Boost bottle vs crankcase volume/velocity - Pocket Bike Forum - Mini Bikes
 
LinkBack Thread Tools
post #1 of 12 (permalink) Old 2 Weeks Ago Thread Starter
verified
 
HonzaTw's Avatar
 
Join Date: Feb 2020
Posts: 6
Boost bottle vs crankcase volume/velocity

Hi guys!

Because of the virus it seems that I will have to stay for a few days at home without possibility to go to garage. So, I've decedided to take abandoned pocket bike home and try to make it running again.

I have read a lot of posts here and I'm a bit confused of following. In some posts there is not recomended to use triangle reed plates because of enlarging crankcase volume hence lowering velocity and in other is recomended to add a boost bottle which enlarges crancase volume...

Which idea is correct? Or am I missing something?

Thanks in advance
HonzaTw is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 2 Weeks Ago
EPR
Banned
 
Join Date: Aug 2009
Posts: 24,102
Re: Boost bottle vs crankcase volume/velocity

The crankcase pressure is important. That's where stuffing of the crank to fill in space. The boost bottle attached to the intake manifold collects the spit when the reeds close and saves it, when you get on the throttle it is supposed to mix the fuel and air into the flow going thru the carb, Many dirt bikes had boost systems, so it must works. Most of my many bikes have a boost system.
Attached Images
File Type: jpg 49cc HP Scooter1.jpg (205.5 KB, 3 views)
File Type: jpg My 43cc Scooter3.jpg (450.4 KB, 3 views)
File Type: jpg Lucky 7 Side Pipe Exhaust2.jpg (405.2 KB, 3 views)
File Type: jpg Red Head PP Engine4.jpg (375.7 KB, 3 views)
EPR is offline  
post #3 of 12 (permalink) Old 2 Weeks Ago Thread Starter
verified
 
HonzaTw's Avatar
 
Join Date: Feb 2020
Posts: 6
Thank you EPR. Explained well. I tried to find it on my dirtbikes but non of them has it. Is there any particular volume? And have another question. Anybody tried to turn cylinder 180 degrees to point exhaus directly backwards to eliminate J pipe?
HonzaTw is offline  
Sponsored Links
Advertisement
 
post #4 of 12 (permalink) Old 2 Weeks Ago
EPR
Banned
 
Join Date: Aug 2009
Posts: 24,102
Re: Boost bottle vs crankcase volume/velocity

Believe it was 2 or 3 decades ago in the 1980s, maybe Suzuki. Volume, some people say 50cc eng. 50cc bottle, but I think up to 100cc bottle is fine and you can make your own. Material has to be good for gas & oil, most plastic like PVC work pretty well. for brass fittings, and gas line go to hardware store, Most fittings have a 1/8 NPT pipe thread, so you need a male tap.
Don't think turning the engine over would work very well, cause the crank rotation pushes the mixture around the top of the crank and rod and up the upper ports if any and the pressure inside the cases pushes up thru the main transfer ports also. It would change everything, the mains are shaped for flow on top. If CAM2 shows up he knows more than I do. You can turn the engine around with a reverse direction transmission to drive a chain on the right side,
Attached Images
File Type: jpg Drag Cag Twin Engines.jpg (391.9 KB, 4 views)
File Type: jpg Twin Engine Cag1.JPG (510.7 KB, 4 views)
File Type: jpg Twin Engine Cag2.JPG (508.3 KB, 3 views)

Last edited by EPR; 2 Weeks Ago at 08:29 PM.
EPR is offline  
post #5 of 12 (permalink) Old 2 Weeks Ago
Banned
 
Join Date: Mar 2008
Posts: 21,721
Re: Boost bottle vs crankcase volume/velocity

Quote:
Originally Posted by HonzaTw View Post
Thank you EPR. Explained well. I tried to find it on my dirtbikes but non of them has it. Is there any particular volume? And have another question. Anybody tried to turn cylinder 180 degrees to point exhaus directly backwards to eliminate J pipe?
They come mainly on Yamaha MX bikes and quads....I have boost bottles on my 83 yz80 aswell as YZ490 also had 1 on my Blaster200 before swapping in a YZ400 engine and a boost bottle setup on my 2001 Banshee 350 and 2002 w/421 stroker kit



You have to realize these engines are TOOL based so the rules of building performance 2 strokers don't fully apply...….

These engines come on Augers, brushcutters and trashpumps…

Modifying them is similar to modifying chainsaw and weedeater engines into racekarts and r/c vehicle powerplants...




If you want to stuff a tool based reed inducted or piston ported engine you just simply add a full circle crank.....It actually overstuffs it.....LOL

As far as boost bottle volume....Its not pertinent nor do they work as well on reed inducted t6ol based engines as they do on piston ported tool based engines.......……….

You'd get way better results from learning how to properly fit an engine together and make the flowpath smooth kinda like blueprinting...….

Once you reduce turbulence and enhance velocity only then will you make any real substantial extra power...……
As far as the engine 180 cylinder flip...Its been done and really doesn't work as you'd think unless you did what I did and also reverse the engines rotation too...……….

Attached Images
File Type: jpg 053-4.jpg (130.7 KB, 3 views)
File Type: jpg IMG_20150719_151628645_HDR.jpg (635.5 KB, 2 views)
File Type: jpg 100-0133.jpg (65.9 KB, 2 views)
File Type: jpg banshee5.jpg (8.3 KB, 4 views)
File Type: jpg banshee1.jpg (9.8 KB, 4 views)

Last edited by CAM2; 2 Weeks Ago at 11:24 PM.
CAM2 is offline  
post #6 of 12 (permalink) Old 2 Weeks Ago Thread Starter
verified
 
HonzaTw's Avatar
 
Join Date: Feb 2020
Posts: 6
Re: Boost bottle vs crankcase volume/velocity

Quote:
Originally Posted by CAM2 View Post
They come mainly on Yamaha MX bikes and quads....I have boost bottles on my 83 yz80 aswell as YZ490 also had 1 on my Blaster200 before swapping in a YZ400 engine and a boost bottle setup on my 2001 Banshee 350 and 2002 w/421 stroker kit



You have to realize these engines are TOOL based so the rules of building performance 2 strokers don't fully apply...….

These engines come on Augers, brushcutters and trashpumps…

Modifying them is similar to modifying chainsaw and weedeater engines into racekarts and r/c vehicle powerplants...




If you want to stuff a tool based reed inducted or piston ported engine you just simply add a full circle crank.....It actually overstuffs it.....LOL

As far as boost bottle volume....Its not pertinent nor do they work as well on reed inducted t6ol based engines as they do on piston ported tool based engines.......……….

You'd get way better results from learning how to properly fit an engine together and make the flowpath smooth kinda like blueprinting...….

Once you reduce turbulence and enhance velocity only then will you make any real substantial extra power...……
As far as the engine 180 cylinder flip...Its been done and really doesn't work as you'd think unless you did what I did and also reverse the engines rotation too...……….

Well, I have 2003 YZ125 and KTM EXC125 and they don't have boost bottle and as a kid I played with Jawa's and it didn't have it either.
So, thats why I was a bit confused about them and it will definitely not be my first mod. Only wanted to clear this to myself to have peace in mind.

Nor gonna bother with FCC crank either. I have read your posts carefully.

First I want to blueprint the engine for sure, but still ordered a few parts to play with. 44mm cylinder with head in one piece, 44mm cylinder with 3part head, 44mm piston without windows with 10mm pin and pumper carb.
a.jpg

aa.jpg

aaa.jpg

Idea of turning cylinder around came up when i saw pipe calculator and there are dimensions of straight pipes only. So, it would be easier to make one than bother with J pipe

I will not test it when you already did it, but it don´t seem me to be necesary to run it opposite direction.

eng.jpg
HonzaTw is offline  
post #7 of 12 (permalink) Old 2 Weeks Ago
EPR
Banned
 
Join Date: Aug 2009
Posts: 24,102
Re: Boost bottle vs crankcase volume/velocity

Good luck with the project. It's a 5 piece billet winged head, you will see when you get it. What you need is a 44mm Piston w/ 10mm rod pin, You are getting a 12mm piston. With the 44/10 you can use the lighter 47cc stock crank w/ 10mm pin. The 15mm pumper carb is better than the stock 13mm piston carb, but there is a gas return line from the carb back to the gas tank, that's for the piston port engine. Om my Lucky 7, I put a brake bleeder screw, threaded in into the gas cap, then ran the yellow gas line from the carb to the cap, See photo.

I bought billet Cag cases from Germany, they had so many problems, 6 years later CAM2, offered to fix it for me. When he worked his magic, he left no stone un-turned, The Cag billet cases are Polini Euro style with the reeds above the crank. You know CAM2, he loves to modify stuff, from the whole engine to the 19mm Walbro We chose parts I had in stock, a 10mm rod FC crank, then a 40mm by 10mm piston and bearing, 40mm cyld and built off that, cause light gives more power and rpms.
Attached Images
File Type: jpg 47cc Billet Cag Eng1.jpg (277.0 KB, 3 views)
File Type: jpg 47cc Billet Cag Eng2.jpg (285.3 KB, 4 views)
File Type: jpg 47cc Billet Cag Eng3.jpg (148.5 KB, 3 views)
File Type: jpg New Cag Billet Eng4.jpg (507.0 KB, 4 views)
File Type: jpg New Cag Billet Eng1.jpg (500.6 KB, 4 views)

Last edited by EPR; 2 Weeks Ago at 03:43 PM.
EPR is offline  
post #8 of 12 (permalink) Old 2 Weeks Ago Thread Starter
verified
 
HonzaTw's Avatar
 
Join Date: Feb 2020
Posts: 6
Re: Boost bottle vs crankcase volume/velocity

Quote:
Originally Posted by EPR View Post
Good luck with the project. It's a 5 piece billet winged head, you will see when you get it. What you need is a 44mm Piston w/ 10mm rod pin, You are getting a 12mm piston. With the 44/10 you can use the lighter 47cc stock crank w/ 10mm pin. The 15mm pumper carb is better than the stock 13mm piston carb, but there is a gas return line from the carb back to the gas tank, that's for the piston port engine. Om my Lucky 7, I put a brake bleeder screw, threaded in into the gas cap, then ran the yellow gas line from the carb to the cap, See photo.

I bought billet Cag cases from Germany, they had so many problems, 6 years later CAM2, offered to fix it for me. When he worked his magic, he left no stone un-turned, The Cag billet cases are Polini Euro style with the reeds above the crank. You know CAM2, he loves to modify stuff, from the whole engine to the 19mm Walbro We chose parts I had in stock, a 10mm rod FC crank, then a 40mm by 10mm piston and bearing, 40mm cyld and built off that, cause light gives more power and rpms.
Thank you EPR for your post! I've seen somewhere here, that 44mm piston with 10mm pin without windows is the best.
So, I bought following https://www.aliexpress.com/item/4000...b5934c4dMDkAZ0

Hopefully I will be able to make it running. I´m from a country where Blata is produced, Blata 2.5 is about 400$ here. But I like fixing stuff, thats why I have 40$ China Cag bike.

Your idea about return line is perfect, I will do that way for sure. Thanks!

In the garage I found old engine from buschcutter equiped with walbro pump carb. Inlet 16mm outlet 13mm is it suitable for my future engine or is it too small? I can't find any letters on it to find out what type is it.
IMG_8507.jpg

IMG_8508.jpg
HonzaTw is offline  
post #9 of 12 (permalink) Old 2 Weeks Ago
EPR
Banned
 
Join Date: Aug 2009
Posts: 24,102
Re: Boost bottle vs crankcase volume/velocity

Sure looks like it's a 16mm WT-603 Walbro. The ID is on the sides of the carb some where, find it, you will see a H & L above the jet screws. High screw is towards the front of the carb. The mount holes are the same amount apart from 10mm to 30mm carb, which means you can use a smaller alum Cag intake and hog it out to fit a bigger carb. I will look for photos today.

The piston you ordered was right, but the photo looks like a 12mm pin, hopefully they send you what you ordered. Any way, you also need the lighter 47cc crank w/ 10mm rod end to go with it. All the parts are lighter than the 44mm/12mm piston and crank setup.
This piston port engine has the 44/10 piston.
Attached Images
File Type: jpg PP Cut Cyld and Alloy Head1.jpg (253.7 KB, 3 views)
EPR is offline  
post #10 of 12 (permalink) Old 1 Week Ago Thread Starter
verified
 
HonzaTw's Avatar
 
Join Date: Feb 2020
Posts: 6
Re: Boost bottle vs crankcase volume/velocity

Quote:
Originally Posted by EPR View Post
Sure looks like it's a 16mm WT-603 Walbro. The ID is on the sides of the carb some where, find it, you will see a H & L above the jet screws. High screw is towards the front of the carb. The mount holes are the same amount apart from 10mm to 30mm carb, which means you can use a smaller alum Cag intake and hog it out to fit a bigger carb. I will look for photos today.

The piston you ordered was right, but the photo looks like a 12mm pin, hopefully they send you what you ordered. Any way, you also need the lighter 47cc crank w/ 10mm rod end to go with it. All the parts are lighter than the 44mm/12mm piston and crank setup.
This piston port engine has the 44/10 piston.
You were right. Carb is marked on the side. Unfortunately it´s not WT-603 but WT-220. Don´t know if it is still suitable.

I´m still waiting for new parts so I decided to use old cylinder and piston as a practise one. It´s cheaper to make a mistake on an old one

First I checked crankshaft for wobble.
Měření kliky.jpg

And here is my first attempt to blueprint Cag...
karter 2.jpg
karter.jpg
válec.jpg

Next crankshaft and reeds
klika.jpg
reed2.jpg
reed.jpg

And finaly I took 6g from piston and made it fragile as a egg shell
pist.jpg
pist2.jpg

Which made balance faktor 51%...
HonzaTw is offline  
EPR
Banned
 
Join Date: Aug 2009
Posts: 24,102
Re: Boost bottle vs crankcase volume/velocity

Looks Great, looks like someone is serious, lol. Not familiar with the WT-220. They have so many different carbs it boggles the mind, The 603 is front 19mm and 15.88mm in the rear and you can buy an alum 16mm manifold for a Cag for $20.

Yours is a 16/13mm think it could work with a few mods, for one a V-stack on the front and good air filter. You could make the front of the carb 17mm/18mm pretty easy, then taper the rear hole out 15mm, and you can get a plastic 15mm pumper carb Cag manifold and use them together leave the middle alone. Your pretty good at modifying, should be easy for you. Can you post some photos of the carb?? I took a 21mm carb and made it fit the Cag alum manifold by hogging it out.
Attached Images
File Type: jpg Red Head PP and Cag 3rd Bearing2.jpg (305.8 KB, 6 views)
File Type: jpg Boosted306 HP Parts13.jpg (411.9 KB, 5 views)
File Type: jpg 49cc Boosted306 engine - Copy.jpg (431.6 KB, 6 views)
File Type: jpg New Style Cag Alum Starter Housing3 - Copy - Copy.jpg (179.9 KB, 6 views)
File Type: jpg 49cc HP Scooter1.jpg (205.5 KB, 5 views)
EPR is offline  
post #12 of 12 (permalink) Old 1 Week Ago Thread Starter
verified
 
HonzaTw's Avatar
 
Join Date: Feb 2020
Posts: 6
Here are photos of the carb EPR...
Attached Images
File Type: jpeg E9226300-158F-4C28-B974-BD1A6429225C_1585247995766.jpeg (30.0 KB, 6 views)
File Type: jpeg 0E7F9D6D-70B9-4850-8B10-D122FF7395E0_1585248013351.jpeg (31.8 KB, 6 views)
File Type: jpeg 27F2F3C6-98D1-47B3-B382-6B771FBC5E58_1585248028745.jpeg (277.4 KB, 4 views)
File Type: jpeg BA5FD4C9-5F31-4D91-8C3C-08A1D06E814F_1585248042209.jpeg (302.2 KB, 5 views)
File Type: jpeg 1C33C431-C3D2-45F3-9127-3ED6D7050DA7_1585248065410.jpeg (281.1 KB, 6 views)
HonzaTw is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pocket Bike Forum - Mini Bikes forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome