Briggs and Stratton Model 6B S basic parts list?

Moisstink

Moisstink

New Member
I am pretty new at this whole 4 stroke approach and have a Briggs and Stratton Model 6B S Type 901010 (I believe it is a 2hp engine) that I want to use on a boartracker type build on a 1940's cleveland welding cruiser frame. My question t is what is the basic parts list to get this thing going? I am going to fab my own engine mount and as many parts as possible on a cnc but I am wondering about what kinds of clutch or drive system would be good. I wanted to keep it chain driven not belt. and I was wondering what type of carb may work. The engine currently has a carb that is functioning but it is a suction type that is a little bulky and I wanted to go with a gas tank that is not attached to the engine. Thanks for all info. I am attaching a photo of the crank shaft side and a couple images of the engine. Thanks everyone.

Kevin
 

Attachments

  • Briggs_and_Stratton1forum.jpg
    Briggs_and_Stratton1forum.jpg
    31.2 KB · Views: 297
  • Briggs_and_Stratton2forum.jpg
    Briggs_and_Stratton2forum.jpg
    29.1 KB · Views: 279
  • crankshaft_side.jpg
    crankshaft_side.jpg
    67.2 KB · Views: 241
  • prelim_setupweb.jpg
    prelim_setupweb.jpg
    178.7 KB · Views: 333
I bought a cheap float gravity feed carb for under 30 dollars on Amazon and use it on my Briggs 3hp 4stroke 80202 0430 engine. It almost worked with free parts from another engines air filter I was not using, but would not idle. Then I found it had to have the matching air filter for the specific carb. Ebay for a used box including the primer bulb for cheap and it runs fine.

I would have spent a little more on a carb though. If you get one have some adjustment mixture screw. Idle and if both then idle and high speed needle valve adjusters.

Lastly oil splash system of lubrication where I mounted the engine platform at about 17 degrees tilted back to fit the frame, it adversely affects the cranckcase breather valve letting more than just vapors back to the carb and wets the paper air filter. I am seeing about moving the valve to a remote higher point on the frame.

Since you are modding the frame, it would probably be best to keep engine level. Others do OK tilting, but they mostly tilt forward. Be sure if it is done like that the fork splasher does reach enough oil in the crankcase bath.

Tilting back the engine puts oil up closer to the baffles that are to keep liquid oil from getting
into the breather PCV valve. This is what I'm up against at the moment.
MT
 
Last edited:
I have had good results from using a simple NT carb and manifold on the briggs flatties.
Remember the engine does not care where the mix comes from as long as it's right.
I get much better throttle response than the stock carbs too.
 
MEASURE TWICE said:
I bought a cheap float gravity feed carb for under 30 dollars on Amazon and use it on my Briggs 3hp 4stroke 80202 0430 engine. It almost worked with free parts from another engines air filter I was not using, but would not idle. Then I found it had to have the matching air filter for the specific carb. Ebay for a used box including the primer bulb for cheap and it runs fine.

I would have spent a little more on a carb though. If you get one have some adjustment mixture screw. Idle and if both then idle and high speed needle valve adjusters.

Lastly oil splash system of lubrication where I mounted the engine platform at about 17 degrees tilted back to fit the frame, it adversely affects the cranckcase breather valve letting more than just vapors back to the carb and wets the paper air filter. I am seeing about moving the valve to a remote higher point on the frame.

Since you are modding the frame, it would probably be best to keep engine level. Others do OK tilting, but they mostly tilt forward. Be sure if it is done like that the fork splasher does reach enough oil in the crankcase bath.

Tilting back the engine puts oil up closer to the baffles that are to keep liquid oil from getting
into the breather PCV valve. This is what I'm up against at the moment.
MT
Click to expand...

Thanks for the info, very cool and very informative. The more I research this the more I am finding that this is a doable cool approach.
I have started laying out digital files for doing cnc cut pieces such as the engine mount and bottom plates for the board track look.
I will post these as they are done. Thanks again!
 
I am just now trying to figure out what I need for a clutch and jackshaft set up for the bike. Any recommendations? I have a 5/8 inch drive shaft. The engine should be around 2 hp (from 1.25 H.P. at 2200 r.p.m. to 1.55 H.P. at 2700 r.p.m. & 1.7 H.P. at 3200 r.p.m ). I am not sure the tooth ratio from clutch to jackshaft to wheel. It's like trying to read a book that you can only find one page at a time. Any help is appreciated.
 
For multiple ratios ie with jackshaft ratio,

engine teeth# to first driven on jack shaft input teeth# MULTIPLY by jackshaft output teeth# to sprocket on wheel teeth#


If pulley used, then it is diameter rather than teeth to find ratio


Speed also has to take into account the tire size. The smaller the tire less fast but climb hills better. Keeping tire the same size and changing ratios with pulleys or gears can change top speed.


Simple Calculator

http://www.csgnetwork.com/minibikepotentialspeedcalc.html


This one has even more information, note the window shows about half the info and you scroll down with not with the webpage slider but the window slider

http://www.eccarburetors.com/technical_15.html


Another simpler calculator:

http://www.bmikarts.com/Gear-Ratio-Speed-Calculator-MPH_ep_84-1.htm


MT
 
Last edited:
maniac57 said:
I have had good results from using a simple NT carb and manifold on the briggs flatties.
Remember the engine does not care where the mix comes from as long as it's right.
I get much better throttle response than the stock carbs too.
Click to expand...

I ordered a clutch and am wondering if I have to use a jackshaft between engine and wheel. 10 tooth to a 44 tooth. I have seen it done both ways. I am still trying to find out what CC this engine is to make sure I get the right carb. It has been hard finding that info. This weekend I am hitting a small engine repair shop to pick their brains. I find that building a jackshaft is pretty cheap so, I am just not aware of the pros and cons.
 
I'm not sure if that close to 4:1 ratio would move the bike. I would guess that you would need 10:1 or higher. Azuza Jack Shaft kit is inexpensive and they have them in 5/8" which is what I chose.

http://www.northerntool.com/shop/tools/product_25271_25271

Lots of places sell this Azuza brand.

If you don't weld or want the other type that have floating mounts that can take up the angle of the shaft inaccuracies and self align they cost a bit more. Some have lubrication points.

The collars I would not use the ones that come in the kit, I like half split collars that do not make any marks on the shaft. The set screw on the collars instead only pull the collar thigh and don't dent the shaft as the others do.

http://www.accentbearing.com/power transmission products/shaft/shaft-collars.htm

http://www.use-enco.com/CGI/INSRIT?PMAKA=990-3537&PMPXNO=3019486&PARTPG=INLMK32

If using Enco, look for free shipping no minimum order and 10 percent off... I'm always seeing it about once a month

A small problem with these collars is that the size for the 5/8 shaft has the outer edge a bit wider than I could use. I made it work by adding a washer with a 5/8 inside diameter and a smaller outside diameter than the split collars. I place it between the collar and the pillow bearings. Now it will not scrape the pillow bearing surface that does not spin.

Maybe someone has some other way to solidly fix the parts on the jack shaft and also not mark up and dent the shaft, making dis-assembly for maintenance and adjustment a big mess.

MT
 
Last edited:
You will definitely need a jackshaft. Ratios from around 10:1 to 12:1 are the most common for engines in this range. If hills factor a then maybe a 14:1, if in the flats then The 10 or 12:1 should be fine. Generally its easier to make the primary a drive belt and the secondary chain. The belt has more adjustablity, than trying to tension two chains. Also has less drive train back lash. Seeing that you have ordered a chain clutch, make some provision for adjusting the chains independently. Like sliding the engine for the primary and the rear wheel for the secondary. In order to keep sprocket sizes small on the primary, a smaller pitch chain(like a 35) is preferable so there are more teeth/given chain wheel diameter. keeps things compact in tight spaces.
 
cannonball2 said:
You will definitely need a jackshaft. Ratios from around 10:1 to 12:1 are the most common for engines in this range. If hills factor a then maybe a 14:1, if in the flats then The 10 or 12:1 should be fine. Generally its easier to make the primary a drive belt and the secondary chain. The belt has more adjustablity, than trying to tension two chains. Also has less drive train back lash. Seeing that you have ordered a chain clutch, make some provision for adjusting the chains independently. Like sliding the engine for the primary and the rear wheel for the secondary. In order to keep sprocket sizes small on the primary, a smaller pitch chain(like a 35) is preferable so there are more teeth/given chain wheel diameter. keeps things compact in tight spaces.
Click to expand...

So I have an 11 tooth centri clutch mount on engine and was thinking going to a 14 tooth jackshaft then a 10 tooth to the 44 tooth wheel. I have been trying out the calculators above and watched a video on the ratio. I did that a couple weeks ago. Does that make sense. I am in AZ so nothing but flat pretty much. Thanks. I think I am looking at 2400 - 3000 rpm. I do not need anything crazy fast. 25-30 and I am good. Let me know what ya think.
 
Thats a 6/1 ratio. WAY tall. A 10:1 would be for instance primary 11t/22t=2:1 secondary 10/50t=5:1 PrimaryxSecondart= 10:1 Much below 10:1 and it gets hard on the clutch. What size chain is the cent clutch?
 
cannonball2 said:
Thats a 6/1 ratio. WAY tall. A 10:1 would be for instance primary 11t/22t=2:1 secondary 10/50t=5:1 PrimaryxSecondart= 10:1 Much below 10:1 and it gets hard on the clutch. What size chain is the cent clutch?
Click to expand...

I bought a 1/2" 420 chain 11t clutch (in hand). I was going to use a 44 tooth schwinn sprocket on the rear. I am using a 24" rim that is a 26 radius with tire. I have not picked up the sprockets for the jackshaft yet. I do have a 25t sprocket that I was going to possibly use as well but have a 32 sprocket I was going to use for the drive chain on the bike I can use any configuration your recommend. Let me know if any of this configuration will work or the best layout of sprockets. I really appreciate the help. As I said I am not trying to burn on this but I do not want to blow components either. Thanks again.
 
Using the 24" wheel helps a bit, but I would still shoot for no lower than a 10:1. You can get the 10:1 in many combinations. Generally its harder due to space constraints to get a super low reduction in the primary, but I would get as large a driven(rear ) sprocket(primary) as I could. Once that is determined then the secondary ratio can be determined. If you can get a 2:1 reduction in the primary, then the secondary would be pretty easy to get with a larger rear sprocket, like a 50t which should be out there if you look.

If you can fit the 24t on the jackshaft then using your 10/44t rear set up would get an overall of 9.59:1 which is close enough especially using a 24" wheel.
Using the above combo would yield 26.7mph@3600 and 29.7@4000rpm if you want to push the old B&S that hard. Seeing as the engine is relatively low HP its pull away at this ratio may be fairly leisurely.
 
You must log in or register to reply here.
Back
Top