White Trash Bobber Resurection and Top end rebuild...IT RUNS!!!!!

[lidirtrider]

Ring end gaps appear to be in spec. But, did you have them installed correctly? There is a top and bottom side to them. The top side is usually marked with a letter or number stamped into it. It must face up or the ring won't work correctly and seal.

I forgot to mention that. Yep, at least one of them was on upside down. The oil rings were way out. I could have measured the gap in full millimeters. both rails and control ring. So I'll need to order rings to get those, and like GLJ said, not worth the risk of the rings being damaged so I'll replace everything.

Other than a ring end grinder, is there another way to do a satisfactory job of filling the rings if needed?

 

[5twins]

You can hand file them but it's tricky and easy to break one. Oil ring end gap specs are usually bigger than the top 2 rings, up to twice as much sometimes, but that would barely put you at 1mm.

 

[TwoManyXS1Bs]

I'm concerned about the vertical striations on the piston and cylinder. Like scoring from micro-grit. Was this engine ever glass beaded or vapor honed?

 

[lidirtrider]

I'm concerned about the vertical striations on the piston and cylinder. Like scoring from micro-grit. Was this engine ever glass beaded or vapor honed?

No. It was a brand new Big Bore cylinder from MiksXS. It was never honed and the ring gaps were not quite right. I'm going to hone it and see how it comes out. I may even take everything to local machine shop and have it double checked.

I have to admit, when this orginally all went together, my friend and I were not as educated in engine building as we have become. Most of that knowledge was learned here, from all the great people on this forum. So it seems we were rather ham handed in our efforts and now we're paying the toll. It's entirely possibly that dirt/grit was inroduced when we assembled it, resulting on some of the striations.

 

[lidirtrider]

Went out in the garage and tried my hand at honing the cylinder. I also replaced all the valve cover studs witht the replacement kit from Hugh's Handbuilt. It's a great little kit. Had to Helicoil 2 of them anyway, so it worked out really well.

I took measurements before and after Honing, and also measured the pistons. Cyclinder measurements were taken at the top, middle and bottom of the cyclinder, both fore and aft, and left to right. Pistons were measured at the measuring point provided by MikesXS. After lots of repeated measurements, and shitloads of math, I came up with these combinations of piston to cylinder clearance values:

Left Cylinder with Left Piston: .0028"
Left Cylinder with Right Piston: .0032"
Right Cylinder with Left Piston: .0025"
Right Cyclinder with Right Piston: .0029"

*NOTE* I labeld the pistons as I removed them from the previously assembled engine.
Based on those values, I'm thinking to keep them as they were, left with left, right with right.

I took a few pics of the honing for some critique. Let me know what you all think.

Next up is to order a bunch of gaskets and new rings and such, and while I wait for that to arrive I'll lap the valves and ensure they're seated and sealed nicely.

 

[GLJ]

Left Cylinder with Left Piston: .0028"

Right Cyclinder with Right Piston: .0029"

You're at the upper end of specs. Will it run Yes. For how long? Who knows.
As far as your honing still seeing vertical lines. Will it run? Again yes. How well will new rings seat? Who knows.

Looks to me you're going to have a grenade motor. When I helped guys race stock cars sometimes we needed a motor to get bye for a couple of nights. We would take the best parts laying around and build the best engine we could. Then pull the pin on it and go racing. Sometimes they ran great and lasted longer than needed. Sometimes we pushed the car onto the trailer after a night or two.

 

[lidirtrider]

Then pull the pin on it and go racing.

Lol. I like that phrasing. But hmmm...seems like I have some thinking to do. Maybe I'll take a trip to a local race/machine shop and have them take look. Might have to go to 81mm piston and have it bored out after all.

Or like you said, hope for the best and wait till detonantion before I go oversize. lol.

And other than the vertical lines, how does the hone/crosshatching look? Complete shit, or not too bad for a first timer?

 

[GLJ]

I strongly suggest making friends with a good automotive machine shop. Like girlfriends, good ones that make you happy are not the cheapest ones.

 

[lidirtrider]

I'll take that as I did a shit job. lol

 

[5twins]

I don't think your hone job looks too bad, you just didn't do it long enough to remove all the vertical scraping. Your near .003" clearance isn't near the max, it's about in the middle between the minimum and maximum. Minimum spec is about .002", max about .004". When I did my topend about a dozen years back, clearance spec was very near that .004" max but I didn't want to spend the extra near $300 to have it bored and buy new pistons. It hasn't given me any issues all these years other than using a little oil, but so what. All I did was replace the rings ($30 deal off eBay) so I think I made out OK. It will get bored the next time it comes apart.

I think the majority of your problems can be attributed to inept assembly. You were missing the dowels which allowed the gasket to shift, and you had some rings installed upside down. Do it all right this time and I think you'll be fine.

 

[Gator xs2]

This is like De ja vu all over again. The first CB750 motor I built in 08 was put together all kinds of wrong. When Roland Stuart tore it down and told me what all I did wrong I told him “I’m a carpenter not a mechanic!! “ I never tried to build another motor after that. He gets them all. For me it’s pay him now or do it myself and then take it to him to fix it and pay him more later. Good luck brother. I hope you have better luck than me. I will say the guys on this forum really know their stuff. They’re amazing. And can probably walk you right through it.

 

[Jim]

Other than a ring end grinder, is there another way to do a satisfactory job of filling the rings if needed?

I use a 1/16" cutoff disc in a die grinder. Chuck it up in a vise to steady it. It's pretty easy to just squeeze the ring together and let the disc cut both ends at once. A quick grind and measure.... little at a time. You'd be surprised at how fast that disc will eat the ends of a ring. To repeat.... just do a little at a time!

 

[GLJ]

I don't think your hone job looks too bad, you just didn't do it long enough to remove all the vertical scraping

By the time he gets rid of the vertical lines gone what will the clearance be? Do it once and do it right.

 

[GLJ]

As I said will it run, Sure.

 

[lidirtrider]

All good advice guys! I really do appreciate it. I've learned to be humble and accept some humilty. I know I made a l lot of mistakes, and have owned up to them. I'm just glad these engines are as resilient as they are. This has been a great learning journey for me. Wrench therapy. I'm thankful for the knowledge that everyone here is willing to share.

 

[Beags64]

A sign I saw a while back read "Making mistakes means at least you are trying"

 

[Jim]

I'm gonna agree with 5twins.... you're mid range on the piston skirt tolerance. Hone it some more. You'll either get rid of the scoring and stay within tolerance... or you won't. Yeah... it's always nice to stay at the tight end of the tolerances (and essential when building a race engine), but a tolerance is there for a reason... because those limits are acceptable. So... keep honing. a trace of scoring left is also OK. It's an experience/feel kinda thing as to what's acceptable. I'll put a pic of my cyl. at the end of this comment. You'll see there's a trace of scoring left. Should give you an idea of what's acceptable.

On the rings... you might want to consider getting the next oversize and gapping to fit. Since you'll be at or close to the limit on the skirts, you might be outside the limits on ring gaps with the standards.

 

[Gator xs2]

When built right they’re a battle wagon.

 

[GLJ]

When I did my topend about a dozen years back, clearance spec was very near that .004" max

Might be why you have had to modify the oil breathier system. My XS2 has 2 open tubes with no appreciably oil coming out of them.
It's one thing to make a motor run. It's another thing to truly rebuild it. LOL

 

[lidirtrider]

It was WAY too hot over the weekend to do anything out in the garage. Over 100 degrees and high humidity both days so so I spent most of the day indoors or at the beach. Anyway, I ordered a bunch of stuff from MikesXS. I missed the suggestion to order to oversize rings before I placed my order, so when everything comes in, I'll check it out and measure up the rings to see how the gaps look. If I have to, I'll order the larger rings.

Since it was actually bearable outside today, I went out and did a few things while I wait for the parts to arrive. I cleaned and painted up some small parts since everything is apart. Also since the head is all apart, I lapped the valves. We did it when we first put it together, but I figured I might as well, even if just to get rid of some of the carbon and oil residue that had built up.

I cleaned out the tank since it had been sitting for a while. Nothing too bad, just rinsed it with some mineral spirits, and denatured alcohol. I installed the petcocks and put a little fresh gas inside and all apears to be clean and sealed.

When I lapped the valves, I brushed on a little Dyechem so I could check my work as I went, and used coarse and fine lapping compounds. Once I get new valves seals and reassemble the head I'll use a little denatured alcohol to check and see if the valves are tightly seated.

Still a few punch list items to keep me busy till the parts arrive, but with all the help I've gotten here, I'm feeling much more confidant about putting this thing together correctly this time.

Before and after of Left side Intake Valve and valve seat