B7100 Piston Installation
- Thread starter Schmotown
- Start date
Following this thread. Unless I missed another thread that you started, what prompted you to rebuild?
I purchased a very nice ~900 hour '79 B7100 about two years ago. After thoroughly going through it, cleaning it, and refreshing a number of aesthetic things, I put it to work pulling a finish mower. During the first summer the tractor performed perfectly - no issues starting, no smoke or blowby. The next summer was fine until about midway, and then I started noticing blowby. This noticeably increased until the mowing season ended and I parked it. Somewhat dejected. The blowby was visible right after starting it, and had significant pressure when covering the tube with a finger.
I finally dug into this Spring, adjusted the valves, disassembled & cleaned the breather screen, and did a compression check (using the glow plug bores). The numbers were a very disappointing 340psi, 180psi, and 190psi.
For now the tractor is parked while I decide what to do. It's far too nice to put up for sale. I grew up with an identical 1980 model, so I'd like to eventually repair this correctly and continue to enjoy it.
Andreas
On my L2850 I found that the low compression was caused by carbon build up on the exhaust valve seats. I lapped in some new exhaust valves and it’s great again.
Wallowed shaft due to missing/ bad key. If there was still a decent fit, a new key and some green loctite sleeve and bearing retainer would make it stay on permanently.
I bought a "well used" B7100 for a project that smoked terribly upon start-up but mostly cleared up a few minutes after running. Before rebuilding the top end and rod bearings (no carbon build-up) my compression readings were 240, 200, 220. Pitting on the head and valves (see previous posts) from what I presume was a leaking head gasket prompted me to buy a Kumar Bros. head. When I start it up I'll report back.