I finally got mine on the track tonight for some race tuning and it was pretty solid to me. Yeah it does not have the rocket bottom, but once it hits the pipe it's a raped ape.

I had a lean bog in the beginning so I richened the bottom and leaned the top. Ran strong and came off at 220 or slightly less.

How much will running the 8mm restrictor improve performance and reduce run time? I have the 7.5 in right now.

Anyone looking for a Ninja .21 carburetor let me know. I have one that
I'm going to stick on Ebay this weekend if no one claims it. I'll make
you a good deal :)

[email protected]

Best regards,

bearing size
 

Does anyone here know what are the bearing size for grp tuned F/R;)

14x25.4x6
7x19x6

All of you guys having flameouts, taking a head shim off got rid of my flameout issue. Not saying it's the gospel but it worked for me.Be careful removing head shims, unless you are a pro that gets free engines. Watch for pitting on top of the piston and on the head button....nobody wants the big flameout!

I know a guy that had the flame out probs and the fix is to put a fuel filter on the preasure line.We went to nitrofest this past weeknd and he told a guy to try that and he came back with a big smile and a huge thanks.Hope this helps.

I am a little confused as to the ""issues" so many seem to be having?? I ran my GRP 21 with a GRP 4 plug, 9853 pipe, 30% fuel, and added one thin copper shim (just to ease the compression a little). It was a raped ape..came off the track at 200 tops, 10 minute runtimes, and it never once flamed out. A buddy of mine is running his without the extra shim, a P3, 30%, and a 9853 pipe and has not had any issues in 4 gallons. If you are flaming out the LSN is too rich and or your plug is too cold...the GRP 6 is way too cold imo...try a GRP4, and tune the engine with the LSN (like noted earlier)..it likes a leaner LSN and a slightly richer HSN...I have run RB's, Novas, Ninjas, Max Power, and Vspecs, and the GRP is likely my favorite mill out of them all.

A bit off topic here

How are the non-tuned GRP's performing? I didn't know they existed before this weekend.

I have a question for you guys, I just got about 1 1/2 gallons on my GRP Tuned, and most of the metal pinch is gone, but still has good compression. I run 20% Byrons fuel. Should I take off one of the shims? I have it at factory (One silver and one copper shim). What would be a good deck height for this motor?

This is my first expensive engine, and I love it, just don't want to trash it.

Thanks in advance!!

Jimmy

I would leave it as is

How do you guys feel the GRP compares with say an RB or OS for the amount of compression needed to run correctly ??

Mine has drank about 2 gallons of Byrons 30% gen2. I ran into what i think is the dreaded flame out issue this past race weekend. I've previously had no real issue's with the motor. In fairness it ran very well all day, thoughout the qualifiers I was running about 4mins warm up, refueling and then doing the 5min quali without any excitement or problem.

But when it came time for the main, First it cut out after I started it, twice. then it seemed ok and i ran 3mins of the warm up. My pit guy refuelled it about 10s before the race start, I cleared it out without issue. Then the main started 15ft later mine cut again ???? pit guy fired it up again and it ran flawlessly the rest of the main and strangely that included the fuel stop which I left till just after 10min. He said i was running on fumes, but it didn't miss a beat...........

After the race I turned over the flywheel by hand and there was little resistance.......Although I can't say I've ever tried this before so couldn't know if this is normal ?

On returning home I thought I'd try the 3 O'c test, now the motor was cool again and well I can't say it'll stay there. It very slowly drops over, That said my Os Vspec's were the same when running well tho. Reading the thread I noticed it was suggested removing a head shim may help, with that done you can feel slight metal pinch, but again it still slowly droops over if you try the 3 O'c test ? So I've put it back in.

I've been running the No.6 plug which Maybe somewhat to blame from what your all saying too. So I've changed that to a 5, 4's dont seem to be available over here and I had the only 5 I've been able to find at that......

Also I see someone suggested a fuel filter on the pressure return piping from the pipe, if possible could anyone explain why that'd help ?? As i simply don't understand why it should make any difference. Not saying it won't just asking why it would ???

Anyhow's if you can tell me what you think the compression should be like with this motor that'd be great. I dont really see how it could be worn out so soon. There so sign of it eating any dirt at all. I change the filters out for new every meeting or faster if conditions are poor.

Thanks

Rod

Rod - that does not sound good...my buddy has been running his all year and the same thing happened to him last weekend...starting cutting off and when he checked the compression, he had NONE. He has about 4 gallons on his, but it is done. I did not get that far with mine as the main bearing disintegrated and tore up the engine, but yours is the 3rd or 4th one I have heard about that has lost all compression prematurely (I would have thought these mills would last longer then an OS, but now I am not so sure)

re fuel flame out
 

my grp has been awsome best motor ever power everwhere never had a falme out til recently been tuning same way ever time lsn then hsn. after ever refuel it dies. re fuel if i dont stay wot for at least a strat it dies. anyone had this problem before. o and as far as the compression thing goes i can turn my by hand farly easy been this way for long time have about 3 gallons on mine. it still runs like a bat out of hell think this is normal for motor been like that since gallon and half and trust me took a whole gallon to break in motor did it slow not paying 400 to rush and have motor last 2 gallons. di 20 heat cycle warm it up to 200 and shut it down. and six tanks of figure eights before it even hit the track. could tur it over by hand after all that break in. and it keeps getting more power. just had this recent flame out after fuel up issue and that is it running number 5 plug works good have 4 but 5 runs great. this thing has been insane fast will out run most mod motors and still get nine min run times love this motor just cant die evey pit stop so please help somone!!!!!!!!!!

one more thing
 

i put 8.5 carb insert and still get 10 min easy no problem running byrons 30 gen 2 11 percent oil