50 hour, Head Retorque
Mike Stuart, a defacto expert on Chinese tractors, recommends to check the head bolt torque on Jinma tractors when the 50 hour service is performed. It is simple procedure to perform, and should not take more than an hour or two. The general procedure is outlined below:
1) Let engine cool to ambient air temp.
2) Locate all valve cover bolts. The 2cyl engine has 6 bolts located around the cover edge. The 3 cyl has three bolts located in the center of the cover. Hood bracket and electrical items, maybe attached to some of the bolts. Note orientation and which bolts have the items. Unscrew and remove all valve cover bolts. Move electrical items and brackets aside.
JM204 TY290 Engine
3) Remove valve cover. The valve cover gasket may break into several pieces, some attached to cover and rest to head. Use a putty knife to scrape free of cover and head. Vacuum up the loose pieces.
4) Locate all head bolts. There are 10 bolts for the 2 cyl engine and 8 for the 3 cyl engine. Check the torque sequence pictures, further down, to varify you found all the bolts.
JM204 TY290 Engine with valve cover removed
5) Using the correct torque sequence for your engine, torque each bolt to 95-105 ft lbs. Note: Do not loosen the bolts first. You are only tightening them.
Close-up of JM204 TY290 engine head
6A) If you have a new gasket, lightly coat the surfaces with Permatex Blue RTV Silicone gasket maker, or equivelent. Align gasket on head, making sure all holes and edges are aligned. The RTV will hold the gasket from slipping.
6B) If you do not have a new gasket, you can place a small continuous bead of the RTV gasket maker around the valve cover mating surface of the head. Don't over do the RTV such that it will be squeezed and fall into the top of the head.
7) Align the valve cover over the head. Carefully set it on the head. Use a couple of the valve cover bolts and just get them started, to keep the cover in position.
8) Get all valve cover bolts started. Make sure you have mounted any bracket or electrical items. Tighten the valve cover bolts evenly. Start at the center, and work toward the ends. Don't have a torque spec for the valve cover bolts, but 3/8" socket wrench tight, should do.
9) Start engine, and bring up to operating temperature. Carefully check valve cover for oil leaks.
Engine Head Torque Sequences
Y385 Torque Sequence, used in JM254/284
TY290 Torque Sequence, used in JM184/204/224
Torque sequence, torque spec, and info provided by Mike @ Maverick Tractor
JM204 head photos provided by Glenn @ Coastal Tractor and Equipment
Links to their websites, will be added soon.
