3.5 hp briggs and stratton question

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  #1  
Old 12-05-04, 04:58 PM
chawin
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Lightbulb 3.5 hp briggs and stratton question

i have a 3.5 hp engine brand new, first tank of gas, i have it on a mini bike and i thought that it would be cool to put a strait pipe(exaust pipe) on it than from having the original exaust, model engine:91232, i was wondering if this will hurt the motor in any way by overheating it or not enough back pressure or DECREASE ENGINE life with proper maintanece and if i would need to do anything different if i changed the exaust such as run different octane or different oil or run lower rpm? thanks for your replies i appreciate it!!
 
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Old 12-05-04, 06:44 PM
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You won't have to do anything different with oil, gas, or maintenance. It will just be louder. If your engine is a two-stroke engine then research a tuned exhaust system for your bike. You can get substantial increases in HP by getting the right one for your engine. The HP gains will only be in a fairly narrow RPM range. That might be ideal if you're racing, but may not be what you want for street use.
 
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Old 12-05-04, 07:32 PM
chawin
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Question thanks

Thank you for the advice and repying so quickly. This is a 4-stroke 3.5HP briggs and stratton. But is this going to DECREASE ENGINE LIFE? Is this going to decrease exaust back pressure? Is this going to cause any overheating? Thank you!!
 
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Old 12-05-04, 09:15 PM
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Yes, it will decrease backpressure, no it won't hurt anything. The length of the pipe is not critical as long as it's not too short. I think 8" should be fine. There are more scientific ways of determining the optimal length of a straight pipe for performance, but unless you're racing and every tenth of a percent counts, then you needn't worry about it.
 
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Old 12-05-04, 09:24 PM
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I can't remember the lawn mower racing guy's name but according to his 'research' you can determine the proper length for a staight pipe in the following manner: Put some paint on the pipe. Run the machine for a while. There will be a point where the paint isn't burned too much. Cut the pipe at that length. Unscientific, but that length would probably be as good as any other. If you make the exhaust too short you'll burn your leg. Like Cheese says, the gain you'll get will be tiny and unless you're racing probably won't be worth the effort.
 
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Old 12-06-04, 05:02 AM
chawin
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Talking Thanks

Thank you for the information, i was curious and these little engines are becomeing expensive and i didnt want to go burn up a new engine. I know with lie 2 strokes pipes and pipes design and fuel and jeting make a major impact on the engine perfcormance and life if not set up properley and can burn the engine down so i was curious if this runs the same with these 4 strokes. THANK YOU
 
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