engine rebuild and more... - Honda Shadow Forums : Shadow Motorcycle Forum

mattyo · 01-10-2012, 05:10 PM

Short story: I have two '83 vt750 engines that both have a few different problems. I've decided to tear them both down and rebuild one "good" engine from the best parts. Of course a better solution would be to buy and replace the bad parts, but I just don't have the cash flow for that right now. I figured I'd post some pics of my progress during the rebuild as I'll have some questions along the way. I know many of you have rebuilt engines before and it's not a big deal, but this is my first, so please excuse any over-enthusiast self-praise.

Long story: I have 2 engines that I've arbitrarily decided to name "hank" and "frank". No offense to people with names hank and frank. Just needed a convenient way to address them. Hank was the original engine when I bought the bike but shortly after purchasing, the starter clutch went bad. After pulling off the left crankcase I also noticed the cam chain was really loose and assumed that should be fixed as well. It was spring and I didn't want to waste any good road time fixing the starter clutch and cam chain, so I swapped out hank and put in my parts bike engine, frank. Frank ran okay, but would squirt a little oil out the valve head when running. Nothing too serious but it was really annoying having oil all over the radiator and then getting blown all over the frame and sides of my bike. In general, hank is in better shape than frank and according to the PO has less miles on it, so the general plan is to rebuild hank, replacing any bad parts with frank's parts, if they're in use usable condition.

So a quick recap:
hank = original engine now with bad starter clutch and loose front cyl cam chain
frank = parts engine with oil leak from valve cover on front cyl
I will hopefully rebuild hank with frank's usable parts.

mattyo · 01-10-2012, 05:28 PM

After quite the ordeal with frank's flywheel, I finally managed to pull it off. To get the spark plug sleeves out, I used the trick from the Clymer manual. I bought a 3/4" bolt which had a head diameter just over 1 1/16" so I had to grind it down a hair but in the end it worked great to pull the plug sleeves.

Then moved on to removing frank's front cyl valve cover to see where that oil was leaking from. What a mess! Someone had obviously pulled the valve cover off before. Looked like a homemade cork-board gasket to me.

And they cracked the valve head and tried to fix it with a little JB-Weld or something.

more to come...

TxShadow49 · 01-10-2012, 05:34 PM

Good luck. I may be doing that myself soon. To a CL350 and a VT500.

SteveSchu · 01-10-2012, 06:01 PM

I have been there almost exactly as you describe. I had an original engine that I paid an established motorcycle mechanic to rebuild....he failed and it leaked oil from the front cylinder. I bought an entire engine and four years later it spurted oil into the radiator. I just rebuilt the original engine and need to rebuild the replacement.
My rebuild of my original engine was unsuccessful and it leaks oil from the rear cylinder.
The cracks in the upper half come from over-torquing it to stop it from leaking. That part is now garbage. The camshaft assist cover, the one with the cork gasket is probably garbage as well....it will never seat flat.

mattyo · 01-10-2012, 09:59 PM

Quote:

Originally Posted by TxShadow49

Good luck. I may be doing that myself soon. To a CL350 and a VT500.

Thanks Tx, good luck to you too, but I'm betting you have a few engine rebuilds under your belt, so you don't need luck anymore.

mattyo · 01-10-2012, 10:07 PM

Quote:

Originally Posted by SteveSchu

I have been there almost exactly as you describe. I had an original engine that I paid an established motorcycle mechanic to rebuild....he failed and it leaked oil from the front cylinder. I bought an entire engine and four years later it spurted oil into the radiator. I just rebuilt the original engine and need to rebuild the replacement.
My rebuild of my original engine was unsuccessful and it leaks oil from the rear cylinder.
The cracks in the upper half come from over-torquing it to stop it from leaking. That part is now garbage. The camshaft assist cover, the one with the cork gasket is probably garbage as well....it will never seat flat.

Do you know why your rear cyl is leaking oil? Any words of wisdom so I don't make the same mistake?

I'm planning on replacing that whole value head with the good/better one. It was most likely over torqued as you said. That was the same engine with the flywheel bolt that way over-torqued. It took 10 min with an 800 ft lb impact wrench to finally break it free. Not to mention torch heating it and a load of penetrating solvent. Whoever was tightening those bolts didn't know their own strength and didn't pay any attention to the torque specs. Oh well...

mattyo · 01-10-2012, 10:26 PM

So on the same cylinder as the cracked valve head, I also found a damaged oil ring on the piston.

That was not my doing. I don't know how that would effect engine performance but I did have a bit of trouble getting that cylinder to not be running so lean. I had to up the slow jet 4 sizes if I remember correctly to eliminate the decel popping.

Another interesting thing I found was a very fine powder or sorts that attached itself to the magnets in the timing pickup coils.

It rubbed off just fine with a rag but I'm curious if that's a sign of excessive engine wear or if that's expected from a 30 year old engine.

Oh, and feel free to critique anything that looks like I'm doing wrong. Any words of caution are more than welcome here.

mattyo · 01-10-2012, 11:05 PM

So now I have both engines mostly torn down. I need to get one of those funny lookin clutch tools so I can pull that off. I also need to get a valve spring compression tool. Am I best off getting the right tools or are there cheaper alternative ways to go about this?

In the meantime I want to start cleaning up the parts I can. I'm thinking I'll repaint the engine while I'm at it. I've read that aircraft paint stripper works like a charm. Is that safe if it gets on the inside of the heads or is that something I need to be careful about not doing? They need a complete cleaning so what's the best way to go about this? Is there something I can soak parts in ie carb cleaner or is that a big no no? I'm just not sure what kind of solvents are safe to use here? I saw the sticky on engine cleaning, I still need to thoroughly read through that. Maybe I'll find my answers there.

And how do I get those tappet shims out of their seats? The oil in there is creating a suction on them and I just can't get them out.

Thanks guys

SteveSchu · 01-11-2012, 07:13 AM

It is in fact oil creating a suction holding the tappet shims in place. Blow them out with WD40. You will see a dimple machined into the valve holder and you will know the shims are gone. You will need a drop indicator when you replace the valve cover to correctly size the distance with those shims. The assist shaft cover with a gasket alone ALWAYS leaks. I used a new gasket and Indianhead gasket shellac on mine and they do not leak. While you have yours torn down you should know that Honda revised those assist shafts and have a more robust design in later models. You should upgrade to those while you are in there.
I do not know why my rebuild failed. I just installed the engine over Christmas and havent been back in to take a better look. This weekend I will. The parts were lapped good and flat, claen and torqued properly. Maybe too much sealant? I am going to try Hondabond next, but the front cylinder came out fine with UltraBlack.

mattyo · 01-11-2012, 01:13 PM

Quote:

Originally Posted by SteveSchu

It is in fact oil creating a suction holding the tappet shims in place. Blow them out with WD40. You will see a dimple machined into the valve holder and you will know the shims are gone.

Sounds good, thanks.

Quote:

Originally Posted by SteveSchu

You will need a drop indicator when you replace the valve cover to correctly size the distance with those shims.

According to Clymer, if I keep track of which shims and tappets belong to their corresponding seats/valves, I shouldn't have to re-shim my tappets. Is that not true.

Quote:

Originally Posted by SteveSchu

The assist shaft cover with a gasket alone ALWAYS leaks. I used a new gasket and Indianhead gasket shellac on mine and they do not leak. While you have yours torn down you should know that Honda revised those assist shafts and have a more robust design in later models. You should upgrade to those while you are in there.

Interesting, I'll definitely be looking into that. Hopefully it's not too much bling.

Quote:

Originally Posted by SteveSchu

I do not know why my rebuild failed. I just installed the engine over Christmas and havent been back in to take a better look. This weekend I will. The parts were lapped good and flat, claen and torqued properly. Maybe too much sealant? I am going to try Hondabond next, but the front cylinder came out fine with UltraBlack.

By "sealant", do you mean the areas where you're supposed to apply some kind of liquid gasket?

01-10-2012, 05:10 PM	#1 (permalink)
mattyo Senior Member Join Date: May 2011 Location: Madison, WI Posts: 1,305	engine rebuild and more... Short story: I have two '83 vt750 engines that both have a few different problems. I've decided to tear them both down and rebuild one "good" engine from the best parts. Of course a better solution would be to buy and replace the bad parts, but I just don't have the cash flow for that right now. I figured I'd post some pics of my progress during the rebuild as I'll have some questions along the way. I know many of you have rebuilt engines before and it's not a big deal, but this is my first, so please excuse any over-enthusiast self-praise. Long story: I have 2 engines that I've arbitrarily decided to name "hank" and "frank". No offense to people with names hank and frank. Just needed a convenient way to address them. Hank was the original engine when I bought the bike but shortly after purchasing, the starter clutch went bad. After pulling off the left crankcase I also noticed the cam chain was really loose and assumed that should be fixed as well. It was spring and I didn't want to waste any good road time fixing the starter clutch and cam chain, so I swapped out hank and put in my parts bike engine, frank. Frank ran okay, but would squirt a little oil out the valve head when running. Nothing too serious but it was really annoying having oil all over the radiator and then getting blown all over the frame and sides of my bike. In general, hank is in better shape than frank and according to the PO has less miles on it, so the general plan is to rebuild hank, replacing any bad parts with frank's parts, if they're in use usable condition. So a quick recap: hank = original engine now with bad starter clutch and loose front cyl cam chain frank = parts engine with oil leak from valve cover on front cyl I will hopefully rebuild hank with frank's usable parts. __________________ 1983 vt750 - "Fra-Hankenstein" (restoration in progress, click for the full story)

01-10-2012, 05:28 PM	#2 (permalink)
mattyo Senior Member Join Date: May 2011 Location: Madison, WI Posts: 1,305	After quite the ordeal with frank's flywheel, I finally managed to pull it off. To get the spark plug sleeves out, I used the trick from the Clymer manual. I bought a 3/4" bolt which had a head diameter just over 1 1/16" so I had to grind it down a hair but in the end it worked great to pull the plug sleeves. Then moved on to removing frank's front cyl valve cover to see where that oil was leaking from. What a mess! Someone had obviously pulled the valve cover off before. Looked like a homemade cork-board gasket to me. And they cracked the valve head and tried to fix it with a little JB-Weld or something. more to come...

01-10-2012, 06:01 PM	#4 (permalink)
SteveSchu Member Join Date: Oct 2009 Posts: 95	I have been there almost exactly as you describe. I had an original engine that I paid an established motorcycle mechanic to rebuild....he failed and it leaked oil from the front cylinder. I bought an entire engine and four years later it spurted oil into the radiator. I just rebuilt the original engine and need to rebuild the replacement. My rebuild of my original engine was unsuccessful and it leaks oil from the rear cylinder. The cracks in the upper half come from over-torquing it to stop it from leaking. That part is now garbage. The camshaft assist cover, the one with the cork gasket is probably garbage as well....it will never seat flat.

01-10-2012, 10:26 PM	#7 (permalink)
mattyo Senior Member Join Date: May 2011 Location: Madison, WI Posts: 1,305	So on the same cylinder as the cracked valve head, I also found a damaged oil ring on the piston. That was not my doing. I don't know how that would effect engine performance but I did have a bit of trouble getting that cylinder to not be running so lean. I had to up the slow jet 4 sizes if I remember correctly to eliminate the decel popping. Another interesting thing I found was a very fine powder or sorts that attached itself to the magnets in the timing pickup coils. It rubbed off just fine with a rag but I'm curious if that's a sign of excessive engine wear or if that's expected from a 30 year old engine. Oh, and feel free to critique anything that looks like I'm doing wrong. Any words of caution are more than welcome here.

01-10-2012, 11:05 PM	#8 (permalink)
mattyo Senior Member Join Date: May 2011 Location: Madison, WI Posts: 1,305	So now I have both engines mostly torn down. I need to get one of those funny lookin clutch tools so I can pull that off. I also need to get a valve spring compression tool. Am I best off getting the right tools or are there cheaper alternative ways to go about this? In the meantime I want to start cleaning up the parts I can. I'm thinking I'll repaint the engine while I'm at it. I've read that aircraft paint stripper works like a charm. Is that safe if it gets on the inside of the heads or is that something I need to be careful about not doing? They need a complete cleaning so what's the best way to go about this? Is there something I can soak parts in ie carb cleaner or is that a big no no? I'm just not sure what kind of solvents are safe to use here? I saw the sticky on engine cleaning, I still need to thoroughly read through that. Maybe I'll find my answers there. And how do I get those tappet shims out of their seats? The oil in there is creating a suction on them and I just can't get them out. Thanks guys

01-11-2012, 07:13 AM	#9 (permalink)
SteveSchu Member Join Date: Oct 2009 Posts: 95	It is in fact oil creating a suction holding the tappet shims in place. Blow them out with WD40. You will see a dimple machined into the valve holder and you will know the shims are gone. You will need a drop indicator when you replace the valve cover to correctly size the distance with those shims. The assist shaft cover with a gasket alone ALWAYS leaks. I used a new gasket and Indianhead gasket shellac on mine and they do not leak. While you have yours torn down you should know that Honda revised those assist shafts and have a more robust design in later models. You should upgrade to those while you are in there. I do not know why my rebuild failed. I just installed the engine over Christmas and havent been back in to take a better look. This weekend I will. The parts were lapped good and flat, claen and torqued properly. Maybe too much sealant? I am going to try Hondabond next, but the front cylinder came out fine with UltraBlack.

Remove Advertisements Sponsored Links
HondaShadow.net Advertisement