There are various break in methods out there, but the one I have cut and pasted below is from Brian at Pro Twister Mods (mugen46). They are Go-Tech distributors and specialise in modding the Go engines, so they know what they are talking about. The original thread is at the bottom of page 78 on this forum. Follow this procedure and you should be sweet. I have broken in my Go engines using this method and they all run great.

¨GO engine breakin

there are alot of ways to breakin a engine and alot of different opinions on which way is right. I use what i think is somewhat aggressive style, but it still gets adequate fuel through the motor without killing the rod and piston.

Needle setting out of the box. where ever it is set, i always putthe HSN flush or even a hour abouve fluch, and the LSN 1 1/2 turns in from flush, this makes idle during breakin consistant and idles well with good temp, when temps drop the motor will let you know, it makes a very distinctive pinging or tinking noise, the sleeve is shrinking and killing the piston and rod, low heat during breakin is the #1 contributer to broke wrist pin tabs on GO pistons, and the high rpms later on. good heat during breakin will keep good compresion in the motor in the later galloms of the motors life with out being to tight. and will hold a good idle at race temps.

Installing the engine.

After run oil is great. I soak the inside with it befor putting it on the car, let the extra run out the exaust port onto a rag, but be prepared for some smoke on start up. once you have the engine in the car and the exaUST on you are ready for some blowing, yes blowing. Blow in to the stinger of the pipe, you will see fuel going through the lines and into the carb, you can hear it enter the carb making a bubbly noise, when the fuel goes into the carb do it for about 2 seconds after that, then lift the car and turn the flywheel back and forth, this will basicly prime the engine without any dry rotation and coat the inside and also give a faster charge of fuel to help it start up, but heat it first, use foil on the head and preheat the engine with the plug just a tic loose, heat it to about 240 and crank it, remember you have fuel in the carb already so if needed you can apply some throttle to help it get going, just not alot, it doesn't take much with the LSN being set where it is, once it fires tighten the plug and go right to watching the temp, on the first tank keep it at 24o or so the entire tank, then return to BDC and let it cool to about 115.

Now is when i put the car on the ground, i adjust my idle screw to help when applying break not to close the carb. Now that the first tank has been done i start from one and go from here with foil still on the head and my needle settings.

Tanks 1 -6 idle to 1/2 throttle
lean LSN 1 hour and turn down idle screw
Tanks 7 - 12 idle to full throttle easy RPM climb

Go to the track and race tune from there, the HSN may only get turned 2 hours, but the low end will go farther, this setting will give great snap on the bottom and a good transistion to mid and top with good smoke the whole way. when you get to the track pull off the foil and go, if the temp go to 240 260 during 7 - 12 it's fine the settings are still fat you will see how much by the smoke, with this breakin the power robbing pinch will go in about a gallon. after that mark the temps will fall and the final race tune settings can be applied, trying to lean the engine with alot of metal pinch can cause iot to lean bog, flush the HS and lean the LS and the temps will be normal 3 or 4 hours leaning on a tight motor will not work during breakin, with these setting out of the box and changed to what i use the engine will be slightly blubbery on top but be able to get the car moving pretty easy off the bottom.¨

Hope this helps

not to bad i just have a little oil seeping

I've got about 2 gallons on my 7 port now. Took it to the track today and I discovered I still had some fine tuning to do. Before today I was temping at around 240 - 250 ish.

But Today I had the feeling my LSN was to lean, didn't have a bog or anything mind you. So I fattened it up about 6 hours. Then I started leaning the HSN again. Up until this point I thought I had hit the max on what I could with the HSN. I ended up leaning it about 3 - 4 hours. With the fatter bottom and lean top it ran a little bit better but most importantly the temps dropped to 230.

I still can't believe how much the LSN controls with these motors. and I may need to practice some more to get used to all this power My timing is way off because I have to use so much less throttle now.

agreed i was able to race all day yesterday w/o any tuning issues. air temp was close to 100F and engine came off around 260F all day but ran great w/ good smoke trail. for you guys have fits w/ lean bog/hard to tune you gotta try the shorter lsn. i was skeptical about it at first but i have been happy w/ mine ever since i changed it out the last 2 weekends now.

I'm assuming I idle the very first tank in the break in metioned above. What if the temps dont make it to 200 just idling, do I need to lean the the HSN?

What is the part # for the shorter lsn?

The number for the short GO carb LS needles that I got
is 21-2003.

So this is the lsn that solves the carb issues?

yes give it a try and you should be good 2 go!!!

too all you guys running the .25 6 port what pipe have you found to work best? time to buy a new truggy engine and i want to try one. what is the average fuel mileage i shoud expect? thx!!!

I started the break-in on my new 5pt. turbo today. I added the shim that came with the engine, runinng on 30%, using a p3 plug and a 0801 pipe. I am using the break in method discussed here on page 78. Man is this engine tight! Anyway.....it will not idle consistently unless the igniter is on. If I remove it, within 20 secs to a minute, it stalls. The temps are where they need to be (230-250). Any ideas????? I suffered through two tanks idling (having to restart alot), but now am ready to start putting it down and running and it just stalls out.

I had the same problem. Ran 3 more tanks yesterday and it idles fine now. I think my problem was it was too fat on both ends.

yeah my needles are (HSN) flush and (LSN) 1.5 in from flush. I have moved them slightly but didn't want to get crazy. DIdi you just continue to idle tanks or did you drive it around with the igniter on?

My uncle runs a JP-2 on his .25 and his run times are a little above 8 mins..

Quick question. I have a PTM 5 port that I had Brian do a bench break on and I have 3/4 a gallon on myself. When do or can I stop pre-heating the mill before I start it. Mind you I tak "SUPER GOOD" care of my stuff and want the most longevity out of it. Now it is in a truggy with a 8mm restrictor in it and soon it is going to a buggy, when I go to the buggy what restrictor do you recommend? what is the smallest made? And who makes it? Because this 8mm one in my truggy is actually too much right now on my local track which is kinda technical.