Rod bearing failure - serviceable?

[BTarb24]

I have a ms660 huztl clone that i built. Ran amazingly for all of about 4 hours and then started having some strong engine vibration. 2 or 3 minutes later (i really wanted to finish the last few cuts) it seized up. Disassembled the top end and found that the rod->crankshaft bearing is completely seized.

I'm fine with spending more time fixing it and I understand that you get what you pay for and all that. I'm mostly just curious on how people typically approach this repair. Is the bearing replaceable or do people tend to just replace the entire crankshaft assembly?

 

[U&A]

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Sent while firmly grasping my redline lubed RAM [emoji231]

 

[Jacob J.]

The rod bearing on those cranks isn't meant to be replaceable. There are people with specialized tooling and knowledge that do it, but in that case it's a lot more cost effective to source a different crankshaft.

 

[cuinrearview]

What's another FT one cost, $3.47? Seems like a no brainer on that saw to me.

 

[Brent Nowell]

What's another FT one cost, $3.47? Seems like a no brainer on that saw to me.

Yea it is to you, maybe me, but he wants to learn how it’s done. Would be invaluable knowledge for an older vintage saw crank repair in which you cannot just replace it anymore

 

[cuinrearview]

Yea it is to you, maybe me, but he wants to learn how it’s done. Would be invaluable knowledge for an older vintage saw crank repair in which you cannot just replace it anymore

You must have read more into it than I did.

 

[s sidewall]

Vintage, oh, I just take the cap bolts off and remove the rod, at least on one of mine. Other than that, play the waiting game and find another good crankshaft.

Steve

 

[Huskybill]

Read about huztl saws with burning up cranks before. What was your mix ratio? If they read the owners manual I think the clone Stihl saws call for 20:1 mix. Running 40:1/50:1 for first starting it. Not good.

options,,,, buy a new huztl crank and pre lube the snots out of it during assembly, run your mix ratio oil rich and break it in slowly.

I split cranks on husky dirtbike engines you need fixtures. I send my cranks out now. Retired lost my access to the press. I made the fixtures. Check out pressing cranks on you tube.
You need to end up with zero on the shafts runout. Having .001” runout isn’t close enough.

Note, I found out during the assembly of the crankcase there’s a chance that the counter weights aren’t parallel to each other. I put the rod journal at the bdc. Take a clean cold chisel and tap it lightly one shot to relieve the stress between the crank weights/pin. Just to be sure the cranks are true in the case. An old timer taught me this.

 

[Huskybill]

Here’s the cheapest fix. Huztl new 660 crank $11?

 

[Huskvarna hotellgäst]

I don't know how Huztl make theirs but the OE items are pressed together cold with tonnes of force, then perfectly aligned by hand by highly experienced personnel using high precision gauges...and a copper hammer. Repair is generally not considered to be a viable option.

 

[holeycow]

Why is it that larger 2 stroke engine cranks (like in a dirt bike) are routinely rebuilt but it seems that chainsaw cranks are throwaway?

Just a question, as it seems odd to me.

 

[Huskybill]

With some stuff we’re a remove and replace or throw it away and get a new one. The newer technicians(aren’t mechanics anymore) just remove and replace now,

I started washing car parts for my oldman at 6yo. Im a old school mechanic remove, rebuild and done deal. I went to buy new brushes for my gm starter in my 88 350 suburban. The auto store sent me to the local auto electrical repair shop the brushes were $2. The rebuilt starter was $45. It’s not the money it’s I know my armature is good.

 

[holeycow]

Nice vehicles, those suburbans. I had an ‘89 many years ago.

1/2 ton, 4x4, loaded, white. A great family vehicle.

Other than some recurring electrical issues with the sliding back window and the beginnings of body panel cancer, it was a vehicle I wish I still had.

 

[Huskvarna hotellgäst]

Why is it that larger 2 stroke engine cranks (like in a dirt bike) are routinely rebuilt but it seems that chainsaw cranks are throwaway?

Just a question, as it seems odd to me.

I don't know enough about bike engine cranks to be able to answer.
I do know that back in the '80s, the only saw/trimmer engines on which the big-end bearings could be replaced were the cheap, low-revving single-counterweight crankshaft types with individual rollers, e.g. Skil 34cc, Husky35/Partner350 & Weedeater trimmers.
And, the main reason you needed to replace them was not because they wore out but because they fell out.

 

[holeycow]

I had a weedeater gti19 apart last summer. It’s a poulan from about 1990 that I bought new about then.

Chrome piston, aluminum bore, single sided crank, stamped rod, plastic case. It was heavily worn after a million hours. Anywho, I put a new ring and a new carb gasket in and voila!, running again. It’s amazing how cheaply it’s made and how long it has lasted being made that way. Due to my cheap rebuild, it won’t last much longer, but that’s ok.

 

[BTarb24]

Read about huztl saws with burning up cranks before. What was your mix ratio? If they read the owners manual I think the clone Stihl saws call for 20:1 mix. Running 40:1/50:1 for first starting it. Not good.

Ah, perhaps this is the reason for it's untimely demise. I had used a 50:1 mix. Any general guidance as to how many tanks to run at 20:1 before weaning back to 50?

 

[Huskybill]

Nice vehicles, those suburbans. I had an ‘89 many years ago.

1/2 ton, 4x4, loaded, white. A great family vehicle.

Other than some recurring electrical issues with the sliding back window and the beginnings of body panel cancer, it was a vehicle I wish I still had.

My 88 suburban was a v20 3/4 ton. Cancer started on the roof so much for rust proof dipped bodies. The 350 block cracked at 52k due to a cost reduction making the cast iron thinner. My previous two suburban were better quality wise when I stripped and junked them. I paid $27k and it was worse then the two I scrapped. Sorry to say it’s my last gm product.

 

[Huskybill]

Ah, perhaps this is the reason for it's untimely demise. I had used a 50:1 mix. Any general guidance as to how many tanks to run at 20:1 before weaning back to 50?

I run my saws at about 38:1 oil rich. Never a problem.

 

[ericm979]

Why is it that larger 2 stroke engine cranks (like in a dirt bike) are routinely rebuilt but it seems that chainsaw cranks are throwaway?

Just a question, as it seems odd to me.

These days many people just buy a replacement assembled crank + rod for single cylinder two stroke motorcycles. Like everything else, modern manufacturing makes the cost of assembled parts cheaper while labor costs have gotten more expensive.

The only reasons to pay a specialist to rebuild a crank is because a new assembled crank costs even more or if you want to use special bearings, like if you are adapting a street engine for road racing.

 

[holeycow]

These days many people just buy a replacement assembled crank + rod

The only reasons to pay a specialist.

Not in my world. It’s been a handful of years tho since I’ve had one done.

Parts are generally a lot more expensive in Canada, so a new crank is lots more than rebuilding here.

Any half decent machine guy who wants to can rebuild a single’s crank.