Originally Posted by
curacing2
Eivind, the gen 5 carb and all later model carbs onwards work well and when tuned right will make the motors fast and reliable.
Shane and I have had a few year running and tuning these motors and Shane has very good tuning guides on his website, check it out.
http://go-racing.vpweb.co.nz/
Well my apologies to you, Sir. In the end I stuck with the Go 2-needle carb, because - well it worked well! hehehe

I don't know why people badmouth them, it was so easy to tune!
I had one of these GX5R's that I had bought on ebay from some guy who didn't want it, it was brand new, and I paid something like $80 for it, along with a 2072 pipe. So I decided to break it in today.
It came with the short needle in the carb, so I bought a long needle for like $10, because I heard that was the easiest one to tune.
Took out the short one, swapped the o-ring over, and today I went to break it in.
I used the "heat-cycling method" described in the "break in bible" thread here in this forum.
After about 5 or 6 tanks ran with heat cycles, running like 3 minutes each time, the next time I tried to start it up, it seemed really rich, and started to run a lot better once I leaned it out.
Like you described on the website, the best way is to tune the LSN first.
I started by getting the appropriate idlespeed, then I went to tune the LSN. Basicly I kept leaning it until when I pinch the fuel tube it only increases very slightly in RPM. Then after that it ran really nicely, and I started to tune the HSN, just like you described in the website.
So basicly your instructions are gold. I don't know why I was even thinking about trying an OS carb, and I don't know why people are badmouthing these carbs - it was really easy to tune and the powerband was really nice.
I am well chuffed with this, very happy. Now I just have to run another half a gallon through it, and then I will replace the conrod and put in some ceramic bearings, and this thing will be ready to race