Cobra/JB 90cc Mod

[Joebyrd7]

Cobra Frame, JB Front end w/TRX front spindles and brakes with wave rotors, JB Swing Arm w/TRX rear end and KFX 450 wave rotor, Motowoz Shox front and rear, Rath Nerf bars, front bumper, and rear grab bar, trackside tuned and jet coated exhaust, Pro Taper handle bars, TRX thumb throttle, easy pull Moose clutch lever and perch. YFZ 450 Fluidine Radiator w/Outer wear mud screen, OMF wheels on front w/OMF beadlocks on rear with mud plugs powder coated, wide billet rear hubs, new DWT JR MX rear tires, shaved seat, Streamline steering stabilizer, RM 85 race motor stoked to 90cc, Custom crank mods, Wiesco piston (stock bore), port and polished, V force reeds, JB steering stem with new spare JB steering stem, tool box, Rm 85 super mini mod motor stroked and bored to 115cc, jet box full of all jets and extras needed for tuning, extra air filters, spare new set of JB tie rods, spare tie rod ends, spare ball joints, spare new clutch, spare new ez pull clutch lever and perch set, spare new gas tank bracket (cobra) , spare new gas cap, spare shifter, spare new intake manifold, spare new set of V force reed paddles, spare new rear brake fluid reservoir, spare new head gaskets, spare new water pump gasket and seal kit, 4 new NGK iridium IX spark plugs, spare new NGK spark plug cap, 2 new spare spacer plates for 90cc stroker, spare full electrical system CDI coil stator, spare new clutch side cover gasket, spare new throttle cable, spare new clutch cable, cover for air filter for mud and rain, ratio rite mix cup for 2 stroke fuel mixing, 3 shock struts for when shocks are getting services, misc. nuts and bolts, rubber cap for carb when washing bike, tools needed for service and race prep, a 2.5 gallon race jug, 1 quart 2 stroke oil for premix, 1 quart trans oil. For sale for $10,500 OBO

[JustinBoots]

Can I ask you a question...I'm setting up an RM85 stock engine in my son's Cobra. I purchased a digital PVL for the engine, but can't find information anywhere on what the timing should be set at. Any ideas? I've always run PVL ignitions on our DRRs, but the RM85 is new to me. Assuming you are running a radiator out of a YFZ 450?

[jungleboy213]

I'll help out a little. We ran a DRR for a couple of years and I realized that it was a money pit. I ran a couple of different pvl's. I bought a Cobra with a RM85 setup. I ran a stock motor at nationals and did quite well. At Loretta's we were winning the heat in the 90 mod class before the carb messed up on us. I used stock RM85 ignition the whole year. We raced 6 nationals and 16 locals. I never had an issue. I would suggest to save your money and long stroke and bore your motor. Chris Grissom did ours and that bike came alive. Try a kx100 intake on it. That really helped, too. We would still be racing it but my kid grew a foot in a year, so I had to go to a bigger chassis.

[JustinBoots]

I'll help out a little. We ran a DRR for a couple of years and I realized that it was a money pit. I ran a couple of different pvl's. I bought a Cobra with a RM85 setup. I ran a stock motor at nationals and did quite well. At Loretta's we were winning the heat in the 90 mod class before the carb messed up on us. I used stock RM85 ignition the whole year. We raced 6 nationals and 16 locals. I never had an issue. I would suggest to save your money and long stroke and bore your motor. Chris Grissom did ours and that bike came alive. Try a kx100 intake on it. That really helped, too. We would still be racing it but my kid grew a foot in a year, so I had to go to a bigger chassis.

Appreciate the info jungleboy. Eventually plan on stroking/boring as well. Can I ask what advantage you found in running the KX100 intake? Alredy running the V-Force reeds and cage with trimmed RM85 intake and 28mm carb that came on it.

[jungleboy213]

I ran the KX100 intake because it seemed like there wasn't enough room for the filter to get clean air. Plus that intake funnelled the incoming air better.
Another tip, we ran both a stock 70 Cobra pipe and a Trackside pipe on ours. The trackside had incredible to end power but when we ran indoors, he prefered the Cobra pipe. He said it produced more torque.

[JustinBoots]

I ran the KX100 intake because it seemed like there wasn't enough room for the filter to get clean air. Plus that intake funnelled the incoming air better.
Another tip, we ran both a stock 70 Cobra pipe and a Trackside pipe on ours. The trackside had incredible to end power but when we ran indoors, he prefered the Cobra pipe. He said it produced more torque.

Good info...we run outside only and run the Trackside pipe. I run the factory COBRA air filter and it works out real nice.