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.
