12 psi of boost on pump gas?

just heard about another motor going down, 14 lbs pump fuel two extra head gaskets, each to his own but just because its a 4 stroke doesn,t mean it will not blow, if you want to go fast it cost money and its alot cheaper running good fuel than rebiulding motors, this is the second time for this guy, and he is a yamaha dealer but just won,t admit he needs to run race fuel with his 4 stroke, I just don,t want to see anybody else lose a motor due to fuel problems when it is so easily avoided. last year I ran 14-15lbs stock motor strait vp110 no problems, went to bigger turbo 3 head gaskets 18-20 lbs strait vp110 no problems, this year low comp. pistons 2 head gaskets and I will try 18 lbs at 50/50, but even at 12-14lbs I will be running 50/50 to be safe, I am sure you can run high boost on pump fuel for a while or short burst but it will get you if you keep pushing it, none of these guys i know blew the first time out it took a few rides.
 
I was also wondering about the gas there in Sweden. Theres NO WAY I'd be running 12 lbs. in the US on pump fuel! You may get by on very short runs, but its bound to catch up to you. Most people don't even realize thier engines are getting fried untill its to late. If you have oil comming from the breather, its to late! If you do a leakdown on the engine and your over 10-20%, its to late. I had a good friend toast a engine in two miles with the boost at 10 lbs last year. If the octane is not there, you will toast it over time. You have no idea on the age or octane of the fuel going in with pump gas. I would not chance it! I know there will be many that say they put on xxx miles this way with no problem. You have been lucky! Or you have damage and don't know it, I suggest you go do a leakdown. 12 lbs. is not pump gas safe at low altitudes in my opinion. I may be wrong, but I would hate to see anyone loose an engine as it gets quite costly to repair these things properly, not to mention the downtime. Mike Knapp #17
 
I did go 3 head gaskets as required by mcxpress to run 10 psi of boost on RON 98 octane pump fuel, as safety I also went with installing 10:1 Wiseco low compression pistons. With this setup I'm able to run 17 psi on 98 octane RON pump gas (Applies to Norway, Sweden and most of Europe)
 
Hey,Mike, I've just seen your reply now and I think you're right on with your boost numbers. Last year I was running 9lb boost on stock motor and had complete burn down. I was running 50% of 110 and 50% 93 octane. I talked to dealer in the UP and he had the same thing happen on two motors with turbos. All 3 motors, shot , in less than 20 minutes on each of them. Each on 9 lbs or less boost. Now I have low compression pistons and whatever else Jeff suggested. Jeff has the sled now, because it's using a quart of oil every 100 miles and top speed is about 105 mph. Jeff thinks he can take care of the problems with jetting and something to restrict the oil, for the oil problem. I'm sure he can get the problems solved. He seems to be the master when it comes solving these kinds of problems. But with my motor being rebuilt with low compression pistons, what kind of boost can I run on pump gas and still be safe? 5,7,9? Any imput would be much appreciated. Thanks, Dutch.
 
I think lots of you guys are just lean and killing them. Jet FAT! I dont think lots of them are from to much boost and detonation.


Skydog
 
I will let you know if i blow at 12 psi with two head gaskets! So far so good!! 290 miles.


Skydog
 
they call vp110 race fuel, not sure of oct. But I'm thinking I should be able to run 5lbs on low boost & 9lbs on high boost without any problems with my motor mods on pump gas. Maybe the bigger issue is jetting. I'm not sure what jetting Jeff has in now, but I'll find out what He's putting in. Any ideas on what would work on motor with mods? And be safe, but can run more then 105mph?
 
I like it right on the edge of rich popping just a tad.

Skydog
 
MCxpress rear with 3 head gaskets is safe using stock RX-1 jetting and settings on pilot screws and needles at sealevel up to 13 psi of boost running on 98 octane RON pump gas. Lambda (WBO2) levels are perfect with stock carb settings and jetting. According to MCXpress 14 psi on the edge of what the engine will survive running on 98 Octane RON. Going higher boost # requires 10:1 low comp pistons and jetting fatter if running on pump gas.

This is not a 2 stroke, don't try to lean it out to make power. Jet on the fat side like skydog suggest and engine is running much safer. Want more power, go low compression, race fuel and lots of boost. Have fun. Ride safe.

Merry x-mas to all of you ty-ers.
 
What a/f ratio are you set at.I have wideband am showing 11.8 at wideopen throttle.It cruises at mid throttle about 12.0.I thought that these readings would mean it is on the rich side.It still gets good gas mileage and doesnt foul any plugs.Thanks.
 
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