I've never seen Ringo be so polite, so I'm going to risk putting in my 2 cents worth here just for giggles.
Most "AVGAS" sold here in the US is what is known as 100LL, or 100 octane aviation fuel, low lead (blue in color). The "LL" part is relative, and is only in comparison to other aviation fuels which had a even higher content of lead (or T.E.L) tetraethylwhatever. Modern 100LL has approximately three times the T.E.L. content of what some of us remember as "leaded" auto fuel and is added primarily to help preserve the valves and seats in aircraft engines which were not designed to run on unleaded fuel.
This LEAD serves no useful purpose in a two stroke engine! It can however in some cases cause premature fowling of spark plugs due to residules that may cling to them.
It is the higher OCTANE(resistance to premature ignition) rating that is needed in high compression engines that prevents pinging and clatter due to preignition and detonation. I believe that most modern trials bikes are recommended to use between 93 and 100 octane fuel. Engine designs vary somewhat.
EXPERIENCE:
It has been suggested that EXCESS octane in your fuel does NOT increase available horsepower. I seem to recall that a recent dyno test performed by one of our resident members proves this to be the case and I believe it to be so, as higher octane fuel is basically more difficult to burn in a engine that does not need it.
It has also been said that the higher octane fuels have a "smoothing" effect on a trials engine. I also believe this to be true because the dyno results show the engine to be producing less actual power. Go Figure!
I have used 100LL in trials engines for the last five years with good results. Maybe I change "sparkies" every four months instead of every six, I really don't keep count, I just change them out if the bike starts getting a little hard to start.
Speaking of hard to start, I have had some problems on hot restarts on hot days similar to what is known as "vaporlock"condition. I relate this to the fact that AVGAS is designed to atomize and combust well at lower relative temps(at altitude) than auto fuel. A hot day in Texas with a hot engine and a carburator on a Sherco sitting right next to the exhaust is quite the contrary!
So I have been running a 50/50 mix of avgas/pumpgas for tha last year or so and it seems to be ok. I'm not sure what the octane really IS as I have read that it only takes 1/3 to 2/3 ratio to increase the octane, in other words, 1/3 gal 100 octane mixed with 2/3 gal 90 octane will yield 1 gal of 95 octane, NOT the 50/50 mix that you would presume!
OTHER FACTS,
As far as I know, RYP/SHERCO has been using straight pump gas for the last couple of years. I do not know if any other octane boosters are added but I'm sure Ryan would tell you. It seems that many manufacturers are either lowering compression or modifing combustion chamber design in an effort to allow the use of lower octane fuels. My old 98 Scorpa (rotax) would ping like hell if I did'nt run the 100 octane in it!
Other engine designes may not be so forgiving, so you may need to vary your mixture accordingly, try it your self and see!
So there ya go Ringo old boy, I hope that makes everything just as clear as mud! If you ask a fuel engineer about all this stuff you can't understand his reply any better than mine, the the end result is the same!
Is there something to the report from my buddy that his clutch engages too far out from the bar and will not adjust properly. He tells me that the screw has no effect?
By the way, good to hear from you "ks", now stop listening to your dumb buddy Scott and go ride expert sportsman class and have a good time while he is getting his butt kicked.
Them guys that ride expert in the nationals are too good or almost so.
I happen to own both a 1.25(wife''''s) and a 2.9 and many times find myself wanting to ride the 1.25 in club events as it IS fun to ride and it seems to do better if it is a muddy day.
I also believe that the 1.25 makes you ride "smarter" because there is not the excess power to rely on and you must think ahead and ride smarter but it is less fatigueing to ride.
Although my 2.9 is "tuned down" a bit with slower timing, I still prefer it for the "big" sections because of the torque!
I just wish that Sherco made a "true" 200cc bike, as every time that I have ridden a 2.0, it just seems like a 1.25 with only a bit more power, and little more, and does not have the flywheel to carry you over big stuff either.
That is just my opinion for what it is worth, just wish I could get the wife to ride a 2.0 so I could borrow it!
Ray Peters, at 31 I believe, is the current veteran in the PRO class here in the states(if he rides PRO this year), although Geoff may be close to the same age.
I recall Ray saying several years ago that he was getting tired of "throwing his body" at the large obsticles and that would probably be his downwall in the end at making attempts at the US championship.
I agree with Ish that more points could be had without increasing the size of the obsticles Ray was referring to and would promote more riders attempting the route.
Colorado Nationals
in USA Trials
Posted
Way to Go, CODY WEBB!
Go Get 'Um Boy!