It's past time to start XS2 Resurrection

RC4MAN said:
It's great that you managed but a single reamer in each size would have done and would have been long enough you could have flipped the cylinder over onto the head gasket side which would have been more stable on your small drill press table.
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I'm sure you are right. If the holes would have needed the precision of a reamer I would have done that. For me drill bits made the most sense.
I guess I forgot to mention the drill bits were not long enough to do the whole hole. I had to drill from both sides.
 
My buddy stopped by and measured things. Was impressed with the uniformity of the bores and pistons. The thing that concerns me is the clearance of the bottom of the skirt. He gets a hair over .001. From a few searches I have done on BBKs it should be .0025 to .003. I called my machinist and explained what we found. Asked what he thought. Long story short he thought for a forged piston it was too tight But he explained every piston manufacture has their own specs. If you have any experience with these kits or forged pistons what do you think?
My inclination is to have them honed to at least .0025. If I do it will be a couple of weeks before he can do it as he is going on vacation next week. I was hoping to hear it run next week. Since I have a very good running engine in it now their is really no hurry.
 
Sooooo.......does that mean the .001 is ok or still a bit small.

never heard or read about the MikesXS BBK's having problems with clearance on assembly...........but then had never heard they had barrel case holes bored the wrong size before either.
 
Unless someone knows what alloy the piston was forged from, you're shootin' in the dark. Common wisdom says forged pistons need more clearance than cast.
Yamaha's book says .002" to .0022" for it's cast pistons. Just speaking for myself, I'm happy if it's between .002" and .003".... but again, we're talking cast pistons here.
I don't have an answer for you Greg.... but I would not run a forged 3" piston at .001" skirt clearance. Unless someone chimes in with some good info, I'm gonna shoot for .003" to .004" when I put the bbk in my speed twin motor.
 
650trader said:
GLG. my BBK 750 kit should be set at 0.0020 - 0.0022 inch or a bit more. (0.050 - 0.055mm. ).
All of the pistons for the kits are within two ten thousands of each other.

Mike Lalonde
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Thank you for your input.
I'm going to put the BBK on hold until my machinist gets back from vacation. No hurries, no worries.
 
A little late in updating this thread. BBK conversion is together and ready to go in. No pics you all know what a motor looks like. I ended up having the cylinders loosened up a little at my machine shop. He was impressed with the sizing of the pistons. I noticed when I pick everything up he hadn't marked the pistons as to which cylinder they needed to go in. He said it wouldn't matter. They were in .0005 of each other. That that amount of difference could be the amount of time he held them in his hand while measuring. Oh I had the cylinders sized to .00275 larger than the pistons. I know I'm the only one that has had a size problem. If you bought a kit it may not hurt to check this.
Now to figure out when I can find a day to install it. Last Tuesday I brought home another XS2 roller and literately a truck load of parts. Plus I've playing with another XS2 I bought a week earlier. Good problems to have!
 
GLJ said:
BBK conversion is together and ready to go in. No pics you all know what a motor looks like.
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Yeah... what Bob said. You think nobody here want's to drool over pics of a big bore goin' together? Sheesh.... :sneaky:
I think you should grab the camera and start over.:smoke:


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Mailman said:
Ha! 2M and I are on the same track.
I think you should repair and keep your original frame, it’s your number matching, and there is no stigma with repairing a break. I think it’s not so much a matter of abusing it in your youth, that caused the break. I believe it was just early in the learning curve for Japanese motorcycle manufacturing. Nowadays the frame would use thicker tubing , and computers to calculate stress points. I read an article about early frame development for the Norton Commando, they kept breaking up by the steering head. One of the engineers suggested a small triangular gusset and bingo! Problem solved.
As Jim stated, I think ideally, replace the entire tube. However if you choose to v out the crack and weld it, you will need to reinforce the entire area to prevent it from breaking again. I have repaired many broken truck and trailer frames in my youth as a fleet garage welder, and the formula was always the same, weld the crack, plate over it, reinforce it with gussets if it was near an intersection with an adjoining frame.
View attachment 129393 View attachment 129394 View attachment 129395
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Nice welding here. Top dog Bob!
 
Since I'm pretty much done with the Survivor bike it's time for a little basic maintenance on my original XS2. Just some cleaning and stuff. The bike had been running well, took a 280 smile trip on it a couple of weeks ago.
1653512880745.png

Almost forgot going to put the original motor back in. It has a BBK kit in it. Nothing cutting edge or exciting.
1653513051450.png
 
Yesterday finished up the basic maintenance on the old girl. Big block engine installed, cleaned chain ect.
Took her out for a 40 smile ride. Definitely not the same bike I bought from my brother 46 years ago. The extra 100cc in size is very noticeable. I like it. More bottom end, runs 70 effortlessly and will go from 70 to 80+ in a eye blink. That's with a 32 tooth rear sprocket. I do notice the difference in the cam I used, it's from a 75. Much more linear, you don't get the 5 grand punch like a XS2 cam. I still like it. Motor sounds great no bad noises.
1654547316323.png

Today put her back on the lift to look her over and check a few things. Good news, bad news.
Good was nothing fell off. Did a compression check and had 160+ on both cylinders. I could tell it had more compression when I kick started it. Once when kicking it I didn't give it my full attention. Brought it up to compression and kicked. Lever moved an inch and then reversed back to where it was. Hmm. I think the bike gave me a warning. Check the plugs and they have a little color to them. I did not change the jetting from stock.
The bad news is the motor will have to come back out and come apart. It has a oil leak in a very bad place. The base gasket. It squeezed out. The pic is after I cleaned the oil off. It's a green gasket but not Athena, it came with the kit. Since I'm not real keen on doing the proper thing to fix it right now (I would like to ride it) I am going to try to make a band-aid work for a bit. I broke off more of the gasket cleaned with brake clean and carb spray and applied Yamabond #4. Tomorrow I'll find out if it helped. As I said it will be just a temp thing, I would be happy if it worked until next winter but I doubt it will.

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