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Discussion Starter #1 (Edited)
Hi, again. Sorry i haven't posted in a while. I mentioned a couple of months ago, that I was close to starting my rebuild, and that I would document everything to post at the end. Well, I encountered a problem that I need help with, so y'all are hearing from me early.

When I was reassembling the crankcase, I thought I was being even more careful than was necessary, and anyone I asked for advice made me feel like I was over thinking it. Anyway, as I was tightening the left side onto the right, I heard the crankshaft bearing squeezing into its cutout, and rather suddenly, there was a bang. Turns out, one of the rods that hold the shift forks in place had poked through the right side of the case. Nothing else was harmed, and the hole is very small. There will be a picture below showing the hole and the broken piece.

IMG_20170320_153443.jpg

Bottom line, is this fixable, or do I need to buy a new case half? Also, is that particular rod longer in the XT/TTR motors, because I used all of the transmission pieces from the donor motor except the machined output shaft.

Thanks everyone, and sorry for bothering you on a Monday.
 

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Is this your first motor overhaul? If so or even with experience a good repair manual helps. Generally speaking, welding thin aluminum, unless your really experienced with the TIG process can be another heart breaker. I have done it and could do it but no longer have the HF and AC TIG welding setup.

So the piece you broke out, is there a hole behind it that supports that rod? BTW when you seek help on the internet you get advice, not the skill of the person giving the advice. Skill in being a mechanic comes from experience and making mistakes sometimes until you learn.
 

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Discussion Starter #4
Thanks for the quick response guys!

To wmgeorge: Yes, it is my first engine build, and I'm learning a lot as I go. I have the official service manual and another aftermarket manual with pictures, both of which have helped tremendously, as has this forum, but there are questions that come up sometimes, leading me to ask those who are far more experienced than I. There are frustrations, but overall it is enjoyable and a source of pride to work on the bike myself. I hadn't considered how it would be fixable yet, maybe just that there was something I could do, although if I must get a new part, it wouldn't hurt too bad.

To TW-Brian: Indeed that is the case. In fact, I believe you were the one who helped me (among others) to get the output shaft machined, so thanks again for that! I have tried to read through every conversion thread on the forum, but I can't remember if those rods were mentioned or not. I suppose I had assumed that other than the output shaft, the rest of the transmission assembly should be migrated whole. I was probably wrong, knowing my luck, haha.
 

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Hello,
Sorry for my translation

I just know that there are 2 axes of different length.
The part number is different for the XT125 & 225.
But when opening the engines, I never noticed different from these engine parts,
TW BV 5 - 6.JPG
Perhaps you have reversed the axes?

Part list fork gear.jpg
 

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When I did my 6-speed conversion I used all the TTR225 parts and just substituted the TTR output shaft with the modified TW output shaft (and one bearing) and I did not experience any problems. I have also not heard of any problems like yours from others who have done similar conversions.

According to christdel's post, it appears that there is at least a part number difference in these parts between the TW200 and the XT225. I do not know if there is a dimensional difference between these two part numbers.

On the TW, these two shafts are the same diameter but one is about 3/8" longer. That means that the correct shift forks could be loaded onto the incorrect length shafts. If this is what happened, and if when the crankcase was reassembled with the short and long shafts switched, the longer shaft may have punched through the right side crankcase when you tightened the crankcases together as your picture illustrates.

Can you check and see if the now protruding end of the shaft is still restrained by the crankcase, or is it able to be pulled through (don't actually try and pull it through, just see if it could be). If these shafts were indeed interchanged, and the shaft is still restrained within the crankcase, then you may be able to just tear it apart and reassemble it with the shafts in their proper position without replacing the right side crank case.

Or, I may be completely wrong!
 

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Discussion Starter #8
Christddel: Thanks for doing all of that research! As soon as I can split the case and remove the rod, I'll use calipers to check the length against the one that came out of the original engine.

TW-Brian: It would be quite embarrassing if I had just swapped the rods on accident... Just to be sure, the longer rod should be the one with two forks, right? I have checked, and the rod is not going anywhere. Are you saying there is a chance to salvage this?

Ronnydog: Thanks, man! If I end up needing a set, I'd like to buy them from you.
 

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Discussion Starter #9 (Edited)
So I got the cases apart...
Christddel was right, they are different, I'll post the pics when I get home, but I have the measurements.
TW short shaft: 93mm
XT short shaft: 90mm
TW long shaft: 102mm
XT long shaft: 106mm

TW-Brian, the rod can be pushed through the hole, but the piece that broke was originally a protrusion, so it fits back flush. Since it is not something under pressure, can the piece be epoxied back on?

Edit: Here are the pics. The darker rod on the left is from the TW, and the chrome-colored rod on the right is from the XT.
Short rod comparison:
IMG_20170321_162349.jpg

Long rod comparison:
IMG_20170321_162300.jpg
 

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I am sorry that you had to be the one to discover this difference!

I don't believe that these rods see much load in their lengthwise direction, so it shouldn't take much to hold it in place. I would suggest using something like J-B Weld. I would not feel very confident trying to bond the broken piece back on as there would not be much for the adhesive to grab onto, and I would worry about the bond letting loose leaving a good size piece floating around in there. You might want to consider cleaning the area well and using the adhesive to create a plug in the protrusion to hold the rod in place. If you use the shorter TW rod, this plug could extend 4-5mm into the case plus some buildup on the outside to grab onto the fractured area. What do you think?
 

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Discussion Starter #11
Thanks for the condolences, and I'm glad it is now found so the next guy won't make the same mistake. I'll also look at my eBay history to see exactly what year it came from.

If J-B Weld can fix it I would be ecstatic, but will it bond to aluminum? I do like the plug idea, by the way. If I can use that method, should I rough-up the inside surface a bit so the J-B Weld will stick better?
 

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I have used J-B Weld successfully to patch up holes in aluminum side covers, and yes, you definitely would want to roughen up the surfaces for better adhesion.

Here's a crazy idea that I had. Since you already have your crankcase split apart like shown in the picture below, see if you would have the space and clearance to place a tiny metal hose clamp (it would have to be smaller than the one in the other picture, but that was the smallest that I had) on the rod to prevent it from migrating out through the hole now punched through the crankcase. Obviously this clamp would have to be small enough to clear the various spinning parts nearby.

100_4626.JPG

IMG_2286 (2).jpg
 

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i have use jb weld on many jobs... will stick to any thing almost and is probably stronger that the aluminum....
As long as its absolutely clean and use MEK or lacquer thinner to get all the oil off. The collar is a good idea, IF there is enough clearance inside? I would use LockTite on the collar set screw for sure.
 

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Discussion Starter #16
Thanks everyone! TW-Brian, if this works, you probably just saved me several hundred dollars!
 

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Discussion Starter #18 (Edited)
I've managed to find the shaft collar and will try it shortly. Another idea was brought up, in case this doesn't work: thread the hole and put a very shallow bolt in. What do you think?

Heli-mech: thanks for the idea, but I don't have access to a tig(?) welder. Might pay someone to do it as a last resort.
 

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Discussion Starter #20
Thank you Heli-mech, I really appreciate that. I'll let you know.
 
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