Long run on high RPM

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DanSpd

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So I just saw the video of baja running in desert. So umm, how does this work?


I believe humster did few passes on high rpm and had piston scratched just like mine was. So how did baja run in desert on high RPMs?


Is that because me and maybe humster had low gears and baja had high gears set?


Or maybe they changed that engine like 3 times during the run hahha.
 
I run richer than I used to, try not to hold wide open more than 5 seconds, put on higher speed gears, and run relieved pistons. If you put on higher speed gears you will be going plenty fast without going wide open throttle but you gotta have a power so you also have good low end response.


I can vouch for the relieved pistons. I had a ported/piped test engine running at stock needle settings on a really hot day with lower speed gears. Lots of flooring it and holding it. It over heated but still ran but w/ blow by. I freaked out, tore it down and it had very slightly expanded. If the top had not been relieved I beleive the piston would have expanded but not had enough room and would have smashed/and scored itself and the ring againt the cylinder. After it cooled it ran great and I corrected the problem with richening and higher speed gears. Never had a prob again. Glad I had a test engine to figure it out on.
 
Everything I read said the culprit of this common phenomenon is overheating not leaning it out. The overheating causes expansion problems with the piston, ring, and head. I beleive it because it can happen to an engine thats properly tuned. I richen not to keep it from leaning but to run it cooler. Richening, running gears (properly) to get the speed you want w/o wide open throttle, and not keeping wide open for a long time all help to keep the temps down.
 
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I did WOT for 15 to 20 +second several time without any problem, not matter what gearing I use, if you have a good air/fuel setting on a two stroke motor, you can keep it WOT all day long if you want.


However I don't recommend to do that on a fresh new engine.
 
More people seem not to have the problem than do have it. I think what overheated mine is the combo: holding wot over 10 seconds+flooring everytime time to accelerate+thick terrain+huge field+90-110 degree sunny day+ported engine w/power adders+low to mid speed gearing+4wd+sucking air at the bottom of the tank when fuel sloshes+non releived piston+stock needle settings, etc. I think that combo of driving it like it was stolen on a very hopped engine on a hot day along with heavy 4wd was just too much without steps for proper cooling.


I think of it like this: a engine can be driven driven hard shortly but if you want to drive it hard long you have to take the proper precautions. A engine all hopped up with a pipe, carbs, filter, stack, flywheel, porting, cylinder bore, stroked stuffer crank, turbo, etc, etc. is operating closer to its limits so it has less tolerance for abuse and is closer to failure.


That is why I have taken engine friendly precautions: gearing that achieves speed w/o WOT, running 1 hour richer, making the Ramp 25lbs, refilling at 1/4 tank, not holding WOT for long, relieving the piston, in addtion to: running 25:1, keeping the HPI filter clean, keeping the cooling vents unobstructed. Im sure you can think of more.


Thats what Ive done so far to prevent my “overheat rpm seize” but even if you disagree it still doesn’t hurt to be kind to you engine.
 
I agree with what you said, and I admit that the engine life will be shortened with a long wot time.


Next time we will go to the sand pit (me and a friend) I will take a video of his Rampage with a ported, piped CY26 in it, that's funny how long he keep it wot, even myself I don't dare to keep mine wot like he does, that's really funny and that damn engine don't want to blow......
 
i love runnin mine wot just can't manage to keep the flywheel side seal in it when i do it,lol. but i think i have a solution to that and will try it soon,lol..
 
So in theory proper tune, high gears along with proper filter, carb and engine can run wot all day? I runned my tt almost on full throttle (8/10 maybe) and still could go faster but not enough space. But I noticed engine is pretty hot even if I do not make high speed passes. My dad says it's normal for two stroker to be that hot. Anyone can tell me top ok temperature?


Thanks
 
Martin said:
I agree with what you said, and I admit that the engine life will be shortened with a long wot time.
Next time we will go to the sand pit (me and a friend) I will take a video of his Rampage with a ported, piped CY26 in it, that's funny how long he keep it wot, even myself I don't dare to keep mine wot like he does, that's really funny and that damn engine don't want to blow......
Click to expand...
Ooops, now you jinxed your friend... ;) ..>.JK
 
makindue said:
Hi yolonda21, can you post some photos of your properly tune WOT?
Click to expand...
What's a good tune for one setup is not the same for another...unless identical cars, engines, pipes, etc...(If that's what your asking to see,


maybe a video with the sound of a properly tuned engine but not a photo)
 
do u guys think the aluminum pull start covers will make them over heat. i just lost 2 motors . i run at higth speeds , one cyl no plating left run 25;1 oil mix .one sezd.bouth had aluminum covers small air holes.
 
No, most of the airflow comes from the inlets around the crankcase. You could probably get by with blocking all the pull start holes.
 
i have prefilters on all my crankcases did,t no y they there doing this.the one that seizd cyl cracked at the base of the cyl leand out.the othert one the plating wore away to mucth blow by.
 
I don't think so either. I think for us to properly identify the prob we'll need more info. What engines they were, build/setup, fuel, driving style, driving condtions, etc. etc. If you dant identify the prob. just safeguard your next one and maybe try driving it not so hard?
 
As promised, I took a video on the fly of my friend's Rampage CY 26, he have make a port job on his motor, this is the first time for him, I think he have made the exhaust port a little too high... loll... but check how the engine handle the high rpm, he drive it like this all day long.


He already have a new zenoah 36mm ready to put in his rampage, but he want to blow the 26cc before.


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martin said:
as Promised, I Took A Video On The Fly Of My Friend's Rampage Cy 26, He Have Make A Port Job On His Motor, This Is The First Time For Him, I Think He Have Made The Exhaust Port A Little Too High... Loll... But Check How The Engine Handle The High Rpm, He Drive It Like This All Day Long.
He Already Have A New Zenoah 36mm Ready To Put In His Rampage, But He Want To Blow The 26cc Before.


http://www.youtube.com/watch?v=0f9rvft28n4
Click to expand...
F*** Yeah! Drive It Like You Stole It!
 
How come when you want them to die they don't?! Tell him to lean it out a bit and drive like that in 100+ degree weather in the same sandy spot. I bet that would speed it up! Im assuming hes not running the stock filter in the sand? :rolleyes:
 
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