GRP 21 Tune line????????
 

ok I got this promo package some time ago. I Have maybe 4 1/2 gal's give a tank or two on my Tune line GRP...mind you this came with the key chain the Team Towel the really nice GRP pipe and manifold. Ok so I figure it's time to send the piston and sleeve off to get a nice clean up and a real good resizing.I bought some new bearings (ceramic) and figured I'd be good for another season. well I open this engine up and it has a squared off con rod its not even knife edged. and the crank is flat on the back, it looks like a real poor turbo job on the crank flute. But it has the dished piston and it looks like a 5 port slevee from GRP. can anyone enlighten me on what GRP this mite be?? Oh and the carb is a GRP but its backwards the idle screw is on the bottom....anyone seen this????

Weird, the tuned line has the GRP and Mario Rossi tuned aswell as the APS logo engraved on the crank (counterweight). It also has a straight turbo scoop. The conrod should be knife edged and should say "GRP" aswell. The sleeve is a 5 port with 1 small fang on either side on 1 of the side intake ports and has ingraving below the exhaust port. The carb is a reverse one specially for use in Buggy.

Found this pic in the for sale part of this forum:

http://i375.photobucket.com/albums/o...t/HPIM1203.jpg

Sounds like you have one that is put together from tuned/non tuned parts with an onroad carb :confused:

can you post pics of everything? I know they did a running change to the P/S sets but it should have a knife edged rod like this

http://i281.photobucket.com/albums/k...x/DSCN0205.jpg

Also pics of the crank and carb would be alot of help.

Did you buy new or used? If you bought used, there is a good chance you may have gotten a sport line .21 with the turbo button/cooling head exchange. Back when I was the GRP go to guy, that was a very popular thing to do. Alot of people wanted to run the turbo plug on their sport line engines and the only way to do it was to switch the sport/sport rally head with the tuned line head as the head and button were machined as one in the sport line and they used standard plugs. Things to look for to figure out if it is sport or tuned or a mix of both are:

-sport crank will be a solid cheek with no fluting unless modified

-sport crank will also have a solid steel intake ramp where the tuned crank will be drilled and filled with silicone

-sport crank will be silver and non-hardened where as the tuned line will be darker in color from the hardening process

-sport sleeve will be a 5 port like the tuned line but will not have the tear drops in the front transfer like the tuned line had

-sport rod is non-knife edged where the tuned line was

-sport case did not have the rear booster port relieved at the base where the tuned line had 2 reliefs cut into the base of the rear booster to allow the incoming charge easier access to the rear booster port area

-sport carb had idle screw located on the front of the carb body and tuned line was on the backside of the carb body

Those are the main differences. The differences between the sport and sport rally editions was the rally had a triple exhust port similar to the onroad engine with similar port timing specs as the onroad version. As mentioned, if you have pictures and a better description of where you got the engine and in what condition may help us determine what is going on.

Thank you very much
 

Ok thats all cleared up.:nod: I bought this engine from what I thought was a really strait up guy. He was a pro at the time and said they had been given these promo kits as a gift at some event that they had been at. Well I bought this back in the end of 08 or right at the very frist of 09 and it was new I could tell there hadn't been any fuel put through it. I had to Brake it in. teach me to open a engine up before I brake it in Huh!!! well I guess I have a really good running sport GRP then...LOL Thank for the insight.:cry::cry:

is this the 2 reliefs cuts that you are talking about??

http://i281.photobucket.com/albums/k...x/DSCN0206.jpg

thanks

Those are the reliefs I was talking about.

Hey Mark would you know the bearing sizes for the grp .21 tuned ? thank you

Cool thanks, how about the back plate, my tuned has a dish milled out of the inside of it well my GRP ninja and G5 do not. any idea on what it is for?

you can see it in this pic

http://i281.photobucket.com/albums/k...x/DSCN0212.jpg

Bearing size (rear) = 14 x 25.4 x 6
Bearing size (front) = 7 x 19 x 6

Milled backplate, my guess is: it increases case volume, maybe to compensate for the putty in the crank that decreases case volume?

Maybe or it is supposed to help fuel get to the ports faster or better??

The milled backplate can be various reasons but the only way to know what the intention was for sure is to ask the engine designer what his theory and take on that idea is. Some of the ideas already mentioned seem decent. It could be the volume theory, it could be the charge entry velocity and angle idea, it could be he wanted to save some weight on the engine not that the cavity in the backplate would do much for weight savings in my opinion but you never know or it could be a combination of all three or maybe something we haven't even thought of yet. I have run those engines with and without the cavity and honestly haven't seen much difference if any between the two.

Cool thanks for the info!

Anyone still running these mills?? What run times are guys getting in truggy? I recently put my Tuned GRP 21 back in service (I had it as my back up engine) Was so impressed that after sitting in my pit box for 2 years, she started with the first hit of the starter box and sat there idling.
I'm using a GRP#4 and the GRP pipe I believe it's a 2053 (not 100% sure), I have my eye on a BNIB Tuned Promo kit (yes another back up for the back up lol)
I forgot how good this engine is !!!!

I have bee trying to use mine. I just cannot get it too stay running. Drained my ignitor, and drained my packs in my starter box. I have set the carb to a few diff. recommended settings and it just wont idle and stay running. As soon as I hit the gas it dies.
Gonna try 4 on HSN and 5.5 on Low.
I dont have any more plugs to try(LHS wont buy OS plugs).
last year it would start right up and GOOOO!
Tried sidewinder 20% and same problem, switched to odonnell 30% and same problem.
IM thinking it could be my starter box, the plugs and the kinda old fuel.