Adapting Briggs Build to accept bigger engine

Discussion in 'DIY Home Built Motorized Bicycle (non kit)' started by MEASURE TWICE, Aug 6, 2016.

  1. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    Last week I adjusted the intake valve lash that was out of tolerance. Gap between tappet and valve stem on the intake valve was 0.0015 inches.

    The intake specification is to be between 0.005 inches and 0.007 inches.

    With grinding the valve stem a bit with sand paper on a porcelain hard surface, I got it level ground after seeing I was going on a tilt at first. Also lapped both intake and exhaust valves in there seats and the result I ended up on target was 0.006 inches in the center or the range for the intake specification.

    Saturday was out at Mendocino National Forest again at another location Stonyford. There was for Sunday a Enduro event and left although maybe trails would have some open not for the event. I was also maybe interested in watching, but they said there was not really much any place to see except a few areas. Also weather was supposed to have rain again, but it was clear.

    As for my bike not restarting after it was run hard and got hot, this was not happening anymore and worked flawlessly. Only thing the area had also lots of rocky trails and dirt roads, so I found a few paved roads for short distance they allowed, but they are not that interesting. The mud puddles I usually avoided if I could, but near leaving time I went few times right through the center of deep mud puddles. These ones differed from think viscous mud type I had done before. There was maybe 3 inches of water and they 3 inches of viscous stuff underneath.

    The past ones I rode through years ago had maybe 5 inches of viscous mud and if you turned the handle bars your sure to take a spill. I did not do that then or this time either. The bike is only 3.5 hp and no match for the very powerful trail bikes there.

    Not very many people see a home made trail bike so quite a few people ask questions what is this. I though one person said something who was with a group of people that saw me riding there, it was this one person that said something like about finishing riding or being there the next day in the Enduro event. Only later I though maybe he was feeling I should have been going faster.

    Going around banked turns and through mud as well as large rocky surfaces, I can't do as well as more powerful trail bikes. Those bikes have tire width 3 times that of mine.

    I had good fun riding and the next day cleaned my riding gear some covered in mud. The bike I will clean some later, but though I did only pay 5 dollars to camp, the riding is paid by my 2 year OHV registration, and I got free under coating on my bike.

    I have to shim my helmet cam mount it is at the maximum to point upward, but it misses seeing a lot higher up in view. I guess I am leaning forward and my helmet may be pointed down some. My eyes are looking up and I thought it was going to get good movies.

    Maybe I will get that fixed soon, but I will get a link from Vimeo for an upload I am about to do of that road scene where I open the throttle up.

    You will not see video here, just see it at Vimeo site.
    When you click on the blue area "Watch on Vimeo you will see video.

     

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    #61 MEASURE TWICE, Nov 13, 2017
    Last edited: Nov 13, 2017
  2. curtisfox

    curtisfox Well-Known Member

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    I knew you had something wrong, glad you got it fixed.................Curt
     
    #62 curtisfox, Nov 13, 2017
    Last edited: Nov 14, 2017
  3. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    I have the other 3 hp Briggs that I also had the same problem with restarting when engine is hot. But also the older 3ph Briggs had also sized up for a little while so that is multiple problems maybe. I have not cracked the case to pull piston out and check it and cylinder. When I do I have 3 old rings that I took out of it as soon as I bought it years ago not running.

    Those old rings might not be as bad as what I might find in there now. New rings I put in way back when, but it may have been low oil and hard use that messed things up bad.
    As you know I save everything almost. So for cheap I may just see what they do.

    Also for cheap on Ebay a seller named "Saved from Scrap" I got new old stock intake valve in the original carton by Briggs.

    It would be good as a backup engine and I can get much lower ratio than 12:1 with the setup as the crankshaft is long enough to have a clutch on it. I have also saved the parts I used before in the dual jackshaft power train. I used to use with 20:1 with it for trails.

    As well in the past tried 35:1 that was to be used for parades when I dress it up as fish. Just to test it out an to see what would happen and yep I had about 5 mph top speed.

    One thing that got me about the old 3hp Briggs was that the intake valve gap on that I put into specification and still the intake valve was not closed until about 1/2 to 1/3 the way up the compression stroke.

    Conversely what I saw on this 3.5 Briggs engine was that the intake valve when adjusted to specifications was at about 1/5 to 1/6 the was up the compression stroke as I estimate.

    Since I have an extra intake valve I may just take the stem tip down to what I feel is right. By that I mean adjust it where the compression stroke has the intake closing similar as on the 3.5 hp Briggs engine at 1/5 to 1/6 the way up the compression stroke.

    Basically ignore the valve gap specification as I can use the other saved extra intake valve to go back to the specification if I find necessary. Maybe the tappet or the cam has something wrong. I won't start grinding any valve yet until I inspect as much as I can.
     
    #63 MEASURE TWICE, Nov 13, 2017
    Last edited: Nov 13, 2017
  4. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    Now one thing I did after riding it a bit in mud and needed cleaning, cleaned the sheave and the v-belt and the pulley on the jachshaft. The chain also lubed and the bronze bushing on the clutch lubed too.

    I looked at the weld or braze butt joint that was done on the sheave at the seam in the manufacturing process that they did not grind smooth very well. I got it in the mail and did a little sanding and filing to smooth it out a few years back.

    What I just confirmed was that when the seam area of the sheave gets to meeting up with the belt as the wheel turns the belt bike rolling resistance for the rear wheel is a bit more.

    When inspecting I noticed that what I thought needed only grinding down some to protect the belt from getting abraded, was not just that.

    It seems this is just generally when there is some dust and or water on the sheave that I feel the bike sort of pulsing kind of power going on. This even when the throttle it not changing.

    If there is a lot of torque going up hill or accelerating it is more pronounced.

    I would like to grind it so that there is the same path width and depth for the belt at this point where they had to join the sheave in a circle. If I do, I was afraid it might crack the way they did what ever they did with weld or brazing. Since I have a MIG Welder, I thought I would grind it down and if I see a gap or crack, I just add some more weld and grind it down.

    Just to grind it down and keep the same continuous groove in the sheave could become a difficult task. I suppose sending 50 buck as opposed to 100 or more buck could have made the difference.

    For a moment I had thought that the sheave could have cracked on one half side and still was working but badly with the same feel. Ask me how I know.

    Yep when I was looking to make my own sheave from pressed stamped steel washing machine pulley as I did back in the 70's, but could not find those, I resorted to today's white metal (aluminum pot metal).

    Past about 3 years now I went through 2 of them and had ridden about 10 miles total on couple of off road rides until I was sitting and eating lunch and saw day light through the crack.

    The sheave the way they make the clones of the Whizzer Sheaves, is such you really can't put it on out of round (centered).

    The clamps just go on at a certain distance from the rim and that is that. I got out a ruler and measured the distance from the top edge of the sheave channel to the axle circumference and it only varied between a 32nd and a 64th of an inch.

    So anyone have made up a jig to use a Dremel to carve a perfect channel on a round surface after welding a butt joint on a Whizzer Clone Sheave made crumily?
     
    #64 MEASURE TWICE, Nov 21, 2017
    Last edited: Nov 21, 2017
  5. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    lowres1122171509d_Film1.jpg

    I do understand what Curtisfox made me more aware of, in how a grooved serpentine pulley has more grabbing power not to slip. Better idea than maybe two sheaves (left and right of rear wheel) that have each a belt to a jackshaft that I was thinking of beside just using a chain with sprocket instead.

    I understand it is not the bottom in the V-belt as also in the Serpentine Belt that grabs. It is the walls of the groove in the pulleys. The serpentine groove has at least 3 or 4 grooves or more I have seen.

    I probably first will attempt to grind away a bit of the blob I think that the manufacturer of the Whizzer Clone sheave left. If it cracks I I would remove the sheave and make a jig to hold it so less chance warping.

    When I widened the rear drop out for the wider profile of the manufactured sheave to my own washing machine pulley set up, which fit without widening, I welded first then ground afterward. This meant that after I would carve away just enough to have the space needed. The jig was actually the frame itself.

    What was nice was that I never completely cut anything. Nothing warped.

    Also when I put on my thinking cap, I was deciphering what it could be that makes it maybe grab less when this blob is on the 12 and 6 o'clock position in rotation, but at the same time has then belt under more tension, if I have that right.

    I sort of think that it raises up the belt just enough so it comes out of the groove and less inside belt wall grabbing on the sheave. The 6 O'clock position maybe not as much slipping as I think the top of then belt has more tension under-load.

    I expect even once done making the sheave to what shape it ought to be, I guess as now I am venturing into new areas to ride in the wilderness and have had a hard time finding places that are not as steep there will be other issues.

    It is ever becoming evident that my bike is going to become limited by more than slipping or intermittently grabbing belt.

    The engine power limit, no gears to shift, only so so front shocks, upgrade brakes maybe etcetera.

    But check out what I found in the boonies. Maybe I find a second of these tank tread rollers from a small Caterpillar, refurbish them and add all the rest plus skis. The single roller probably weighs 25 lbs. Maybe from a small tractor with treads to clear narrow trails. The part was probably broken onsite repaired and left behind as scrap? Joking though about the part as it is a bit to heavy gauge.
     
    #65 MEASURE TWICE, Nov 23, 2017
    Last edited: Nov 23, 2017
  6. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    I replaced two chains on my bike which has no pedals. Just these two chain and a belt for the small ohv motorcycle. One is about 3 feet in length and the other about 1.5 feet in length. The 3 foot section looks to be stretched about two thirds the width of the solid pin in the chain assembly. The half link (offset link) is not part of where I made a mark with twist tie for cutting the regular #35 chain. The 1.5 foot section looks like to be one half the width of the solid pin in the chain assembly. This section I don't need the half link as I have enough adjustment. The new chain I'll be inspecting each time I take the cover off to oil the bronze bushing on the centrifugal clutch which is about every 6 hours of engine time. Even while I am idling the 3 foot section of chain is always in motion. It gets a work out. If the engine had a longer shaft the clutch could on it, but now the clutch must ride on the first jackshaft. After the engine climbs rpm from 1750 to 2000, then second jackshaft starts spinning. CAM39176.jpg CAM39256.jpg
     
  7. curtisfox

    curtisfox Well-Known Member

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    How is it running now? maybe to cold............Curt
     
  8. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    I will get pictures in the snow again soon as I just was out yesterday. Next time some videos. At 40 degrees it has more power I would think. You know denser charge. In any case the valve (intake adjusted), I know helped the engine power a lot and not starting again that ended a few times out prior to the last. I did grind but, gently and checking often grinding with Dremel disk, smooth the inside of the sheave on the rear wheel where that damn bump from the weld seam. That was left from the manufacturer of the Cloned Whizzer mid 40 dollar part I bout 2 to 3 years ago, should have done this grinding way back then. Sanding originally just helped the belt not get cut. The bump even though smooth was causing slippage and surging of power when a lot of torque applied up hills and acceleration. Now it is just bad $%^& up hills and restarts no problem, even many times without the primer bulb. Steeper hill climbed with ease when I thought it would not.
     
  9. curtisfox

    curtisfox Well-Known Member

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    Good to here, more fun when all is working right.........Curt
     
  10. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    There is a difference when you go up the mountain. My turn around point.
     

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  11. Dan

    Dan Staff
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    Fun read, MT.

    Thanks for posting
     
  12. Tony01

    Tony01 Active Member

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    nice. I ran a 13:1 with the briggs as low gear once. It'll climb pretty good. advance the timing around 3-4deg, gives it a little edge.
     
  13. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    20:1 is what I had before with the 3hp Briggs. When I get to it and refurb the 3hp I can swap the 3.5 Briggs out and have the 20:1 again. Another thread for the refurb of the 3hp Briggs to be. It is cold below freezing and day time only like 40, some times 50. Maybe work in the wash room with the orange tree as an inspector. I have to get a mask to cover what goggles and the full helmet don't keep warm when riding. Neck up to cheeks get frozen while riding in this weather. There is every day frost and ice, but probably will have snow at 3000 feet at some point.
     
  14. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    Outback.
     

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  15. MEASURE TWICE

    MEASURE TWICE Well-Known Member

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    Some side trails are just as good as the main, no kick stand required.
     

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