Just guessing (obviously) I'd say it's the top end not the bottom. A rod knock would only make half as many noises as a top end issue. Dave
On 3 August 2012 16:24, Ross M. Jamison <[email protected]>wrote: > Sounds like rod knock. > > Thank you, > > Ross M. Jamison > Sent from my iPhone > > On Aug 3, 2012, at 1:13 PM, Matthew Webb <[email protected]> wrote: > > Here'a a much belated update: > > I started removing and dissasembling my engine (photos > here<https://plus.google.com/photos/118089145265544102347/albums/5757262905493724129?authkey=CPXK5L2a99-HngE>) > which turned out to be a pretty big challenge without having much > experience. But it was tons of fun and I learned a lot while struggling > and cursing in my blazing hot shed. While I was doing this a used engine > with 22k miles popped up on eBay and just so happened to be located in my > city so I scooped it up. > > By some miracle, I manage to succesfully install the new engine, put all > the pieces together, and get the bike started! I think I remember hearing > a slight noise from the engine but I was probably too estatic notice. I > took the bike for a short test ride and at some point during the ride I > noticed a tapping noise coming from the engine. So I'm not exactly sure > when the noise started. Its possible the engine had been sitting for a > while before I bought it. During the ride the bike seemed to perform 100% > fine, aside from the noise. Back at home I took a video to capture the > noise. > > I used a tube to listen to the engine and I think the noise is coming from > the back of the lower crankcase. From the reading I've down it sounds like > that type of noise means a valve needs to be adjusted? But the Clymer > reads the valves adjust themselves automatically? So maybe a piston ring > is off or something? > > Can anyone watch the video and help ID the noise? At this point I think > my best bet is to take it to a shop and have pros look at it. Even if I > have to shell out an arm and a leg I just want to be on the road again. > > http://youtu.be/PurYX89KWzc > > Thanks! > > - Matt > > > > On Friday, April 20, 2012 10:44:30 PM UTC-4, Matthew Webb wrote: > >> Hi my name is Matt. I'm new to the group and I recently got my first >> bike, a 1992 CB750 with 3,800 miles for $1,800. It was always garage kept >> and in very good condition. >> >> I had had the bike for only about 2 months but had put almost 2,000 miles >> on it already. At the time I was getting home from work in the dark and >> the cold and kept putting off my first bike maintenance until a weekend >> when I could do some work in the daylight. I made a big rookie mistake and >> ran my bike dry and the engine locked up when I stopped at a traffic >> light. The low oil indicator light had turned on that morning but I was >> hurrying to a meeting and thought I would be able to make it before things >> got serious. >> >> I got my bike back to my house, and a few weeks later poured some oil >> over the top of the engine, manually turned the engine, and then was able >> to get it to start with no problem. However, the engine didn't seem to >> respond right. So I looked into the top more and found some pretty serious >> scouring on the exhaust camshafts, exhaust camshaft holders, and >> crankcase. It also looks like some of the rubber stuff on the defoaming >> chamber covers melted, but I'm not sure. The rest of the top end looked >> completely fine, even the intake camshaft. See >> pictures<https://plus.google.com/photos/118089145265544102347/albums/5733673720992831665?authkey=CKH1v53yteGPnAE>for >> details but be warned, they are depressing. >> >> I am worried that pieces of metal may have gotten into the bottom of the >> engine and wrecked more havoc. I'm also wondering if there may be more >> damage than I've seen from when my engine locked up. Does anyone know what >> damage is typical when you run your engine dry? Is it likely the entire >> engine will need to be replaced? >> >> I have searched past messages but have not found much. Possibly because >> I don't know what is best to search for. I've done a lot of other reading >> so far and have some ideas but wanted to run it by the group first. >> >> To me it looks like I have a few options: >> >> 1) Sell the bike as is on CL for parts to someone who knows what they are >> doing >> 2) Purchase replacement parts for the damaged components and replace >> them. With a quick search I have found these on ebay: cylinder >> head<http://www.ebay.com/itm/CYLINDER-HEAD-CB750-NIGHTHAWK-91-93-92-1991-1992-1993-VALVE-TOP-END-ENGINE-MOTOR-/140691166315?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item20c1d8d46b> >> , another cylinder >> head<http://www.ebay.com/itm/Honda-CB750-SC-Nighthawk-Good-Used-Original-Engine-Cylinder-Head-1992-BDK-/150711279313?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item2317179ed1>, >> camshafts.<http://www.ebay.com/itm/Honda-CB750-SC-Nighthawk-Good-Used-Original-Engine-Cam-Camshaft-Pair-1992-BDK-/400261036787?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item5d316abaf3> >> I don't have much experience working with engines but I do have a Clymer >> manual. The camshafts and holders look easy to replace but the body of the >> crankcase is also damaged where the camshafts sit. Would it be possible to >> have a shop re-machine it so that I wouldn't need to replace it? >> 3) Take it to a shop, have them replace the parts and open the bottom of >> the engine to look for more damage. >> 4) Purchase another CB750 and use my first one as a parts bike. Also >> part out my first one on ebay since the rest of the bike is in excellent >> condition. >> >> Any suggestions would be appreciated, thanks. >> >> - Matt >> >> >> -- > You received this message because you are subscribed to the Google Groups > "Nighthawk Motorcycle Lovers!" group. > To view this discussion on the web visit > https://groups.google.com/d/msg/nighthawk_lovers/-/3tYvbgQMpagJ. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/nighthawk_lovers?hl=en. > > -- > You received this message because you are subscribed to the Google Groups > "Nighthawk Motorcycle Lovers!" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/nighthawk_lovers?hl=en. > -- If you forward this e-mail please remove my address. -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. 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