Jase Posted August 28, 2009 Author Share Posted August 28, 2009 now running 30% honed jet in carb, 10% nitro methane 35-1 2 stroke premix, goes good just sorting plugs wheelstands now lol Quote Link to comment Share on other sites More sharing options...
Jase Posted August 30, 2009 Author Share Posted August 30, 2009 took this to the 2009 mud drags, popped the back tube blew a 2" hole in the expansion chamber, still runs pretty good just no power due to the holey exhaust, got a tig lined up and will fit a modern chamber and can, exhaust blew due to the back can i believe, full of oil and shit and was real restrictive, real hard case riding style needed up on the tank for the launch and hanging off the side for the corners , even held some sweet third gear powerslides before the exhaust went, Quote Link to comment Share on other sites More sharing options...
Black Francis Posted August 31, 2009 Share Posted August 31, 2009 now running 30% honed jet in carb,10% nitro methane 35-1 2 stroke premix, what premix ratio do dirt bikes usualy run? does it get extra hot with that low ratio? i know weedeatezr blow holes in pistoins if you run like anything less than 30:1 with low octane haha needs 25 to:1 or things get hot on all my shit/ does the methane make it run alot cooler? What octane petrol do you use? whats it smell like?/what oil do u use? where do u get nitro methane? pics of mud? Quote Link to comment Share on other sites More sharing options...
shizzl Posted August 31, 2009 Share Posted August 31, 2009 was just gonna say 25:1 till i read blackys post...^^^ Quote Link to comment Share on other sites More sharing options...
johnnyfive Posted August 31, 2009 Share Posted August 31, 2009 I run 40:1 on 95/96 in my bike. Quote Link to comment Share on other sites More sharing options...
Jase Posted September 1, 2009 Author Share Posted September 1, 2009 heres my brew 9 litres 98 octane from bp, 1 litre nitromethane from the model shop, pure stuff not premix, sorry 400ml of 2 stroke oil ie 25:1 not 35:1 hard to describe smell like model fuel minus the oil, got thrashed all day and blew one plug out and a 2" hole in the expansion chamber at the end of the day, could still touch the head briefly after 2 hours thrashing and the exhaust blew, so would say ran colder than on shitty ole 91 Quote Link to comment Share on other sites More sharing options...
Black Francis Posted September 1, 2009 Share Posted September 1, 2009 yeh i def notice a big difference between 91 and 95. Starts to knock if i run 91 with a 30:1 mix unless i run fancy fuchs oil. My shits all comercial tho and dosnt get any airflow to cool even tho they're aircooled haha victa fo lyfe. / i have no idea whats going on i just make up a new cocktail every week and see what happens. my nsr likes 91 + motul the most. Standard specs, water cooled and oil injection tho so prob not relevent 40:1 is quite crazy waimaks. you gota rmx aye? i duno shit about water cooled mx bikes. this post was pointless. Quote Link to comment Share on other sites More sharing options...
Black Francis Posted September 1, 2009 Share Posted September 1, 2009 so yeah i was just reading some shit about ktms and they run like 60:1. mean. edit lols this: I have run Dyno tests on this subject. We used a Dynojet dynamometer, and used a fresh, broken in top-end for each test. We used specially calibrated jets to ensure the fuel flow was identical with each different ratio, and warmed the engine at 3000 rpm for 3 minutes before each run. Our tests were performed in the rpm range of 2500 to 9000 rpm, with the power peak of our test bike (an '86 YZ 250) occuring at 8750 rpm. We tested at 76 degrees F, at 65% relative humidity. We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall. Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer. Quote Link to comment Share on other sites More sharing options...
Jase Posted September 2, 2009 Author Share Posted September 2, 2009 makes sense man my first brew when i just got it going was like 15:1 as i thought the rings may have been stuckin place and it just fouled plugs if you tried to idle anywhere then left 200m smoke trails when it was tapped Quote Link to comment Share on other sites More sharing options...
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