I have run GRP faithful since they came out last year. Recently I purchased an OS Speed and what a difference in the tuning. The speed tunes like a breeze compared to the GRP engines. I cant believe the difference and ease of tuning compared to the GRP engines.

im breaking in a GRP .28 motor, heres how its set up

#6 plug
three copper shims, 1 alum. shim ( to take stress off con rod)
o'donell 20%
msr 1005 pipe.

4turns out hsn, 3.5 turns out lsn.

i have it in my MBX5T, and i cant get it to start to save my life. it just turns over with no signs of smoke coming out the exhaust. i did notice air bubbles moving back and forth in the fuel line. is that bad? i checked the glow plug and it working fine.. any help at all is appreciated.

this is just getting real irritating

if you are pre-heating the engine then the heat forces the fuel out of the carb. i have had several grp engines and they all do that. i just prime it a little more.

thanks for the response...its getting fuel...ill prime it little by little then it just gets flooded....ive tore this motor down twice and dont see anyting wrong...im thinking about throwin my NINJA carb on there to see if that helps.

a Ninja carb is the same as a GRP but it might be worth a shot.......are you Sure its getting fuel ? it has no reason to not start if you got spark and fuel.

total BS!! i put i put my ninja carb on, same story...im getting a little smoke out the exhaust but it wont start!!!...im freakin lost now...ive tried differnt gas tanks... and my starter box started smoking.....lol that about all i can do now lol

the ninja carb needs a bushing to fit the grp. other than that they are the same

http://www.amainhobbies.com/product_...etor-Bushing-1

Ok. This is my story. When I would pre-heat my tuned .21 and try to start it, the fuel line looked like I had a huge air leak somewhere. Tons of large air bubbles in the fuel line. I checked the tank and seal many, many times. Nothing solved the issue. I checked the temp of the carb one time and it was near the same temp as the pre-heated engine. So I used a small toothbrush with some water to cool down the carb while keeping the engine warm.

Then when i'd put the car on the box Whalaah!!!, instant fire and purring like a kitten. The carb might be getting too hot and boiling the fuel before the fuel passes through the carb. So try to keep the heat off/away from the carb when you're pre-heating. I'll bet this solves your issue.

Let us know what you find.

sweet, ill try that out....also i just put in a OS P3 plug. well see if that helps first...keep them coming guys...

if your talking os in your grp you will strip the head button threads. try a odo97t. best plug for grp tuned unless you use grp. os plug are a totally different taper than the odo or grp plug

No, its not, but it might leak easier.
The cone is slightly different, but it works this way. Using GRP plugs in a O.S. would be murder - but then againg - who would do such a stupid thing?

I've been running OS p4's for ever in my GRP .21 tuned and never had a problem

i think that you should do some research...Geo-Y-Rock did a measurement and the os and grp are the same...

in fact, i have been using an os plug in my grp since day one.....and the was 2 years ago....so rest assured....they will work...

Ok, been told something else. Did not bother testing, why on earth should anyone put GRP plugs in an O.S anyways? Or even use GRP plugs?
Compared to OD or O.S. they're rubbish, IMO.

if your turns out are from bottom you will never get it to start ...it may be too lean on bottom ...stock settings are
hsn 3.5 turns out
lsn 6 turns out
idle gap 1-1.5 mm
take it back stock and leave the hsn alone and lean the lsn an hour at a time until it will idle ...you should be able to get it going ...but its all been said on this thread ..just search back about 20-30 pages