D17 Runs poor after rebuild

CNH Guy

New User
Looking for advice. I'm helping a friend who has a D17 that, as I understand, has new pistons and sleeves and a valve job done as the engine was getting weak. Prior to the work it ran decent but smoked. Upon reassembly it will start pretty decent but the RPMs surge, it smokes bad and floods out. We went through the carb, verifying ALL passages are clean. Installed a new float and set the height to spec. The only issue I saw with the carb is the needle jet that the fuel mixture main screw threads into is dinged up where you'd put the screwdriver and the needle would pass into.

When running the engine will surge, and cannot be controlled manually with the governor lever or when disconnected from the gov. From idle to WOT it more or less does what it wants. We can impact the air fuel mixture enough to make it lean backfire. He says the intake manifold is new. We verified good compression (118-122) on all cylinders. Also to note is raw gas will actually leak from the spark plugs. New points and condenser and strong spark, and it pops right off when starting.

What are we overlooking?

Thanks!
 
Why a new manifold?? Sounds like a bad case of China junk manifold and it has vacuum leaks and or passageways that are not up to spec.
 

I'm unsure why a new manifold, I'll have to ask. I cannot see signs of external leaks, though wanted to use some propane gas around it to see if I could verify. However, wouldn't a poor seal or fitment result in a lean burn?

Thank you!
 
Any vacuum leak WILL CAUSE AN ENGIEN TO RUN ODDLY. RPM higher then they should be and some times hunting and other such things. A poorly made manifold will also cause all sorts of odd next to impossible things to find problems. Also having the firing order off like say to plug wires crossed so runs on 2 cylinders and fires wrong on 2 cylinders
 

We did verify proper firing order, so that's squared away. There is no doubt it is running very rich due to the black exhaust and raw fuel from spark plugs and even carb to manifold mating surface.
 
I don't see anywhere that you've used a TIMING LIGHT and set the timing at the "FIRE" or F-25 mark on the flywheel with the engine at wide open throttle ?? Sounds like you have multiple issues. I'm assuming the pistons and sleeves are after-market?? because a D-17 has 140-145 psi of compression with OEM pistons/sleeves.
 
(quoted from post at 10:20:46 04/06/18) I don't see anywhere that you've used a TIMING LIGHT and set the timing at the "FIRE" or F-25 mark on the flywheel with the engine at wide open throttle ?? Sounds like you have multiple issues. I'm assuming the pistons and sleeves are after-market?? because a D-17 has 140-145 psi of compression with OEM pistons/sleeves.
Pistons and sleeves were installed at a machine shop. The intake was on prior to and the engine ran normally with it, at least at that point. The crank, cam and base timing were not altered at any point of the procedure as I was to understand. That said, I was not able to verify the timing with a light as we wanted. That will be something we do, thank you. I believe the tappets are adjusted as per spec also, but will double check.

Thanks!
 
(quoted from post at 10:20:46 04/06/18) I don't see anywhere that you've used a TIMING LIGHT and set the timing at the "FIRE" or F-25 mark on the flywheel with the engine at wide open throttle ??

Also, there is currently no WOT as the engine will not vary the RPM even manually adjusting the carb linkage.
 
Does it run better with the air cleaner unhooked?? If it does air cleaner could be clogged up
 
(quoted from post at 12:25:04 04/06/18) Does it run better with the air cleaner unhooked?? If it does air cleaner could be clogged up
We tried that also, make no change hooked up or unhooked.
 
Any chance when they rebuilt the carb that they left out the float needle seat gasket?? Or the float it self is bad and does not float like it should
 
(quoted from post at 13:22:35 04/06/18) Any chance when they rebuilt the carb that they left out the float needle seat gasket?? Or the float it self is bad and does not float like it should
No, that is all good. I did it myself and reopened it last night and checked again. Float is new and the fuel flow does shut off when the bowl fills.
 
Ventura upside down?? Or maybe the main jet is wore out to the point it lets way to much gas through. Can you turn the main jet adjustment all the way in and kill the engine?? If not then that is the area of the problem
 
(quoted from post at 13:41:43 04/06/18) Ventura upside down?? Or maybe the main jet is wore out to the point it lets way to much gas through. Can you turn the main jet adjustment all the way in and kill the engine?? If not then that is the area of the problem
I double checked the venturi wondering if it was upside down, but it does have two notches that allow it to fit "properly" just one way. I was able to turn the main in all the way, the engine would only run on choke then. I tired to slowly adjust it in after it was running to find a sweet spot and it goes from the blubbering and surging to a lean backfire through the exhaust then it stalls.
 
If you put your hand over the air intake of the carb when trying to start it do you get a real good suction and gas on your hand??
 
When its running shoot some ether around the intake ports on the manifold. You'll discover real quick if you have a leak. Is the throttle and choke operating properly? Something about this makes me think the gov linkage is all wonky.
AaronSEIA
 
I'll try the hand over the carb intake, my hunch is it is a good suction but we'll verify.

The throttle and choke both operate properly, I've disconnected from the governor and even manipulating the throttle manually makes no difference. When hooked to the gov the governor does try to maintain a stable RPM range as well, best I can tell.
 
If running the throttle plate by hand makes no difference, it almost has to be a timing or spark issue. Timing light is in order. You could try pulling plug wires one at a time, but start by verifying the firing order and plug wire orientation.
AaronSEIA
 
(quoted from post at 14:24:59 04/06/18) If running the throttle plate by hand makes no difference, it almost has to be a timing or spark issue. Timing light is in order. You could try pulling plug wires one at a time, but start by verifying the firing order and plug wire orientation.
AaronSEIA

I certainly want to verify base timing, just to eliminate that possibility. I know the firing order is correct, we checked that last night.

Thanks!
 
You also might try new plugs. I cannot remember if the NGK3112 is correct for the D-17 but that is what I have in the WD45 I have due to it fouling plugs pretty fast
 
Which carb do you have the Marvel Schebler or Zenith. I am think you have a problem in the carburetor. Find a diagram of the carb you have and take yours apart piece by
piece and verify you have all the parts. I realized you took the carb apart and checked to see if its clean but if all the jets seem clear still doesn't mean its ok.

Also please check to make sure the linkage isnt backwards on the choke. If its choked all the time it will start but smoke and flood out

YT has a rebuilt carb for that tractor part #1128 carb and its a Zenith.

My 17 uses the Zenith
 
I just re=read your original post. Please re check the valves. 118-122 is not good compression on a D17 with new
pistons and sleeves. It should be around 150 psi. If the valves were set tight it could also cause some of the issues
you now have.
 
(quoted from post at 21:38:04 04/07/18) I just re=read your original post. Please re check the valves. 118-122 is not good compression on a D17 with new
pistons and sleeves. It should be around 150 psi. If the valves were set tight it could also cause some of the issues
you now have.

The carb is a zenith. When apart I did verify the passages are all open and the jets are the correct size per the manual. The compression should be rechecked, we used a small engine gauge as that was all we had at the moment. That said, all cylinders being equal, well within 10% anyway, it seems it should still be able to idle, run mid range or high RPM yet it really does none of those three. The choke linkage is correct, and does operate normally. Having said all of that, is there something with the sleeves that could cause intake/exhaust bleed from cylinder to cylinder if something isn't correct?
 
Please; I realize you have tried and checked a lot of issues but PLEASE check the valves. I think you are a little tight on 2 cylinders. Intake exhaust bleed as you
described is caused by a tight valve setting. Pull the plugs and take the time to roll through and check to valves for each cylinder.
 
(quoted from post at 08:43:55 04/09/18) Please; I realize you have tried and checked a lot of issues but PLEASE check the valves. I think you are a little tight on 2 cylinders. Intake exhaust bleed as you
described is caused by a tight valve setting. Pull the plugs and take the time to roll through and check to valves for each cylinder.
Are you saying we should recheck the lash at lifter to rocker measurement?

Thanks!
 
Yes

Check the lash at the lifter to rocker measurement. You can do that cold, meaning the tractor does not need to be running. Its easiest to pull the plugs and roll the
tractor engine by hand to get the right valve lash. If you have an IT service manual it should explain how to do it.

You start by turning the engine by hand until the front piston is at top dead center. The valves should be set at .012 -.014 hot. I normally set mine at .012 cold. All
gas 4 cylinder Allis engines can be set with number 1 piston at TDC on the compression stroke. This will allow Exhaust (E) and Intake (I) valves to be set. It also
allows the (E) valve on number 2 cyl and (I) on number 3 cyl to be checked for valve clearance.

If you turn by hand the engine and bring the #4 piston at TDC on the compression stroke you can check tappet clearance for (E) and (I) on #4 plus (E) on #3 and (I) on
#2

By concentrating on those 2 cylinders 1 and 4 you can check tappet lash/clearance on the entire engine.

Since your having engine problems, a cold valve set may help solve your issues or at least not add to other problems. Once you have fixed your trouble then you can go
back and recheck the valve clearance with a Hot engine.
 
Save yourself a lot of work and adjust all valves to .015" COLD. No need to recheck when hot. Been doing it like this for 45 years and haven't ever done one hot yet.
 
(quoted from post at 13:50:25 04/06/18)
(quoted from post at 13:41:43 04/06/18) Ventura upside down?? Or maybe the main jet is wore out to the point it lets way to much gas through. Can you turn the main jet adjustment all the way in and kill the engine?? If not then that is the area of the problem
I double checked the venturi wondering if it was upside down, but it does have two notches that allow it to fit "properly" just one way. I was able to turn the main in all the way, the engine would only run on choke then. I tired to slowly adjust it in after it was running to find a sweet spot and it goes from the blubbering and surging to a lean backfire through the exhaust then it stalls.
I had a lot of problems with my D 17.
The tractor guru told me to buy a good quality set of points and condenser from Napa or Advance auto. I did and it came out of it,'
So I recommend the same thing.
 

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