Top end tuning question

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1RC5

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Another tuning question.


I have a 32cc MT with a Jetpro rear mount and HPI baja filter with inclined stack. The motor runs really well and has great low end torque. When going full throttle, it will go well for a good amount of time, but after it gets some heat and maintaining wide open throttle for extended periods of time it starts bogging down. It only happens when it's WOT for long periods such as going across a baseball field.


I've tried richer and leaner HSN settings and it doesn't change much. Bashing around with short bursts of WOT is great, but long extended WOT on a large field will cause it to bog down after a few seconds.


Input and suggestions appreciated.
 
bog

the hotter a engine gets, the leaner the fuel settings become. much more so running car gas with ethanol in it. Vent the fuel tank. I use a du-bro in line fuel filter and a du-bro metal "clunk" in the gas tank- the clunk has no filter, its just a weight to keep the end of the gas intake hose in the dimple molded into the gas tank. Check your lower engine vents- could be clogged with grass--
 
Also, in racing circles- bikes- cars-trucks- full sized ones-- the symptions you describe are called "heat soak " produces more heat than the engine can get rid of.
 
As alfred said, check for grass under the engine cover. I have telemetry on my car and going WOT and maintaining the high speed actually COOLS the engine down, so heat shouldn't normally build up. Granted, I'm running a Dunerunner, I think the engine gets more air flow than the MT does with the body on. Other than that, it's an identical configuration (32cc, jetpro rear mount, baja air filter with inclined stack).
 
I just removed the engine to install outerwears for the crankcase/flywheel and removed all grass. It also has outerwears for the pull starter and air filter. I guess I could go a bit richer to compensate for the heat soak. Besides this, I'm pleasantly surprised by stock engine's performance.

Alfred, do you use the large or standard sized clunck?
 
agree ! a properly tuned 2 stroke with a pipe will run cooler at wot. IF its not running lean. here is a can o worms to open-- whats the best 2 stroke oil in the planet? Red-Line. period. the high end priced stuff. 2nd best? castor oil. Maxima 927. The redline oil is 7 times better. There are hundreds of oils out there, making all these wild not backed up claims. Red line mikes engines before running them, runs assorted oils in the same conditions identical motors. tears them down, re mikes the parts. numbers do not lie. yes, just about any oil will make a motor last if its too rich- but to build power, you have to lean out-- this is where red line is vastly vastly better. even if you run the redline a little rich and at a rich fuel-oil ratio- say- 25 to one, its still runs better-- this oil burns cleaner- better at high fuel-oil ratios.
 
1RC5 said:
I just removed the engine to install outerwears for the crankcase/flywheel and removed all grass. It also has outerwears for the pull starter and air filter. I guess I could go a bit richer to compensate for the heat soak. Besides this, I'm pleasantly surprised by stock engine's performance.Alfred, do you use the large or standard sized clunck?
Click to expand...
i use a large sized clunk.
 
when i say 7 times better-- this is running 20,000 + go cart engines-- measuring the lower connecting rod pin. castor has the same measurements in 45 minuets that the redline has in 7 hours. Best to not ever attempt to break in a new engine with this redline oil, rings will not seat, too high film strengith. pardon the spelling.
 
alfred e numan said:
the hotter a engine gets, the leaner the fuel settings become. much more so running car gas with ethanol in it. Vent the fuel tank. I use a du-bro in line fuel filter and a du-bro metal "clunk" in the gas tank- the clunk has no filter, its just a weight to keep the end of the gas intake hose in the dimple molded into the gas tank. Check your lower engine vents- could be clogged with grass--
Click to expand...
How do I vent the gas tank?
 
A cold engine runs lean compared to a hot motor. Same is true for outside air temps. If it runs better under cold conditions than hot it's on the rich side. If runs better hot than when cold it's on lean side.
 
Well, the problem was caused by the tank pressure(or in this case vacuum). What was happening was that the tank had so much negative pressure that it caused the tank to physically cave in. Upon opening the fuel cap the tank would return to it's regular form. Since it had so much vacuum inside the tank, it caused the the engine to run extremely lean. I fixed this by venting the tank by drilling a hole in the cap and inserting a fuel line that I routed up through the cage. I also installed a fuel filter in between as recommended in this thread. Now I can run the truck wide open for extended periods without a performance hit. I was even able to lean it out a bit.

Thanks for all the help.
 
Great info. My only question is how does venting on the cap work when there is a 2 peice system under the cap made of black rubber? What is that black rubber for anyways on the backside of the gas cap? Help with pressure I'm thinking.
 
rroberson7805 said:
Great info. My only question is how does venting on the cap work when there is a 2 peice system under the cap made of black rubber? What is that black rubber for anyways on the backside of the gas cap? Help with pressure I'm thinking.
Click to expand...
It is a one way valve. That usually only works for a few months. Most people get an airplane one way valve and mount it about 6 inches away.
 
alfred e numan said:
agree ! a properly tuned 2 stroke with a pipe will run cooler at wot. IF its not running lean. here is a can o worms to open-- whats the best 2 stroke oil in the planet? Red-Line. period. the high end priced stuff. 2nd best? castor oil. Maxima 927. The redline oil is 7 times better. There are hundreds of oils out there, making all these wild not backed up claims. Red line mikes engines before running them, runs assorted oils in the same conditions identical motors. tears them down, re mikes the parts. numbers do not lie. yes, just about any oil will make a motor last if its too rich- but to build power, you have to lean out-- this is where red line is vastly vastly better. even if you run the redline a little rich and at a rich fuel-oil ratio- say- 25 to one, its still runs better-- this oil burns cleaner- better at high fuel-oil ratios.
Click to expand...
what ratio do you mix redline oil at? I've been looking at amsoil and they claim they can run at 50:1 ratio might be a little to lean for my liking especially since these engines are run at pretty high revs for a long period of time
 
1RC5 said:
Well, the problem was caused by the tank pressure(or in this case vacuum). What was happening was that the tank had so much negative pressure that it caused the tank to physically cave in. Upon opening the fuel cap the tank would return to it's regular form. Since it had so much vacuum inside the tank, it caused the the engine to run extremely lean. I fixed this by venting the tank by drilling a hole in the cap and inserting a fuel line that I routed up through the cage. I also installed a fuel filter in between as recommended in this thread. Now I can run the truck wide open for extended periods without a performance hit. I was even able to lean it out a bit.Thanks for all the help.
Click to expand...
Same problem I was having in the "Racing at idle thread". Noticed the tank was caving in. Ordered the Snappy kit but haven't instaled yet. In the meantime I pulled the plunger out from under the rubber piece. It spills a little fuel but vents just fine now.
 
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