| Author | Message | ||
     Smokinjryan |
I brought to shop and guy checked to see if there was any play in com shaft. He said he could tell if the rod was bad by turning engine by that shift? Does this sound right? I had knock sound from top end sounded like from exhaust valve.Souned like piston was hitting valve. He said it is and it's caused by rod end play.He didnt take any of top end off just said easy to tell from com shaft. Any input would be great as I feel sick knowing the cost of my fix!! (Message edited by smokinjryan on September 08, 2006) | ||
| Rocketman |
I'd at least want the top end off to have a look see. Rocket | ||
| Pammy |
What the Rocket-man sez... | ||
| Smokinjryan |
Is it possible to be something else? like a wrist pin??? Just hoping. | ||
| Rocketman |
I doubt the pin itself could be subject to damage. There are numerous reasons an engine can make a noise of some description or other. The sage advice here is to fully inspect all the suspect areas before you give anyone the go ahead to carry out any repairs on any engine. More so if you're paying. You want to know that you're not having the wool pulled over your eyes for say a simple failing of a pushrod lifter that sounds like a big end knock. Besides the costing of any repair, it's pointless arranging a repair without knowing what the failure is or what caused it. You're simply asking for trouble mechanically and financially. Use your head. If in doubt check out the BadWeB sponsors or put your trust into someone you really know you can trust. Even the best get caught out. I'm speaking from experience here. Rocket | ||
| Phat_j |
any so called mechanic that is telling you its a bad crank is full of shizzzzz without atleast taking the top end off..... thats a load of crap. | ||
| Smokinjryan |
well I think I can handle taking the top and off. What should I look for after I do this? I would have to go all the way to tell is rod is bad? Heads then down to the base? Then check for all types of play? | ||
| Rocketman |
If you remove the heads, generally speaking you should be able to feel play on the piston crown with some fingers placed on it when you rotate the motor through TDC and BDC. If the big end is worn so bad it allows the rod \ piston assembly to move significantly up and down from the bearing you should feel it, and expect to find piston to valve contact too. The piston will show valve marks on the crown, and the valve(s) maybe slightly bent or worse, which you might be able to see when you look at the combustion chamber with the valve you're looking at in the seated position. That said, at head removed stage it doesn't take much effort to just pull the cylinders for a far more involved inspection then you won't have to mess around feeling for anything, but I understand if you don't want to 'waste' the base gaskets and mess with piston rings etc. Frankly, my advice before you remove anything off the motor would be to put each cylinder at TDC and conduct a leak down test. Only then, if I were going to remove the heads I'd remove the cylinders anyway. It's pointless not to at this stage and bad mechanics not to either. Rocket | ||
| Smokinjryan |
Rocketman Thanks for your help. I will take apart top end but why do a leakdown test 1st Cant I still have a rod knock and not have damaged the piston to much. Couldnt the cylinder still have proper pressure? | ||
| Crashm1 |
A leakdown test will confirm if you have a bent valve or not, it will also let you know what kind of shape the piston rings are in. Of course the sensible thing to do if you tear it apart is to replace the rings and get the valves cleaned up just because then you don't have to think about it for a good long time. If you have been thinking of hot rodding it now is the time. | ||
| Akbuell |
The usual cause of valve-piston contact is excess RPM's. The leakdown test will quickly tell you if the valve is bent (leaking). A "bad" con rod means the big end bearing is failing or failed, and that means big noise and big vibration, esp if it is enough to cause valve-piston contact. Take your oil filter off, cut it open, and look at the filter material. Failing bearings leave LOTS of debris in the filter. Personally, I'd get a second or third opinion. And since you are concerned, pull the top end. Not that hard, and all questions will be answered. Good luck; hope it's not as bad as you fear. | ||
| Phat_j |
just a quick fyi rocket..... if you pull the heads, the base gasgets are done already as you have removed the clamp load.... dont reuse them, you will regret it. | ||
| Rocketman |
Ah but I use Cometic. But you're right. I thought about what I'd wrote later and should have corrected it, so thanks for doing so. The poor chap must be pulling the complete top end by now anyway, after listening to us. Thank you. Rocket | ||
| Smokinjryan |
Yes I will be taken it apart when I get it back on Mon...Will have to see for myself for real damage. Thanks I see what my options are to upgrade but it looks like if I were to take the top end off myself and send out bottom end to have it rebuilt will cost about $1100 if anyone knows better let me know. Then get bottom end back and put top end together myself and choose my options to upgrade. | ||
| Phat_j |
smokin... stop thinkin bout that bottom end rebuild untill you get it apart....... as i'm sure many will attest to... the bottom end is the most reliable part on our bikes........ they dont go bad often.... not saying that its not possible..... just get the facts first. | ||
| Rocketman |
In my book, if you're capable of getting the top end off, and of getting the bottom end out of the chassis and separating it from the various components, you are easily going to be able to strip and rebuild the bottom end IF YOU NEED TO. The transmission is cassette and remains on the trap door so no real messing. The cams are straightforward. The tough part is getting the crank out of the case as it really needs to be pressed out. Nothing is that difficult if you're willing and able. For me, time and space was my biggest problem. Rocket | ||
| Smokinjryan |
ok thanks for info,,,I guess phat_j is right. Let's see what I'm dealing with 1st.It just helps my stomach to prepare for the worst. Time and space will be tough also but good thing is my uncle owns a welding shop and has lots of tools. Just space will still be tight. | ||
| Spiderman |
it is easy to do a complete tear down in a tight space...  this was in a very tightly packed one car garage... | ||
| Rocketman |
Not if you're running a business outta the same space it ain't. Trust me! Rocket | ||
| Smokinjryan |
ok doesnt look to easy but I think this means I must be organized. I will have to have boxes with labels and take pics of everything!! | ||
| Tunes |
I agree with everyone... HD bottom-ends are damn near bullit-proof... but high rpm's (like a missed shirt) will cause all sorts of top-end/bottom-end problems. When dis-assembling, I would mark and place the entire front cylinder in one box, rear in another, tranny; all primary parts; all timing cover parts; bottom-end; chassis parts; misc mnting parts. I always place the parts in the box as I see them on the bike, ie. I place the exhaust pushrod to the left, intake to the right, rocker box parts at the top, etc... You get the idea. Take pics and notes along the way. I can take a bike apart and leave it in boxes for several years and pick up where I left off with this system... cause, I have done so and the bike went back together nicely. In my experience removing top-ends, I strongly suggest you rebuilding it. Unless the parts have very few miles, you're better off just refreshing the parts. In my experiences, rings wear more than valves. I've been able to keep my valves in and hone/replace the rings. If the valves are worn, the rings usually are too. I agree, knock could be a wrist-pin and not con-rod play. If the piston was hitting a valve, the noise would scare the crap outa ya and you'd WANT to remove the top-end. When rebuilding, use quality parts. Your piece of mind is worth it. | ||
| Phat_j |
knock could also be loose motor sprocket nut......... | ||
| Smokinjryan |
Yeah that was checked |
