| Author | Message | ||
     Deanh8 |
Just put some XB9 Pistons and new rings in with a bore done on the cylinders. Valves were lapped and cleaned and new valve springs were installed. Have about 500 miles on it since install. Bike has high idle when stopped, runs bad under 3k rpm and feels like it is lacking torque, it hasnt been tuned but I still feel like it should ride better. So I did a compression test and... Im getting 150psi front and 150psi rear. on a very warm motor. I guess its good that it is consistent. But is this around the normal? I did a search and see people are getting 160+ on stock motors. Maybe I messed up my rings during break in? | ||
| Greg_e |
Even significant gaps will allow a compression test to pump up to that number. A leakdown would show what is happening and you could listen to a breather, intake, or exhaust to find the leak if one shows up. I think you are probably fine except that the fuel and timing for those rough spots is probably wrong. | ||
| Deanh8 |
did another compression test with oil and a dead cold motor. Rear cylinder was 180 and front cylinder is making a hissing noise when letting off the starter but did go up to 160psi. weird noise from the inside of the throttle body when you let off the starter. Wish I had the funds to do head work when I had it apart. | ||
| Deanh8 |
Air is pumping out of the PCV breathers when cranking with injectors unplugged and coil unplugged going to run a leak down tonight | ||
| Natexlh1000 |
Perhaps the rings just aren't seated in yet? I wouldn't freak out just yet. (Unless it's running crappy!) | ||
| Greg_e |
I would be more concerned if you had dark wet plugs as the oil build up will wreck the valve seats. It will also get down to wreck the rings if you ignore it long enough. | ||
| Blake |
What bike, assuming the XB9... 1. Were pistons oversized to match the new bore? 2. Was boring performed with proper pressure plate setup? 3. Proper honing done? 4. Proper sized rings for oversized bore and pistons? Leakage at throttle body indicates poor intake valve seal, but if you are just spinning starter, valve may not be closed. Need leak down test. From memory, 150 psi is on the low end of acceptable compression per the service manual. You have a service manual? | ||
| Blake |
Did you do a TPS reset after engine re-assembly? | ||
| Blake |
"hasnt been tuned" Dude. | ||
| Fast1075 |
Many things come to mind....was the boring done with a torque plate?? What is the piston clearance?? How fine was the cylinder fall finish?? What are the ring end gaps?? What kind of rings?? Do the cylinders have any taper or out of round?? has this been checked?? Results from the leakdown??? The leakdown will tell the true story. | ||
| Deanh8 |
sorry no bore, just hone done. rings were "not in spec" compared to the 03 xb 9 manual I have, but they were factory rings and I have an XB12 they were on average .005 larger then the XB9 specs in the book, but they were factory rings and I have factory bore, so I dont see that being that big of an issure? unless I am wrong.. leakdown I feel air out the breather... maybe I need different rings?  (Message edited by deanh8 on October 23, 2011) | ||
| Fast1075 |
Are they new rings, or the rings that were on the pistons? If you mean the ring gaps are .005 beyond the maximum wear limit, you have a problem to begin with. Buell pistons are very short skirt barrel pistons...it does not take much to have them rocking in the bores, especially if the bores are tapered as used ones tend to do. If it was me, I would ride it the way it is until it either gets loose enough to rattle or start pumping oil...there is the possibility that it can actually improve if the rings and cylinders can shake hands and be friends....keep a close eye on it, recheck the leakdown in 500 miles. If it gets worse, you have a winter project..if it comes to that, spring for a quality piston/cylinder kit and send the heads off to Wes and Pammy at Cycle Rama for a little refreshing. | ||
| Greg_e |
If you don't want to go full piston and cylinder replacement, you can probably get the cylinders bored 1 oversize and get new pistons. Not sure if any money will actually be saved though. The head work from NRHS looks very good on my rebuild, but the raw Axtel cylinders leave a few things to be desired so you may want to check on different cylinders. Note it is not the machine work that NHRS did on the cylinders, it was the raw cylinder supplied to them that I have issue with. In the end they should be fine but I also haven't finished assembly yet (but finally have the heads sitting and ready to be torqued). Also note that if you go with a full Cometic engine gasket kit, it will not include the thick rubber gaskets for the stock pushrod tubes. I had to clean mine and used some Hylomar goo to make sure everything would stay leak free. | ||
| Deanh8 |
I put new OEM piston rings, as I didnt bore the cylinders. They were used XB9 pistons out of my 03 XB9, with 14k miles,and they went into my '06 XB12 with 12k miles. The "new" factory rings were (out of the box) on the loose side of the buell spec manual. I figured they should be alright as the cylinders were factory bore and thats the rings they sell for factory bore size. | ||
| Deanh8 |
I put about another 400 miles on her and got it tuned. Made 106hp and 98ftlbs. Guess shes doing alright.... | ||
| Spacecapsule1 |
what didn't you like about the axtell cylinders? | ||
| Hogs |
Dcanh8 IS that all you did was put xb9 pistons in a 12 and got them 106hp and 98ftlbs Or did you do other mods as well...plus how does it act with that 12 to 1 compression now? pump gas or? Thanks for all the info may be doing something like this down the road... | ||
| Deanh8 |
Had the Throttle body and intake manifold bored out to ~51-52mm and replated with a bigger butterfly and cleaned up the heads real good & lapped the valves, heavy duty valve springs as I have floated valves before on my XB9 (which is why I had extra XB9 pistons) Also a XB9 primary setup to free up some weight right off the crank, and I made up for the shorter gearing with my rear sprocket, revs much faster that way with the same gearing and maybe free'd up a hp or two. Milled a few thousands off the tops of the pistons as I was afraid the 91 crap gas we have out here might give me issues, so I figured dropping the compression wouldnt hurt. It made 94hp before the pistons and throttle body. Micron exhaust, Open Air, Dyno Tune by JTS Performance Which I had money to do a valve job, or have the heads done when I had it a part... but I gotta finish my xb-tube frame bike. | ||
| Hogs |
Thanks for that reply Appreciate it.... About the butterfly who did that work? I guess they bored it out and then made a new Butterfly out of Brass or... |
