The extra shims help increase fuel economy at the expense of a little power loss. There are a lot of variables that affect run time. Pipe and driving style probably being very high on the list. Track size and layout are also major factors.

Dont forget that runtime also is based on how u work ur throttle-finger,track conditions, car conditions, use of a fuelfilter etc. And not only by how much u can lean it out...

I am expert racer, even though I am hearing impared. So I was just wondering so i can talk my pit man into the tuning setup. Uhmm maybe I should try put one shim in because I dont like bottom end too much power but at top end.. So I like mild power at bottom end and nice power on top end.

I know about the throttle situation on my finger, I just am new with grp motor and the tuning seems to be alot different than Vspecs that i have been running for 2 years.

This how i tune my engine, and most grp factory guys. You lean out the LSN till it starts pinging. then richen the bottom four hours. The bottom should be set. Then the HSN should be almost flush. You want it just to clear out on the top. Its not a big revving motor. Then when you come in after warm up, it should be around 170. and if it is then its good to go.

Hope this hepls

Yes I've heard this from another factory driver too. But this part with leaning out till it pings is this something you do while on the starter box or on the track? I am assuming that you have the motor warmed up somewhat before doing this.

After breaking in today this is where I'm at: LSN=4.5 out from bottom and HSN=3.5 out from bottom. Am I in the ballpark? Temped out at 205 and still a little sluggish.

what exactly is pinging? thanks

Does anybody run this motor and if so how about some feedback. My local hobby shop has one at a good price and I am considering buying one.

http://www.amainhobbies.com/product_...ducts_id/26092

it should be similar to the standard mr ninja, just with a standard head isntead of turbo head button

if you wanna switch it to a turbo button let me know i have a new turbo button and glow plug for sale from a mrt tuned that i parted out on ebay

JPZ-67 - That engine should be fine. Its just not a "tuned" version. Essentially its not modded from the factory. Which is what most people should be running anyways.. lol

and its good for rookie to sportsmen..

i have the promo kit.. it comes with the factory tuned pipe along with the motor. so it should be a set right?

First off i have to say this engine is running awesome, nearing the 4ltr mark.

But im having major problems with the carb binding with the engine in my 8ight and flexing of the radio tray, which in an 8ight can only mean certain death for a servo.

I've tried adjusting my linkage and carb set-up every which way possible, different length servo arms and all. The funny thing is when the engine is cold and i think i have it set right the carb movement is buttery Smooth and no radio tray flex at all but when it gets any heat into it its a totally different story.

When up to temp it totally binds up, so bad that it wont get past half throttle. I've tried adjusting this thing every way possible, different length servo arms, different carb rotation positions and different ball linkage positions. No matter how good i get it when its cold, once it heats up it binds like hell.

Any ideas?

I love this engine so much that im almost to the point of selling this damn 8ight with its stupid servo set-up and getting a conventional servo tray set-up buggy.

Jonro - Pull your carb apart and inspect your slide. i have a feeling that it has a bur on it where the idle gap is adjusted. I would be lead to believe thats what happened...

This can happen when you adjust the idle without pulling throttle slightly.. Dremel the bur off or use some scotchbrite. Also when you remove the burr dont be afraid chuck up the slide on a drill and run it some while in the carb body. It helps free it up some and may prevent additional sticking.

Some guys have this problem some dont. It seems hit or miss.

Hope that helped...

GRP tune 21 buggy vs OS speed
 

I have the os speed with the mag head in my RC8 and looking for an engine for the RC8T. how are those 2 engine compare?

Thanks