I'd say rod knock or exhaust leak. Feel around really close to all the exhaust ports and see if you can feel a pulse of air coming out.
-James O On Aug 4, 2012, at 21:36 PM, Greg Holuban wrote: > Did you put in new exhaust seals? Make sure they are tight. > > Date: Fri, 3 Aug 2012 17:02:22 -0300 > Subject: Re: [Nighthawk Lovers] Re: rookie looking for suggestions > From: [email protected] > To: [email protected] > > 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) 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 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, another > cylinder head,camshafts. 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. > 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. -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. 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