Originally Posted by j8ight13 (Post 6195397)

I just picked up a used GRP .28 MRT with grp exhuast (2053). I got it for $100 bucks and its not in the bad of shape at all.

Until i thought. I have a really high idle after high speed passes. This is my first GRP so i had to do some research to get the correct needle settings and to read about all the different things people go through. Well the guy i got it from used OS p3 which i found out after is a bad idea. Im assuming the plugs will leak. Would that be the cause of the crazy idle?

When i do a high speed pass. the engine will be revving high then it will go down after 20 seconds or so. then if i just tap the throt it will go right back up.

Well i couldn't figure it out for the longest time and it was about to just be a shelf queen at this point. I really wanted to use this mill. so i picked up new p/s, rod, pin, clips, front and rear bearings. cleaned up the inside put her back together than started her up. Well same problem. I sealed the engine's carb and backplate while it was apart too as i do with all my engines.

I still dont know what is wrong with it, maybe its the plug that im using. i just ordered a new head button so i can run the grp plugs. Im hoping that is what the problem is.

has anyone ever had this problem? If so, what did you do to resolve it.
i just got my untuned grp .21 yesterday. So if i can't fix it, im just going to swap the parts that i can with the .28 and .21.

thanks for all your help guys.

Originally Posted by mr. losi (Post 6195655)

the guy you bought it from used os plugs, what did you use???

i am sick of ppl saying you cant use the os plug, because you can....i have not changed back to grp plugs....i will put one in, and i will bet it wont leak...

the os plugs are fine and about 5 dollars per plug cheaper than the grp plugs....

Originally Posted by casevac (Post 6196069)

I know this sounds crazy, but I strugguled with the same problems with my MR Ninja (GRP)

The cure:
Lean idlegap and lean LSN propotionally.

Do it.... Dooo it ;)

Originally Posted by j8ight13 (Post 6196138)

do you know how many turns out the LSN is? Someone else told me that I had my LSN to rich so it can't burn all the fuel that floods into it.

I'll give it a shot. GRPs are so much different to tune IMO. you have to make the smallest adjustments.

Originally Posted by casevac (Post 6196340)

As a general rule i found:
Idle gap - smaller than you'd think
lean bottom - rich on top

Originally Posted by j8ight13 (Post 6197506)

Zixxer, thank you man! I was so rich on the LSN. Im going to put a OD 97t in tomorrow and give that a shot and see how it runs. I can get those for like 5 bucks a pc. If they work great im in luck.

Also Zixxer, Ill check tomorrow at the shop if they have any rods left and let you know ASAP. i think they are like 30-40 bucks. Have to double check. But, i'll get back to you.

Thanks everyone for all your replies! :)

Originally Posted by j8ight13 (Post 6197506)

Zixxer, thank you man! I was so rich on the LSN. Im going to put a OD 97t in tomorrow and give that a shot and see how it runs. I can get those for like 5 bucks a pc. If they work great im in luck.

Also Zixxer, Ill check tomorrow at the shop if they have any rods left and let you know ASAP. i think they are like 30-40 bucks. Have to double check. But, i'll get back to you.

Thanks everyone for all your replies! :)

Originally Posted by beta bob (Post 6199866)

Hey guys i bought the non tuned grp with the silver head and was wondering what plug i should put in it and is it a turbo or standard plug engine. Also if i were to find a tuned crank and psiton sleeve do i have to buy both of those for it to run properly when/if i decide to change all the internals

Originally Posted by TVMRocket69 (Post 6199907)

I run the ODO99 in my non tuned. It is a standard plug engine.

Originally Posted by j8ight13 (Post 6199950)

I just picked up the untuned myself. I love it so far! Im going to break it in then switch that brick(conrod) and maybe the crank. Then to a .21 button head and orange head. for my upgrades.

Does anyone run nitrotane with their GRPs? I took my engine apart last night to check on the wear so far and after 5 tanks I noticed that it leaves a dark brown residue on the top of the piston.