My build.

KMI, I have a multiple jack shaft that is for parade speed and with 40:1 ratio belt drive. Alternately I take off a cover and remove a 10 inch pulley and put a smaller one in its place. I expect about 20:1 ratio for OHV dirt biking with that change over.

I am first hearing of springs replacement that can get a much lower rpm clutch engagement that was better than what I heard for the Max Torque Belt Clutch I got. I was told what the one I bought I could not opt for a lower rpm range, but buy them later to be installed by myself.

With that the difference was from original 2000 rpm to 2200 rpm and then it would lower to like I think was told would be 1800 rpm to 2000 rpm. This would not be enough to make a noticeable difference on my Briggs 80202 0430 3hp 4 stroke side shaft 70’s era engine. It is supposed to idle around 1750 rpm and max out at around 3500 rpm.

I looked at some other brands besides HillardCorp Brand you mention in this thread. I saw still only 1800, but another Noramclutch 750 lowest from someone. Maybe it was you mentioning this and it was a hit!

The only trouble there was having to shell out money and have a left over belt clutch. Since I have such a radical reduction, I think I can get by OK as is. Also there clutches seem to be limited to shaft bore size ¾ inch and 1 inch and I need 5/8 inch bore and to keep expense down.

http://www.noramclutch.com/centrifugal-clutch/1600-sp3.html.

Test riding I am also in the same situation with some things needing some more tending to. I fixed the slipping of the twist grip throttle. The replaceable grip slipped when the heavy return spring pulled back on it. I got some good information as I saw on a TV show for kids how BMX bikes are made and assembled. They used hair spray to glue it. A friend was going to a dollar store anyway and so I said I’d pay him to get a can for me. Turns out I owe him a few oranges from my dwarf Valencia Orange tree next summer for payment.

I have to modify the dual jackshafts to allow for tensioning the belt between the upper and lower jackshafts. A few recent test rides were fun, but slipping on 1 of the 3 belts was way too much to be acceptable. I was hoping there would be enough friction with a belt I got and just pop it on. I ended up with the Link-Belt (section type belt). I know I can take links out to get the belt tighter when it stretches some. The problem is that the links are not so short that a fine degree of adjustment can be had. This means at some point adjustment by taking a link out of the belt make it so tight the links fray so much and deteriorate. Also sometimes the belt twists and will not pop onto the pulleys.

The friction attained on these section type belts also seem to not have quite the same surface area in contact with the pulleys I am guessing and I am now in the market for between 17 inches and 18 inches regular heavy duty v-belt.

I already know what I have to do to make a slotted mount for the bottom jackshaft where I will have clearance available to tension the belt. I'm waiting out the storms in NORCAL to get time to work on it. Dang the windy times are always night to early am or I would be out windsurfing!

MT

http://motorbicycling.com/showthread.php?t=29678

I understand more about your situation after I just read some of the posts in this thread again. I have a Briggs 5S and also 6S that are around that 1.5 hp rating and idle really slow. I never had experience using a centrifugal or even a manual clutch with those engines on a motor bike because before I just went direct belt drive and chugged from a start. Stopping motor bike then meant the engine jerked a little bit when you stopped but was not super annoying.

The rpm range / horsepower / torque on those old cast iron Briggs engines I have would probably be comparable to your Clinton engine.

I know that you have another motor bike already built and tested in some thread here that I think also has similar qualities with regards to rpm range / horsepower / torque. That one I remember I heard you say that you use a manual clutch that uses a belt idler that tensions up to engage the engine.

The new clutch your are working to change the springs to get engaging rpm range up higher in otherwise similar conditions, I say would equate to more torque and the engine hopefully will not be stalling out as your previous clutch had done. Also it could start and idle needless to say.

In comparison to your other bike with manual clutch and similar conditions otherwise stalling out should not happen for the fact that you carefully exercise caution when engaging the manual clutch and the new centrifugal clutch should act the same and work.

If I got it right, your prior clutch probably engages at 800 rpm to 1000 rpm. Your engine idle is possibly right in that range if I got that right.

I did some calculations for speed range for what you have. I used the rpm range 1200 rpm to 2400 rpm. Ratio looked to be 8:1 and wheel size, I expect you have are 26 inch wheels. I got 11 mph to 31 mph with only those parameters which other things to consider would make this a just crude estimate.

If need be a larger pulley on the jackshaft you could do as I did if necessary. I would only add that if a pulley as large 10 inches as I have use in that place is ever used, you have to put a cover over it for safety. I really would say it is best for safety to put covers over pretty much everything. I expect I am doing that except for rear wheel drive pulley. I failed for approval for art vehicle not due to safety, but my depiction of art cover was not enough cover to hide the motor bike I had to rethink the covering.

My situation in comparison:

In my situation, I was thinking that for parade speeds I could have either the newer Briggs of mine or the Older Briggs using a clutch that engages at a lower rpm, but never really thought about it such that starting the engine would be a problem like you have found out. This helps me understand more of what to consider for any future build I make. I also have this old cast iron belt clutch that was on one of the older Briggs and never tested out what kind of rpm range it engages at. I think I might see if I can make with my electronic junk lying around an rpm meter or see if there are those mechanical ones that are for cheap.

I think your motor bike has what I previously I had before an 8:1 ratio. I tried my 3.5 Briggs 808202 0430 70’s era engine on my motor bike with an 8:1 ratio and here is what happened with it. I start the engine an idled around 1750 rpm no problem. Then I guess I was trying to bring idle up to 2000 rpm to 2200 rpm and that is where it was suppose to go through the start of engagement to fully engagement.

The engine did not stall but I heard the clutch shoes scraping the bell at the some rpm range whatever it was and I was only creeping along. I then just put it max throttle and the engine never hesitated. The scraping continued and I slowly accelerated to about 15 mph. The scraping never really stopped and I was not prepared to go any faster where I was testing it. The scraping may have gone down a little when I got up to 15mph and maybe it would have stopped all together if I got going faster but as I said it was not the right place to try that.

To fix the problem I figured I would gear down way more as I was going to do that anyway so I could go under 5 mph for parade speed. Alternately I would have a gearing down but not as much so I could do dirt biking speed. Now that I have gotten to changing to 5 times a lower ratio with this 40:1 ratio, the testing went fine except now I have one of the belts slipping and need to modify one of the two jack shafts to be able to tension up the belt and not by using a section type belt and removing a link or two.

Now it occurs to me that it may have been the new clutch and the shoes wearing in. I don’t know if that is a possibility if the manufacturer really never wears them in and then tests the clutch or that they just see that the shoes move enough to figure it is a good clutch and ready it to ship out. You have a breaking period and have to deal with that? In combination with a new untested design, that can be daunting.

With both the Briggs 5S and also a 70’s era higher revving 2hp engine I think I may have at times in the past tried starting those direct drive motor bikes with someone holding the rear wheel off the ground while I started engine with the recoil starter.

Then with the engine going and the rear wheel is spinning while being held up off the ground by me or an assistant here is what I attempted. If in a somewhat precarious situation here, I tried to hop on the bike and at the same time let the rear wheel hit the ground and expected to be starting to accelerate out on the motor bike, I remember doing this and it would just plain stall out. There was not enough torque and no I did not see the front wheel try to pop a wheelie before the engine stalled.

I stopped trying this approach immediately as I remember and ended up not using a rope pull anymore. Instead I just pushed with both feet straddling the banana seat and this being after the engine was warm, just once or twice worked out perfect. Just about 2 feet forward with a push and I was chugging at a below idle speed starting out.

I hope you can get the bugs worked out before snow fall and it works great for you.

Ya know a heated garage is dream for me, so while it is a mild winter in NORCAL compared with where you are, I opt to windsurf the storm winds if they arrive during daylight hours. Prey for wind!

MT

I suddenly have the urge to go get a classic coke, looks good , well done.

Kestrel Motors Inc. said:

Last set.

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Im all friction drive myself..but that is a nice build! I like the coke colors and its just all around a slick looking bike!

Kestrel Motors Inc. said:

Thanks RR. MT, the only reason that my clutch engages so early is I tried to use springs that weren't meant for the cluch (I.E. springs I got from the hardware store that are WAY too weak). The original springs that were in my first clutch engages at 2500 RPM, it said so right on my box. The new clutch has springs that engage at 1200. Thanks! If I can get 30 out of this bike, I'll be happy, because I can always pedal to go faster eh?
Yes! The "scraping" of the shoes is exactly what my old clutch did, I tried to test it but couldn't get faster than a slow walk at full throttle. I'll keep you informed to what happens when my gear gets here.

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Maybe I'm wrong but I'm still fairly certain that you need to lower your gearing also. As I said earlier your primary drive sprocket and primary jackshaft sprocket look the same size, so you are relying on your secondary drive to reduce your gearing.

If you look at some other bikes with stationary engines that the primary drive belt or sprocket are considerably smaller then the primary jackshaft belt or sprocket.

You may need to change your springs but having too high a gear is like taking off in a car in 2nd or 3rd gear and would cause the bike to be slower like you were describing.

Have you gone to the DIY section "Gear Calculator" and entered your sprocket and pulley sizes? I'm not 100% certain (other members may have a better idea) but I'm guessing you want around a 10:1 reduction. Hope that helps

Although changing the primary jackshaft sprocket size would change the RPM on the clitch and therefore effect which springs are needed O_O

harry76 said:

Although changing the primary jackshaft sprocket size would change the RPM on the clitch and therefore effect which springs are needed O_O

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The RPM out of the engine will stay the same, only the RPM at the jack shaft will change and of course at the wheel it will change.

dracothered said:

The RPM out of the engine will stay the same, only the RPM at the jack shaft will change and of course at the wheel it will change.

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Yes thats what i was saying, The RPM at the motor will stay the same, obviously, but the RPM at the jackshaft will change, therefore the RPM where the clutch will operate will change therefore new springs may be needed.

Oops my mistake, for some reason I thought Kestrel had the clutch mounted on the jackshaft O_O........ Well that makes for an easy fix, and I'm guessing you definitely need to lower your gearing. A bigger sprocket and smaller pulley on the jackshaft will do the trick.

harry76 said:

Yes thats what i was saying, The RPM at the motor will stay the same, obviously, but the RPM at the jackshaft will change, therefore the RPM where the clutch will operate will change therefore new springs may be needed.

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His clutch is on the motor output shaft I believe. OOPS didn't your correction... hahaha

The ratio with the 20 teeth, 19 teeth, & 4 diameter, 16 diameter = around 6.7:1

With a 26 inch wheel then 14 mph at 1200 rpm to 37 mph at 3200 rpm.

Mind that this is the math only using the factors above, and the missing factors will only slow it down considering its on straight level ground.

You could just see how it rides if you have all other things fixed yet you were talking about.

If you look at my large pulley on my top (of the twin stacked jackshafts) jack shaft which is 10 inches diameter, that is what really does the most besides the 10 inch pulley on the rear wheel.

Cost wise the sprockets that are above 4 inches in diameter that are solid made just sky rocket. If you can find some way of using one of those steel mini-bike or go-kart large 10inch sprockets and for less than the heavy cast iron ones that I see on Grainger for close to 200 dollars, you could try that.

It was the figuring out how to get the 5/8 bore with a key way on the flat steel sprocket so it would mount on the 5/8 jackshaft and key way, that eventually had me switching my clutch to a belt type as a large washing machine pulley I already had. It had a larger bore, but I went to Yard Birds Lawn Mower Shop and for around 27 dollars got a 10 inch A section Vee Belt type pulley and that is what I have now.

The safety factor of the larger sprocket or pulley right by my leg and thigh meant that a cover was necessary before I ever even tested it out. I used some old bowls and coupled them together, melding into a single cover over both the centrifugal clutch and the large pulley in line with it on the jackshaft. It sort of looks pretty ugly as I didn’t have a torch welder and the thinner metal does not weld well with my MIG even on lowest setting, but it is plenty strong. I stood on it before installing it and it holds up. I’ll add fiber glass and epoxy resin and paint over at some point if I care about the looks, but it is first I am covering the whole bike to go the Art Fish Fabric Cover for parades. For the alternate use, I can dirt bike when I swap the 10 inch pulley for a 5 inch pulley if I care for a little more speed. My build on the top to bottom jack shaft very short belt, has a 2:1 ratio so over all it will be a drop of 40:1 ratio to about 20:1 ratio.

6.7:1 ratio you have, if not expecting to be used for 5 mph an under at parade speed is quite close to a bike I built long ago with 24 inch wheels. The 8:1 ratio with a 2hp Briggs I used direct belt drive and no clutch at all and did some great fun riding in the woods. Sure it would stall out if I tried to go up a steep hill if without a long run up of 75 feet, but that was what I looked for and sailed off the crest of a hill and heard the rear wheel at least one of those times clear the ground and the engine speed up without the load. Then back on the ground a puff of dust and the engine lowered its rpm!

MT

Hey MT, love your creative problem solving, not bogged down in convention, or enslaved by fashions. I love it, just great. Its in a catagory of its own.....it doesnt ask for permission or make excuses...it just 'IS'. Maybe its Design-Freestyle. I look forward to seing more of your creativity. Thanks.

How is the connections made along the path of the corrugated muffler pipe. The tail section how was that made too, it looks real cool!

I see you have a link type belt and I have had problems with my first experience with them and thought they could only be good used for small loads like an alternator or such. I also have seen in the Grainger store a demonstration stand where with this other brand Power Twist Plus from Fenner Drives, has most likely a better grip and that their product may be a more suitable link type belt for my application. I have not yet tried it at home yet, but will soon.

With their installation instructions for Power Twist Plus, there is a minimum 3” diameter pulley requirement.

Maybe that is what I was doing wrong with the other brand Accu-Link, but I had not seen this mentioned on their product.

For one of the 3 belts I use, I will still probably go with a regular belt since the pulley is 2 inches diameter.

Second, Power Twist Plus mentions that there is a direction of rotation that should be observed when installing their belt. The part that goes through to the bottom of the belt where it is angled and should point away from direction of rotation should be noted. See Pdf file instruction and the picture I took of this specific. (sort of like feather on an arrow or like the wind barbs that show direction and speed on weather pages)

When looking at how the direction of rotation would affect the links staying tight together, it does make senses to observe this installation.

http://www.fennerdrives.com/FetchFile.ashx?id=ce1b86b2-9b28-4295-808e-89adff81c351

I have got what I think is a better type of A section Vee-belt that you can add and remove links. The Power Twist Plus. The cost is about 2 to 3 times as much, but I was going to switch to regular A section Vee-belt anyway. I still may just keep the Power Twist Plus belt for emergency where in much less time swapping in a broken belt would be easier, especially in inclement conditions.

I used Accu-Link and they were popping apart under the stress I put the belt under to get slipping to stop. The Power Twist Plus seems to grip well with less tension and does seem sturdier where the links do not seem to come apart and or fray. There is less stretch with this brand I feel.

The Accu-Link
http://www.jasonindustrial.com/Products/index.cfm?ID=6&Type=Product

The Power Twist Plus
http://www.fennerdrives.com/powertwist-plus/_/PowerTwist-Plus-A/13/4L/

Hey KM, Haven't heard from you for a while. You have been on this project for a good bit of time and I'm glad to see it finally coming together. It's a BAD A** bike bro, GREAT JOB.
fatdaddy. AKA Big Red.