I just purchased a Bolens ST 160 tractor off of craigslist. the seller new little or nothing about the history of the tractor. It looked good: tin was excellent, oil clean, full, motor would spin (by hand). I jumped it and I heard the starter spin, but no engine crank. I decided to buy.

Now, at home I tear into the engine, found the bad pinion gear on the starter, replaced it and HOORAY the engine fired right up! Only problem was the hydro unit squealed in forward, and silent in reverse with no movement. Now, I am thinking what a dumb #@##@@%%! I am, buying junk!

Then, I found the valve that puts hydro in "free wheeling", flipped the valve and YEEHAH! back in business!

Except: for a sixteen horse, the power felt low. I found out number one cylinder was not firing at all. No spark. In addition, the compression was only about 30#.

So I need help. I am savvy with some briggs engines, not this v twin.

Model 303777-0017-02. I found the magnetron (one of two), the lead to the plug chewed badly by a rodent. pretty easy fix for that...I just have to get the part.

the compression is another issue. I went to check the head bolts and found two very loose, one actually ready to fall out. I took the valve cover off and the two pushrods just sort of fell out. Is this normal? wouldn't the intact rocker arm keep the push rods in place?

the manual says exhaust pushrod is aluminum, intake steel. Both of these pushrods grab my magnet......could the push rod be wrong?

It looks to me like the head gasket was leaking.

I don't know if someone tried to fix this engine, and put back together with wrong parts or ?

any, and all help appreciated!

Ed

 

Well, here is some additional info. the exhaust valve guide had slipped upward. I could feel the valve would only depress 1/8th inch or so. After popping the spring I could see the valve guide raised up 1/4 inch. the push rods were not bent, just both steel, instead of exhaust side aluminum.

I have now read this is common in Intek, but not so common in Vanguard engines. Overheating is blamed and I can testify I found a dead mouse, and his whole house wrapped around the side of the #1 cylinder.

I am in need of Walt's repair system for these raised guides.

Walt C. can you help?

 

I would start by replacing the head gasket. The gasket with the loose head bolts may account for the low compression. Certainly the valve drive would. The valve pushrods shouldn't fall out. The rockers set to the correct clearance (usually .005) will hold everything in place.

I would get everything back in place and valve clearances set correctly and see where you are with the compression.

You might try peening the aluminum around the guides to tighten those. They should be tight in the head.

 

marbobj, thanks for the feedback. yes, I will address the head gasket and set valves etc. my concern now is for this valve guide that migrated up. I have read that this happens a lot on these v twins.

hoping to find how to "fix" this, so I don't end up tearing everything apart a month from now.

 

Peening is often used to tighten a valve seat in aluminum and that would be a more difficult fix than a guide. This is assuming the guide just moves up and down a little, but is still tight enough to stay on its original line.

If it has movement side to side it may need machine shop work or replace the head, whichever is cheaper.

 

Peening can be done, but I would be tempted to just hop on ebay and pick up a used head cheaply. Vanguards are really good engines (the Japanese made ones are anyway), so this would be a worthwhile repair. If the guide fails again, you might not be so lucky as to avoid damage the next time. These engines don't have clearance for the valve to be hanging open and the piston to come around to TDC without hitting the valve. This can bump the valve back closed, poke a hole in the piston, break the valve off int he cylinder and then gouge the cylinder, ruin the head, etc... The vanguard in my generator did that... ruined the piston and head but not the block.

 

Cheese, thanks for the good information. I checked both heads and only the guide on #1 moved. Due to the mouse house packed around the cylinder, it seems overheating could have indeed caused the issue. Maybe I got lucky and a loose valve clearance adjustment allowed my pushrod to pop out of position and saved my piston?

Since my last post, I took the head to the local machine shop to replace the guide. His suggestion was Loctite and peening. I am waiting for the head work to be done. After I put it back together, I will keep an eye on it periodically by pulling valve cover and checking.

ebay used head ?. how would that be better than my head? are there different designs, or do you think my overheated head Loctite/peened, wont grab the new guide as tightly as one that has not moved?

 

I'm really not sure if one that has been repaired would be less viable than one that has never moved or not. If the job is done right, it shouldn't ever move again. I'd just hate for it to come loose again.