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High Performance Bicycle Engine Tips and Motorized Race Bicycles We all want our bicycle engines to push our bikes faster. Get exclusive engine modification tips and suggestions from us. Also check out some of our racing members builds

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  #21  
Old 03-08-2015, 07:23 AM
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cannonball2 cannonball2 is offline
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Default Re: Modded Boost Bottle

Yesterday I removed the 1/4" valve and drilled the nipples out as far as I dared. It had not come to mind that the sizing is the tube size not the opening(I know this just didn't occur to me at the time). The original opening was probably between 1/8 and 3/16. Drilling it made the flow much greater. Low end was improved slightly but midrange seemed a bit better. The bike was pretty snappy when accelerated from below 10mph.
At just under 30 it begins to 4stroke which I attribute to restricted exhaust flow, my built in rev limiter.
Actually now the bike is faster than it was but only in acceleration top end is the same. The more immediate response is the difference.

KC is right about the longer intake doing the same thing. The only difference is then your are tuning the intake tract and that requires some times longer runners than are easily practical for ideal tuning. Also I assume it to be tuned for a specific range?

I don't think the valve affects much over early midrange, but its overall affect would appear the whole range due to the fact it pulls cleanly and strongly to the top, since excess fuel from reversion is mostly eliminated.

Interestingly with the larger opening in the valve the flutter of the valve disc is now audible, its not objectionable but you can hear it. I have been trying to listen for when you cant, that would indicate when the flow through the tract is all positive(or nearly so), but I cant tell.
Now that I have a nipple in the intake. I may do as Snork suggested and run over to Tractor Supply and buy a big graduated syringe and experiment with boost bottle displacements. Be nice to stack up the data between the two systems.

It occurs to me that a decent/cheap boost bottle can be made from PVC pipe and caps. The cap can be drilled and tapped for pipe fittings and the displacement can be easily determined before gluing it all together. The above syringe can be used to determine the displacement. I doubt the seals on the syringe will last very long in the fuel environment but probably long enough for teating.

Last edited by cannonball2; 03-08-2015 at 09:48 AM.
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  #22  
Old 03-08-2015, 01:44 PM
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cannonball2 cannonball2 is offline
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Default Re: Modded Boost Bottle

OK heres the variable displacement boost bottle from TSC. You get two for $4.

I checked the volume of the hose it was exactly 5cc the syringe is 68cc fully retracted for a total of 73cc, nearly perfect. You can use one syringe to calibrate the other, handy!
So what did I find? At the optimum displacement the low/midrenge suffered compared to the valve. It was rather four stroky until around middle mid range, it then ran clean and reved higher than it ever has, I was amazed! I then rode trying the plunger at different settings while riding. It all degraded as the displacement was reduced.
The quick conclusion as has been stated the bottle must match the displacement with hose included. Those bottles seen for sale that indicate that they will work on 48-66cc engines wont work well on all the displacements only the one closest the actual bottle/hoses displacement.

In MY ENGINES case the valve is superior until above mid range, the bottle beats it there and really adds top end. Im thinking an ideal situation would be two nipples in the intake one to a valve and the other to a bottle. I think the valve will negate the effects of the bottle until above mid range where the bottle will take it to the top. Im hoping so any way! BTW you must lock the plunger somehow as at low throttle settings it will slowly be sucked in. I used a tiny pair of vise grips.

Stay tuned!
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Last edited by cannonball2; 03-08-2015 at 04:32 PM.
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  #23  
Old 03-08-2015, 02:42 PM
KCvale KCvale is offline
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Default Re: Modded Boost Bottle

Funny, I was thinking that last night as I dossed off to sleep, I tend to do that.

Totally impractical but if you arranged four 4 valves like you would 4 diodes in a full wave bridge rectifier you could dump the back pressure to an open air catch can, and the vacuum side would shut off sealing the other side with no side effects.

All that is silly to me over an intake reed, but who am I to judge without trying right?
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  #24  
Old 03-08-2015, 11:40 PM
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maniac57 maniac57 is offline
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Default Re: Modded Boost Bottle

Well, seeing as how I never expected any decent change in the first place, I think it bears experimentation.
I've always felt the USEABILITY was more important than max power on most non-race motors.
I've long wanted to try adding some flywheel weight to a chinadoll to improve low end smoothness as well.
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  #25  
Old 03-10-2015, 07:18 AM
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cannonball2 cannonball2 is offline
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Default Re: Modded Boost Bottle

The poor little check valve gave up the ghost yesterday. I had damaged the little disc slightly drilling out the nipples and I guess with the high number of cycles its subjected to plus the damage caused it to spilt. Had to ride home with my finger over the nipple end.

Will replace with a different type, probably one of the larger automotive versions like has been suggested. Had thought about making one may give that a go. For now will just tolerate the mushy low end.
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  #26  
Old 03-10-2015, 09:26 PM
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Davezilla Davezilla is offline
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Default Re: Modded Boost Bottle

You might get away with a small reed valve like off a chainsaw or RC engine... The RSE reeds are for the DLE 50cc RC engine and the reed valve it's self costs a whopping $8, but this size reed might be a little bigger than needed for what you're doing, but it would also take next to nothing to make a small plate to bolt onto the valve inlet and weld the right size nipple for the hose connection... There are some smaller reeds out there for the smaller RC engines that might also work better.
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  #27  
Old 03-11-2015, 11:36 AM
KCvale KCvale is offline
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Default Re: Modded Boost Bottle

The more I think about it....
The goal is to enhance the intake flow, I think perhaps an intake shape like an X-chamber that acts the same way, catching and throwing back the shock wave forcing unburnt mix back into the cylinder while drawing in more through the carb might be a feasible concept.

With a nice balance of shock wave resonance on the intake and exhaust you could really cram a lot of fuel into the combustion chamber and not slow the carbs ability to deliver it.

It would have to be long intake I figure, but even just Z shaped offset intakes improve lower end, perhaps just a shape change of that pipe could make a difference.

If it works well on the exhaust, why not the intake?



Free 'pressure reeds' that balanced right might just turn out to act more like valves on a 4-stroke hehehe ;-}

Just thoughts while I wait for paint to dry.
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  #28  
Old 03-11-2015, 01:25 PM
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Default Re: Modded Boost Bottle

Cool idea KC! With all the high tech materials we have these days why not put reeds in the exhaust tract? Soon as the positive pressure of out going exhaust subsided and the piston started down to open the transfer the reeds would close shutting out any back flow compromising the incoming mixture. If the reed threshold was higher than the incoming transfer pressure none of the mixture would be lost. Would negate the need for a finiky expansion chamber. Must be some reason its not done?
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  #29  
Old 03-13-2015, 10:05 PM
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Davezilla Davezilla is offline
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Default Re: Modded Boost Bottle

Fred's already done something similar by using a small compact chamber in the intake tract... I know he used to sell them individually but last time I visited his site he didn't show them up for sale, but are included on his stage 2 ported cylinders. The chamber basically makes room for the reversion so teh pressure wave stays in the chamber instead of coming out the carb but at higher rpm's it's pretty much invisible to the engine. I wanted to get one of those chambers he makes because it makes it real easy to install a larger carb by making a new intake plate with the right sized pipe to clamp the carb of choice to, or a new plate could be made to put the carb at an angle or offset from the center for tighter frame clearances. From the looks of his chamber it looks to be about the same volume as the cylinder displacement. Mounting a carb offset from the center of his chamber but still having the intake pipe pointed toward the intake port would be another way to trap the reverse wave and prevent blowback even more without it hindering higher rpm performance.



Not sure if he sells these by themself anymore but maybe a quick phone call or email might get you an answer...
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  #30  
Old 05-17-2015, 06:32 PM
Rolling2High Rolling2High is offline
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Default Re: Modded Boost Bottle

Are the boost bottles effective on a stock Flying horse to make smoother ride and add low end torque plus add to top speed as claimed?
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