Engine movement

[Rat]

It's not exactly a new issue, I'm just out of ideas how to stop it without welding some sort of stop rail along the engine base to keep it square.

Basically my 208 makes enough power that if I really crawl the throttle the cylinder head slowly pivots to the right side where the chain is attempting to draw the wheel and engine together. I have cranked bolts as tight as I dare, being grade 8 if I go any tighter I'm concerned something is going to snap.

The only bolt that seems to never move is the only one not grade 8 or even grade 5, it's just a crummy old carriage bolt fed from underneath and nutted top side. The only reason I say it seems to never move is it is in the left leading corner (transmission side, under the starter motor)
I just haven't had the chance to swap all of them for carriage bolts to see if the theory tracks at all about the head surface area being what's "holding it better" or if it's simply the least leveraged bolt of the 4 given the nature of what is causing the engine to rotate slightly.

It's only enough that I'm sure it's probably not good for the chain, but it's not going loose or derailing either. All visible factors say chainline is dead on between sprockets too.

 

[Master Hack]

I had to upgrade to 7/16 bolts with, 2 inch x 3/16 flat washers and nylock nuts underneath. Still slipped. Problem solved now, but it wasn't easy.
GX 390 have heap big tork!

 

[Rat]

I had to upgrade to 7/16 bolts with, 2 inch x 3/16 flat washers and unlock nuts underneath. Still slipped. Problem solved now, but it wasn't easy.
GX 390 have heap big tork!

LCT [Husqvarna] 208 with the works thrown at it and no governor. They are listed as 7hp/9 ftlbs @3600 out of the box but test more consistently at 8.2 hp 12 ftlbs @ 3800. Mine makes solid power all the way up to 4600 ish on the retarded cam I have.

I just got done stuffing the fatest 1¾ carriage bolts that would fit without redrilling the block... some aluminum shavings were kicked out of the holes tapping them in from underneath but I think it should be done moving considering I used some really thick fender washers (1/16) under the heads.

Seems we went the same direction, but now there's nowhere for mine to move to at all unless all 4 bolts snap off simultaneously and I just can't imagine that being a realistic issue to worry on. The evidence says that what was actually happening is the washers were reforming and allowing the bolts to skew in the holes ever so slightly as the engine twisted.

There's just no room now, the engine just wont do more than wiggle in place with those suckers loose, thankfully I have slotted rear facing dropouts and axle pull adjusters to draw the chain tension and wheel alignment.