View Full Version : What does a boost bottle do for a 2 stroke?

Tri Moto
11-25-2002, 11:41 PM
I saw one for sale for my LT 250R and wonder if its worth the 20 bucks hes asking?


11-25-2002, 11:44 PM
they let the air mix with the gas and some crap like that.....its goes inbetween the carb and engine......its crap, waste of money, they dont do anything....dont even bother

Tri Moto
11-25-2002, 11:52 PM
No wonder hes selling it....

Thanks, my friend....

11-25-2002, 11:53 PM
yup, no problem, jsut tryin to help you save some money, all the ppl i know (including me), who have bought one just end up taking it off and throwing it on the corner of the garage BECAUSE THEY ARE JUNK

11-26-2002, 12:02 AM
what i heard isn't quite like that. i HEARD that when you let off the throttle, the excess fuel/air mixture is put in the bottle, then when the throttle is hit again, the mixture is just sucked fromt he bottle and doesn't have to go through the carb, and improves throttle responce or something like that. i perosnally haven't had one so i dont know for sure.

11-26-2002, 12:49 AM
I dont know about the one for the LT250R, but the Yamaha TriZ comes standard with one, in it makes a huge difference. The theory is that when the air/fuel mix is pulled out of the carb, any excess is stored in the boost bottle, like a temporary holding tank, so that when you hit the throttle again, it is easier to pull from the bottle than the carb, and it improves throttle response off the bottom end. If you remove it from your Z, it will be quite noticeable. Some of the aftermarket ones, have too small of a hole, and too long of a hose to work properly.

11-26-2002, 09:52 PM
..... to ad to Tim's point ..... On two strokes, sometimes the charge (fuel/air mixture) dosent get used up all the way before the piston closes the intake ports and never makes it past the reed valve - this is called spit back. Some engines were designed to use this spit back to their advantage. What a boost bottle actually does is momentarily store that "spit back" charge via an expansion chamber or "bottle" then releases it at a higher than normal velocity due to recompression in the tube caused by low pressure at the base of the boost tube in the manifold which is in turn caused by the current strokes intake draw and new charge starting to rush by (picture how a straw works). This creates an effect similar to a supercharger (but no where near as powerfull) and it "boosts" the new charge into the cylinder where the process starts over again. Now this works well in engines that were originally designed to use a Boost bottle but I would have my doubts about its effectiveness in a mill that never had one. However, I know Banshees respond well to an after market boost bottle but they do sort of come with one in the form of the equalizing pipe between the two manifolds.

11-27-2002, 12:19 AM
The reason we have reeds are because of the "spit-back" you describe Tejas (i dont know if u said that, i didnt read all your post). A person who says they are junk probably doesnt know much about motors, because they help a lot. If a 2 stroke is ever out of tune (without a boost bottle or reeds) the air/fuel mixture will spit out the carb really bad, and you will even get exhaust fumes sometimes. A boost bottle catches that fuel coming back, and lets it go easily back into the cylinder each time piston comes down to let in fuel/air. Thereby improoving throttle response, and power. This idea is rather new and very true. I know a guy that uses this technology in conjunction with other technoligies of his own design and makes engines get 50% better gas mileage and 10 times better throttle response. All this with a carbed engine too. His 350 chevy of this design with a 550 holley 2 barrel got 30 miles to the gallon while making close to 500hp. He uses this technology on all his machines and twin turbo V-max 600 sled. You may not believe this, but it is very true. He has had this idea for over 10 years, but has tried to been bought out by oil companies, manufactures, and other but none of them wanted to pay him. One company in particular stole part of the idea and made engines that ran worse but didnt know why, yet sold them anyway. Tucomshe to be exact (I tried the best on the spelling).

11-28-2002, 10:08 PM
A boost bottle is just a poor jetting band-aid.