Bonneville America Forums Forums Technical Forums Performance Mods What big bore for an 865?

anyone who's done an 865 was it worth it, what kit did you fit and what would you fit if you had to do it again?

Thanks ladys and gents xxx

I haven't done the big bore yet but here is the thread with my current build info (Carbs, cams, head work, high compression 865 pistons and TTP igniter) Zmilins build

If given the option to do it all again I would. If not for my mistake and bending my valves the install was, to me, easy.

A 904 BB will gain you more torque over the 865 even with the minimal cc increase. Still worth it and its really the only bolt on big bore you can do without machining the cases.

You want a bit more, you wanna feel like your getting some ccs for your money... go with the 994 big bore. The only dyno Ive seen for that is on an EFI bike but it got him up to 80hp/63tq. 994 EFI BB

Whatever you do my recommendation is TPUSA for your performance needs.

What kind of machining? We talking new studs etc or just widening the hole?

Opening up the lower case to accept the bigger barrels.
I learned that our barrels actually slip into the top case. Theres a couple inches of sleeve that extend down past the casing. With a bigger bore there needs to be clearance but it does not seem to be as simple as just opening the hole. Looks like there is a lip to machine as well.
Ill know more this winter and cant find the thread with pictures (on another forum - triumph rat.net).

I've got the wiseco 904,cammed,freaked and exhaust.The difference between that and stock 865 is day and night(got a spare in garage)I'm in the process of getting head work done but not sure if I can go bigger on the valves.Getting conflicting storys as to weather or not they will hit the pistons.So if Iwere to do it again,I'd make sure to use pistons that I can use bigger valves.Oh I got some FCR's comming in the mail too. good luck,Ill let you know what happens.

I was thinking just higher compression pistons and 790 cams would do the trick on an 865 engine.

Post deleted by Fizzyhair

How do you find it?

As Z said, seems the TPUSA HP kit is the way to go rather than the BB on the 865 and more cost effective. If you can get cams and high compression pistons and I imagine gaskets for under $1,000 all in one spot that is the way I would go.

I think I'll look into that! Thanks guys