Orderd both pumps on monday (vp-30 vp-20 ) they where to be in today (friday) but they did not arrive so much for exspres mail......I was hoping to do some tests on the stand this weekend but will have to wait till next week..####
I did do some more test runs and took the stand outside so the GLOBEE tack wood work......moved tank up to centre line of carb....14x6MS prop ..omega 15% fuel ..os#8 glow....
STOCK MUFFLER = 10200 rpm
SLIMLINE PITTS = 10700 rpm
BISSON PITTS = 10850 rpm all with muffler pressure

no muffler pressure but with air pressure in fuel tank ( 1 to 2 lbs )
STOCK MUFFLER = 12100
SLIMLINE PITTS = 12650
BISSON PITTS = 12700 as this shows pressure in the fuel tank sure turns these motors on
the bisson pitts seems to rve up more but I think the slim line has better ideal and trans............... cant be realsure till the perry pumps get here......

PS IF you wought the ture story on the OS91FX please go on the perry pump web site or phone Gary Conley 1-630-858-3160
and he will tell you of the problems and some of the fixes.....
he said IM not alone with bad running 91fx he gets calls almost evey day about them....vp-30 is what he wants me to use as the vp-20 is realy ment for a 4 stroke because of the vibrations.....it may still work and stop dead sticks but the 30 will give more increase in rpms because the pressure can be cranked way up....
the real problem is the carb..it is not wellmached to the motor and this causes low fuel draw......OS knows this but refuses to fix it????????beging to sound like the super tiger 3500 motors.....

I TRYED ANOTHER LITTLE TEST I put the 14x6 prop on my old OS61FX and put it on the stand and MACS muffler (pn 6860) replaces stock muffler no more long bolts to brack off....I could hardly beleave it almost 9900 rpm with or without muffler pressure??????? with air in tank only increase about 400 to 500 rpm.....but still it was better than 91 with stock muffler and no air???????
COULD SOMEONE PLEASE TELL ME WHATS GOING ON HERE????

IN hobby services web site they say os91fx should turn a 14x6 at around 10800 but I think this is low for a 91 2 stroke????
IN the rcu review SUPER KRAFT EXTRA 300 they used a TIGER SHARK 91 motor and got alot more then that ......I guess when I orderd the SUPER KRAFT ARF last week I SHOULD have orderd a TIGER motor to go alone with it ?????????
oh well live and learn I guess :sunsmiley