Took off the valve cover. My valve clearance was really tight (always pushing on the cam) which could have caused my compression issues. So I either try to just adjust the valves and check compression again out of the bike or I continue with tear down to confirm pistons & rings are okay, which is the direction I think I will go. I think I also need to lift the cylinders to make sure the balancer chain guide is the cause of the black bits in my oil strainer. Just need some tools (chain breaker, riveter, and new link for cam chain).
I took off the Head last night. Looks like some of my compression issues stem from not just the tight valves (I have yet to be able to get 3 of the 4 valve adjustment covers off) but also some carbon buildup on the valves. Didn't take any good pictures but I will hopefully document checking the cam, valves, and pistons to make sure everything is good there.
I'll need to get a new masterlink for the cam chain. I've seen a few comments about it on other threads but I'll pick up that kind of stuff once I buy the bits to put it all back together.
The plastic bits in the engine don't seem to be coming from the cam chain guides (there are tracks in there from the chain but it isn't all chewed up to make bits of plastic everywhere, so I think it is the balancing chain but I'm going to look into that after I check the top end to make sure everything is in spec.
I've never bought pistons and rings before, is that a somewhat generic item based on measurements or do I need to find a tx750 specific set (NOS)?
I've never taken the head off a motor before so we are now entering the great unknown but I was sure having fun doing it.
Last Edit: Aug 15, 2018 8:59:35 GMT -5 by tr1ppler
After the bike sitting for a few weeks made some progress this morning and hoping to spend at least one day this weekend on it.
I took out the valves this morning. They came out nice and easy and they felt like they moved pretty easy without being loose but tomorrow I'll hopefully take some careful measurements.
Measured the lobes on the Cam Shaft and everything seems good there. There is no flaking or scratching on the lobes, but the contact point is a different color. Hopefully that is okay.
The rubber on quite a few bits (where the battery acid didn't spill on it) seems to be doing pretty good for 45 years old.
Valves out. Pretty crusty on the face as well as the stem. Could have caused some of my compression issues along with the bad valve adjustment.
Last Edit: Aug 31, 2018 10:20:17 GMT -5 by tr1ppler
I don't really know what constitutes "Excessive wear" but none of the scoring on the pistons is noticeable to the touch. I was afraid to try and get those piston rings off by hand and none of the local auto parts stores that were open on Sunday had a pair of piston ring pliers in stock. Once I get those off I will confirm they are in spec but they look pretty good and pretty clean. Almost feels like someone saw that bad compression assumed it was a bad piston/ring set and replaced or cleaned up those but didn't adjust the valve issues. I've done similar things before, only attack the solution that you know, but I was hoping that was the only issue this bike had...
I don't know about the lines on these wrist pins though.
There was strange crinkling in the metal on the sump cover inside and out. I don't know if this is the porous metal issue I've heard about on the tx750?
The Omni-weight balancer seemed to have about the right chain tension using a caliper and eyeballing it, don't have the proper gauge for measuring that. Seems pretty close though. Maybe an issue but without a chain tensioning kit handy the only option may be a new chain there. I remember some specs they used for the omni-balancing chain in Germany on the website.
The Bad news is that when I tested the wires coming out of the stator instead of getting the .7 ohms of resistance between windings I was getting about 20 on my harbor freight multimeter. The readings were pretty consistent but they were way off.
I didn't want to remove that cover since a glob of silicon is "assisting" the rubber grommet where the wires come out and I was hoping to leave that alone. But I'm going to next take that apart and check for more measurements. The plug for those wires shows some heat so I do think there is an issue there, but it also looks like the battery exploded so was hoping it was "just" a bad battery in there before.
So it does look like the bike was parked due to a bad stator. The 4 wire plug from the stator was toasted and the battery visibly boiled over at some point (damage to starter wire, dechrome of the exhaust, and toasted rubbers).
The field coil tests okay.
The stator is supposed to have 0.7 ohms resistance across the 3 wires. I get these numbers: 22 22 7
Even with the cheap harbor freight multi-meter those are way off of what they should be.
So I'm either going to try re-winding it or look for an ebay one unless you guys tell me otherwise.
Post by scrambler on Sept 27, 2018 20:31:25 GMT -5
Hi,
Great progress! Crinkling is not an issue here, everything seems normal to me. Actually, this engine seems to be in a good condition, much better than mine was. Easiest is to buy a used stator on ebay. I think I also have one spare somewhere, in case you can`t find one message me.
I am really leaning towards rewinding the stator. I think it could be interesting, maybe even fun. Might play with trying to produce more power for the bike.
I made my own wiring diagram to help understand the circuits. Grouped them functionally instead of the maze of the manual diagram. I'm sure there are mistakes but it helped me visualize what is going on.
I may be adding a fuse or 2. Not a lot of protection built into the harness. I may need to put in a modern Reg/Rec if the power is increased.
After having -23*F windchill last week we had a break in the weather and two days in the 50s.
So I decided to try and re-paint before putting the bike back together again. With the time rush of finishing disassembly and getting things prepped and painted in one day, I'm not sure how the long term results will be but I cleaned up a lot of the surface rush and she's nice and shiny. I really wanted to have the parts sandblasted and powder coated but I don't think that is in the cards. So I went this way instead. I did a lot of reading on various forums and everyone who used appliance epoxy was pretty happy with it, and being a card-carrying member of the CBMMA I thought that it would work for me too. It is a huge improvement but I wish I would have had more time to really clean the frame down nice and smooth.
Good job! I got mine blasted and then powdercoated, as that gives you very good results in no time but it`s pricey. In the old days I always painted my frames myself, I remember spending days with a wire brush in a drill to grind off all the rust and old paint. I hope my lungs have got rid off all the dust of old paint by now..
Yeah, I should have spent a little more time with it but I was pushed by the weather to get it done that day. Found later some places that I needed to re-clean and spray. But It is significantly less rusty and more protected than when I started. Starting re-assembly now.
I have a roller again. I'm going to try and paint the engine and get it back in and make sure the engine can now start and run before doing anything with the suspension, etc.
Waiting for engine painting weather. I have it out of the frame and the clear on it is very yellow so I figured this is a good time. But that just means waiting for spring or a few warm days...
Fun weekend. We had the promise of a warm Sunday so I decided it was Engine painting day. I think that with the new(ish) stator and fixed valves the bike should be in a better place to actually run.
I finally pulled the trigger on some parts to put the engine back together. Besides the Alternator and some paint I hadn't really spent any money on the project. We are now at the point where I need to see if she'll run before moving onto the other fun stuff.
I've never tried to paint a motor before but the clear had turned a nice "Smoking Grandma's fridge yellow" and really detracted from the look of the machine.
So I spent a large piece of saturday scrubbing off old grease and stripping the paint.
Then I raced against the evening rain showers to get the cases primed and painted with VHT ceramic Engine Enamel.
I'm really excited to see how it looks finished. It won't be fully cured until the engine has run. but it is a huge improvement. I couldn't get good photos of the final product but it matches the side covers pretty nicely. Once those are polished up it should be great.
Gaskets, o-rings, piston rings, all came in! I got the cylinders and head re-assembled last night. Cam chain and valve train and then I can see if this work has all been worth it!
Good job! You are pretty far from that, but once you get there make sure your carbs are not leaking because the gas might dissolve the nice engine enamel. Don`t ask how I know...