Originally Posted by
barnett468
Hello bigdaddyvw185;
I hope your holidays were good.
A small group of people “attempt” to berate me at every opportunity they get for making posts that they consider overly lengthy and/or overly detailed. Unfortunately, you might see more of those types of posts on your thread. My previous post was just a general example to give you a little info on carbs since you were asking for info on them. I wanted to keep it fairly simple and therefore simply felt no need to clutter up a page with calculations like PI X R2 and E = MC2 etc..
My comment about a 72 mm carb in effect becoming a 36 mm carb if opened only half way was merely intended to be a general example and not an exact number. Since imo, one person seems to be unhappy with my generalization, in the interest of accuracy, I will supply a much more accurate estimate for the size which is 50.92 mm, not a 50.0 mm as stated by another or the 72 mm size stated by me.
I calculated the 50.92 number in my head, therefore, unfortunately, it still might be off by around .0001 mm or so either way. The member that seemed to take exception to my post might voluntarily calculate the number to its final digit for you.
I never suggested that anyone do this as a matter of common practice. Imo, as this particular person occasionally does, they are "attempting" to twist my comments around and make unwarranted abrasive comments to, or about me, simply to serve their own agenda.
The quote posted below is inaccurate due to what imo, is its ambiguousness which is “created” by its lack of detailed information.
My interpretation of said quote, is that the author is suggesting/implying that running a carburetor that is too “big” for a given engine will cause it to go so lean that one’s engine might become damaged. Since this is not necessarily the case, imo, for the benefit of at least this person, it appears that another brief physics lesson is required.
Since as I previously mentioned, I feel it is unnecessary to fill the page with a bunch of numbers, I will once again simplify and generalize my comments.
There are several ways to say the following, I have only mentioned a few.
All carburetors need to be PROPERLY jetted irregardless of their size. For all intents and purposes any carburetor can be jetted to avoid a dangerously lean condition, it’s simple physics. I should also hope that it is unnecessary to say that a 70 mm carburetor is too big for a 250 cc engine.
When a carb is too “big” for an engine, it will, in general, have no adverse effect on idle. This is because the throttle is closed and one can typically set it to flow exactly the same amount of air as a smaller carb at this speed.
A large carburetor will only affect performance differently than a smaller carb once its throttle slide/butterfly etc. is opened to a point where its area [the amount of air it is capable of flowing] is greater than the maximum area of a given smaller carb when its throttle slide/butterfly etc. is opened to its limit. This is one of the points I was trying to express in my previous post.
To determine/calculate what the optimal size carb for ones engine is, one of the factors they would need to know is the volumetric efficiency of their particular engine.
PS – Bigdaddyvw185, although, my understanding of your question is that you are not looking for info on how pressure waves, elevation, air density and humidity, etc. affect carburetion, I apologize for not posting this info for those that might have had an interest in it. Perhaps the author of the quotes above would like to accurately explain their effects in detail if they are able to.
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That being said....I welcome any help / suggestions that i can get... Especially with this build god knows i could use it, I new nothing of 2 strokes back when this build first started and i would not have it in its current condition without the help of the fellow members on these boards....without a doubt...iv learned everything i no on the subject from these forums!... now without kicking dirt on Anyone's feet... can we please keep this kinda stuff to a minimum. i have kept my nose out of the drama for good reason, As this is not what we should be here for. We are all here for the love of our trikes.