84 Engine Rebuild

[bpratt18]

Hey everyone,
I've recently removed my 1984 VT700c's engine and it's sitting in my living room. I'm attempting to diagnose a seized engine, but wanted to ask if there is anything I should replace/clean/repair while I've got it off the frame (granted I can fix the original problem ) I'm planning on starting with the top covers and working my way down till I find the break. Thanks!

[csmbt]

might be a good time to rebuild the starter and maybe replace the clutch plates

and honestly it's one of those situations that where your that deep in you may as well replace the rings and cam chain and all the gaskets

depends if your going to keep the bike for a long time - if so do it ... if not let the next guy worry about it!

If you do replace the rings you will have to break the engine in again

[csmbt]

Originally Posted by bpratt18

Hey everyone,
I've recently removed my 1984 VT700c's engine and it's sitting in my living room. I'm attempting to diagnose a seized engine, but wanted to ask if there is anything I should replace/clean/repair while I've got it off the frame (granted I can fix the original problem ) I'm planning on starting with the top covers and working my way down till I find the break. Thanks!

oh btw - a tip from a been there done that ....

The hydroloic tappets can be a total p.i.t.a if you don't do this ..

first be real careful taking the top part of the head, I STRONGLY suggest that the second you get about 1/2 -1in of daylight inbetween there try to stuff a rag or shop towel into the hole where the camchain is as the tappets which each have a couple of spacers on them can lift up with the head and drop right into the bottom of the crankcase

I was DAMN lucky and was able to fish out the spacer that dropped with a magnet as it had not gone all the way but that was blind luck

Also it is REAL important you record which tappet goes where and how many spacers it had ... DONT BLOW THIS OFF other wise you will have to do a valve adjustment - use a notepad and small baggies and mark whats what - they go back in the same way your golden

Also unless you have another pair of hands only do one cylinder at a time as there will be several times you will need to turn both camchains at the same time which is pretty much impossible to do on your own

gl

[bpratt18]

Thanks for all the insight! I bought this bike as a basket case (the tappets were handed to me with no labels in a plastic bag) and I plan to keep this bike as long as I can. Is a valve adjustment difficult? I look around a bit, probably something I should have done the first time I was putting it together.

[mattyo]

Originally Posted by bpratt18

Thanks for all the insight! I bought this bike as a basket case (the tappets were handed to me with no labels in a plastic bag) and I plan to keep this bike as long as I can. Is a valve adjustment difficult? I look around a bit, probably something I should have done the first time I was putting it together.

Am I hearing you correctly? When you got the engine it was already partially disassembled and you built it back up and had to randomly reinsert the tappets (and shims) because they weren't labeled? I must have missed that point in your other threads, sorry.

If that's true, then that's probably the source of your problems. I don't know enough to explain how incorrectly set tappets would lead to an engine seize, but I do know it's pretty critical to get those set just right. Kudos to you, I'm surprised the engine would even turn over.

Please explain in more detail what you did to piece the engine back together.

[bpratt18]

Haha thanks! Basically yes to Mattyo's question above. I got the bike with the engine out of the frame, tappets and shims in a ziplock bag tagged "Misc." This was about 3 or 4 years ago, and the bike was running up until this past fall. I followed the clymer manual as best as I could, bled the tappets in a mason jar of kerosene, then reinstalled. Most of the engine work was on the head covers, so I was able to stay clear of the pistons, cam chain and transmission. I was going to prepare for a work meeting I have in the morning, but now I think I'm going to start disassembling instead wish me luck, I'll post pictures soon.

[bpratt18]

Okay so I've taken both head covers off and every thing looks good (not smashed, crackled or popped). I took a look at the cam tensioners and noticed that the top piece (see pics) of the front tensioner was free to be pushed in and then spring loaded back to normal. The rear however, was locked up and only after some "persuasion" was I able to get it to move up and down. But it sticks on its way back up like the metal to metal surface has worn a grove that prevents easy sliding. So, I'm trying to remove the chain on the rear side, I've removed the tensioner, but since I can't turn the engine, the second bold holding the cam in is so far inaccessible. Any hints? I was thinking I'll have to take the cylinder off to get to it, but would like to avoid it if possible. Ohh and I took the timing gear off (maybe a mistake, but I wanted to check this) so that I could isolate where the problem was. Since the clutch and transmission were no longer connected to the cylinders I thought if I can spin the clutch basket, while in gear, then the problem isn't in the transmission, and likely in the cylinder heads. Any thoughts? Thanks!

[bpratt18]

Had to cut the cam chains in order to get them out But at least I can get to the pistons now. I removed the cylinder heads and cylinders exposing both front and rear piston. Aside from some expected soot, they look okay. Although the piston rings on the rear seem loose. Not sure how to explain it, but they can sort of hula hoop inside their grooves, unlike the front where they are essentially locked into place. Is this normal? But, I still can't turn the engine over, so my idea of locked up pistons causing the seize is false. Must be some sort of bearing between the primary drive gear and the alternator. I'm thinking that I'll have to split the case, which I've never done before, any suggestions? It will take me a while since I can't get the nut holding the clutch basket without an impact hammer...anybody in CT have one to borrow Throwing up some pictures to show the "progress", appreciate the suggestions.

[mattyo]

Originally Posted by bpratt18

Although the piston rings on the rear seem loose. Not sure how to explain it, but they can sort of hula hoop inside their grooves, unlike the front where they are essentially locked into place. Is this normal?

Well, all I can say if based off what I've come across in the two engines I'm still in the process of rebuilding. Also my first rebuild. WEE! engine rebuild and more...

All my piston rings (in both engines) were loose and could do the hula-hoop thing you described. I would think that's the way it's supposed to be so the piston has some room to flex while the rings still keep a seal on the chamber. Take this with a grain of salt but I'm guessing your engine seize was from the locked rings. The rings could have dug into the chamber just enough to seize it up but with a little hands-on persuasion you were able to get it moving again? Not sure.

Let us know what you find.

[bpratt18]

Originally Posted by mattyo

Well, all I can say if based off what I've come across in the two engines I'm still in the process of rebuilding. Also my first rebuild. WEE! engine rebuild and more...

All my piston rings (in both engines) were loose and could do the hula-hoop thing you described. I would think that's the way it's supposed to be so the piston has some room to flex while the rings still keep a seal on the chamber. Take this with a grain of salt but I'm guessing your engine seize was from the locked rings. The rings could have dug into the chamber just enough to seize it up but with a little hands-on persuasion you were able to get it moving again? Not sure.

Let us know what you find.

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.