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MG TD TF 1500 - Crank starting an XPAG
|I am posting this over 3 forums to canvas the experience of many.|
Crank starting an XPAG is totally dependent on the driving dog nut on the front of the crank having the correct orientation. There are shims placed to adjust the angle of the dog nut.
You need the crank handle to be at the 9 o'clock position on the compression stroke, so you can pull up in a smooth action, and at TDC the crank handle is at 12 o'clock.
But when you are at the engine assembly stage, what is the correct position ?.
I am just re-assembling an engine that was easily started on the crank handle. There were no shims behind the dog nut on stripping the engine, but I did note the driving "pin holes" were at 12/6 position at TDC.
Can anyone confirm this is the correct orientation of the dog nut - I am confident it's OK, but would appreciate a 2nd opinion before the engine is returned to the chassis.
|A L SLATTERY|
|I don't change or add shims when assembling the engine, and only adjust them after the engine is in place, as needed. I tend to shim to start with the handle closer to 7:30-8 o'clock, to get a good pull upward.|
And keep your thumb off the crank!
|Tony, don't be concerned about the TDC mark for cranking. You just want to be on the compression stroke of some cylinder, not necessarily #1 or #4. I'm with Tom on the shimming. Bud|
|Thanks Tom & Bud,|
I will rotate it around a bit then with some shims & aim for TDC at 10:30 and see how that goes. I will adjust it again with a test start before fitting the front on the car.
Yes, I am aware of the thumb issue. Setting the dog bolt at the correct angle helps to keep the thumb out of the way, as you can pull up with an open hand from outside the swing circle of the handle.
|A L SLATTERY|
|Just remember, don't try to spin the crank! A lot of farmers back then wound up with broken wrists and thumbs by trying that on their tractors. Just pull up, don't push down! PJ|
|I am one of those people. My right wrist hurts all the time now. My back is so bad I had to grab the handle, with my thumb over the handle. I thought once I grabbed it I would slide my thumb out of the way. Nope, Bang!|
|Tony, I'll go and look at mine tomorrow to see where the TDC mark is when the compression stroke is there. Bud|
|Thanks Bud, I should add that another reason I need to get this right is an inability to straighten my left arm, so I need to be able to start it with my right in a "backhand fashion" if you get my drift.|
I just noticed in the workshop manual "Illustration No.C.9." - it shows the dog pins at 12/6 at TDC !. Now this is how I found the engine on strip down.
Going back to first principles, and using Illustration C19 in the manual, there is only 112 degrees between the inlet valve closing and TDC. If the dog is set for 10:30, then the inlet valve will be closed at 6:45 and rotation to 7:30 should start to feel the compression.
I think this will be the ideal.
Thank you all for your advice and assistance.
|A L SLATTERY|
|What's wrong with a battery charger or jumper cables?|
|Tony, I had an interesting time working on it this morning. The point of "it's ready to pull" is very subjective. Once I had it down to being consistent I saw that the TDC timing mark was either at about 3:00, or I couldn't see it at all. Finally figured that out - there are two cylinders getting compression strokes per revolution. The following one was with the TDC mark at about 9:00, under the fanbelt. (BTW, in my WSM Section C is Ignition.)|
For Gene: back in 1958 our only car was a 52 TD whose battery was totally kaput. Couldn't afford a new one until next payday. By the end of two weeks I had it down to a science. Bud
|Tony, just realized that I hadn't anwered your query as you asked it. You wanted to know the orientation of the dognut pins in relation to the TDC mark on the pulley when the dognut is located for crank starting. My dognut is so located. It matches right up with the image from the WSM. A pin of the crank is almost right at the TDC mark. It's a bit puzzling until you realize that the dognut pins are at a rioght angle to the crank handle. Here's the image from the WSM: Bud
This thread was discussed between 21/11/2013 and 23/11/2013
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