I have a QT 50 with a malossi 70cc kit, vm18 carb, 18mm intake, 100 main jet, middle notch needle jet, 25 pilot jet, MLM sidebleed pipe, stiffer clutch springs, and boyesen reeds. Stock CDI.
Unless these things run this hot and im not aware of it I am having troubles keeping my head at a good running temp. When I run it really rich I can keep it under control but whenever I jet it reasonably I get right up to 350+, no problem getting to 400. Jetted really high I sit around 320 at WOT, but it runs like shit.
I was wondering if this HPI CDI is worth getting for the curve at high rev http://www.treatland.tv/HPI-CDI-mini-rotor-ignition-system-for-yamaha-QT50-p/yamaha-qt50-mini-rotor-90.htm or if a $20 jog CDI like this http://www.ebay.com/itm/CDI-Box-2-Stroke-Gy6-50cc-1PE40QMB-Tgb-Key-West-Qingli-JOG-Vento-Verucci-NEW-/151659054581?vxp=mtr will retard it enough to lower the temps at the head.
Otherwise is there something im missing? Any recommendations or advice?