Model 70 Engine issue

[Horseshoe1970]

I rebuilt a model 70 with original engine. New everything. Runs beautifully for about 10 minutes, then it appears to bog down like it is under too much load. Not sure what is going on. New piston, rings, connecting rod, valves, gaskets, carb, plug, wire. Starts right up, and runs great for 10 minutes or so. anyone have any ideas?

 

[glippert]

Horseshoe1970 - I can't answer your question, but I have a suggestion: You should consider moving your question into the main forum area
(IH Cub Cadet Technical Forums), where more people will likely see it and respond. This area (IHCC Forum Tech Support and Questions) is intended for introductions and questions about the forum itself. Just my two cents worth.

Either way, welcome to the forum. A lot of the members here have a ton of knowledge on these old tractors!

 

[bfleisch]

Did you check the ring end gap before installing? When I rebuilt my k161 on an original I was surprised that the ring end gap was almost nonexistent with the new Kohler rings. I had to file them down until I got the correct end gap. Just wondering if when it starts to heat up they might be binding. You didn't say if you had any work down on the cylinder walls. Did you just replace with same size parts?

 

[mfrade]

Welcome to the site.

Have you done any of the easy checks? Like is the fuel cap vent actually open? Or have you flow tested the fuel line at all?
It could also be something like the coil is breaking down or the condenser is failing. A simple check might be to run it until it fails and once it does (quickly) pull the plug wire and see if the ignition system is firing the plug. It's going to take a process of verifying and elimination of possibilities.

 

[dschwandt]

Hmmmm…..
And all this has what to do with.???..

IHCC Forum Tech Support and Questions
Information and questions on how this forum software runs, etc.

 

[Horseshoe1970]

Okay! Tried the following suggestions:

1. Gas Cap venting. Gas cap was venting properly. I even removed the cap drilled the hole a size bigger and replaced the gasket making sure new gasket hole lined up with hole in cap. No improvement.

2. Coil. I had the original coil and replaced the new coil with the original. No improvement.

3. Condensor. I replaced the new condensor with the original condensor. No improvement.

New finding! I did notice that when the issue occurs I could see backfire flame in the muffler. Too Much Fuel? I also notice when I first choke the carb for startup the exhaust is black. This is new carb, adjustment per the book. I do not have the original carb to swap and see if that improves the situation.

Anyone have any advice?

 

[mgonitzke]

Sounds like the timing is off. Grab your multimeter and check it with these instructions.

 

[kashaver]

Flame in the exhaust leads me to believe that your exhaust valve is not closing properly when the engine gets hot. Check the valve adjustment one more time. Did you do anything like replacing the valves or guides?

 

[Horseshoe1970]

Yes the valves were replaced with new ones, ground and seated. I have been leaning this way as well. I really did not want to pull the engine again, but looks like I might have to

 

[mgallas]

Long shot... check the breather and make sure it’s venting? Installed correct or clogged passages!

 

[dramsey]

Okay! Tried the following suggestions:

1. Gas Cap venting. Gas cap was venting properly. I even removed the cap drilled the hole a size bigger and replaced the gasket making sure new gasket hole lined up with hole in cap. No improvement.

2. Coil. I had the original coil and replaced the new coil with the original. No improvement.

3. Condensor. I replaced the new condensor with the original condensor. No improvement.

New finding! I did notice that when the issue occurs I could see backfire flame in the muffler. Too Much Fuel? I also notice when I first choke the carb for startup the exhaust is black. This is new carb, adjustment per the book. I do not have the original carb to swap and see if that improves the situation.

Anyone have any advice?

The black exhaust on starting with the choke is perfectly fine.
So at what point do you see the backfire flame in the muffler?
Your running issue really sounds like fuel starvation. IF I recall I believe the 70 has the glass fuel sediment bowl with a shut off valve. If you have the bowl check the fuel level in the bowl, check the shut off valve to insure it is completely open and not clogged.

 

[bfleisch]

You don't have to pull the engine to check the valve lash.

 

[bharvey]

I would replace fuel line from gas tank to engine. It is very possible that it is collapsing on the inside. These same symptoms happened on one of my cubs.

 

[dray]

Have you checked the float in the carb? Could be getting fuel in it. Do you have another fuel supply you could test with or you could use a clear fuel line for testing. Will it start back while it's hot? Just some thoughts.

 

[buck]

HI BUCK HERE, I WOULD SUGGEST TRY THIS,RUN IT UNTILL IT QUITS, IMMEDIATELY TRY TURNNG THE ENGINE OVER BY HAND, IS IT STIFF, IDENTIFY YOUR ISSUE, IS IT RUNNING OUT OF RUNNING CLEARANCE, STIFF RINGS, SEIZING EXH VALVE, OUT OF FUEL U SAY IT HAS PLENTY OF FUEL, DOES IT HAVE SPARK?? AS SOON AS IT QUITS TEST FOR SPARK, sorry my finger bumps caps lock and i dont spot it rt away, if you eliminate whats wor4rking, then whats left is whats not working, back when i worked on briggs i used to test mags by turning the flywheel by hand, if it was sharp i cud tell what it needed, capacitor, points filing, whateber, cant do that anymore, pacemaker,, if it has a flywheel, as soon as it quits, get plug wire in one hand and, gently turn the flywheel sharpness will tell you if u have a week spark, if you have a wico impulse type magneto, dont do that!!!!!!!, it will screw your penis into the ground like a screw type dog stake, take my word for it dont hold an impulse magneto and turn it!!!!!

 

[Horseshoe1970]

I do know that after it quits, the engine is harder to turn over. If I let it sit for an hour or so it will start right back up. I will try your sugestions when I get back to Indiana. I just retired and the wife and I are spending January in Florida.

 

[buck]

OH as soon as the engine quits, IMMEDIATELY turn the flywheel by hand, does it have compression?? if it does not then perjaps you do have an exh valve trying to hang open, as iin valve stem bind, all the things these friends have suggested have merit, once you have elimenated those things then u have a fresh field of possibilities to look at but do the obvious easy to check stuff first, buck, have fun, let us know what u found

 

[kzintner]

You don't have to pull the engine to check the valve lash.

I have a model 70 too (see photo). It’s my 2020 project. As I get into it I possibly can help contribute.

 

[buck]

oh i see your up,, do you mean it is physically harder to turn over???
if so then its going to have to come back apart, id start wi ring gap as your friend suggested he has a similiar issue, also did u replace piston?? mebbe something to that too, but if u only renewed the rings id look at that

I do know that after it quits, the engine is harder to turn over. If I let it sit for an hour or so it will start right back up. I will try your sugestions when I get back to Indiana. I just retired and the wife and I are spending January in Florida.

if your engine is stiff, hard to turn over, then bite thhe bullet, tearit down, you have something certinly binding, probably the new rings or perhaps piston and ings, to continue to run is asking for trouble a scored cylinder, something, there are no easy no work answers, , u must go back in there, its a tough job but somebodies got to do it,, take your compression rings off the piston and use the piston to push them back into the cylinder so they are square to the bore, chek the end gap, if it doesnt confirm to book specs, make it so, this would also be a good time to chek the piston fit with feeler guages, look for scores, if that engine has stalled a few times u will have some scoring,, polish them out, buck, give your lil engine every chance for a long and happy life, buck