Yikes! Sorry for your loss on this one. I guess someone had to try what you did eventually. Just sucks you were the guinea pig.
Id probably search for a new motor at this point. Finding replacement parts will be a bitch. Especially if your cylinder wall is scored from the particles, then you will need a fresh hone and new rings. Not to mention those Pistons are now done. It will probably cost you more vs getting a donor engine.
The funny thing is, I got a 78 bottom end from Dean j already (i really thought the whole issue was a rod knock, which may still be the case),so the bottom end is taken care of.... The issue is, now I need another replacement head. Or at least 4 exhaust valves and a skim.
As an aside, the reason this happened was at least partially my own damn fault. I'll explain later....
So, the reason the exhaust valves contacted the pistons was at least partially my fault. I had issues timing the exhaust cam. No matter what I did, the timing marks wouldn't line up. Either the mark on the cam was on one side of the pointer or the other. I picked one, buttoned it up and never bothered checking if there was an issue. Mostly because I only had one had gasket and couldn't afford another one at that time. So.... I'm thinking I picked the wrong side of the pointer. Better luck next time?
Although the casting process improved for the one piece head and improvements were made over the years ,such as the round port E exhaust , the actual cams and valves are the same parts on all of the TX/XS500's heads '73-'78. The the higher comp 2F1 pistons in that E motor are also a common upgrade when rebuilding the older 371 engines.
With the timing pointer at the "V" on the plate and all of the cam chain slack to the exhaust side with full pressure on the tensioner, the dots on the cams "pretty much" align with the arrows on the caps. "pretty much" means they are not precisely aligned, however if they are off a tooth either way, it is absolutely positively obvious it is incorrect.
Yeah, I had it on the exhaust side of the mark, so I thought for sure it was right.... Guess that wasn't the case this time.
Either that, or trying to put a 76 head on the 73 bottom end isn't the hot ticket.
Just to clarify, it's taken me this long to remove the head from my old motor- this isn't the 78 bottom end I got from you, Dean. That's still waiting to go in.
Lol yeah, I probably should have mentioned that.... I do know that the 73 motor was the only year that had compression as high as the 78s.... And I had some interesting issues with fitment. If, as you say, the slack should be towards the exhaust side, I had had it right after all... So maybe it's an issue with deck height...
Some closer inspection has revealed what caused this debacle..... I mentioned someone had been inside this motor before, right? Seems they knew to fit the'78 pistons. The bike had 1mm over '78 pistons fitted already. The addition of the late model head to that is what caused the valve-to-piston contact. The valves are indeed bent. Even worse, it looks like the exhaust cam journals are worn out from the extra pressure, as well.
Anyone looking to part with a Suzuki GS500e motor, cheap?
I really hope this project isn't stalled permanently. I'm in the process of tearing my 74 TX apart and I'm noticing the same issues with mine as yours, so I know what to look for now! LOL. But seriously, did you ever finish her up?
No.... Unfortunately I haven't had a lot of free time since my son was born. Lol. I'm actually considering going to a different engine, even though I bought this beautiful '78 bottom end. I wrecked the '76 head, and I'm not sure if it's worth buying another one. Tri-maha maybe?
I've decided to sell my Hyosung GT250R to finance the completion of this project. If anyone has an old two-stroke single over 350cc, or a complete but wrecked parallel twin over 450cc, I'd do trades, but I'm not holding my breath.
Well.... There hasn't been any progress in a while. The bike has been sitting in pieces in my grandma's garage following the breakup between my son's mother and I. With no time or money, or even a place to work, it's been put on the back burner.
That being said, I've got a line on something really unusual for tax time... A guy at work has a couple APU's sitting in his yard, with good engines. (In case you didn't know, APU stands for "auxiliary power unit". They're basically little diesel generators that also run the heat and AC on semis when they're parked up. Saves fuel and wear and tear. Since they don't have to have the main engine idling the whole time.)
The engines in question are 570cc liquid-cooled diesel parallel twins. I'm told they're rated at 28hp. Or the same as my Hyosung 250cc.
But that's without adding a turbo. Sounds like I might be doing something a little unorthodox....
Alright, here's a picture of an engine like the one I've procured. It's a 2TNV70 Yanmar, for those that are interested in the specifics. I chose this shot to showcase how narrow the motor actually is. Specs say 18 inches wide, 21 inches high, 16.9 inches from front to back. It should fit fairly snug in the TX frame. The reason things are taking me a awhile is I'm trying to figure out what sort of transmission I'm going to be able to use behind it. My first thought was to try and use an aftermarket Harley trans, like a Revtech 6 speed, but I hate Harley's enough (and the prices associated with them) to find that idea distasteful. Perhaps a Norton Commando unit, or something like it.
Well, looks like the diesel idea isn't going to work... I found an Enfield 5 speed trans, and worked out the dimensions, but the cost if the tranny and the machine work to mate it to the engine just wasn't worth it.... So I bought a non-titled Honda Rebel 450 for 600 bucks. I'm working on getting some Chinese-made Keihin-clone flatslides to fit the Honda motor, and then it's getting shoehorned into the TX chassis. Most likely with the Honda lower frame cradle. We'll see. Onward and upwards!
It's funny the little things that can hold you up and get on your nerves.... The Honda Rebel 450 came with a 525 pitch chain and sprockets, and my Yamaha came original with 530 pitch, which I converted to 520, to match the YZ250 rear hub I used. Now, I can't for the life of me get the two to match. I can't find either a 520 front sprocket for the Honda motor, or a 525 sprocket to fit the YZ250 rear hub..... I might resort to welding my Yamaha front sprocket's teeth onto the Honda sprocket.... But I hope I don't have to resort to that.