Dan,
...good idea NOT to force-start that engine! The following may take a while to read, probably longer than it takes to do...
20 or more years ago, several runs of Fox 35S were released with the heads tightened on without regard for a "torquing sequence," and felt tight because of the distortion created.
I've never had a warped sleeve in one, but have had one or more that had a VERY SLIGHTLY distorted crankcase casting. Proved this just as Jim T did, except other sleeves were as tight as the "bad" one I was checking. And there was no bind on the OEM piston in its OEM sleeve when they were out of the casting.
Used a worn-out sleeve and a thin Lava soap grit paste to lap the casting to a uniform, slightly looser fit. Cleaned it scrupulously, afterward, of course.
If you do disassemble your engine, you'll very likely disturb any run-in surfaces that had formed, but with the problem you describe, it is better to disturb it, correct the fit, reassemble it carefully, and give it an abbreviated repeat of what a proper break-in would have been.
Reassembly:
Not a bad idea to see how cleanly the head fits the top of the sleeve. A drop of the lapping paste, above, between the head and top of the sleeve will polish up any high spots where the head can't sit square. Probably won't turn up any, but only accomplish a cleaning of that joint surface... Clean all traces of the lapping paste off the parts. (Lava bar soap is mostly pumice. That's soft enough that it crumbles down to less than running fit clearance before it can cause serious damage, but why take the chance anywhere you don't need to.)
You can likely find 4-40 X 1/2" Allen socket head bolts at a good hardware chain store (red, orange or blue jacket stores) These are much easier to use for good results as replacement head bolts...
Torquing sequence: Look at the 6 bolt locations, pick one as 12 o'clock position. I use the front one... Fit the head on loose, and run the six bolts down until you feel them touch. Back them all out a half turn.
Start from your 12 o'clock bolt, and turn it in a quarter turn. Got to the 4 o'clock position bolt and do the same. Then the 8 o'clock bolt. They are all still loose, right? Okay...
Cross over the head to the 2 o'clock bolt - same. Then the 6 o'clock - same. Then the 10 o'clock - same.
Turn the shaft back and forth to make sure nothing is binding. If it is back 'em all out and start over.
If all is well after this first cycle around the bolts, again cross to the 4 o'clock bolt and continue the sequence. Just barely turn these to where you feel resistance. This sequence is 4 - 8 - 12 o'clock.
Again, check that the shaft, piston and sleeve do not bind. Contrinue the sequence with a small increment - say another 30° of wrench movement - until you've gone around all 6 and checked free motion. Each pass around all six draws a sort of Star of David pattern with the overlapped triangles.
Continue until all six bolts are as tight as you can get them using small, even increments with ONLY the short arm of the key.
At any time, if any bind appears, back off at least one step and recheck.
This takes a while to describe, but once you've done it it goes very quickly. The fully-torqued engine shaft rotation and piston motion should feel just as free as before it was tightened at all. (A good piston fit might feel snugger near top dead center, or like an ABC engine, not go through TDC when turning the shaft without mounting a drive washer or prop for leverage.)
For an older engine, of course, as mentioned in prior posts, conrod freedom to move on the piston pin is important. Gummed, in the wrong position, it can increase wear.
Topic: Sticky fox 35 (Read 1089 times)