I started restoring a Dolmar 112 and in the process of pulling the flywheel I cracked the end threads using a puller, see image for the damage. Can/should I run this? Anything to do here besides replacing the crank?
Cracked crank threads...what do
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Guys have those welded and redone.
Thanks. I've never had anything like this form, what sort of shop would do this?
That was my first thought. Thought I'd ask here before I buy anything. I don't have a case splitter and never done a bottom end so I'm reluctant. If anything, I'll just buy a full bottom. There's a few available on fleabay, I'm fearful of buying from fleabay, sellers are less than honest when describing the condition, as you all know.
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What kind of puller did you use? Looks like the main bolt of the puller has been driven down the side of the crank and the damage was done on the way back up- the last thread is peeled and pulled upwards and the straight line thread damage below the centre of the broken section.
Man I'd just replace the crank
That's just a reflection on that crank. I know it looks bad, I tried to take a better picture to show what it looks like:
I took care to make sure I centered the main bolt if the puller on the crank shaft end, and the bolt is dimpled so it would've stayed in the recess. I'm not sure what happened here. Here's the puller I used.
Chainsaw Pete
ArboristSite Operative
Looks to me like the centering spike on your puller might be bigger than the depression in the end of the crankshaft. As you tightened the puller's center bolt, it broke a portion of the cast(?) crankshaft off. Or, if the spike is smaller than the hole in the end of the crank, one of your two bolts into the flywheel was not screwed in as far as the other. The pull was uneven applying pressure to one side of the end of the crank and the metal gave way. It is also possible there was a flaw in the metal at the end of the crank and it was just waiting for someone to use any puller and the metal broke off.
Welding cast metal is not a job for beginners, and then the threaded portion would have to be tapped. Needless to say, getting weld spatter on the tapered section is a no-no. All in all, I'd opt for a used crank.
Welding cast metal is not a job for beginners, and then the threaded portion would have to be tapped. Needless to say, getting weld spatter on the tapered section is a no-no. All in all, I'd opt for a used crank.
You should have left the nut threaded on the crank , just enough to catch all the threads on the nut, when using the puller.
The centering spike seems to be the right size. It's one of those universal pullers found on fleabay. What most likely happened, as you said, is that the bolts weren't evenly screwed in and the centering bolt unevenly applied pressure (my screw up), and in a distant second place, the crank had a flaw that I unearthed using the puller.
Just out of curiosity, what would happen if I reassembled with the damaged crank? Premature bearing and oil seal failure?
I'm fairly certain I could get everything tightened down with what's left, but fear not, I've already started the quest for a replacement crankcase.
Best solution would be another crank. Are there enough threads to install the nut with the flywheel in place? Can you screw the nut on with the threads as they are? I had the threaded clutch end of a crank break off once. I made a centering guide and drilled and tapped the crank for a 1/4" bolt. Worked fine as long as there is clearance beyond the bolt head. This was the clutch side so I had to use left-hand threads.
If there's enough good threads left for the nut to fully thread onto the crankshaft with the flywheel installed i bet you could just run it.
I'm pretty sure there's enough threads there to secure everything down. I'll take a closer look.
It's one of the easier saws to split because both tanks are part of the handle assembly. And because you already have a bad crank, you can split it by tapping the crank out of first one side and then the other with a hammer. Your chances of getting a reusable used crank are very good, bottom rod bearings seem to survive quite well.
When I pull a flywheel, I turn the nut back on to the crank until it's just about even with the end of the crank. I then pop the flywheel loose with the puller, remove the nut and then the flywheel.
After I tighten down the puller, I give the puller center bolt a couple light whacks - sometimes the shock will pop the flywheel loose - so you don't risk over-tightening the puller.
Many of us have learned how fragile the end of a crankshaft can be, the same way you just learned. Remembering to leave the nut at the end of the threads is pretty valuable.
Mark
Mark
Thanks Mark, lesson learned. I've removed flywheels in the past using the nut-at-end and brass hammer/punch method. In this instance, for whatever reason, I initially used a knocker but couldn't get it loose, so I moved onto the puller. I guess it didn't cross my mind to keep the nut on the end since there wouldn't be an impact like there is from a hammer.
Husky77
ArboristSite Operative
A sad sight, I realise you want to keep it original so I would get it repaired and remachined. BUT.... next time your doing this, instead of just keeping cranking with a spanner. All you need to do it tighten it up and give it a tap with hammer and off it will pop. Instead of breaking it. Every day we learn a little more.
