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What all is involved in getting the engine casings apart in one of these Bruin / Grizzly 350 engines?
Just to swap out the right side casing (the side with the clutches and the front and rear outputs). Aside from what's required to remove and reinstall the clutches, are then any special tools or procedures that I should be aware of?
Is there no gasket between the two main halves of the crankcase? Just a bead of RTV?
A full top and bottom end gasket kit seems to be pretty cheap, and considering already have good hard parts to swap around, it appears that all I would need is the gaskets.
Long story short, I got screwed over on a deal on a used 05 Bruin 4x4... Finally got it to start, it has a bad rod knock and it smokes... I have a great running 2wd engine just sitting in the garage, and figured that with just a gasket kit I could tare them both apart far enough to just rob the right side casing from the smoked 4x4 engine and install it onto the good running 2wd motor, converting it into a 4x4 motor.
I've rebuilt car and truck engines before, I'm pretty familiar with all the mechanics of it involved, but I've never torn down a small engine like this that far.
From the looks of it, all I need to do is:
1 - Pull the clutches off (CTV and wet clutch)
2 - Remove the timing chain from the head (while also keeping tension on it so it stays on the crank sprocket)
3 - Pull the head and cylinder off
4 - Split the casings
5 - Transfer the 4x4 crank case half over to the 2wd engine
6 - Reassemble with new top end gaskets and seals (being sure to line up the timing chain with TDC)
First be very sure the "rod knock" is the big end, before splitting the engine. Air cooled, roller big end engines rarely give trouble that way. Mostly, knock is the piston slapping away as it has been seized and freed off after cooling. That would account for the smoking too. I have never split a Yam crankcase, but done loads of Hondas and they hold few terrors despite being full of gears. Suzuki Eigers were worse as some gears fall out of the alternator case when you open it, and the rings that the gears spin on have oil holes that have to line up with the shaft oilways.
As far as I have been with 350 engines is replacing the cam chain, and the balancer gear can be put back five wrong ways, which puts its timing out, even though the marks line up. I think you need a flywheel puller too, though I bodged something up. Crankcases will be machined as a pair so forget fitting non-matched case halves together. If you must, fit the crank assembly from the 2wd into the 4wd cases, and get a workshop manual first, if you are going down that route.
First be very sure the "rod knock" is the big end, before splitting the engine. Air cooled, roller big end engines rarely give trouble that way. Mostly, knock is the piston slapping away as it has been seized and freed off after cooling. That would account for the smoking too. I have never split a Yam crankcase, but done loads of Hondas and they hold few terrors despite being full of gears. Suzuki Eigers were worse as some gears fall out of the alternator case when you open it, and the rings that the gears spin on have oil holes that have to line up with the shaft oilways.
As far as I have been with 350 engines is replacing the cam chain, and the balancer gear can be put back five wrong ways, which puts its timing out, even though the marks line up. I think you need a flywheel puller too, though I bodged something up. Crankcases will be machined as a pair so forget fitting non-matched case halves together. If you must, fit the crank assembly from the 2wd into the 4wd cases, and get a workshop manual first, if you are going down that route.
That is a very good possibility, that it's coming from the top end only. It does sound maybe a little more like piston slap (more high pitch and up in the cylinder area) than a lower rod knock.
I guess I can start by just pulling the head and cylinder off the noisy 4x4 motor and checking for slop in the connecting rod, both at wrist pin area at the piston and the lower end on the crank. If it just seems like either the piston has slop or it looks like there's been a lot of play in the cylinder with the piston, I could get away with just swapping over the piston and top end from the other engine. Worse case scenario at that point, I put it back together and it still makes noise, I'll just order another top end kit to replace the gaskets I used and go through with a complete strip down to swap the case half anyway.
Well I pulled the top end off the noisy 4x4 motor. I think it's safe to say it had some piston slap...
MAJOR scoring on the skirts of the piston and some nice scoring on the walls of the cylinder too. The oil rings hardly move, so that probably wasn't helping with the oil burning, but that could also be valve seals, I'm not really sure. Didn't seem to be a ton of play in the wrist pin, and there's no unusual play on the big end of the rod either. So I'm just going to try moving the top end and piston over from the good running 2wd motor to it and see how it goes! Worse case scenario, I just have to tare it all back apart again and actually do the engine/case swap lol.
Dec 21, 2020 | 09:09 PM
Bruin / Grizzly 350 engine case splitting
