Won't idle.

[Stormin 9,981]

 Since rebuilding my C-125's engine, I've been unable to get it to start and idle properly. Starting tales a bit of juggling with choke and throttle, even when primed.

  Once started it will run fine when the revs are up. But it will not idle properly. Run for a bit then die. Also at low revs getting pops and sporadic bangs and flames out of the exhaust.

  I've had two different carb's on. The original and a rebuilt one by Anglo Traction. With either carb' the results are the same and adjusting the idle screw makes no difference to idling. Neither speeds up or slows down. Carb' manifold gasket and flange are ok.

  Points have been checked more than once. No sign of a leaking head gasket.

  Now my train of thought is leaning towards valve clearances. Although they should be ok. But I will be checking those soon. Bit cool in the workshop now.

 So now what thoughts do anyone else have? All suggestions appreciated. Just no rude ones.

 

[stevasaurus 22,764]

I'm wondering if your timing is not a tooth off from the cam shaft.  That would explain the timing advance when at high idle.  That is also the worse scenario.  

[gwest_ca-(File Mod) 11,046]

Have another condenser you can try?

 

Garry

[Stormin 9,981]

23 minutes ago, stevasaurus said:

I'm wondering if your timing is not a tooth off from the cam shaft.  That would explain the timing advance when at high idle.  That is also the worse scenario.  

 

Thanks! That'll be an engine strip. Not something I wanted to hear.

 

 I'll try another condenser first.

[squonk 41,155]

Popping and banging are usually one of 3 things:

Engine firing at wrong time. (not good) 

 

Engine still has fire in the hole when intake valve opens  (Worse) 

 

Dougie is in the kitchen popping corn and is banging around trying to find a clean bowl. 

[squonk 41,155]

At least nORM you can yank the head and see what your valves are doing at TDC 

[Stormin 9,981]

 That's what I've been thinking. I'll need to get a head gasket first.

[Bill D 1,926]

New plug wire?  Old one may be "leaking" which can cause problems at low speed.  Also try a new condenser.  Is the wire between the points and coil new?  If not, make a new one using high temp wire.  Try a different plug as well.  Tight valve clearances will also cause issues.  Bill

[ranger 1,750]

I had this problem with my C121 when I first got it Norm. When it warmed up it would only run at higher revs, no idle. 

It turned out to be the exhaust valve “tappet” setting - Too tight! Adjusted it, problem gone. 

 

Doug.

[Stormin 9,981]

15 hours ago, stevasaurus said:

I'm wondering if your timing is not a tooth off from the cam shaft.  That would explain the timing advance when at high idle.  That is also the worse scenario.  

 

   I've been going back over my rebuild thread. I couldn't be sure how far I stripped the engine. But just as I thought, the bottom end, crank, camshaft etc were not disturbed. So valve timing won't have been disturbed.

   I'm going to check the clearances later. I think it can be done without taking the head off. Thumb over the plug hole should tell me when coming up to TDC on compression stroke. By watching the movement of the valve stems, should tell me when they are both shut.

   First though I'll swap condenser and plug lead off one of the other tractors.

Edited May 9, 2021 by Stormin

[ebinmaine 67,619]

18 hours ago, Stormin said:

suggestions appreciated. Just no rude ones

 

 

I'm out. 

 

 

[953 nut 55,320]

2 hours ago, Stormin said:

Thumb over the plug hole should tell me when coming up to TDC on compression stroke.

The crankshaft keyway is aligned to TDC, when the keyway is at the top so is the piston.

[Stormin 9,981]

  Been having a play this morning. Change condenser and then plug lead. No change.

  One problem has been I think, I've been trying to get to slow an idle speed. I was brought up on long stroke ohv single cylinder motorcycle engines. So I decided to see what it was running at. Should be, according to the manual 2,100 rpm.

 I have a digital hand held rev' counter and after taking off the pto pulley so I could get at the end of the crankshaft it read, 2,090ish. Slight fluctuation but negatable.

  That'll do me for now.

[Stormin 9,981]

3 minutes ago, 953 nut said:

The crankshaft keyway is aligned to TDC, when the keyway is at the top so is the piston.

 

Now that's a usefull piece of info. Thanks for that.

[squonk 41,155]

nORMSTER, my Kohler manual says 1200RPM for idle. Where did you get 2100 or do you have dyslexia? 

 

If I ran my C-160 that high when I shut it off it would blow my muffler clear to Chineee! 

Edited May 9, 2021 by squonk

[Gregor 4,846]

If all else fails. This helped me a lot.

 

 

[Stormin 9,981]

mIKe. Just had a look in the Kohler manual in here. 1,200. I'll check what I have. 2,000 did seem some what high. And I do need to get an eye test.

[Stormin 9,981]

   Well I've had another go it this afternoon. First I checked the points gap. Was a little tight. Set at .020" thou now. What a maul to adjust those points. You need a touch like an elephants midwife.

   Anyway, after much messing about I've got it to idle? between 1,500 - 1,600. It'll run fine for about a minute or two then slow down, splutter and pop then die. I've removed the mixture adjusting screws and blown out the jets.

  I'm starting to wonder if the fuel pump is not delivering enough fuel at low rev's. I've two spare so I'll try those. Not today though. I've had enough.

 

BTW Squonk here's the manual print out I was given when I got the C-81. Doesn't  cover the C-125 but does the C-121. Same engine except for the throttle cable - governor set up.

 

Says A B C D down the left hand side.

 

 

 

[squonk 41,155]

You guys drive on the wrong side of the road over there so that increased idle speed will allow you to outrun the cops with out messing with the throttle! 

[squonk 41,155]

[ranger 1,750]

1 hour ago, squonk said:

You guys drive on the wrong side of the road over there so that increased idle speed will allow you to outrun the cops with out messing with the throttle! 

We drive on the same side of the road as you, we just happen to be going in the opposite direction.  🤪 There was talk of the UK changing over to driving on the other side of the road. They were going to Introduce the change over in stages, Cars and Bikes first, Vans and Trucks the following week.

Edited May 9, 2021 by ranger

[Stormin 9,981]

  Got the old girl onto the operating table this afternoon. The C-125 that is, not SWMBO.

  After taking off the bonnet/hood, next was the carb and one or two other bits so I could get to the breather cover. Exhaust was rather close. Not tight, but nowhere near what it should have been. Readjusted that and after making a new cork gasket put everything back together, except for the bonnet/hood.

  Fired up the engine and it was a little bit better, but not much. So I rechecked the points. 19 - 20 thou so are at 18.

  With the engine warmed up, set to too adjust the carb. After much twiddling, fiddling and got it to keep running just below 1600rpm. Any less  and it slows down, splutters and stops.

  Tomorrow I'm going to check the float level. Wish me luck.

 

[ranger 1,750]

52 minutes ago, Stormin said:

  Got the old girl onto the operating table this afternoon. The C-125 that is, not SWMBO.

  After taking off the bonnet/hood, next was the carb and one or two other bits so I could get to the breather cover. Exhaust was rather close. Not tight, but nowhere near what it should have been. Readjusted that and after making a new cork gasket put everything back together, except for the bonnet/hood.

  Fired up the engine and it was a little bit better, but not much. So I rechecked the points. 19 - 20 thou so are at 18.

  With the engine warmed up, set to too adjust the carb. After much twiddling, fiddling and got it to keep running just below 1600rpm. Any less  and it slows down, splutters and stops.

  Tomorrow I'm going to check the float level. Wish me luck.

 

Hi Norm, Is it at all possible for the A.C.R. Mechanism, (if worn / faulty), to cut back in whilst engine is running at low rpm’s and slightly opening the exhaust valve??? 🤔

 

Doug.

[Stormin 9,981]

No idea Doug. I hope not.

[Tuneup 1,433]

Sounds to me like your weak fuel pump suggestion has merit. try a gravity feed to see if the problem goes away (after you check the float height).