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.
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.
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...
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.
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.
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.
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.
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.
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.
I've had the top end of those engine's apart, twice.
No "funny lookin clutch tool" required. Internal snap ring pliers, large metric socket.
Shims need to be "kept track of". They arent all the same, and diff. sizes used in various places..... Magnet should get em out easy. Careful some aint still stuck to top of cover! Pay attention closely, and you can re-install w/o needing indicator.
If you reuse the same parts and keep track of what shims were used where, I agree...you do not need a drop indicator, BUT if you replace that cracked camshaft cover, which I think you will, you should measure and re-shim the lifters.
The engine (frank) with the cracked valve head is really the parts engine. The better engine (hank) is in good shape but needs the cam chain and tensioners replaced and the starter clutch replaced. So as long as replacing the cam chain and tensioners doesn't require re-shimming the tappets, I should be okay.
And using a magnet to pull the shims out worked great! Tappets and corresponding shims are itemized in separate bags and labled to which cylinder and valve they belong, so unless I do something careless in the process, I'll know exactly where they need to go back in.
Interesting thread. I will be following along as my timing chain in my front cylinder is loose and rattles some. I'm sure not much difference between the 700 and 750.
Did you find much carbon buildup on any of your valves?
My cycle mechanic told the 84 700 and 83 750 have the same left crankcase starter setup. I'm not that means they have pretty much the same engine or not but it sounds promising anyway.
I don't know how much carbon buildup to expect but I personally didn't think the valves looked too bad. Could be completely wrong though. The pistons definitely looked worse.
Still trying to get the clutch off. I have about a foot of aluminum bar stock that slid into the union joint that connects to the final shaft to use as leverage to hold the clutch in place while trying to get the clutch bolt off but I just couldn't do it. Also the aluminum started to bend. I might swing by the local hardware store and pick up a piece of longer steal bar stock and hopefully avoid buying another special tool. Is is safe to give the impact wrench a try? And I still need to get a valve spring compressor ordered. Any suggestions on a "good" one to get or one to stay away from?
Okay, I did some interweb searching and it sounded safe to put my 1/8" bar or aluminum between the gear teeth to hold the clutch in place, and that does work pretty well. Except the bolt isn't turning, the whole sleeve is turning and I can see one of the clutch plates turning, but not the bolt, well it's turning but not off the threads. This is a lefty-loosey bolt right? What am I missing here?
I believe a 1/2" impact and tranny in gear will spin it off, although I admit I have not taken the clutch outer drum off. My valve spring compressor belonged to Grandpa, it works perfect. Looks like large C clamp, with ratcheting "bar" to compress and hold spring. Label where all the springs and keepers went. Measure springs and compare to spec.
Here's the only pic I could find of the spring compressor. I wish you could see all of it, it's the aluminum color "C" shape around the Dr.Pepper can.
Vesrah gasket set is O.K., but use/buy OEM head gaskets. Cam plugs (4)and coolant tube seals (6) sold seperatly, not in Vesrah set.
The engine in mine had around 34K on it, despite piston/bore AND rings were in spec...stock. The valve's were burnt, they had a fair amount of carbon on them. I tore mine apart because of lower jug to block oil leak. It wound up with new crosshatch in cyl, rings, valve job, porting/polishing of the heads, etc.
Last note: I hope you haven't really damaged the clutch outer drum. An impact will usually spin (impact "hammer") off stubborn bolts on "moving" parts.
Last note: I hope you haven't really damaged the clutch outer drum. An impact will usually spin (impact "hammer") off stubborn bolts on "moving" parts.
I hope not either. I'm not sure how I would have damaged it. I haven't tried the impact wrench yet no abuse was needed to get things spinning. After putting the 1/8" aluminum between the gear teeth I was able to "gracefully" rotate the inner sleeve and clutch plate. Nothing cracked or snapped and I did not do the old "wack the wrench with the hammer" to break things free, so unless it was already damaged.....
Just to clarify, when I say the inner sleeve and clutch plate rotate, I mean they rotate with the socket rotation and with a bit of friction. They by no means rotate or move freely. Also if I change gears, a different clutch plate will rotate. Kinda cool actually, but also annoying.
I'll have to do some searching on clutch rebuilds...
I got my valve compression tool in the mail today! Pulled the valves and did a little cleanup with a scotch-pad. On one of the valves, I sanded it down with 150 grit (probably overkill but it's all I had at the time) and then did a little finish scrub with the scotch-pad. I'm going to take them in to get resurfaced since I don't have the tools and would like this job to be done correctly. Should I clean them all up good and shiny before having them resurfaced? I would assume so, but just checking.
Brought out the impact wrench last night and after a bit of penetrating oil and working the clutch nut for 10 minutes it finally broke free. When I pulled the clutch housing off the two sprockets shifted relative to each other and now the teeth don't line up? What's the deal with that? I guess those sprockets must come apart so the springs can be replaced? Here's some pics.
xsive requested some cam tensioner pics so here they are. Let me know if you want a different angle or something. The two threaded holes are where the tensioning bolts screw in.
The tensioning bolts push that piece of rail shaped steal out which applies more pressure to the tensioning chain guide. In the picture, the rail is at it's maximum travel. You can see it hitting the inside wall of the outer square assembly. I should get another pic with the tensioning bolt in place.
The clutch inner and the clutch housing (the two things with the teeth that do not align) DO come apart. Possibly the pins that align them together became bent with the impact wrench and now stick the two pieces together.
That is a possibility but my objection is that the two sets of teeth were flush with the timing sprocket teeth so I don't see how the impact wrench could have moved the clutch inner or clutch housing relative to the other without breaking a tooth or something. But I'm a n00b and don't know how these things work so you could be right. I'll try to separate them and see what happened. Thanks for the advice steve.
I've been a bit nervous about pulling the whole crankcase apart. It's not really necessary but I kinda want to do it so 1) I can clean, strip, and repaint the whole deal and 2) just to learn more about this thing called an engine. I just decided to go for it. What's the worst that can happen? I end up with a non-working bike and loose some $$ on the thing, but I still learn a lot in the process right? It's still cheaper than college. Well now I'm glad I decided to jump in over my head because I found out the oil pump had a big chunk broken off. The bolt was still holding the chunk in place thankfully but who knows how long that would have lasted before catastrophic failure. So I'm getting closer to the point of separating the crankcase. Woopy!
Is there a place where you can insert a pin to hold the tensioner away from applying pressure to the chain, good for reassembly. Always good idea to change chain tensioner bolts when reassembling also. The heads can break off down the road. Look forward to following this thread. good luck.
I scratched the gasket surface a little bit with the screw driver (knew I shouldn't be doing that) but doesn't look serious (I hope). Assuming the scratches are "serious" how should I go about repairing the gasket surface? I'll try to get some good photos of the scratched part. Also there didn't seem to a gasket other than that liquid gasket stuff. Is that normal?
Pulled the trany out. Not as difficult as I thought it was going to be. Put some wires through the gear assemblies to make sure things don't slip off and I have a mental break down. Both sides of the crankcase have all parts removed except for the bearings. Please advise if this is a bad idea, but I plan on bead blasting the case. If I go ahead with the blasting I should get those bearings out of there too shouldn't I?
I feel like the dog who finally caught the wheel. Now what....
Sure wish I could give you some educated info but I have no experience rebuilding engines. I think you have done well so far. I am hoping all goes well. Looking forward to seeing it when your done.
And I discovered an oddity between the two engines. Supposedly they are both 1983 vt750c but they have different gear shift spindles. I guess one must have been replaced at some point? Just thought it was strange that they weren't the same.
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