Adapting Briggs Build to accept bigger engine

[MEASURE TWICE]

Finished making shims for the bearings in the hangers and they fit snug. Also the snap ring fitting tight and engages the tab of metal I welded and shaped to fit will keep the outer bearing surface from turning inside the hanger (or creeping slowly, I saw this when I was testing the jackshaft).

 

[MEASURE TWICE]

I got to putting stuff back and was at first part to test out how well the engine idles before hooking up in sequence first chain, then second chain, then belt.

The engine started OK. Then screech, the pawl clutch on the recoil is bad. Thought I sheared a flywheel key also, but not.

I was I guess a bit wanting to really check out the idle, but the engine stalled from the pawl clutch. One more try and it was not starting now. I used the primer bulb. That was a mistake as it was already having un-burnt gas from the quick stall from the pawl clutch.

I had another engine with a pawl clutch I know works without problems.

When I took apart the doner pawl clutch I saw a fiber washer that was inside. The one on the engine I got used, had that washer missing. Duh... maybe had something to do with the screeching.

I just kept 1/2 of the pawl clutch on the flywheel of the new used engine. It can be detrimental to remove that from the flywheel threads, so I mixed and matched parts. I did however take measurements of the missing washer and will get a replacement to keep the other engine complete.

I also noticed a few screws missing holding the screen on the flywheel, but two screw was not so big an issue. The missing fiber washer that allows the pawl parts to move smoothly though is imperative I think.

I also got out the level to see the bubble was centered when I was having it make sure the part of the pawl to recoil coupling dot mark was facing straight up true. My engine platform is on a slant of about 15 degrees back, so the level by itself was right on.

This supposed to help be sure that at least one ball bearing catches when trying to start with the recoil starter. Otherwise you pull it sort of maybe catches and the your are get thrown out of wack when it slips and all the line pulls without turning the engine at all.

Tomorrow to start it up as it was too late when done. I did however lube the linkages I made for the throttle to the carb and adjusted the return spring.

 

[Tony01]

Finished making shims for the bearings in the hangers and they fit snug. Also the snap ring fitting tight and engages the tab of metal I welded and shaped to fit will keep the outer bearing surface from turning inside the hanger (or creeping slowly, I saw this when I was testing the jackshaft).

I could not believe the crap fit those things came with. I wonder how the rest of the world deals with the problem.

 

[curtisfox]

I see oil streaks in the first picture, them pawls are suppose to be dry. Just a little oil on the shaft top. Chatter, had a lawn mower that keaped on doing it, no mater what i did, new parts or not. One day it just would not work any more, tore it down and found to much end play in the crank. Would rise up and catch the pawl and squeal, wind the rope backwards. Just plane wore out, but didn't smoke or burn oil, dug out another motor, Lol .........Curt

 

[MEASURE TWICE]

Those oil streaks are dried up long ago on the part. I may also think that it was not the original pawl clutch since the fiber washer was missing as well as two of the 4 screws on the screen for the flywheel.

There is no loose end play on the crankshaft.

I'll hope that is it and look at the hardware store for a fiber washer like what I found missing and scavenged from the older engine.

 

[MEASURE TWICE]

Almost all put back together. Anyway it is just the rear brake and the carb engine side cover.

All the tranny works. The ratio 13:1 I cant yet tell if it will be enough for some small hill when trail riding. I'll take it to a off road park that I know that has enough flat and small hill to get an idea. This will also allow me to ride it and tell if where I really want to use it will it have enough torque.

No problem with the recoil starter pawl clutch, no so much as a peep.

Probably will eventually get another carb at some point. The carb I have just won't idle very slow. If the governor was on it it may work better, but the elbow bend in the manifold for the intake makes it some special design to be able to retain the governor. I'm not thinking it is worth doing that.

The carbs that have a separate idle mixture screw I may try again getting. Just the way they make them now, compared to once I remember back when is not at all the same. I guess you have to do some fixing up the gaskets that are used and use fuel proof RTV or something when putting them back together to do simple float adjustment.

I'm ready to also see the 3.5 hp Briggs newer used engine, in how it does not do as the other engine mess up wetting the air filter with gas. The valve timing is better and higher compression.

Soon to next look inside that older Briggs 3hp and see what gives if the intake cam back side has a extra little lobe for Easy Spin Start.

 

[MEASURE TWICE]

I am a little concerned about the play in the centrifugal clutch I have. This gear type is quite old, but I did test ride it just about 30ft. I will get to checking it out more thoroughly and maybe to the trails soon.

The belt clutch I also have for the other setup I was using before was a newly bought clutch and also is a bit loose.

As I remember it was like that a bit I remember from when it was new.

The looseness is not a problem really, as when the shoes lock to the bell, then it is stable and less noisy.

What I was judging a bit was when I roll the bike when the engine is off an not running. This makes the bell try to spin quite fast as the 13:1 gearing in the opposite direction, 1:13.

The cover to the gears I made are the greatest at resonating and amplifying the screeching sound. Theft deterrent if you cant start the bike it sounds off?
Have to hold the rear wheel up and walk it.

I did lube the bushing, but if that is what may need replacing so it is a bit tighter, I might instead just but a new clutch for not much more.

I also put graphite power lubricant on both the brake cables and adjusted them. Set the rear wheel axle end play. Throttle is moving nice an smooth too.

 

[MEASURE TWICE]

https://vimeo.com/201601124

A short clip of me testing out the newer used Briggs 3.5 14:1 ratio.

I did noticed after the engine was run a while and was cooling there were a few drops of oil. They were from the bottom of the air filter. The crankcase vent to the air filter is what is doing this, but I did not see any smoke out the muffler.

I'd be very hesitant to put less oil in the crankcase and hope there is enough lubrication. Lots of power compared to the other engine and don't want to harm the engine.

 

[cannonball2]

MT

Thoughts on the starter clutch. Seems you have it handled but here a bit of info.
I was in the small engine business. When we did a seasonal service on a Briggs with this type of recoil we removed the outer parts of the clutch cleaned everything and relubed the shaft. You are right there is a fiber washer. However many are lost over the years, and the clutch will work with out it. Should have it though.

What caused the squealing is lack of lube. There is a hole in the top of the clutch. It was intended to have several drops of oil added to a felt inside that held the lube. These get hard over the years and don't function. We always lubed(sparingly) the shaft with hi temp axle grease. This doesn't melt and migrate into the balls. Lube(grease or oil) in the balls will stick them and the recoil will not grab. This is very common on over lubed clutches. If it ever happens hit the recoil with your fist to knock em loose to get it started.

What Curt said is true. I have fixed many recoils where the clutch seized and turned it backwards. It destroys the spring usually and tries to spit the rope out.

Also if you have an engine that wets the air filter but runs ok with the filter off, generally there is no valve clearance. The valve is being held open just enough to leak under power. Just remove the valve and re-establish the proper clearance by grinding the stem.

Check that the crankcase breather holes in the case are not clogged where the oil drains back. Also with engines with a bit of blow by you can add a bit of Scotch Brite in the breather to catch the oil before it exits.

Enjoy your Briggs escapades! Hope this helps.

 

[MEASURE TWICE]

The valves have already been check for the gap and I even did a check to feel for pressure escaping like the older Briggs. I had that one where the intake valve had worn into the seat and lost all clearance and it was raw fuel doing the venturi effect the opposite way out at the air filter. The new used Briggs is in spec, I measured with a feeler gauge.

There is oil that is not thinned out with any gasoline in it that I found dripping just a few drops under the bike. I saw the protective cover that I put over the engine and carb on that side of the bike, inside near the bottom air opening in the air filter covered with a sheen of oil.

You mention to use Scotch Brite to try to keep the oil from, I think you say going past that sort of reed valve in the breather. I have seen stuff like that in some of the breathers of older parts for Briggs that I owned in the past. The breathers that I have now are crimp metal sealed shut. It would be difficult to open and reseal the breather to add this. I also would wonder if there should already be the stuff in there. Or also if not would it interfere with that reed valve operation if stuffing it with any or more of Scotch Brite.

Just to be sure I would not think Scotch Brite is OK to add inside the area with the valves, springs, and tappets.

The oil mist or maybe droplets as since I have the engine unfortunately tilted back (not forward) maybe 15 degrees, has probably too much oil getting through the hole from the crankcase by the cam shaft up into the valve springs area. I have a hose that run in a downward sideways direction to the air filter case opening for the oil mist to be burnt along with the carb intake air. Maybe the engine angle again makes it so the oil cannot go back in to the engine when you turn it off.

That breather, I am not sure how oil can go back into the engine anyway, if the breather reed valve seals perfect, if I did have gravity working for me if the air filter was higher than the breather. It is not and I am not planning on changing this design, but I learned that the forward lean of an engine to max 15 degrees could have been a better choice. Others on MB show not problem with breather having so much mist getting into the filter.

Lucky I am using no longer a paper air filter as I made my own foam filter to use with that special oil. I don't need oil for the filter now, laugh! Paper air filter cloggs when wet with fuel, not sure about oil spray.
An oil separator is something that is an idea. I would empty it once an a while and keep a check on the oil fill level in the engine too. I tought maybe a 12 oz steel can to use. I would have a hose run through the top down the middle to an inch of the can bottom. There would be foam half way up to the top of the can. A hold in the side of the can by the top would be the output. That output would have less oil spray and hopefully just the vapors that would be routed to burn along with the air filter intake.

I am wondering if I do nothing, then aside from the few drips of oil, I was concerned that the oil may clogged the foam air filter and choke the engine to a stop. This is quite similar to having fuel doing clogging. At least I can say fuel is not a problem now.

There are two clutches and the pawl clutch to the recoil starter, I understand about the fiber washer can be missing and still work.

You mention the squealing sound and putting some oil in there where there is that felt for the shaft that the pawl clutch rides on. Thanks I forgot to do that on this engine as I remember a tech at the shop mentioned this too. To note, he also said that the ball bearings should not have any oil and remain dry to operate. I understand where you also mention about a high temp grease that would not migrate and used sparingly.

The other clutch I use for the power train, I oiled the brass bushing and under engine power it runs and is just a little nosier than the belt clutch I had been using. Both would make quite a bit of noise when rolling the bike with engine off. The bell has to spin 13 or as before 20 times for one revolution of the rear wheel. That is when it is noisy. I would actually remove the belt connection to the rear wheel for any long distance I would want to push the bike. And for storage, the belt would be best to take tension off it anyway.

 

[MEASURE TWICE]

I took the bike out to the motorcycle OHV park. It has quite enough power for the 13:1 ratio and climbs hills great. Lot of get up and go!

No hard starting due to any of what I saw a little oil around the air filter from the breather tube. I did not take the filter out to see, but there was no more dripping.

There is a sort of a problem with starting the engine, but it is not the engine per say. The clutch grabs good too. It is when the engine is off and you pull the recoil starter, the clutch sometime still grabs a little. If you do not have the rear wheel off the ground you cannot get the engine started when it is doing this.

I found a work around before I try to repair or replace the clutch. Could be lubing some other area than just the brass bushing?

What I did to get by today was with engine off move the bike a few inches forward and then reverse and feel when it frees up. Then I stop moving the bike and start as normal.

Still this is not desired, so as soon as the next storm is gone I will look and see whats grabbing when it should not. I could think maybe the springs on the clutch could be worn. I don't think anything uses lube for the shoes as it could then get on the grabbing surface of the shoes and the bell.

Also take a look at the critters that were in the road. I was in my truck, but I had to stop. So I got a few pictures.

 

[MEASURE TWICE]

Found the issue with the clutch was that the bushing was gummed up with maybe the oil I put on that maybe gathered some dust. I cleaned it out with paint thinner and then oiled it up and it is smooth. Just don't know if it will be happening again soon needing cleaning. There are some groove scratches in the bushing. The springs although rusty and maybe worn are cleaned with wire brush before and are not a problem.

I got some springs from the hardware store thinking I would maybe need them, but they were the wrong size anyway. I just want to ride it some more and just put every thing back. Another time I'll bring the clutch springs to see if I can find a match, but it probably is not an issue.

Was wondering if I could get a replacement bushing sleeve of brass from the company that makes the clutch. I already contacted them and they probably either did not have any support life for such an old clutch or they forgot. The bushing may be something I will just try to find else where as well, like at the hardware store. Otherwise I saw a Max Torque 35 chain 3/4 clutch with two sets screw and a full length key way for about 32 dollars on Amazon. Free shipping.

A fiber washer broke, I will get another to replace inside the clutch. It was where I pointed to. Probably could run without it, but I'll even cut some material to the right size with a gasket cutter set I have if necessary. OSH has a lot different sizes of these fiber washers.

I really like the feel of my whole torso being pushed back from the acceleration as I twist the throttle.

This is da beast!

 

[MEASURE TWICE]

Tried the bike today after oiling the sleeve bearing and it rolls easy with the engine off and starts so easy.

I will replace the fiber washer in the clutch when I find a better supplied Hardware Store. One fiber gasket that needs just a little trimming will make a couple and have an extra for the pawl clutch in the older engines recoil starter. OSH did not have the exact size one for the clutch or the pawl clutch I replaced by scavenging one from an other recoil starter.

I have a punch set for gaskets I bought at HF for cheap. It got a but rusty, but some how the sharp cutting edges were left untouched. I'll make the pawl clutch gasket for a extra spare part. Finding a fiber gasket big enough for ID and OD, did not happen.

I did see Granger and some Ebay sellers have a oil lite, or called bronze brass sleeve bearing. From today's ride I don't think it is going to be necessary to replace with a new one, but nice to know I can get the part for the old clutch.

 

[scratchbuilder]

Mt, didn't you add-on to your 3/4 short crank..i might have to do that..although it means going outboard with my clutch.

 

[MEASURE TWICE]

Parts or parts and shipping to make the crankshaft longer to fit the clutch was not worth the cost. Buying a used Briggs would be cheaper.

Also to make longer these clamp on adapters also makes some of the added length unusable. So the total length would have extended the cover. I would have to work on the cover too. The cover is already more than I like sticking out, but it is not so uncomfortable that I would redo everything I built.

Considered this is a learning experience and another build when I can do it will take all this into account to try and have things work out best.

As you said about turning the clutch around, it will usually with most clutches not matter as far as the shoes grab.

The thing I did notice in either gears or clutches, if there is a full length key way or not, when you try to put a key on the crankshaft up next to the crankcase wall, is that the darn key way slopes upward right at the crankcase wall.

This makes a key not fit flush. It does not matter if there is enough key to do the job and you resort to shortening the key a bit. If there is not much key left though to fit, then like what I have is 1/2 inch length key. Is this enough?

I think so and I'll see.

I did something in the past to modify a key which rather than cut it shorter when presented with this problem.

I took a Dremel and carved the mirror image shape of the slope at the inboard end of the key way on the crankshaft, onto the key I made. Half of the key had a square shape and the rest was carved to a shape enabling me to use the sloped section of the key way all the way up to the crankcase wall.

I think it was Fasteddy said the reason for the carved slope shape on the Briggs crankshafts inboard end of the key way slot, is for removal of keys that might get stuck. I though could be as if you chew up a key and damage the key or the key way slot then it would be difficult to remove the key. I suspect tapping the key in the direction of the crankcase wall, the key naturally gets pushed up at that curved sloped angle. The with screwdriver and needle nose vise-grip type remove the worn key.

 

[curtisfox]

I think it was Fasteddy said the reason for the carved slope shape on the Briggs crankshafts inboard end of the key way slot, is for removal of keys that might get stuck. I though could be as if you chew up a key and damage the key or the key way slot then it would be difficult to remove the key. I suspect tapping the key in the direction of the crankcase wall, the key naturally gets pushed up at that curved sloped angle. The with screwdriver and needle nose vise-grip type remove the worn key.


I think the real reason is because they us a rotary cutter, and can only get so close with it. All do to automation,and modern machining ............Curt

 

[scratchbuilder]

Yep..the next build I'll get everything right....wrong! I agree I've got my eye out for another engine. I'm gonna put the 3.5 crank back where it goes...maybe a belt drive. I don't want to set in on the shelf not right.

 

[curtisfox]

Can always put the clutch on a jack shaft......................Curt

 

[MEASURE TWICE]

That is what I did, but lost one of the mechanical advantage of one pair sprockets small to large to gear down. Not a problem now since I found this replacement engine doing just fine at a 13:1 ratio instead of 20:1 ratio.

As far as a 1/2 inch key length I think it won't shear unless maybe hit a log, but then there is a problem as the front wheel would probably also crumble.

 

[MEASURE TWICE]

My new clutch works great. There are 13 teeth on this new Max Torque clutch instead of like my older clutch with 12 teeth.

Now my Overall Ratio is 12:1 instead of 13:1 on to a 26 inch rear wheel, but still the engine handles it really well and start very easy always.

Looking forward to trail ride and explore soon.