| Author | Message | ||
     Rick_a |
I've had some ordeal getting my S1 together after some issues with a chassis part. Well, it continues with the engine...I finally had her mostly together only to find that the pistons need much machining of the valve pockets after headwork. The heads have an oversized intake valve and the head has been milled some...the extent of which I now know. There is now basically no eyebrow clearance on either side and the exhaust valve pocket needs to be sunk .040". Of course it's all part of the process but it really sucks. I waited 'till now to check as I was out of $$ to do anything about it anyway. The heads stock were close to minimum on all piston to valve clearances with this cam. Oh well...at this point I guess another couple weeks hardly matters  | ||
| Blake |
What cams are you running? | ||
| Pammy |
The in and ex valves are hitting the eyebrows? The eyebrows should be laid back and then measure again. You can't get proper measurement until you do this.Tell me what the clearances are after this is done. You are welcome to call anytime and get advice from Wes. | ||
| Rick_a |
It's an Andrews N9. 0.240" TDC lift makes 'em a PITA for setup. With stock XB heads and valves all they needed was a 45 degree clearance cut on the valves. I took the rear piston out and found some serious damage. The wrist pin keepers have dug into the pistons substancially...both radially and having worked themselves towards the outside...on one side so bad that there was barely anything holding the pin in. I haven't removed the front piston yet. There was a small shelf of built-up material outboard of the keeper that made the pin very difficult to remove. I'm frustrated but glad this was noticed before there was a failure. Besides that the piston and wrist pin look perfect. I'll put up some pics later.
Laid back? Please explain. | ||
| Pammy |
"I took the rear piston out and found some serious damage. The wrist pin keepers have dug into the pistons substancially...both radially and having worked themselves towards the outside.." THAT sounds like a bad crank... Laying back the eyebrow is just relieving the shelf there. Not machining the actual pocket. | ||
| Rick_a |
I gotcha. I'm sure that'd do it. The exhaust pocket still needs deepening, though. I measured the pinion shaft runout 7500 miles ago when I replaced the oil pump drive gear. It was on the limit. The rods are both perfectly good and both small and big end bearings are in good shape. A bad crank would be a real disappointment. The front piston should show similar signs. I guess I'll find out. | ||
| Rick_a |
I found a good article covering all lockring failure scenarios. Diagnosing Lockring Failures The only one that could apply is excessive crankshaft endplay...though without even checking I am almost certain that is not the case.  Regardless, the bicycle will be doing many miles this year. | ||
| Rick_a |
Here's the pics:  Looks great from the outside  7500 miles and the bottom looks like new...it hasn't even been cleaned  There a squished-up aluminum shelf beside the clip  The other side  It doesn't look as bad through the camera but there isn't much clip protruding through there  The pin was so tight that the pin removal tool compressed the aluminum slightly. There was a slight shelf of aluminum on this side that the pin got rammed through I've seen first hand what happens when a clip busts through the piston...and it ain't pretty. | ||
| Rick_a |
The wrist pin  Nothing shocking here  Not a mark on the end of it |
