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Welding on a YZ250 Engine Case?

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can it be done effectively and which welder is needed, a TIG?

I have just cracked off the area that holds in my oil drain bolt,

the only problem is that it is right by a seam of the case.

Pictures to come soon

thanks in advance.

Steven

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More then likely not. Welding cast never ends up very strong and wont be as strong as the rest of the case but hey if the case half is ruined anyway you might as well try it. and if you are going to try it. tig is the only way to do it

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thanks for the input so far, im going to get a few quotes from a welder on Monday, or tuesday depending if they are open.

What should I ask the welder to do, keep the temp or electricity turned low?

What if I did split the case, would it be repairable then or would we still see some distortion?

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thanks for the input so far, im going to get a few quotes from a welder on Monday, or tuesday depending if they are open.

What should I ask the welder to do, keep the temp or electricity turned low?

What if I did split the case, would it be repairable then or would we still see some distortion?

get them to preheat the cases in an oven, now with a touch to around 500 degree's (any decent shop should have an electrode oven that will go this hot) welding at low ampe's can easily cause cold fusion, look for somone that does alot of high quality aluminium work, or evan better an engine shop that can do it since they will have a much better understanding of what to do and not to do.

there will always be a small amount of distortion, the only real option there is if it's not to bad, skim a few thou off of the mating surface in a mill, if it's to far gone and it need's more then a few thou the cases are a throw away, chances are if it's only a few thou though that it will pull together when you bolt it up, the risk obviously is that the crank and transmission shaft bearings may not sit perfectly square which maye cause them to overheat and seize once the engines back together.

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dont try to weld on it while it is together you'll end up melting the seals and damaging the bearing in the engine, disassemble the engine then have it repaired.

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i have a spare set of cases, so i might just take it all apart and then replace the cases as a set, instead of risking the engines parts getting damaged, its just alot of work and time and I don't want to fix it cheaply but wanted to see if the welding was an option withou splitting the cases.

thanks for your input so far everyone, i will have photos tommorow and i will consult a machine shop to let them have a look.

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Cases have to be split either way. Just order the gaskets and take a night and swap the cases. should be able to pull the motor, strip it, split the cases and have it all back together, in the bike and running in 4 hours or so. Easy as pie with a 2stroke

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I've personally welded up a cracked drain plug hole for a friend on a kawi. i'm no welder and I used a mig machine. Didn't take anything apart. It was easy.

Without seeing your problem, i will give you option B. Weld over the hole or weld a plate over the hole. Drain your oil out of the clutch cover from now on.

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I've personally welded up a cracked drain plug hole for a friend on a kawi. i'm no welder and I used a mig machine. Didn't take anything apart. It was easy.

Without seeing your problem, i will give you option B. Weld over the hole or weld a plate over the hole. Drain your oil out of the clutch cover from now on.

What kind of mig did you use? Did you use aluminum wire?

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a shop mig welded the top mount of my xr400 motor back on and it is very strong, he said it depended on the quality of the metal weather it would work or not. i tried in the past to weld on part of a case on a china bike and it did not work at all.

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a shop mig welded the top mount of my xr400 motor back on and it is very strong, he said it depended on the quality of the metal weather it would work or not. i tried in the past to weld on part of a case on a china bike and it did not work at all.

Cast aluminum/iron contains alot of impurities and takes a special process to weld it correctly. A structural weld of these meterials requires preheating the material to prevent warping and requires the use of a TIG welder, a more controlled and precise weld.

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(any decent shop should have an electrode oven that will go this hot)

Found this rather amusing myself 👍

Lots of good comments and options for you in this thread 🤣

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well im dropping the motor out first thing tommorow so ill post some photos for you to see and then maybe i can get a little more input, thanks for every bit of opinion so far, The motor and trans are perfect so if I can get it welded without the split I would love it, and its a rather small piece that broke off so we'll see if its repairable.

thanks again and have a great weekend riding

i guess the down time is good for fixing other things on the bike that need love.

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well im dropping the motor out first thing tommorow so ill post some photos for you to see and then maybe i can get a little more input, thanks for every bit of opinion so far, The motor and trans are perfect so if I can get it welded without the split I would love it, and its a rather small piece that broke off so we'll see if its repairable.

thanks again and have a great weekend riding

i guess the down time is good for fixing other things on the bike that need love.

Did you forget about your thread here?

torch

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I second jb weld... suprisingly works well. Had a friend repaired a big old hole in his engine case that was made when the chain broke and whacked a hole in it. It has held up for many thousand miles now without a leak.

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My brother also used JB weld on his crf when he hit a rock and put a small hole on the bottom of his case. JB fixed the problem and has never leaked since.

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My brother also used JB weld on his crf when he hit a rock and put a small hole on the bottom of his case. JB fixed the problem and has never leaked since.

Going to try this on my cr250, chain guide cracked at the case and took it's mounting with it.

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