14x25.4x6 is the correct size. The tko bearings are the best I have used. I usually do not change the stock bearings till they go bad. That way you know the motor is fully broken in and there is no metal pinch left. The tko bearings last a long time when the pinch is gone.

Thats one of my gripes with this brand. The parts prices.

O.S. P3 plug.

nothing will ruin a GRP head button faster then a OS plug........ Do not run OS plugs in these motors.

I always ran p3's in my ninja and falcon with no problems.

Why is that?

Have to agree, why is that? I've been running O.S plugs in my Ninja without any issues what-so-ever. I routinely open my engines to ensure all is well, and I've not seen any issues.

Making a statement like that you need to back it with some facts or at least observations otherwise your statement is meaningless...

Thats because the taper on the OS and GRP plugs are different. They are close, but different. I've seen people use OS, GRP and Sirio plugs as interchangable, but they have some slight variations. I have seen someone screw a OS plug in a Novarossi and it pushed the top of the combustion chamber in, so now a Novarossi plug will never seal correctly in that button anymore.

Hmmmm, I don't buy that....

No offense, but I don't believe that or else GRP would make a point that you can ONLY use GRP plugs and thats not the case. They recommend their plugs but make no mention that its mandatory....

I think if an different brand of plug "deforms" the button head or threads, they would definitely make it clear that was the case. How many engines would be ruined this way...

With my ninja, I usually run the OS plugs, but have used mugen turbo plugs, and O'Donnell turbo plugs after an OS without issue...

I just compared my p3 to the plug that came in my GRP they look identical.

I don't think any company says you had to run their plugs, they expect you to. If you owned a Novarossi engine and screwed in the OS Turbo plug, you would see what I'm talking about.

Ive used OS plugs in a P5 and a Nova 28 no problems ran them in my ninja and falcon I actually ran for falcon and they told me to use them at the time.

Hopefully we'll solve this question pretty quick. I e-mailed GRP directly asking them about plug selection....

If Novarossi's are that temperamental, thank gosh I don't own one. I'll stick to my O.S, Mugen's, RBs, and GRPs!

I guess I don't know anything, then. LOL.

I have seen several Ninja motors with OS plugs pissing fuel...they are not the correct taper.... you can torque a OS plug to seal but it can mess up the button if you ever go to run a Ninja plug again... Every manufacturer has a slightly different taper on their plugs...OS plugs will leak in both Ninja's and Picco's, tho I do know many people who manage to use them anyways....... When you thread an OS turbo in tight into the Ninja button you can see a gap between the plug and the button if you look from the underside, as if the plug is a little to short to fully fill the taper..... But before everyone jumps all over me I still have seen OS plugs used successfully in both Picco's and Ninja's...but I have also seen just as many needing to replace their head buttons because the OS plugs damaged the button when they tried to get it to seal...Fuel bubbling out around the dam plug no matter how tight they tightened it..... Safe bet IMHO is to match the plugs to the motor and be done with it.....