16.5 HP OHV - thought I had a compression problem

[IndyDude]

I recently traded a handgun for a Craftsman riding lawn mower.

The guy I got it from told me it was a little hard to start, but if you rotated the engine past the compression cycle that it usually starts right up. He was correct in that part.
After reading online, I found that there are a few things that cause high compression on these engines, so I initially adjusted the valves and that actually seemed like it solved my problem.
Now, a few weeks later, I have run into the very same issue where it is hard to start. I thought that it is possible that the valves have gone out of adjustment, so I looked at that again. Upon further searching, I found that some directions online for adjusting the valves are inaccurate. The big discrepancy is they say to rotate the engine 1/4" past TDC, when actually it is to rotate the engine where the piston moves down 1/4" past top dead center. Once I got that cleared up I was hoping it would start....nope!

I then found that it is possible that the compression release mechanism on the cam shaft could be faulty. After rotating the engine while viewing the rockers and valves, I can clearly see when the cam is rotated over the compression release, as the bottom valve slightly opens then closes, so I know that part of the system is in place and functional.
The next thing I read is that there can be carbon build-up on the head which could cause higher compression than normal. I pulled the head and inspected it. It really wasn't that bad, but I did clean off what bit of carbon was present.

I see that the starter has been replaced and seems to be one of the newest parts to the engine, but I am actually thinking that there may be a few coils inside that have heated up and thus isn't producing as much torque as necessary to rotate this bad boy. I did pull it off and disassembled it. I really couldn't see anything wrong, but it did appear that some of the coating was melted off of some of the coils. The brushes and everything else inside looked to be in really good shape.

I removed the spark plug and the starter can easily rotate the engine with no issues, but once the plug is back in, the compression is just too much for it to get it started. From everything I have read thus far. I think it is the starter and if I replace it that should solve my problems.

Anyone else have any ideas as to my trouble?

 

[ILENGINE]

Could be a starter problem, because the valves out of adjustment for any length of time can damage the starter. I would start by making sure that the battery cables are clean, and also check that the spot were the ground cable hooked to the frame.

 

[SeniorCitizen]

Have the starter tested before thinking of buying rebuilt or new. There are usually shops in towns of any size that do starter and alternator work and will test them. There is even one in my small jerk water town a few miles away.

 

[Fish]

Put up your engine's model numbers, as well as the clearances that you set the valves at, and go into detail how you determined tdc.

 

[IndyDude]

Put up your engine's model numbers, as well as the clearances that you set the valves at, and go into detail how you determined tdc.

31C707 Type: 023E1 Code: 040430ZE

Exhaust .005
Intake .003

Rotated flywheel while watching valves move up and down. After seeing both valves open and close, I continued to rotate flywheel until the piston was at TDC by using a screwdriver in the sparkplug socket. Neither valve moved when the piston moved to TDC.

 

[IndyDude]

I purchased a new starter off of eBay for $35.
I'll post an update once I receive it and get it installed....

 

[SeniorCitizen]

i done

 

[IndyDude]

i done

lol...just because I didn't take your suggestion to get the starter tested?

For what I purchased this new starter for, I can use it as a backup or parts when the other one gives out. Being that starters are one of the most widely replaced parts on a mower engine, I didn't see the harm in having a backup on hand.

To elaborate a bit more on my testing...

I thought my battery may have been part of the problem, but it isn't even 3 month's old. I charged it and my charger has a "start" mode in which the engine was still having the same issue where the starter wouldn't rotate the engine a full revolution.
I then removed the battery and used a set of jumper cables running directly from my Jeep while it was running to the starter connection and engine casing.
Again, the starter couldn't rotate the engine a full cycle.

That pretty much told me that the starter may have some issues, like the windings being melted as I had described earlier.
I can fairly easily rotate the engine by hand, so I don't think there is anything internal that is causing resistance as a problem.

 

[SeniorCitizen]

lol...just because I didn't take your suggestion to get the starter tested?

Not at all. Other reasons.

 

[IndyDude]

Not at all. Other reasons.

Reason enough to state that you are done, but not reason enough to elaborate as to why...got it.:thumbsup: