Thread: Need Advice
11-25-2006, 12:53 AM #1
This is a 2 part question:
I have all this crap I have listed on my signature and can't get over 7000 RPMs. Any advice? I have tried adjusting the high speed screws (stock jets) with little effect. It seems to do better with stock plate and tabs. I'm wondering if it is not the right prop? It does have great low end though. I can can get 6-8 lengths holeshot on a new 1300r but they catch up and pass after a bit. HELP!
With the above in mind I have decided to big bore and blackjack 48 the carbs over winter. I think I will go 86mm. I called Kerry and he sells the 89mm. It seems that would be a bit big for a rec boat. Any thought on this?
11-25-2006, 02:05 AM #2
First off you need to rejet.
1.5 needle and seat
95 gram springs
120 main jets
1 turn out on lows
1 1/2 turn out on highs with 1 3/4 on #3
Then put a stock length nozzle on it
put a stock cone back in
get a Nu-Jet 6.5 repitched to a 13/19 and set back
put some angle on the plate. There are plenty of good threads about it
put stock stepped sponsons on it. There are many good threads on that as well.
That should give you a good starting point at a low cost.
My suspicions are the jetting and the cone. I tried one of them cones in the past and my ski lost a lot of rpm's
Keep us posted.
About the big bore good luck. I'm sure Kerry will do a good job for you. There isn't a lot of press out on the boards about 89's yet, but I'm sure the hotrodders have some time with them.
Last edited by spud; 11-25-2006 at 02:09 AM.
11-25-2006, 08:00 AM #3
As Spud said and also
there are several other factors that can limit top rpms
trailing edge of impeller (pitch)
reduction nozzle size
type of reeds
I'm sure there other factors...
11-25-2006, 02:23 PM #4
I 'm with Spud as well. The Riva cone needs to be gone first and I don't know a thing about the skat prop other than skat products are usually good for the holeshot but not top end. Like he said, you also need to re-jet with those Riva F/A's you're probably running too lean.
11-25-2006, 02:25 PM #5
I have a Nu-jet 6.5 that's been setback and re-pitched by Island to 12/18.5 along with his race finish. PM me if interested.
11-25-2006, 02:59 PM #6
Thats a good impeller for the old style pump. GPRINSANEDIEGO might have one laying around.
I forgot about the powervalves. That is a good thing to check
11-25-2006, 07:23 PM #7
You guys are awesome. It looks like alot of the stuff I've bought from Riva hasn't worked very well. I sold the stinger 1 at the first of the summer. Of course I have lost the stock cone so I guess I get to buy another one. I took the boat out today and it ran worse than ever. I only saw about 6840 Rpm. I'm guessing it must be lean as well and have thought that for awhile. Where is the best place to get 86mm pistons? Thanks again for the help. With a little time and luck I think this boat will eventually run like it wants to. -Mike Simon
11-25-2006, 08:21 PM #8
Search Philip GPR and read his post on a fast rec ski. There is a lot of useful information there. That will make your stage 2 GPR run good. Kerry sells, or used to sell custom ski modifications, Fercho sells a package that is a spec book of information to build the ski.
As far as 86mm pistons go, Wiseco is whats used. When is Kerry going to do the mods for you? One thing I like to do is get three core cylinders for the conversion. That way you have a good set of 1200's to put back on the ski.
Hypothetically if you decide you want to move on and sell your ski you can take the big bore stuff off and sell it, put your ski back together as a 1200 and sell it. You will be money ahead.
Last edited by spud; 11-25-2006 at 08:23 PM.
11-25-2006, 08:41 PM #9
I have 3 gpr 1200 cylinders if anyone is interested. PM me an offer on them
11-25-2006, 08:46 PM #10
Bore-able cores or good condition? I don't need any, but it would be useful info for someone that does.
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