| Author | Message | ||
     Ochoa0042 |
How do these look to ya? front piston  rear piston  I can soak them in acetone, then get a razor and scrape off whats left from the acetone breakdown, that should clean them up But how do they look to you, worthy?  | ||
| Nillaice |
theres more to it than the dirty tops, but i'm sure you know. those look gnasty. but i'd stick with stockers, as more compression would draw into question reliability issues. sorry that yer bike took a poo on ya, but love to see you take the time for a tear-down. and love the lotsa pics  | ||
| 72sbc |
dont even consider putting those in anything. | ||
| Ferocity02 |
How many miles on them, from what engine, year? You won't be able to tell if they're good until you clean them. But no matter what, since you already got the engine apart, get the cylinders honed and get new piston rings. Cheap insurance. | ||
| Aptbldr |
Soak in Simple Green to soften/loosen carbon. | ||
| Teddagreek |
time for some 9 pistons.. http://www.trackdaymag.com/Articles/Red,-White-and -Buell-Part-4,-More-Power!.aspx | ||
| Ourdee |
The second one looks juicy. | ||
| Akbuell |
Eh, without knowing the mileage, and why it was necessary to pull the engine apart, really can't comment much one way or the other. About what to do: If the cylinder and the pistons are within wear limits, break the glaze, clean the pistons and put in new rings, and go on. Since you are already in there, and given what new pistons cost, I would go ahead and replace them. You have already done the hard part. Dave | ||
| Ochoa0042 |
just cracked 19k miles, they're from a XB12 I will get some new rings.. but cylinder's honed?  with the dirtbike i was able to get a '1up' piston to clear the cylinder gap without messing with the cylinder itself, but a buell is not the same and they dont have 1ups. whats up to check out with the cylinders? | ||
| Aptbldr |
Hone cylinder: just very light re-surfacing of cylinder walls, 'scratching the surface'. New rings and re-surfaced walls wear-in together: good seal. Boring cylinder to larger diameter: fit larger dia. piston. Check needle bearings of shaft-within-shaft @ output to counter-shaft pulley. Post more pictures. : ) | ||
| Ochoa0042 |
Check needle bearings of shaft-within-shaft @ output to counter-shaft pulley ¿que?  where are you speaking of? what about the tranny counter shaft? | ||
| Fast1075 |
Ourdee is a man of few words  the rear cylinder has been oiling a bit...not at all uncommon since it runs hotter. You will have to clean and measure the pistons and cylinders to see if they are still within spec....whatever you do...DO NOT go digging into the ring lands with anything...or the possibly usable pistons will be junk. | ||
| Ferocity02 |
Putting in new rings without honing the cylinders is practically useless. They break in together. The new rings won't seat right and you may have oil consumption issues. Just my 2 cents. | ||
| Aptbldr |
Right end of transmission mainshaft rides inside main drive gear (carrying pulley). Two sets of needle bearings inside main drive gear. See service manual, 6.11. | ||
| Iamarchangel |
bearing: it's not even that clear in the manual. Subject is well covered here: http://www.badweatherbikers.com/buell/messages/327 77/463326.html#POST1472076 Pistons: are probably okay. Scrape the carbon off and try and do more highway runs. If you clean the ring grooves, you will need new rings. New rings always mean honing (unless it's trackside but if you've got the tools and knowledge to do it, you probably have a honer already). I'd like to hear more details from Fast1075. Otherwise, I'd first measure the cylinder to make sure it's in spec. If it's still tight, I'd probably put the pistons back in. If I had any doubt, I'd carefully clean the lands with a broken ring and put new rings in. (The rings wear as the carbon builds up behind them so once you clean, you have to replace the rings.) Honing is important, there's hardly any material removal with iron cylinders. Dirt bike cylinders are spray (right?), they can't afford any material loss. | ||
| Fast1075 |
First..I'm sorry I have no computer skills, so I can't post drawings and such. Pistons...the skirts of the piston are important in that they control the position of the piston in the bore. The piston to cylinder clearance is all about controlling the position of the piston in the bore. As a result, piston to cylinder clearance is incredibly important. It is especially important in an engine like the Buell V-twin...because of the design there is little room for much skirt lenght..making the piston to cylinder clearance even more critical..too loose and the piston rocks in the bore..too tight and you end up with friction damage. The rings: There is a common myth that says the rings "hold" the piston in place. That idea is complete hogwash...the piston must be stable in the bore to allow the rings to do their job...if the piston is fitted too loose, the piston rocks in the bore. this prevents the rings from doing their job, which is to seal the piston/cylinder interface.. More ring related stuff: The rings have one sealing surface...which is the bore surface...right???? (loud obnoxious buzzer noise) WRONG...each ring has THREE sealing surfaces...top, bottom and cylinder surface... Ring lands: the grooves the rings live in..the rings seal on the bottom of the groove and the top of the groove...if the lands are worn, the rings will be able to move up and down in the groove...they cannot seal..they will literally pump oil into the combustion chamber in a worse case scenario..and is a prime cause of detonation.The other side of poor ring land fit is worn lands allow combustion gasses to blow by. Taper worn ring lands allow the rings to flex...the rings never have a chance to seat or work... Go to the NRHS website and read the tech articles...well written with very good information. Lastly...if there is question about what condition the top end is in...it is a good idea to have a leakdown test done before you tear the engine down...the leak down test will tell you how much leak you have and whether it is past the rings or past the valves...then you know where to look..if it passes leakdown with a good low number of less than 5 percent...leave it alone...nothing is seriously wrong. Learn to read plugs...a properly selected plug that is read properly will tell you an amazing amount about what is going on in the engine... Lastly...now that you have the engine apart...take the heads to a good shop for a valve job...the oiling on the rear cylinder is very likely from loose intake guides or bad valve guide seals...use good aftermarket seals...not OEM seals. | ||
| Iamarchangel |
Fast1075: thanks, all good stuff. | ||
| Ochoa0042 |
talking to a friend, he said its not worth honing cylinders and getting new piston rings and cleaning the pistons without doing a decent head/valve job.. T/F? | ||
| Akbuell |
Your friends suggestion comes down to a time/money thing. You already have the heads sitting on the bench, so the hard part is done. Before re-assembly, do you want to take the time and spend the money to do a valve job and have port work done on the heads. And since oiling in the rear cylinder was (apparantly) the original reason for the teardown, I would definitely consider replacing the valve guide seals. | ||
| Iamarchangel |
Buddies will always want you to try weird and wonderful things because it doesn't cost them a thing. In this case, most of the work has been done so the cost is down and there is a suspicion that there is a valve issue here so valve work is not a bad idea. | ||
| Ochoa0042 |
rear  front  | ||
| Fast1075 |
Good job cleaning those up James...how bout some pics of the skirt areas...(the domes are a non-wearing part of the piston). | ||
| Ochoa0042 |
what can be wrong with the skirts? i see nothing    (Message edited by ochoa0042 on July 30, 2009) | ||
| Spatten1 |
Skirts look good to me. Late input now, but I'd be careful with a razor, sharp edges scratched in the aluminum piston can cause pre-ignition. Use some 400 grit sand paper on any scratches you make in the dome while cleaning. | ||
| Fast1075 |
Looks pretty good from here...lol...the oil control rings look pretty worn...if everything measures to spec...have the cylinders ball honed, toss on some new rings and have at it. |
