rider-man82

Member
Jul 7, 2002
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is race fuel worth the money when only riding trails. i have a 96 cr125 and only used vp c12. it's about 40 bucks for a 5 gallon jug and go throw about 3 of those a month. so thats over 100 bucks a month. i'm going to be getting a new 250 but with the higher payment i'm trying to save money where ever i can . so what do you guys think should i stop buying the c12 and start using the good stuff from chevron.
 

Senior KX Rider

Super Power AssClown
Nov 9, 1999
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Thats a call only you can make for yourself. Does your bike need race fuel??? Prolly not. My fuel(MR-2) costs more than C-12. I jet it sharp and the fuel is consistent. Performance advantage??? You bet. :) Is it worth it??? It is to me :aj: I would find something else to cut out of my budget if I had to so I could run it. But thats just me ;)
 

nephron

Dr. Feel Good
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Jun 15, 2001
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Why not just try pump gas? Your app. definitely does NOT require race gas per se, but switching to pump is going to bring a level of jetting inconsistency you've not yet experienced. You're the only one capable of determining whether or not it's worth it to you.

IMO, for a 125, C12 is the wrong fuel. Better than pump, but not as good as say, MR2 (if you're stuck on VP fuels). For a complete discussion on this, see the previous plethora of material.
 

jmics19067

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Jan 22, 2002
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I use the c12 and wont go back to pump for my old 250. IMHO you might have a better need<?> for a consistent low boiling temp, more complete burning fuel at trail riding speeds and conditions. I believe that you will less likely to foul up plugs and run erratic at low speeds, even if you are not particlular about perfect jetting, compared to pump crap I have around here.

But again it is your call I think it would be better to be riding than not no matter what the fuel or bike. Personally I would give up beer for a month to afford to go riding for one day with c12.
 

Superchief

Member
Feb 11, 2003
103
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When i bought my 03 CR250R the sales rep told me all i should run i race fuel ( C-12 or MR-8). i bought the bike last septtember and it's all i've ever ran it.
THE BOTTOM LINE:
does it make a difference? i could'nt really say one way or another since it's all i run in the bike. it makes a difference in my street car when i run it at the track, and that would be a huge difference. i'd give up whatever i had to and run the race fuel. The better the fuel the cleaner it burns, more power you make and bla bla bla bla. i notice a difference after the race fuel is out of the car and i put 94 octane back in it, why would'nt the bike be the same.
 

bclapham

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Nov 5, 2001
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Originally posted by nephron
IMO, for a 125, C12 is the wrong fuel. Better than pump, but not as good as say, MR2 (if you're stuck on VP fuels). For a complete discussion on this, see the previous plethora of material.

why is that Nephron??? what does the MR2 have that the C12 doesnt??? maybe i should look,:) i am sure the MR2 doesnt have anything that i cant find in my garage!;)

its a real shame the search function has broke there is sooo much good stuff locked away in history:(
 

nephron

Dr. Feel Good
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Jun 15, 2001
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uh oh, called out by the master... :o

I'm a neophyte at this, but from what I could gather from previous explanations on this topic (unless misunderstood) is--in general terms ;) --it seems most 'lubed' tuners prefer fuels with low 10% evap point temps and higher E.P.'s for 125's.

I'm not sure about the other characteristic differences of these fuels, and have heard, e.g., that C12 is highly aliphatic and that is one of it's main assets as far as fuel for mx/sx equipment--but I really don't know if the same holds true for MR2 or not.

MR2 also has an oxygenate of sorts, as you know. But interestingly, despite having more Pb--has a lower MON, for whatever reason.

I realize there's more to it all than that...nuff said.
 

bclapham

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Nov 5, 2001
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on the contrary nephron, it seems you have a much better idea about this than myself! sounds like the MR2 has the oxygen content which might be a good thing in the 125 and 250s. i am just lucky that i can add the O2 myself, i am building a rm144 right now from a scrap bike, it will fed with C12 and 10%MTBE, its worked well on the yz250, but its so fast now its hard to ride, LOL!:)
 

nephron

Dr. Feel Good
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Bruce, have you played with NUTEC PRO MX yet? This stuff stinks like hell. First thing that comes to mind is fingernail polish, piss and maybe some Everclear mixed in 1/3rds.
 

bclapham

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Nov 5, 2001
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Nephron: i just stick with the C12, its easy to get here and the nutec costs so much more. ive gt all the throttle response i need and the added MTBE works well, much better than the paint thinner F&L sell!

theory says my bike is jetted especially lean but it runs well and i always get a small bit of spooge, i think its more to do with my riding, the bike is a real handful on the mx track, i used to use mainly 3rd, but ive made some changes and it will rev out well in 2nd now also. i could not imagine what a kx500 would be like on the track....i rode a stock 02rm125 the other day, it was a breath of fresh air not having to fight the bike, obviously, i cant wait to get my rm144 running!:)
 

GeoffM24

~SPONSOR~
Jan 19, 2003
182
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50:1 is worse. If you are fouling plugs you need to rejet. Going from 32:1 to 50:1 increases the amount of gas therefor making your bike even RICHER.

Rich is all about the gas not the oil.
 

rider-man82

Member
Jul 7, 2002
25
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after i switched to 50-1 i fouled plugs less. at 32-1 it would do it like ever other trail ride, so like twice a day. now it does it like every other trip. i have my jetts just like to fmf web site says for year and pipe. witch is also the same as my owner manual says. it seemed to me that the oil or gas was building up in the top end and after a while it would just soak it. i think the ring wasn't sitting it the piston groove right so i re-did the top end.
 

nephron

Dr. Feel Good
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If you're fouling at either 18:1 bean base or 100:1 Amsoil snake oil crap, you're jetted wrong, chief. Jetting has little to do with what FMF says, and more, obviously to do with riding style, altitude and temperature.

It's still so damn funny to see MXA say things like: "16 things you HAVE to do to your xx250 to make it better" (or you're an idiot, cuz we're the bestest and if you're not with us, then we'll laugh at you at our REM race cuz you're wrong and we're superior)--..."go up to a .xx spring up front, .xx spring back, and change you're jetting to xxxneedle, xxx main, xx pilot....blaah, blaah..."

MORONS
MORONS
MORONS :silly:
 

Superchief

Member
Feb 11, 2003
103
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Originally posted by nephron
If you're fouling at either 18:1 bean base or 100:1 Amsoil snake oil crap, you're jetted wrong, chief. Jetting has little to do with what FMF says, and more, obviously to do with riding style, altitude and temperature.

It's still so damn funny to see MXA say things like: "16 things you HAVE to do to your xx250 to make it better" (or you're an idiot, cuz we're the bestest and if you're not with us, then we'll laugh at you at our REM race cuz you're wrong and we're superior)--..."go up to a .xx spring up front, .xx spring back, and change you're jetting to xxxneedle, xxx main, xx pilot....blaah, blaah..."

MORONS
MORONS
MORONS :silly:

AW come on now,you mean they don't know what's best? To bad more people don't feel that way, we could do away with all the corporate bs that's in the magazines and maybe get some real world specs on products what they do and so on. It's nice to get free stuff for your bike and say: THIS IS WHAT EVERYONE NEEDS TO RUN....when what it should say is: THIS IS WHAT EVERYONE NEEDS TO RUN CAUSE WERE GETTING PAID BIG MONEY TO SAY YOU NEED THINGS THAT YOU DON'T.
 

rider-man82

Member
Jul 7, 2002
25
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sorry to say but t is not the jetting. i've tried every main and slow jett my local shop had. before i seezed the motor it ran fine no problems at all then i had to total re-do the top end and get a new crank assembly. i think when the piston ring was put on it wasn't sitting in the groove right so i think to much oil/gas was getting buy. i'm going riding tomorrow to break it in so i'll just have to wait and see. but thanks to every one helping out.
 

GeoffM24

~SPONSOR~
Jan 19, 2003
182
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Originally posted by rider-man82
sorry to say but t is not the jetting. i've tried every main and slow jett my local shop had. before i seezed the motor it ran fine no problems at all then i had to total re-do the top end and get a new crank assembly. i think when the piston ring was put on it wasn't sitting in the groove right so i think to much oil/gas was getting buy. i'm going riding tomorrow to break it in so i'll just have to wait and see. but thanks to every one helping out.

Needle?
Clip position?
Air screw?

There is more to a carb then a slow jet and a main jet.
 

Rich Rohrich

Moderator / BioHazard
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Jul 27, 1999
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Originally posted by rider-man82
sorry to say but t is not the jetting.

If I had a buck for everytime ... :silly:
 

jmics19067

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Jan 22, 2002
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I can't see how an improperly placed ring on 2 stroke piston can run without some sort of immediate malady.

If it was a keystone type ring placed upside down it wouldn't fit into its groove right. if the end gaps weren't lined up with the pin you should of had some type of problem from that.If you were able to get the jug back on and run it I would think either way would involve a catastrophic failure.But that would not be from jetting or poor ring sealing , that would be a mechanical forcing of a square peg into a round hole type deal. It is not going to fit and work right without destroying one, the other , or all involved.

as for the jetting itself
Is it possible that your transmision side engine seal is bad. allowing trans oil to get sucked into the engine. Is the needle and seat of the carb<fuel inlet valve> leaking allowing your engine to flood at trail speeds or when parked ? Are the floats set right, are the reeds in good shape, are there any air leaks? These things would have to be correct before you can start to jet. And as Geoff said there is more to it than just the screw in jets.
 

JTT

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Aug 25, 2000
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Accidents/mistakes are only stupid if you repeat them. Buying a new bike will teach you nothing, meaning you will likely repeat the problem down the road. Figure out what happened and how to fix it before simply moving on, then at least you will have gotten some education in return for that parts bill.

You said, everything worked perfect until you did the rebuild? If so, then backtrack at all the things that could have possible changed. jmic may be on to something with the crank seal suggestion. Did you put new seals in at the time of rebuild? ...did you leak test the motor after the rebuild?
 
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