| Author | Message | ||
     Bumpnzx3 |
I am looking to do a few engine upgrades to my xb12r track bike. I'm not sure if I want to go with a 1250 big bore kit. Right now, I am just doing track days, but I am limited to the current engine size given the class the bike would run in. I am thinking I am going to go with the first oversized piston set from Hammer and their stage 2 light head (can't remember what they call that head). I might look into a cam upgrade- but something under 550 lift because I don't want the cost of upgrading everything to accommodate big cams. Just curious if that head service will bring much of an improvement over stock, given a stock'ish cc engine. The fact that same head was used on the XB9, makes me think the XB12 would benefit from a better flowing head. It's also my understanding that the XB already has a pretty hot set of cams in it. Would a set of cams with under 550 lift bring much of a power improvement. I guess what I am asking is- are my plans worth while? I'm just not sure if the head/cams are undersized for a 12 or oversized for the 9 since they are shared between the engines. | ||
| Natexlh1000 |
I would guess that a small bump in compression ratio and a dyno tune would be better in terms of bang/buck. Nothing crazy diesel compression but if you're not riding it to work in traffic, you could perhaps configure it to run race gas to great effect. | ||
| Bumpnzx3 |
The bike is actually a xb9 w/ a 12 crank- so I am already running a high compression 12. I run a half and half mix of 93 octane and VP C12 with good results. It's just getting tired and could stand a refresh. While I am in there, I was thinking of doing some upgrades to increase flow- assuming it was even needed in the first place. | ||
| Greg_e |
Increase in flow is almost always a good idea, getting the XB12 throttle body and maybe bore it out a little larger and the XB12 headers would be a good idea. Port and polish should make a few more horses. Could you go to the shorter XB9 crank and some nice big cylinders to get back up to about 1200cc? That with head work and other flow work would certainly be an improvement. Kind of cheating but it would still be around the same displacement. You could have the piston done to whatever compression you want. | ||
| Rageonthedl |
you could get the weisco xb9 piston. have the heads done. maybe some crank work. i really hope you already did the t body and header when you did the crank... | ||
| Bumpnzx3 |
Yep- header and throttle body were done quite a while ago when the crank was done. I thought about going back into the motor and swapping out the crank, but I don't really want to go through that much work and added expense. The engine could just stand a refresh. With that would come a head job (insert funny joke here). Just trying to decide if a head from Hammer would be a worth it. Whatever they call their stage two head has slightly larger valves- not much, but a little. Not enough to where I think port velocity would be of a concern. I know I don't need their best head. I could go with their head and piston both of the 30deg. variety. Their piston sets are only about $30-$40 more than Wiseco and I could have it to whatever compression I wanted and their reverse dome 30deg. design. Ultimately my best bet would be to call them and tell them what I am after- a refresh with a little added power for a reasonable amount of money and labor on my part. They would be able to suggest the best options for me since they have most likely seen and done it all. | ||
| Teeps |
Save your money as nothing you do short of dropping the bike off a cliff will ever equal performance of other similar displacement I4's or OHC twins... For track days, I would just rebuild with stock parts and call it good. | ||
| Bumpnzx3 |
I am fully aware that it won't compete with I4's in terms of power. I have no delusions that will happen with a reasonable amount of money. That's not the class it runs in anyway. Running in the GT Lights class I would mainly be running with SV650's. There's a few others as well, but the SV is the usual bike of choice. I am doing the mods for me, not for everyone else. I was just curious how the heads were in relation to the displacement of the engine. I didn't really know where the bottleneck was. After talking to Hammer a bit today, I think we have a good, cost effective solution for my goals. | ||
| Natexlh1000 |
Have you put any thought into one of those exotic cylinder platings instead of the cast iron? Same displacement,compression,breathing but dissipating the heat better. Just curious. It seems that you do good research so I imagine you already looked into this sort of thing  | ||
| Teeps |
Bumpnzx3 Posted on Tuesday, January 08, 2013 I am doing the mods for me, not for everyone else. Understood. I just don't think the improvement is worth the cost. | ||
| Bumpnzx3 |
I didn't mean for that to come off w/ a smart-ass tone. I'm not really spending much more money than would be required on a stock re-build....maybe $250-$300 more at most. I'm not doing the refresh simply to throw parts at it. The bike needs it, so for a few hundred more, I might as well get more power out of it. Kinda the same as upgrading the exhaust in terms of added cost. I certainly don't know everything, but I don't think anything besides a standard cylinder would be needed for my mild build. I've had good results with cars by coating the piston crowns and skirts though. I would assume the same would be true on a bike engine- especially an air cooled unit. |
