I picked up an LT100 parts bike that was totaled in a crash. I took what I needed from it and now I still have the engine. It was seized up but I was able to get it free, pulled the cylinder off, unstuck the rings, cleaned the bore and piston up, went through the carb, cleaned the points  and it fired right up and runs good. I was thinking of turning my HT90 into a 100 by switching the top end like you can with the CT AT and was wondering if anyone has tried it before. 

I just have to say I love your engine stand!!! 

Looks like they had the same base gasket and stroke...  so chances are decent it could work?  Connecting rod seems to be different part number though.

Let us know how it works out it you try it.

Be interesting. rod length or pin height of the piston 'might' change but easy to dismantle & check it out. My HT1 went extra good as it was & think there's only two mm between bore size--plus reed inlet of course. Look forward to the results.

From the pictures i've seen i can see the big end eye has lubrication holes in it as the HT1 doesn't.
The crank pins a different part number but the big end bearing is the same - 9331042237-
I too have thought of this, that's how i know.

Mark T there was no time to fart around building a proper stand, we had an engine that had been waiting 40 plus years to be risen from the dead.
I think I could just switch the whole engine easy enough and probably would be the best way to make it into a 100 but my HT is still pretty original and I  hate to bastardize the matching numbers engine situation for a couple CC’s. I’ll let you guys know if I try the top end swap though 
youtube.com/shorts/sD7iPakrJME?feature=share

I wasn't kidding.  I like the jury-rigged stand.  Good old fashioned ingenuity.   

Yep, swap the complete motor & keep the HT in one piece, good idea. My LS3 is much the same motor but road porting gives more top end & ratios might be closer--must compare on parts lists. There's a video up here somewhere of road racing my HT1.

There's a video up here somewhere of road racing my HT1.

Man alive !!! That i have to see RT.
I looked to see if the crank was the same number . HT 1 is 2761140001, LT is 3041140002
But the primary side crank seems to be different
HT 1 Gen side # 2761142200 . The LT is 3041142200 .
HT 1 Pri side # 2761141201 . The LT is 3041141200.
Both primary gears are the same part number and amount of teeth and the distance collar is the same number. Possibly something on the bobweight that's different to do with width or lubrication maybe. Or maybe nothing at all.

Yep son was riding it & narrated the video. Racing with the school build dodgy engineers 110cc Honda clone engine big mini bikes. Bike was a rusty corroded wreck found outside a few years ago. Forced it free on the flywheel & arc welded a new header cut of a kdx pipe. Never had the cylinder off. Cleaned carb & went racing. Sat on 55mph all day long. Had about one mph on the mini's haha. Video goes on for a bit so drag it on if you like. I'm the bald old bugger in my leathers as raced my bucket that day too but against YZF400's etc who were having a run before a Motard even coming up. Was maybe 5 years ago--time flies--or fly's lol. I'll find the vid shortly.