Bonneville America Forums Forums Technical Forums Performance Mods Big bore (904) gains???

Hello all, i know the 904 big bore kit is popular here. Is there a big gain in power over stock? I am planning to use Uncle Sam's rebate check for something with the bike and i was wondering what type of performance gains were obtained.
thanks
Jack

about 10hp and 10tq. does not sound like much but figure it out in % and its a good gain worth every penny imho

Frank

I am also thinking of the 904cc kit. $500 seems cheap for the kit. Does anyone know how much it is to install? How long it should take? Will I have to muck with the carbs again?

If that 1500 triumph doesnt show this year then the kit goes in.

Also saw a 988cc kit by Wesco on newspeedmaster. Is that worth looking into? Does Wesco make a good product?

You also have to consider machining costs. The 988 is a stroker and additional machining has to be done to the lower case. bonnevilleperformance.com has a drop in kit, cylinders already machined and sleeved for between $7-800. I'm waiting on my oversized valves, but the dealer said mine should be less than 5 hours labor, and thats including swapping all the head components to a new port/polished head I have. I think just for the cylinder and piston swap they were between 3-4 hours for labor, and that was a Triumph dealer going by the book. I got the wiseco pistons with my kit, I think a lot of guys here have those, and haven't heard anything negative. I hope to get mine done, it should be already, but the valves have me waiting I also bought a second head to have the work done so I didnt miss any ride time, so basically I am putting on a whole new top half. D&D cycles has another version of the drop in kit, they bore and replate with nikasil. However, they wanted a thousand dollar deposit for the cylinders until I returned the old ones, Bill Gately at bonneville performance just told me to return my old one when I'm done He's a good guy to deal with, as others here will agree

The cost for D&D (Pensacola) to do it all is about $1250. That includes swapping your barrels for ones bored and re nickeled (like factory), Wiseco pistons, gaskets, etc. and all labor including dyno runs to set up properly.

if you do the work yourself the weisco kit can be done for about 1000, minor carb changes will be needed but nothing major. well worth it imho. the 988 stroker does not need the cases to be machined but needs the crank to be rewelded. thats a cool 3k i think but it does offer some big gains. the 11 and 1200 kits need the cases to be machined. its all in how much money you have. also if you are near florida bill will do any big bore minus machine work for 500 bucks

Frank

No where near florida. Does anyone have any recommendations for the Tri-state area.
I will not do the work myself. I learned that lesson with the freak and bubs. even though I did it all myself it took me 2 visits to the shop to get my bike running correctly again. Even know i am sceptical about what I have done

Anyway... So about 1250 to have the kit done before any head work... Is that what I am hearing?

All I was trying to convey in a long explanation is that the cost will probably depend most on the hourly labor rate of the shop you choose. If they all use the same time rate quote, then yes, between $1000-1300.

do it yourself...........