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Discussion Starter #1
Couple days ago when I was riding my 2017 FJ09 home, my chain came off the rear sprocket (neglect on my side) and eventually broke the support rods of my front sprocket cover. There are three supports all of which are from the crankcase. The two at the top broke kind of nicely but the third one left a hole on the crankcase. Below are the photos. The hole is right below the chain. From what I have read so far, welding is the best option but I don't know if the welder can access there easily. I may need to pull the engine out but I have no idea how to and if I can possibly do that in my garage.

Any advice is much appreciated. If you think pulling the engine out is necessary, can you please help me understand how difficult it is? Does anybody think JB weld would hold there despite the heat and vibrations? I have all three support rods that fits right in.

60796

60797
 

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I think you have enough room with out removing the engine. Just remove the chain, maybe the sprocket as this would be easy enough. Get all the wires out of the way.
I think you might (emphasis on might) be able to use JB weld. But welding would be a much better option.
 

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Discussion Starter #4
Made some research about PC-7 today. Looks like a very solid stuff. Very nice for vertical surfaces like this where JB weld's liquidity may become a problem. The only downside is temperature tolerance. I heated up the bike today and it looks like it doesn't get super hot there. I am in contact with a welder so if that doesn't work I might end up using PC-7.
 

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remove everything around those tabs and remove motor and go get them TIG welded back on.
That is absolutely the best way to go. For some reason I got the idea the OP needed something quick and dirty to get by temporarily.
 

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Discussion Starter #7
Oh no, need a permanent fix. I plan to ride this bike for many years to come.
What could be the issues with welding on the bike without removing the motor? How hard is it to remove the motor? I guess I am afraid of making more damage somewhere else while removing the motor.
 

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A good welder won't hurt anything welding that in place, from the pictures it looks like there is enough room, no need to take the engine out.
I wouldn't consider any epoxy repairs, just take off what's in the way, bring it to a skilled welder and let him or her fix it the right way.
 

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I can't argue the fact that welding is the best way to go. It is. But I will say this, epoxies have come a long way in the last 25 years. Todays epoxies are not your mothers epoxies. Can anything go wrong welding, no.

On an unrelated note:
I have a brother-in-law (Sparky), a master plumber with license and all that set an apartment complex on fire while soldering pipes.
 

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Discussion Starter #10
I could not find a welder that is willing to do this. They all think they may damage the engine. So I decided to do the following:

I will JB weld all the supports. I do not want to mess with the one that made the hole too much after epoxying it back in there so I bought one of those front sprocket covers that only uses the above supports (looks better too). Here is what I got:

Graves Sprocket Cover Yamaha FZ-09 / MT-09 / FJ-09 | 5% ($3.45) Off! - RevZilla

I did a quick measurement and static engineering stress calculation. Looks like there is way more tensile strength on JB weld than required to carry that cover (about 100 times more if I remember correctly). The issue is bonding, epoxy itself is strong but it needs to bond to the surface as strongly, otherwise that will be the weak point. I sanded the sides of the support along with the area around on the crankcase where it will be epoxied to in order to increase the bonding area. I cleaned both surfaces very very thoroughly first with cerosene and then many times with aceton. Applied the epoxy last night. The biggest problem is to make some sort of a structure to push it in place until the epoxy is cured. I used the wires there which was not easy but doable with some imagination. I will post photographs of the process once I am done. Hopefully this will guide whoever is in my position in the future.
 

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This info may be a little late. But the main thing to consider when doing this is to make the prepped area bigger than the epoxy/JB weld area. If the repair you made happens to fail down the line, and for the reason I just stated, keep it in mind for the next repair.
 

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Discussion Starter #12
I cleaned the entire area, shouldn't have a problem with that. I am curious though, what happans epoxy area is larger than the prepped area?
 

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When the epoxy is applied beyond the prepped area, that's where it can start to pop loose. And then it can just continue to pull off the prepped area also.
 

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Discussion Starter #14
That is what I thought, makes sense. I cleaned everything like a lunatic so I believe I am good. Thanks for the input!
 

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Use a can of BRAKE cleaner on the area as it leaves NO residue.

JB weld and other epoxy's typically hold very well only if the surface is clean.

I have seen 2 stroke track bikes that have blown rods through the crankcase be repaired with JB weld, sanded and painted and no one could tell and the repair worked perfectly.

Welcome to a great forum!

Sam
61024
 

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Discussion Starter #16 (Edited)
I finished it today.

After cleaning the surface very thoroughly first with kerosene to get rid of the chain lube and then aceton many times, I epoxied the parts one by one. After curing (about 24 hrs), I applied another layer to the sides of the supports. JB weld seems to be holding them very strong but I will see if it will hold in the days to come. After epoxy, I installed new sprockets and chain, and the new sprocket cover. I also changed the oil considering it may have been contaminated during this whole process.


Thanks for all the help everyone! Here are some photographs:
 

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Nightfly
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If the metal is cast aluminum it would be very difficult to weld. It can be repaired and I've found several products that claim to do a wonderful job. Not going to list any of them because then it just becomes a pissing contest. But with luck you should be able to accomplish the fix. Cleaning of the surface cannot be overemphasized.
 

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A little late but this video gives evidence to the miracle that is JB Weld!


Also, this guy does a lot of really good product testing with all kinds of stuff. Worth checking out!
 
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