The first time i ran the little rm with the hpi, it made a remarkable difference. But, the bike was still pinging. So i left it for 6 months. Next time i started it, it was missing. Could be old fuel, crap in carb, dirty plug etc.. I cant really compare hpi to pvl. PVL seems better quality but is much more expensive. Both seem to be really good. I am still having issues with both the yellow YZ and RM, but am sorting through them. The HPI was good value for money and made a huge difference to the stock RM one. The biggest difference to the YZ was the cone pipe made by Jemco. I can swap the pipe between my yellow and white YZ and it completely changes power. Turns the 125 from a broader power band into a sharp, short and snappier power band, which i like on a 125... just keep it on the boil...
I have a lot of work commitments, but i have a new ProX piston kit for the 125 which i am giving to Ray Easson in Perth to match up. I will also jet the bike a little richer so hopefully i get rid of the nipping up problems.
I also have a cylinder and head from a JR80 which are identical to the RM80 parts externally. I have not looked yet, but i suspect the ports will be different. The cylinder is still on its first size, so i also taking that to Ray Easson to match up and fit a new piston kit. I also have the new pipe and muffler coming from a 78 model rm which was more free flowing. So, hopefully with all these mods on the two bikes, i will be able to get them both running they way they should, and me and the boy can go out and enjoy some VMX.
Cheers,