Please call to order 608-842-0680
Price: $649
Quick Overview
KX99 Big Bore Specifications: Fits 1998-Current KX85 and KX100
Choose Option:
Send us your KX85 top end and we will make it a 99cc Kit
Product Description
Displacement = 99.15cc
Engine Modifications Required:
Cylinder: Bore, Port and Plate.
Power Valves: Modify
Head: Re-chamber to work with the Big Bore piston. 100 octane suggested for most conditions.
Crankshaft: No crank mods required.
Notes: This kit requires you to send us your cylinder, head, and power valves for modification.
Crankcase: No crankcase mods required.
Up to 2013 the KX85 was basically the same engine since 2001. During that time you could get a KX100 top end and slap it on the 85 and have a nice timid trail bike. They are not bad if you don’t like the hit a MX bike is supposed to have but in most cases the 85 made better power than the 100.
This kind of gives you the reasoning behind why Max Power will only build the KX99 kit from KX85 core parts. Long story short, the KX85 modded out to the KX99 specs will run circles around the stock KX100 cylinder. It is possible to modify a KX100 cylinder so it is better but it still will not run like our KX99.
Now there is larger Wiseco pistons available for the KX85 all the way out to 54.5mm (48.5 is stock). We have built them in the past for testing and we advise against it for various reasons. However if you really want one we can build it, just call us, the price is the same. But be forewarned, the power is not as good. That is why we don’t advertise them.
This kit uses a Wiseco KX100 top end kit. You can use an OEM piston just as easily if you are sponsored but it will rev a tad slower because of the extra weight. That also means you can buy spare pistons from pretty much anyone. However if you are cool and you like the kit (you will), just letting you know that we do keep a few of these in stock and we would love to sell spare top ends to you for dealer cost.
Pro Circuit power valves can be used for additional bottom and mid but you need to use the KX100 valve kit. We can supply these kits for an additional cost. The kit is plenty good without the PC power valve but you can never have too much.
PS: This kit can later be stroked to 105cc with head mods 😉