Triumph Rat Motorcycle Forums banner
1 - 10 of 10 Posts

· Registered
Joined
·
49 Posts
Discussion Starter · #1 ·
Anyone install the Wiseco Big Bore 988 or 904 kits in their standard Bonnie? What kind of power gains can be expected. Any idea on the gas mileage afterward?
 

· Registered
Joined
·
258 Posts
The 988 kit is actually a big bore and stroker combined. Uses stock rod length by moving wrist pin further up in the piston, but requires stroking the crank 1/4". I plan on doing it to my bike this winter. Will let you know how it goes about March, as our racing season starts then.
 

· Registered
Joined
·
49 Posts
Discussion Starter · #3 ·
On 2006-11-08 11:36, tcb wrote:
The 988 kit is actually a big bore and stroker combined. Uses stock rod length by moving wrist pin further up in the piston, but requires stroking the crank 1/4". I plan on doing it to my bike this winter. Will let you know how it goes about March, as our racing season starts then.
Thanks for the reply, I'm thinking about doing this but if the power gains aren't what I'm looking for I'm thinking about simply upgrading to a different bike. I'm not familiar with the term "stroker" what exactly is it?

Thanks
 

· Registered
Joined
·
258 Posts
To "stroke" an engine, the crank pin(where the lower end of the rod attaches) is moved towards the outside of the crank weights, so that as the crank rotates, the piston moves farther up and down in the cylinder, thus increasing displacement. Usually, this requires a longer cylinder to accomodate the increased travel of the piston upward, but in the case of the Wiseco kit, this step was eliminated by fabricating a piston with the wrist pin located farther up in the piston( the exact amount of increased stroke) therefore simplifying the process. Power increases should be substantial, not only because of the increased displacement, but because of the mechanical leverage advantage the stroke angle provides. In high RPM motors, piston speed becomes excessive, but in an engine like the triumph, that is not a concern. However, if all you are interested in is horsepower, and not the type of bike it is delivered in, you are better off changing to almost any other bike, as they are all more powerful than our triumph twins.
 

· Premium Member
Joined
·
11,951 Posts
just to clarify, this basically means a total engine teardown and rebuild, I think the labor for stroking the crank is in the neighborhood of $600 US, along with another 300 for dynamic balancing (you will lose the counter-balancers) and probably another $400 for Carillo rods, and don't forget the $500 or so the kit costs, along with the engine teardown/rebuild.

Parts alone it easily knocks on $2000, plus you'll need gaskets (not cheap either, but maybe included with the kit), and clutch upgrades, and brake upgrades...

I'd think with good exhaust, some aftermarket carbs, etc this would net about 95rwhp or better, and probably 75-80ft lbs of torque.

Point being, you could destroy any HD custom with a 120'' motor, and hang with most sport bikes up to a point.

It'd be one bad sleeper...
 

· Registered
Joined
·
258 Posts
988 wiseco kit (includes gaskets)-$500
Carillo rods -$654
Falicon Stroking (balancing included)-$545
Installing and prepping cylinder-$160
INITIAL TOTAL-$1859
BUT!-You would also want to install cams-$900, bigger valves and port-(do it yourself~$200; someone else~$1000)
and probably carbs-$500
See what I mean about wanting it in your bike or it's not worth it? For me, it's winter therapy and the desire to be competitive in BOT racing and surprise track day participants(they hate it when you pass them with what appears to be a relic!) :-D
 

· Registered
Joined
·
1,999 Posts
I've added the 904 kit to my 790 bonnie...along with airbox removal, predators, upgraded ecu and jetted properly it's around mid 70 hp


...I recently added 42mm mikuni's, big gain's from this mod by seat of the pant's.


Fuel mileage prior to the mikuni's wasnt alot different, still neighborhood of 40+ mpg.
 
1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top