84 Engine Rebuild

[mattyo]

Originally Posted by bpratt18

Your thread is great! Exactly what I needed to start my own rebuild, so thank you very much. Looks like I have a long road ahead of me...are you close to finishing? Now that the pistons are out of the cylinders, I would think that I could turn the primary gear clockwise (if in fact, the cylinders were causing the problem), but it still won't budge. Do you think it could be a bearing? I'm 90% sure that I want to split the case so I can see what's inside, but right now I'm having trouble getting that dang nut off the clutch basket. I'll keep trying and let you know how it goes.

Yeah, I need to update my thread. I've been doing a LOT of sand blasting, cleaning, gasket prep, and valve lapping and it's taking a lot longer than I thought. I'm a bit OCD when it comes to cleaning parts. I'm still trying to find a bearing puller that will fit the trany shaft/countershaft bearings but I've started painting the parts I can. I'll get some pics up soon.

Yep, sounds like you'll have to spit the case to find the source of seize. I'm surprised the engine still won't turn with the pistons out! I have no idea what could be causing that (but I'm a n00b). I had to resort to the impact wrench to get the bolt off the clutch basket. So annoying! Keep us posted. I'm very curious as to what caused your engine seize. I'm sure I'll be dealing with that at some point. LOL!

[bpratt18]

After reading Mattyo's thread I decided that I too should venture into the unknown and split the case. After a lot of pulling and swearing I finally got it split. And I you're right about the front piston causing the seize Mattyo. The front piston arm does not spin on the crankshaft like the rear piston arm does. It was literally locked into place, not until I unbolted it from the crankshaft was I able to get it moving. Even then, it took a lot of work to get it free. So, I'm wondering....what would cause this to seize and what should I replace? If I can find them, I'd like to replace the crankshaft main bearing plus all the others (anyone have a link plus a link to a bearing puller?).

Also, there was a lot of metal shavings in the case and stuck to the oil pump's filter. When I was first putting this bike together, I installed the clutch bearing backwards and burned through two sets of plates before figuring it out, so I'm guessing that's where the metals from. Does it seem possible that the large amount of metal caused a block in an oil pass and the piston wasn't getting its share? Also, the front (presumed faulty) piston seems to have some rust where the rings are, which I think it what it preventing them from moving. Well, a lot of work for one day, I'm going to let it sit and "cool off" for a while and enjoy the rest of the day, hope to hear some comments soon! Thanks!

[bpratt18]

I'm making a list of the essential parts I'd like to replace and piston rings and piston rod bearings is on the top. But, I can't seem to find a vendor anywhere. Does anyone have any suggestions on where to find these things, again I've got an 84 VT700. Thanks!

[jpr1968]

good luck finding engine parts unless you can find them on Ebay. If it's as bad as it sounds, uou would probably be better off finding another motor for it.

[bpratt18]

Originally Posted by jpr1968

good luck finding engine parts unless you can find them on Ebay. If it's as bad as it sounds, uou would probably be better off finding another motor for it.

Hmmm. Well if I can't find new ones and the old ones are within spec I guess I'll have to keep them. Will I have to hone the cylinder because I've moved the rings out of alignment w.r.t the cylinder? Ohh, and does this look like a decent tool for the job if I end up having to?

4" Engine Cylinder Hone

[mattyo]

Here's a few links for the 84 vt700 crankcase:
1984 Honda Shadow 700 VT700C Parts, 1984 Honda Shadow 700 VT700C OEM Parts - BikeBandit.com
OEM Parts Honda SHADOW (VT700C) 1984 CRANKCASE - Cheap Cycle Parts
Huntington Beach, California, Honda, Police, ATV, GL1800, Motorcycle, Watercraft, Dealer, Used, Parts, Accessories, Apparel, Service, ST1300PA,
1984 Honda SHADOW - VT700C OEM Crankcase Parts | MotoSport

You can find the fiche of the piston assemblies there too. They should sell the piston rings? I didn't check. Anyway, hopefully that will help.

And if you're going to pull the bearings, I have the "special" honda tool for getting those nasty trany shaft pilot bearings out that I can send your way. I bought 3 previous bearing pullers and none of them would fit around that protruding shaft seat thing (I don't know what it's called, I'm still a n00b). You saw the thread. Anyway, give me a shout if you want to barrow it! Hopefully I'll only need to use it ONCE!

[bpratt18]

Okay so a little progress made so far. I threw the front cylinder with the locked up rings into the ultrasonic cleaner, and made it shine. The rings loosened right up, I'll check their dimensions tomorrow, if they're within spec should I even worry about replacing them?

Also, I'm beginning to think there was an oil blockage preventing flow to the front piston rod bearing. When I took it off the crank the two halves were nearly fused together. Definitely going to have to get new ones (if I can find them) Another little clue was a gouge made in the right crankcase outside the main bearing by the timing chain (I'm guessing). This was the same side that had the stuck timing chain tensioner. I'm going to put on my detective hat and take a guess, please feel free to call me crazy

1)Had previously burned and cracked friction plates and was unable to clean all fillings out of crankcase.
2)While riding, felt the engine seize and then took a short flight through time and space to meet my friend the ground.
3)After removing the front cylinder head, noticed cam chain tensioner was stuck
4)After removing front cylinder noticed piston rings were also stuck.
5)After splitting case and removing crankshaft and front piston rod noticed the piston rod bearings were piled on top of each other. This was the actual cause of the seize.
6)Cam chain wore into the right side crankcase.

I think, the fillings clogged the oil jet, and both the piston bearing and the piston rings continued to move dry and then seized up. The cam chain may or may not have been involved, but regardless the tensioner was stuck and allowed the loose chain to come in contact with the metal and shave some off. That or Professor Plum did it with the candle stick

[bpratt18]

By the way, I was able to get the piston rings and bearing at HB honda!!! I'm super pumped, thanks Mattyo

[gjordan8981]

Great deductions! Sounds logical to me.


Sent from my Motorcycle iPhone app

[mattyo]

Not to pick apart your diagnosis in anyway but just curious.
When you say the cam chain tensioner was stuck, do you mean it was difficult to pull the tensioning wedge up thereby loosening the tension or did you mean it wouldn't move at all? In my tremendous experience (sarcasm) with the two engines I pulled apart, all the cam tensioner wedges were a bit stuck and took a little force to get them to pop free. Saying that to say, I think being a bit stuck is normal? but if you couldn't budge it at all, well that's a different story.

Glad to hear you found the parts you needed. It's pricey but it's still cheaper than the local mechanic!

And it looks like I'll need to buy an ultrasonic cleaner! My wife will be so pleased! LOL!