Wed Oct 13, 2004 5:47 pm
A neighbor had his cub worked on, and after the shop kept it several months and never got it running right he picked it up and left it setting in his barn lot for 3 or 4 years. About 2 months ago he rought it over and asked if I would try to get it running right when I felt like it. I rebuilt the carberator, and timed it.
Today I decided to give it a try. It started easy, but there was no power and if the throttle was suddenly advanced it would die. I rechecked the timing and switched carbs with my 48. Problem stayed with the neighbors cub. Listening to the intake I hear the intake valves opeing, and the intake sounds like an engine under load. Exhaust (underslung) sounds normal and very quiet. I don't know what the shop did to it but the block has been sprayed with primer, so I assume it was probably ovehauled. I had always assumed a cub would be hard to start if the camshft were off by a tooth, but this one makes me believe it is off. I have not pulled the head yet to check when the valves are opening. Any Ideas?
Wed Oct 13, 2004 6:22 pm
John,Just because the blocks painted (paint covers up a mulitude of sin.)Check Governor?or late valve timing?I'd come over but I have to watch the Yankee game on t.v. tonite.Do me a favor and and have your Cards beat Houston. So we can have a World Series like 1964
Wed Oct 13, 2004 6:25 pm
John, since it has sat quite a while on a fresh rebuild, could maybe be low compression???
Would you be able to check when the valves open by pulling the side plate?
Wed Oct 13, 2004 6:59 pm
Just got off the phone with the owners son. He said the shop that worked on it installed new rings, valves, etc., and it has had the symptoms I described ever since. I can tell if the valves are opening and check the clearances from the side cover, but don't think I can tell when they are opening in relation to the where the pistons are without pulling the head. I have a motor from a parts tractor I can use as a reference.
Wed Oct 13, 2004 7:08 pm
Before you pull the head, try just pulling the plugs and putting a piece of wire (coat hanger ect.) in the cylinder (at an angle) that should tell you where the pistons are in relation to fire or valve opening, assuming the side plate is off.
Wed Oct 13, 2004 7:53 pm
Regardless of valve timing, the pointer should still find the TDC mark on the pulley. With the pointer lined up it seems either #1 or #4 should have both valves partly closed... at least enough to use up the clearance. (overlap)
Thu Oct 14, 2004 12:18 pm
I'm with George on this. Try putting a .002 feeler gage on the #1 intake valve lifter. Rotate the engine until you have the .002 when the intake valve is closing. This should put the engine right at TDC.
I'm not 100% sure of the .002 gap for the Cub - but that's the double check for the correct gear mesh on old Allis engines. This should be close enough to tell if the Cub is one tooth off.
Thu Oct 14, 2004 1:38 pm
I&T manual, IH-8, page 23, paragraph 56 has the check for correct valve timing. Basically crank engine until the #1 cylinder exhaust valve is closing and intake valve #1 cylinder is just beginning to open (all lash taken up). The DC notch on crank shaft pulley should be approximately 13/16 past the pointer on the crankcase front cover.
Thu Oct 14, 2004 10:04 pm
Thanks fellas, had to go to the Dr. today to get some insurance forms taken care of. Takes nearly all day to make a trip to the city from here. I plan to check it tomorrow. I never thought to check the service manual for how to check valve timing. Told you I was having memory problems.
Fri Oct 15, 2004 4:00 pm
Eugene wrote:I&T manual, IH-8, page 23, paragraph 56 has the check for correct valve timing. Basically crank engine until the #1 cylinder exhaust valve is closing and intake valve #1 cylinder is just beginning to open (all lash taken up). The DC notch on crank shaft pulley should be approximately 13/16 past the pointer on the crankcase front cover.
As Eugene pointed out the I&T manual IH-8 (cub, A, B, C, H, etc.) calls for 13/16. The I&T manual IH-150 (cub and numbered lowboys) calls for 3/16, which is what the one I'm working on has. I did check both manuals. The IH service manual says"intake opens 10 degrees before TDC", but does not say if this is when it starts to open, or if it's half open, or full open. Does anyone have the side plate off that could verify what is correct?
Fri Oct 15, 2004 8:20 pm
10 degrees is when the cam lobe hits the lifter and the valve lash is 0.000, poised on the cusp of opening.
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