it your linkage you either need to knock the trim back a little or tighten the spring a little. or just leave the servo arm right where it is and loosen the set collar on the throttle linkage then with your fingure push the carb closed and hold it there then put the collar up against the arm and tighten it, then put enough tension on the spring that when you go full throttle to neutral is goes all the way back. hope this helps

With all the talk always centered around the "big named" engines I never heard of radical til I bought my st-rr off my cousin. Let's just say when it's time for a new engine I won't hesitate to buy another radical 621 t. This thing is stupid.

I never really went over the truck when I got it I just put fuel in it and raced. My run times were good, but always seemed to not have that bottom end punch. Well I found out why, the clutch shoes were toast. I replaced them and a new clutch bearing, and wow.....did I happen to mention WOW.

Runs about 230, idles forever mated with a jp2 pipe runnin cold fusion 25%. Now with a lil squeeze she gets all stupid. So far I've pulled off a 3rd and 4th place finish out of 3 races with it. Yes, the truck get's some of the credit for being awsome, but the engine is what makes it go round with ease.

Great engine.:no d:

thank you for the post and glad you like it, these are very good engines just nobody knows about them. if anybody has any questions or needs any help regarding these engines post up, anyone looking for a new engine will not be disappointed in a new radical 621t.

lve been running the Eureka OPS for a while now and everbody that has seen it really likes the amount of power and tune ability,the only bad comment is that the case design looks really old and not trendy enough (like that really matters) but lve heard that there is going to be a new looking crankcase next year

Happy Holidays to all. Will be ordering another 621T after the new year.

Well first off. THANKS Dave! This is my 2 year with the Team but have been running Radical motors for about 5 years. I have 3 different types of heads in my motor box. Not much has changed on the inside. I run the glow plugs that Dave sells and the Radical pipe also. The inside of a Radical motor is a piece of art. Go to the web site and √ out the pictures there of the inside of the motor. Thanks again Dave for supplying me with a GREAT motor. Also Thanks to Mike Stanton.

Hello everyone.
I'm new to the forum but wanted to give a shout out on this thread as I am purchasing 2 Radical621P's for my Uncles 8T and one for my CRT
I spoke with Dave at Got Nitro Online and he's a great person to talk to.
I cant wait to run these motors as I ran one back in 2008 and it was incredible.
I've been out of RC's for the last two summers so i'm anxious to get back into the hobby.
Any info on the motor's, pipe and plug combo's break in methods, etc would be greatly appreciated.

Take care and Happy RC'in !!!

I run the plugs Dave sells. #7 summer plug. As for the pipe I have only ran the Radical pipe with 2 or 3 shims in it. Not sure what pipe is comparable to the Radical one. And for break-in.....???? There is a ton of ways! The one alot of guys are doing is Josh Cyrul's way. Lots of RPM'S and adjusting the High speed needle. Hope this helped.

Thank's.
So I actually ordered 1 621 T and 1 621 P.
The T is going in my 8T 2.0 and the P in my Uncles 8T 2.0.
He is going to use a JP 2 pipe and i'm going to use the Radical pipe and header. I'm not sure how many spacers to use on the pipe. We are both going to run Dave's plugs.
It will be interesting testing to see how each motor runs and with each pipe combo.

hello every one im getting back into the truggy seen and I just purchased tow radicals from Dave(thanks Dave) I am using the 621 p in my eight T and my neph will use the 21 t.But any way This is for Mike Stanton,Mike I have some guestions about the new rear shock tower for the Eight t Truggy is you got the time please pm me I would really appreciated It also I will break the beast in with a jp 2 then I want to use my Buku pipe Dave told me to ask for your help Thanks
Bud have fun every one

Hello

I'm new to this forum but have been racing for a coupl
e of years. I have 2 radical 621t,s 1 with a gallon and the other with 1 half gallon. I use byrons 30% nitro and 11% oil. I used 2 different ways to break them in both provided by gotnitroonline. I noticed on both motors there is a line on the piston on the left side of the exhaust port if your looking in threw the exhaust.I pulled the head off both motors and noticed the mirror surface where the piston and sleeve create compression. Right around where the line is on the piston the mirror image is not visible.the line on the piston is not a scar or gouge but looks like brownish color like burnt oilM the motors run great no problems has anyone noticed this on there 621t,s?

also guys for all you out there with these motors whether its the 621t 621p 628 IF YOU RUN THE LOW SPEED NEEDLE ALL THE WAY IN it will cut the inner oring on the low speed needle making your motor run rich and lean depending on where you are at with the throttle. I read alot of posts with these symptons (blowing plugs,sucky fuel times,and lean bogging,ect....)so if you are having issues with tuning check your orings man there hard to replace to.

hi there,

i thought i would post a picture of my first win with my radical engine. i have had it for about 4 months and it is getting better and better everytime. the acceleration this engine has is out of this world. i can easily jump from 3rd or 4th up to 1st easily. anyway i finished 2nd in the winter series my local track was holding. it might not be much but it is my first podium finish and my first trophy. i know it says first on the trophy but there was a mix up with the trophies. lol



many thanks comments welcome

lewis

congrats on the wiin, i love my engines. I tq and won at the pro series last weekend, good start to the season.

Man these motors kick ass but the carbs are the weak link. I have had it and almost was done with these motors until I mounted a 2010 werks carb on it. I wish ops would update there carbs. They have been using the same carb for as long as I have seen these motors. I even did research and found the mantua model in united kingdom where they sell the ops motors and probably where got nitro gets his stuff and all there motors use the same carb. I do know that this issue has hurt the radical market as I talked to alot of racers and they dont like the motors for that reason.