BIG BORE / STROKER KITS
Our Big Bore/Stroker crank kits are winning races and championships all over the world. These kits improve the horsepower, mid-range and overall powerband. Our test riders and pro racers report increased power that’s easier to control, allowing them to get on the power earlier when exiting corners. This increases straightaway speed and lowers lap times, while reducing rider fatigue.
We offer billet stroker cranks, modified OEM stroker cranks, big bore cylinders and modifications, as well as complete kits for several models.
Big Bore kits
Changing just the cylinder and piston is easier than splitting the cases and installing a stroker crankshaft.
Cheaper than a crank, but not by much.
Head is not designed for that diameter cylinder.
Too large bore results in incomplete combustion
Too large bore reduces cooling jacket.
Larger piston adds stress to rod and crank.
Excessive vibration from heavier piston. Still need to remove crank to rebalance for heavier piston assembly. But if you do all that work, you might as well use a stroker crank.
Stock Piston sizes are cheaper to replace and easier to get.
Easier to control
Complete combustion using head designed for this bore.
Longer stroke breathes deeper while valves are open.
Generally, better power than bore kits
If done poorly, can result in vibration
Very large stroke may require case modifications
Somewhat more expensive than big-bore kits.
Few companies can do it properly.
Big Bore / Stroker Crank Combinations
Properly done, you get the best power
Overcome design problems with OEM design
Tailor power/reliability to application
Overcomes limitations of just bore or just stroke
Tailored bore/stroke ratio
Adding stoke allows larger bore
Non-drop-in kits can be more work to install.
DESIGNED FOR THE EXPERIENCED ENGINE BUILDER
We design these kits for experienced race engine builders. They do not contain complete how-to step-by-step instructions on building an engine. When the installation is complete, tuning will be required, including jetting, valve timing, ignition timing and other issues.
Sometimes the engine manufacturer will make slight changes to an engine that could cause interference with our crank, rod or other part. The engine builder should check all clearances, and modify the cases to provide proper clearance. Please keep in mind that we cannot always know if this will be necessary with your cases, and you should take this into account.
If you don’t know how to build and properly tune a race engine, including the installation of a crankshaft, we suggest you contact a professional engine builder or your dealer.
This is not rocket science, but you do need to realize that improper installation or tuning can ruin your engine.