Top end rebuild (XS1B)

[richard]

So after returning from my business trip I took my bike out for ride to warm it up. When I returned I did a compression test on it and got 100 on both cylinders. The rings just didn’t seem to be reseating like I hoped it would. The timing chain was still noisy and it just seemed like time to do something about it. So I decide now was as good a time as any. The next morning I started removing the engine. Well I started at about noon after running some errands. By 4:30 I had the engine out and set it on on a cart.

Standing there looking at the engine on the cart I decide I’m just too dammed old to rebuild this thing bent over that cart. I have a bench in the garage put like most it's full of stuff. So I decided to make something to hold the engine. I got on the internet and found that Harbor Freight had an engine stand for $39 bucks which seemed reasonable to me, all I needed was a bracket to hold the engine on the stand and I would be set. The next morning I bought the engine stand and a length of 1 1/4 black pipe from Lowes. I have a Hydraulic tubing bender so I laid the engine on its side and bent the pipe to match it. Allowing enough room on the bottom of the bracket so that I could split the case while the engine was mounted if needed to I figured 10 inches should do it. I welded the pipe to some plate I cut and drilled to match the engine stand and once it was welded I shot it with black spray paint. Once it was dry I mounted the bracket to the engine and set it in the stand. Let me tell you that engine was heavy for a single person lift. I wouldn’t do it again. Next time I’ll use a lift to pick it up. The next day I started pulling the engine apart and this is what I found.



Bike with engine removed



Engine Placed on cart for the time being



This is the engine stand with Engine mount I built




This is the engine in the stand before I started taking it apart



One of the #3 screws heads stripped so I had to drill the head off of it and then us an extractor to remover it.



Lifting the rocker off the cylinder head



This is the timing mark at TDC on the Crank. Off center is due to cam chain wear.



This is the cam tensioner in the head between the barrols it is all the way in rubbing on the head between the cylinders as I suspected. I could hear it while riding.



This is the head with the cam removed before lifting it off.



This is the cylinders Before I lifted them off. I thought they looked pretty salvagable and the measured at 75mm with the telescoping guage and caliper. I'm going to re- check the clearance before going any further. The new piston fit was snug but slid in just fine from the bottom. I think I'll just hone the cylinders and use them.



This is the grooving done by the cam chain as the tensioner pushed the chain up against the vane between the heads.



The engine with the head off. I check the slop in the rods and pins briefly and there was no movment that I could tell but I do I better check tomorrow with a dial indicator.



The Valve pockets on #1 they both look like they are burning rich but this one is the worst.



This is number 2 it's not as bad but it is still too rich. I am not sure if the carburetion is wrong or it is just the other factors like low compression or the timing being advance because of cam chain wear.



These are the barrel markings. I'm not sure exactly what they mean other than the oversize? As far as I know these marking indicate that the left cylinder was originally 75.001mm inside diameter and the right was 75.000mm in diameter.



I also wasn't expecting this strange numbers on the piston. this indicate the pistone was originally 74.949 in diameter.



Here is the other with 950 on the crown which indicates 74.950mm in diameter.



This is a pic of the cylinder bore. There are no scratches or ridge at the top to speak of. I think they will clean up just fine so now I have to sets of stock cylinders and it looks like two sets of pistons.
I am going to mic the piston skirts and pins tomorrow but they look ok visually at this point. I may change the pins on the pistons just to be safe but I want to mic them first to see if there is any wear. they may be ok. It's hard to tell at this point.



Well that's it for now. I hope you enjoyed this post

Richard

[5twins]

I like that engine stand. I made the basic angle iron one and set it on an old A/V cart I pulled out of a dumpster at work .....



For getting the engine in/out and moving it around, you can't beat having a helper. Something to grab onto is nice, too. I made up these pipe handles so me and a buddy can wiggle the engine in and out of the frame and carry it around easily afterwards .....

[richard]

Nice ! 5twins
I like the outrigger to hold the chain I could have used something like that. I dropped my chain and fished it out twice during the process. It is so much easier to put the new chain on if you can attach it to the old one and guide it on.

I have some pipe left over maybe I'll make some lift bars too when I'm ready to go back in. Great Idea.

[5twins]

You could easily add an out rigger to yours. Stick it in that front or rear pipe. You might also consider adding "U" brackets to the tube loop that would utilize the lower rear and center motor mounts (like my stand connects). That would free the upper mounts for use with the pipe handles.

Your heads look normal. The exhaust valve area is usually always lighter like that because it runs hotter there. To decarbonize the head and piston top, use paint stripper. It may take a couple applications but it will literally melt the carbon off so you won't need to scrape much at all. On the sides of the pistons and in the ring grooves, after the stripper sits for 10 minutes or so, scrub with an old toothbrush and they'll clean up nicely. I finish the piston tops off with some chrome polish then scrub them with soap and water.

[richard]

I started cleaning up the pistons and valve chambers yesterday. I wish I had known about the paint remover because I ended up using my pocket knife a toothbrush sized wire brush and a Scotchbrite pad.



While I was reading your reply it occured to me I could telescope my outrigger into the end of my U-pipe bracket since it's welded to the plate. It's 1 1/4 and a 1 inch nipple will slide right in next to the mounting plate. I just have to weld my outrigger to the 1 inch nipple. I'll have to dig through my scrap pile to see if I have the pipe to do it.

[5twins]

Oh, a scrap pile, I love scrap piles, lol. Looks like you got things pretty clean. A bit of chrome polish now will remove the remaining discoloration and you may end up with something like this .....



The valves can be wire wheeled once removed. They're really hard so it won't hurt them. I would test them for leaks 1st before removing. Stick some old plugs in the head, set it upside down and level on the bench, then fill the combustion chambers with solvent (I use kerosene) so the valve heads are covered. Blow compressed air in the exhaust and intake ports (up against the bottom of the valves) and watch for bubbles in your solvent around the valve edges. You can't put the blow gun too close to the valve or you'll literally blow it open (then you'll see bubbles, lol). Play around with how far into the port you're sticking the blow gun and you'll find the right spot - in enough to pressurize and test for leaks but not enough to blow the valve open.

[boots]

wow. and here i was going to buy an engine stand so i could polish it up... what a sucker i am thanks for the ideas.

[richard]

Boy that's clean!

I've checked the valves that way once before only back then the guy that was showing me how used a cup of water to fill the chambers then let it set for an hour. We dumpred the water out, blew them off with air and shot them all with WD40 to prevent rust. Blowing air up through the chambers would sure be faster but could be kind of tricky too. I like the idea of solvent because I have seen valves rust up just from setting them on a cement floor.

I'm hoping my valves will be ok because I have always had them done in the past. However I have seen my Dad lap them by hand on a TR6 when I was a kid. I think I could do it if necessary.

So if I had 100 pounds of compression before and when I'm done I'll have 150 does that mean I'll have 30 percent more horse power?

[650leo]

Richard, The markings on your cylinders are the inside diamater of the cylinders when stock. 75mm + the three digit number on the cylinders. So one side is 75.001 mm and the other is 75.000 mm. If you take the piston diameters, 74 mm + the three digit number on the piston which are 74.949 and 74.950. Subtract the piston size from the cylinder it came from and you will get .051 mm. Thats what the factory set the clearances to. The factory spec is .050-.055 mm.
I think when they cast the pistons, they measure and mark them so they can match them into sets. A bit of difference won't matter much. Then they bore the cylinders to match the pistons. They then mark the cylinders with the bore size.
When a machine shop does a rebore they will do the same. Bore the cylinders to match the pistons. The shop that did mine marked the piston and cylinders left and right because one piston was a bit bigger than the other.
Very nice documentation of your tear down. I like your engine stand too, very well done.

[wideload]

Richard those are some fantastic pictures! This is one of the threads that has to be in my bookmarks for future reference. Would love it of those pics kept coming.

[richard]

Thanks
I'm using a little Cannon Elf which takes reallly nice pictures.

After loolking at 5twins excellent stand I decided to build myself an outrigger to hold the cam chain ends. These things are indispensible when it comes to dealing with the cam chain. Since 1 inch pipe will slide right into 1 1/4 pipe I welded a piece of 1 inch onto the end of a piece of 1/2 inch pipe and bent it at a 90 degree angle. I drilled the 1/2 out with a 5/8 drill to slide a 5/8 in order to slide a 5/8 rod into the end. then drilled and fitted a ring on the end. I was going tap in a set screw at the top but it seemed to hold just fine with the plastic cap that cam on the pipe, so I just shot it with black paint and left it.
Here's a pic

[XS Rod]

Very nice set-up...
Makes it alot easier when you spend some time to set-up the shop.

[richard]

Thanks
Yeah it does. Having the right stuff makes a world of difference :-)

[XS Rod]

Oh and by the way ... with all the cool machine work in your pics I couldn't help but notice the "lowly" screw removal... ahh the simple pleasures in life. Question Richard... do you smile when you do that? Drill a screw that size dead freakin nuts and remove it without damaging one single thread? On a larger scale with an equal opportunity for disaster, back in my 20's, I drilled a broken head stud from my sister's Triumph TR4A. Got a couple of stories to go with that car ...

[richard]

LOL!
More like a sigh of relief. There is always a little pucker factor when extracting small screws from blind holes. I think the bike likes me so I got away with it this time. :-)

The last job I had was in a creamery where everything is stainless and a nightmare for things like that. Stainless looks neat but for a mechanic it is nasty stuff.