 1/8th of its travel before any movement takes effect? I've sprayed eay start roun dteh carbs but it doesn't alter in its revs so I dont think its an air leak? So what te hell can it be? Any ideas or thoughts on what else to check gratefully appreciated!

Many thanks.

The setting for the butterflys is only a guide, adjust if wrong, the important thing is they are even side to side.

is it fast once off choke??

andysimpson wrote:The setting for the butterflys is only a guide, adjust if wrong, the important thing is they are even side to side.

Its such a small opening at hat setting though I cant believe that is the cause of its over revving?

jason k wrote:is it fast once off choke??

Yes.

You mention nothing of adjusting/setting the idle speed.
I assume you are still running the twin solex carbs?
If so the idle is not adjusted by the butterflies but by opening closing a screw at the rear of the LHand carb.
I'll explain further if you need me to, as reading this back it doesn't sound like a very thorough explanation.
Another thing which is sure to cause fast idle on any T25 is a sticking throttle cable.

Andy

NewarkNutter wrote:You mention nothing of adjusting/setting the idle speed.
I assume you are still running the twin solex carbs?
If so the idle is not adjusted by the butterflies but by opening closing a screw at the rear of the LHand carb.
I'll explain further if you need me to, as reading this back it doesn't sound like a very thorough explanation.
Another thing which is sure to cause fast idle on any T25 is a sticking throttle cable.

Andy

Hi Andy
Yes twin 34 solex pdsit. I found that adjuster but i can adjust that all the way in and it does slow the idel down but even with it fully in it doesn't cut out. But the idle is a lot more accpetable. I'm guessing this still isn't right though and I need to keep digging?

You may be too tight with 0.065, the correct gap is 0.1mm, if you are too tight then you will generate a lot of vacuum, this will hold the vacuum advance open on the dizzy, pull off the tube from the left carb to the dizzy, this should slow down dramtically, if this is the case then either remove the carbs and reset the gap or if you have a flow meter then set the flow down each carb to 7-8.5mbar at tickover.
Either that or you have a serious air leak somewhere, the favourite is the two small steel plugs at the back of the left carb in the idle bypass tract.
Hope this helps.

steve8090 wrote:You may be too tight with 0.065, the correct gap is 0.1mm, if you are too tight then you will generate a lot of vacuum, this will hold the vacuum advance open on the dizzy, pull off the tube from the left carb to the dizzy, this should slow down dramtically, if this is the case then either remove the carbs and reset the gap or if you have a flow meter then set the flow down each carb to 7-8.5mbar at tickover.
Either that or you have a serious air leak somewhere, the favourite is the two small steel plugs at the back of the left carb in the idle bypass tract.
Hope this helps.

I'll reset to 0.1mm anyway and then follow your advice.

Thanks to all for the help.