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Discussion Starter #1
Recently I found a cosmetically rough, but good running XT225 for a pretty reasonable price. A friend of mine has been wanting to upgrade his TW, so I had him ride the XT to see if the engine felt good to him. He liked it, so I swapped it over for him, and the result is fantastic! It feels like more than a 25cc upgrade, and I definitely think it was a worthwhile project.

The key is finding the right donor bike... the more complete, the better. Being able to ride it before tearing it down is a big confidence booster. I actually did some additional work to this engine on my bench before the swap, but if you have a running engine that you're comfortable with, then the swap itself is pretty straight forward.

First things first, I had to get both engines out of the bikes, and on my bench. The TW engine is on the left, and the XT engine is on the right. You may notice the XT has deeper cooling fins on the cylinder, creating more of a square profile... this causes a couple of issues, but nothing insurmountable.
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Next, I pulled the side covers off. To get the XT engine to work with the TW electrical system, the TW flywheel needs to be mounted to the XT engine, along with the TW side cover (after a few changes).
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Here's the tool for removing the flywheels. It's just a bolt, really, but it does the job nicely with an electric impact driver.
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Here, both flywheels have been removed, and the TW flywheel has been installed on the XT engine.
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Next, I'll work on the TW side cover.
 

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Discussion Starter #2
Since the XT engine has no oil passage to lubricate the countershaft support bearing, the original open ball bearing must be replaced with a sealed ball bearing. The screws that hold the bearing retainer are tough to break loose, but with an impact driver like the one shown here, it doesn't take long.
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I pried the seal out, then pulled the bearing with the contraption shown here. It's just a ground down carriage bolt with some nuts and spacers... crude, but effective.
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Then I pressed in a new sealed bearing. A hydraulic press works nicely for this.
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Since I had another original seal on hand, I packed some grease behind it, and pressed it in as extra protection.
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I re-installed the bearing retainer, and the side cover is ready to go!
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Discussion Starter #3
One of the problems I mentioned before, is that the cylinder on this engine is not machined to accommodate the TW clutch cable bracket.

Here is the bracket on a TW engine:
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But here is the same location on this XT engine:
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I don't know if all XT engines are like this or not, but in this case, I'm going to have to use the XT cable routing, along with the XT clutch cable.

If you find an engine that can accept the TW clutch cable bracket, and want to use it, then you'll need to swap over the clutch actuating arm as well. You can change that arm by removing the retaining screw shown here:
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This needs to be done before replacing the side cover.
 

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Discussion Starter #4
Now that the block is ready (I also replaced the output shaft seal, and the shift shaft seal), it's time to start putting things back together. Here's the Placerlode countershaft extension in place, with a drop of blue loctite on each set screw:
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The sprocket:
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A new gasket:
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The side cover set in place:
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Making sure these wires are free to move (not pinched) before tightening down the side cover bolts.
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Now, lets put this thing back in the bike!
 

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Discussion Starter #5
Well, I got the engine set in to the frame, supported by the top bolt and the swingarm bolt. When I went to install the front mount, I discovered that it wouldn't fit in to place, because the larger cylinder cooling fins were in the way!
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I was just about ready to take a grinder to the TW mount, when I decided to see if the XT mount might fit.
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Amazingly, three of the four holes lined up! Rather than grind (and weaken) the TW mount, I just elongated the one off-center hole on the XT mount, and bolted it up.
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The XT mount is more robust anyway, so I'm happy it worked out this way.
 

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Discussion Starter #6
Now, it's just a matter of putting the bike back together.

Here's how the clutch cable is routed. It looks like it's touching the throttle assembly, but there's actually plenty of clearance.
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I forgot to mention that the XT engine is vented through the timing chain cover on the cylinder head, rather than through a hole in the crank case. The hose routing is a little tight, but there's room for it.
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And it runs!
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I hope someone finds this helpful. ;)
 

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That was one heck of a sweet build report bro!! (y)
 

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Absolutely GREAT writeup and GREAT pics!

Do you know what year your XT225 engine is? The reason I ask is because I have transplanted both a 1992 XT225 engine and a 2000 TTR225 engine and did not experience the cooling fin or TW clutch cable bracket problems that you encountered. Looks like Yamaha made some minor evolutionary changes to the XT225 engine.

Also curious, did you notice any improvement with the XT's 6-plate clutch, and how do like reaching for that 6th gear and actually finding it?

Brian
 

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Thank you so much for this excellent write-up. It's extremely timely for me as I am swapping in a '96 XT225 motor this Tuesday. I am curious as to what yr your XT motor was - the square-ish cyl with the long cyl bolts, coupled with the camshaft cover vent loc would make me think that it was a '01 or newer. That would mean it is a Nikasil cyl with the wider case mouthed bottom end, good for future big-bores if desired. All of the steel lined cyls seem to be contoured more like the TW's cyl and also use short cyl bolts. Interestingly, I thought my XT donor was a '95 until I read this thread and double checked the registration papers. I wish it was a '95 as it appears that '95 and older XTs used the same left-side clutch cable arrangement and bracketry as the TWs, but it changed in '96 to right-side. Oh well, I'll just transplant the XT's clutch cable and re-route as per your pics. Your post above definitely will help with that! I know for a fact that the '96 XT vents out of the crankcase so that shouldn't be an issue. I will endeavour to get some pics of the '96 XT225 tomorrow and post them.

Long term, my 265cc is based on a set of '03 XT cases for the convenience of the wider case mouth - I am swapping the guts of an '02 TTR225 into it as it was just simpler for me to do it this way. I had to get the parts for the camshaft cover vent set-up as a result. As per my "build saga" thread, that has been put off for the next while...

Many thanks again. The sharing of knowledge on this site is one of those things that keeps me coming back. Take care, stay safe and healthy,

James
 

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Discussion Starter #12
Wow, thank you for the nice comments! I tried not to make it too pic heavy, but there were certain things that I thought were important to illustrate.

As for the engine, it's a 2007 with a nikasil cylinder. I figured that might be why the cooling fins were different, but I didn't have an earlier model for comparison. If you can run the TW style cable routing, that's probably easier. That's how I'll do it with my 250 engine, if I ever get it done. ;)

I mentioned I did a few things to the XT engine that weren't relevant to this thread. I installed a kick starter, a new EBC clutch, top end gaskets to address a pesky base gasket leak, and I put a ball bearing on the cam, just for the heck of it.

The clutch is light years ahead of the stock TW clutch! This alone almost justifies the swap... and the six speeds are icing on the cake. I like, like, like this conversion!
 

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Discussion Starter #13
Performance wise, I was surprised at the level of improvement.

We took it to an undisclosed location for some speed runs, along with my '87 TW (which is a pretty good runner). From a full stop, my friend on his XT/TW225 accelerated away from me from the very start... which never happens, because he shifts too early! Then we switched bikes, and I accelerated away from him just as quickly, and I'm 50 lbs heavier!

When I grabbed 2nd, the front wheel came off the ground (just an inch or two), which is something I've never experienced on a TW. The closest I've ever come was on Little Tommy's black '87... but that was a special bike. Although he denies it, I still think that engine was stroked. ;)

Anyhow, I'm really happy with the way it all turned out. I think it's running a little lean at sea level, but my friend is moving to a higher elevation (about 4500'), so I told him we'd look at tuning the carb once he gets there.
 

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Yep – the XT225 will have the front wheel skipping until you ease off the throttle or get it into third, same with the factory TW225 – bit of a shock if you’re not expecting it – lol

Great write up, descriptions and pictures are perfect – well done ……
 

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Performance wise, I was surprised at the level of improvement.

We took it to an undisclosed location for some speed runs, along with my '87 TW (which is a pretty good runner). From a full stop, my friend on his XT/TW225 accelerated away from me from the very start... which never happens, because he shifts too early! Then we switched bikes, and I accelerated away from him just as quickly, and I'm 50 lbs heavier!

When I grabbed 2nd, the front wheel came off the ground (just an inch or two), which is something I've never experienced on a TW. The closest I've ever come was on Little Tommy's black '87... but that was a special bike. Although he denies it, I still think that engine was stroked. ;)

Anyhow, I'm really happy with the way it all turned out. I think it's running a little lean at sea level, but my friend is moving to a higher elevation (about 4500'), so I told him we'd look at tuning the carb once he gets there.
I seriously thought about buying that bike back from you when you offered, but I just didn't have room for it, wish I had... Great job on this build bro!! (y)
 

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Discussion Starter #16
Thanks, Tommy! That bike is in good hands now, and is being used as intended! (y)
 

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Top notch write-up. Can’t wait for the 250.

Dumb question - can you adjust the clutch engagement point while the retainer screw is backed off.
 

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Discussion Starter #18
...can you adjust the clutch engagement point while the retainer screw is backed off?
That screw just keeps the clutch arm shaft (I'm not sure of the terminology) from sliding out. As far as I know, the clutch can only be adjusted by removing the right side cover, and turning the adjustment screw to line up the clutch arm pointer with the mark on the crank case. The clutch cable slack/tension can be adjusted from the outside, but not the clutch itself.
 

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My donor-cycle, 96 XT225:

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Cyl detail:

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Clutch cable detail:

20200420_135347[1].jpg

From the above pics, I don't think there should be problems WRT motor mount/cyl fin interference, so I think that is only an issue on XTs from 01-up. As you can see, XTs from '96-up route the clutch cable on the right side. I am going to fol CJ7's advice and switch over to the TW clutch set-up. Luckily I had the required parts set aside for the TW265 project.

I will post updates on my swap on the TW Build Saga thread.

Thanks and stay safe, stay healthy, and stay busy!

James
 

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I did the same thing but I kept the complete electronics from the 225 to me made it a lot simpler I was also able to retain the 225 clutch cables and throttle cable
 
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