Now I have a 79cc Harbor Freight 4-stroke. Next step please?

[Nehmo]

I bought the Predator 79cc Harbor Freight 4-stroke engine from the brick & mortar HF here in Kansas City . They were out of 99ccs, which appear to be the same engine except for bore & stroke, and I was satisfied with the smaller 79cc because that seems like an adequate displacement for my ambitions, and the less noise, the better. I paid total $90, using a 20% off coupon and a tax resale number.
I have a rack to mount the engine behind the seat post and above the rear wheel. I'm currently planing on using a 29" Walmart Deception.

My next need is a centrifugal clutch.
To me, it seems a centrifugal clutch with a small pulley (1.5-2 inch?) with its belt going straight to a very large pulley (maybe the size of the rim of the 26” wheel, which is 21.5") would work and give something near a 12:1 ratio. But nobody seems to use that arrangement, so there’s probably a reason.
I’d prefer belts to chain, but what’s the suggestions at this point? The pre-made jack-shaft (like http://www.affordablegokarts.com/mm...&Product_Code=2600&Category_Code=99cc)systems seem a little pricey for what they are.

Anyway, for you experienced builders, do you have any suggestions?
For starters, what are the clutch suggestions?

 

[Artificer161]

It’s a nice looking engine I wish I knew the answers to your questions. Good luck and I will be watching this build closely.

 

[Rocky_Motor]

I don't think you're going to fit that engine into that bike. Not to mention that most members here won't recommend aluminum, especially with a heavy torquey motor like those. It's your safety though, up to you.

There are tons of builds using this engine. The 99cc is not out of stock, it has been discontinued. Performance wise, I think the box claims the 79cc to have the same HP as the 99cc. I believe it is also the same size.

Take a look through past builds and you may find answers.

http://www.google.com/cse?cx=partne...4j13#gsc.tab=0&gsc.q=99cc predator&gsc.page=1

Good luck though, you can have a real fun and dependable bike after all is said and done

 

[bairdco]

Now I have a 79cc Harbor Freight 4-stroke. Next step please?

you can use it to wash your car, paint your house, for an air compressor...

(sorry. two stroke vs. four stroke jokes...)

 

[professor]

Nehmo, I have a 79 engine on my frame mount bike.
Great engine but I did open the main jet a tad. (All the engines now are too lean because of the stupid epa.)
For a rack mount, the engine is heavy, but it can be done (IF you do no drilling in the frame you probably will be OK, but I would rather see you with a steel frame like a Jaguar bike).
What I don't like about the rack idea is the engine is unprotected during a fall and it is weight offseted to one side and easily falls over with a heavy motor like the 79.

One of the guys here (Lowracer) attaches another bike rim to his wheel as a pulley- great idea- and drives it right off the engine with a cent. clutch. I love belts to drive stuff.
A rear disc brake would be great because the rear section of the frame needs to be able to clear the xtra pulley in that zone, but you can use a narrow wheel for a pulley like he does.
See if you can search older posts by Lowracer for his rim attachment method.

 

[shwnrttr]

I bought the Predator 79cc Harbor Freight 4-stroke engine from the brick & mortar HF here in Kansas City . They were out of 99ccs, which appear to be the same engine except for bore & stroke, and I was satisfied with the smaller 79cc because that seems like an adequate displacement for my ambitions, and the less noise, the better. I paid total $90, using a 20% off coupon and a tax resale number.
I have a rack to mount the engine behind the seat post and above the rear wheel. I'm currently planing on using a 29" Walmart Deception.

My next need is a centrifugal clutch.
To me, it seems a centrifugal clutch with a small pulley (1.5-2 inch?) with its belt going straight to a very large pulley (maybe the size of the rim of the 26” wheel, which is 21.5") would work and give something near a 12:1 ratio. But nobody seems to use that arrangement, so there’s probably a reason.
I’d prefer belts to chain, but what’s the suggestions at this point? The pre-made jack-shaft (like http://www.affordablegokarts.com/mm...&Product_Code=2600&Category_Code=99cc)systems seem a little pricey for what they are.

Anyway, for you experienced builders, do you have any suggestions?
For starters, what are the clutch suggestions?

if you have some room on your rack mount. you could mabee use two pillow block bearings like these http://www.thebigbearingstore.com/servlet/the-4/5-fdsh-8"-Pillow-Block-Bearing/Detail.
then just buy a shaft clutch and sprockets separate. i also recommend using the clutch that agk sells.

 

[Nehmo]

Nehmo, I have a 79 engine on my frame mount bike.
...
For a rack mount, the engine is heavy, but it can be done (IF you do no drilling in the frame you probably will be OK, but I would rather see you with a steel frame like a Jaguar bike).
What I don't like about the rack idea is the engine is unprotected during a fall and it is weight offseted to one side and easily falls over with a heavy motor like the 79.

Good advice. I'll have to protect the engine from the bike falling over. But I'll work on that last.

One of the guys here (Lowracer) attaches another bike rim to his wheel as a pulley- great idea- and drives it right off the engine with a cent. clutch. I love belts to drive stuff.

Lowracer posted a bunch. To save me some searching, can you point to (the URL of) the post in particular?

A rear disc brake would be great because the rear section of the frame needs to be able to clear the xtra pulley in that zone, but you can use a narrow wheel for a pulley like he does.

I'll like to keep the rear disc brake and have a pulley on the same side. I've seen some sprocket arrangements that keep the disc, the Top Hat, for example.

See if you can search older posts by Lowracer for his rim attachment method.

 

[calvynandhobbs]

Lowracer posted a bunch. To save me some searching, can you point to (the URL of) the post in particular?

I had this one bookmarked. I've got a 99cc predator that I'm debating on how I want to mount it and have been thinking about this. Also have a CVT, both brand new and haven't even opened the box. Debating now if I'm going to do anything with them or sell them since my 2 stroker is going strong and I really don't need two.

http://www.motoredbikes.com/showthread.php?31691-How-to-make-a-V-belt-drive-sheave

 

[Nehmo]

...I've got a 99cc predator that I'm debating on how I want to mount it and have been thinking about this. Also have a CVT,..http://www.motoredbikes.com/showthread.php?31691-How-to-make-a-V-belt-drive-sheave

Lowrider uses 2 Part Epoxy (JB weld) to simply attach a spokeless hoop from a rim to the rim of the rear wheel of the same diameter.
At this point, I'm considering something a bit different. The bike has 29" wheels.
(First, I'll see if pre-made sheave are available. I've seen large pulleys on blowers. A possibility.)

I'll use a 26" spokeless-hoop from an old rim and attach it to a 29" wheel by drilling holes to accommodate the spokes.
With a vice and a drill press I can drill over-size holes going roughly radially in the right side of spokeless-hoop.
I will then, using the 29" rim of the rear wheel, remove the spokes on the left side of the wheel, thread them through the holes in the spokeless-hoop, and re-attach them to their places in the rim and hub of the wheel. The spokeless-hoop will now be attached to the rear wheel and the spokeless-hoop will function as a sheave for a belt.
I'll use a small pulley directly attached to a centrifugal clutch on the other end of the belt.
Here's a pic of something like the idea. This one uses bolts, nuts, and a plate to make the attachment.

I suppose I'm limited to using a centrifugal clutch. A manual one would be better, but I don't know where to get one and making one is problematic. Although many champion the arrangement, I don't like The idler-pulley-clutch. It would eat the belt, and anything else would take some work.
Can anybody direct me to where to get a centrifugal clutch with a small pulley?
Searching "centrifugal clutch 5/8 pulley" eBay, I get no results. The sprocket is much more common.
A 1.8 inch pulley to (what's called a) 26" rim (actually 21.5") hoop will give 12:1 ratio.

 

[wayne z]

The smallest belt clutch you can buy is a 3" from MFG supply
http://www.mfgsupply.com/gomini/gom...hutility/gominiclutchcometscp350/200181a.html

An idler clutch isn't very hard on the belt. Nearly every mower deck uses this set-up. I built one with an in'frame friction drive. The belt squeals a little when taking off from dead stop but if you help with the pedals it ain't bad at all. I put 300 miles on it with no noticable wear on the belt before I converted to a 2 speed.

 

[wayne z]

I think Lowracer epoxied the sheave rim on and followed up with machine screws. Just epoxy won't keep it on there.

 

[young grease monkey]

a rack mount bike will not handle well at all. i would go with an idler pulley clutch if i were you. and find a different bike to use, the deception is junk. i suggest finding a cruiser type bike on craigslist. i would not trust it above 20mph. i had one and it sucked, the front suspension is cr@p. it had decent brakes, not very good for discs.

 

[Nehmo]

The smallest belt clutch you can buy is a 3" from MFG supply
http://www.mfgsupply.com/gomini/gom...hutility/gominiclutchcometscp350/200181a.html

$76 plus is a lot.
Actually, going form a 5/8" shaft geared-down to a bike wheel is a simple enough job that any reasonably supplied mechanical shop should be able to scrap it together from stuff lying around. Unfortunately, although I used to literally live in one, I don't have access to one around here now.
Yes, I also searched&found the same clutch and decided against it. I figure I'm in a good-size American city, Kansas City. I should be able to just get a clutch locally and pay less. But now I'm debating centrifugal verses idle pulley manual.
Today, in my meanderings, I asked a few Mexican mechanics and body people where I could get a centrifugal clutch. Surprisingly, only one mechanic even knew what I was talking about. I used the English word for centrifugal, but I don't think my weak Spanish was the problem. I suppose mechanics, who've learned by experience with cars, don't encounter small engine clutches often.

An idler clutch isn't very hard on the belt. Nearly every mower deck uses this set-up. I built one with an in'frame friction drive. The belt squeals a little when taking off from dead stop but if you help with the pedals it ain't bad at all. I put 300 miles on it with no noticable wear on the belt before I converted to a 2 speed.

Today, I came upon a plastic wheelchair wheel.

I could remove the hard rubber tire, hand wheel, and center section, and I'd be left with a 22" plastic sheave that looks like it has good cross-section for a V-belt. It appears to be superior to a wide spokeless rim.

I'm designing ideas for a idler pulley clutch. I'm somewhat concerned about the slack belt jumping off the pulley. I have a 4 pulley (2 idlers + drive and driven) arrangement idea that would keep the belt tight, but maybe it's not necessary.

Another idea I'm toying with is using a rear wheel from a 16" bike plus enough of the frame to hold the axle of the wheel. I'll disable the freewheel by fixing the sprocket to the the wheel. I use the sprocket to drive a chain that goes to a lager sprocket on the rear wheel of the bike.

 

[Nehmo]

a rack mount bike will not handle well at all.

Yes, as a general policy, the center of gravity should be kept as low as possible, but I have plenty of experience carrying loads heaver than the 22 lbs (10 kg) engine. The handling isn't impaired much.
Actually, I'm more concerned about the lack of protection in that position. But I'm trying it anyway. I always can move the engine to a better suited position or bike later.

i would go with an idler pulley clutch if i were you.

I suppose I'm going to have to. The other threads on the subject don't provide an economical alternative - if I want a manual clutch.
I've never made one before, but it doesn't look daunting. I'm thinking on using a roller skate wheel for the idler tensioner. I presume I just mount one on a lever on the slack side (front, in this case of drive shaft on the left) of the belt and have the idler push the outside of the belt inward.
I use a spring to keep the belt tensioned and a control cable to loosen it.

and find a different bike to use, the deception is junk. i suggest finding a cruiser type bike on craigslist. i would not trust it above 20mph. i had one and it sucked, the front suspension is cr@p. it had decent brakes, not very good for discs.

I'm partial to 29" wheels, and I like disk brakes. The Deception is the cheapest with those qualities. But as it is, I need a new back wheel anyway (stolen; had quick-release), and the way these things are priced, I might as well get a whole new bike.

 

[professor]

I use an idler off an old riding mower- they come in various sizes. A roller skate wheel would need to have the tire section flat or removed. You then need a lever to disengage it- I use a HT clutch lever on both my bikes with this clutch set-up.
The one good thing about a rack mount is you need to remove nothing on the motor to fit it (unlike in the frame). But you will always be looking for a wall or post to lean it against.

 

[wayne z]

On both mine I used ball bearing mower belt idlers from NAPA. They're only about $8. come in several diameters. They are flat with slight flange on each side to keep the belt from wandering off.

 

[Nehmo]

I use an idler off an old riding mower- they come in various sizes. A roller skate wheel would need to have the tire section flat or removed. You then need a lever to disengage it- I use a HT clutch lever on both my bikes with this clutch set-up.
The one good thing about a rack mount is you need to remove nothing on the motor to fit it (unlike in the frame). But you will always be looking for a wall or post to lean it against.

• Idler pulley from riding mower
• Lever on which to mount the idler clutch
• Sheave 5/8" 1.5"-2.0" diameter
• Driven pulley, hoop from either bike or wheelchair
• Belt
• HT clutch lever
• Throttle linkage and control
• New rear wheel or entire new bike

I must say I feel fortunate to have the benefit of the experience of you and wayne z.

 

[Nehmo]

• Idler pulley from riding mower
  • I'll just buy this locally at a mower store. Does it matter what kind?
• Lever on which to mount the idler clutch
  • Make from hardware store metal
• Sheave on engine 5/8" hole and 1.5"-2.0" diameter
  • 1.75" diameter gives 12.5:1 using a 22" hoop on the wheel. They sell them at Ace hardware
• Driven pulley, hoop from either bike or wheelchair
  • a bike spokeless-rim seems a bit wide for a V belt, but does that matter? I previously was leaning toward using the wheelchair wheel rim, but that would be an experiment. Maybe I should just stick with what worked for other builders.
• Belt
  • The 1.75" motor pulley, which I'll get first, only takes a V belt. I usually get those at AutoZone. I'll make the drive and then measure with a string.
• HT clutch lever. Which one? Where should I get it?
• Throttle linkage and control
  • Suggestions?
• New rear wheel or entire new bike
  • Since I need a new rear wheel anyway, I might get another bike (if I can at a discount), but I don't like so-called beach cruisers. I like disk brakes and at least a front suspension and some gear ratios for non-engine travel.
    Actually, I do have a ezip step-through 26" steel frame. It's strong and could take a motor in the center. I'd need to do a lot (replace bottom bracket) to return it to running condition. I could use that frame I suppose.

I'll get the engine pulley and bike or wheel tomorrow if things go as planned.

 

[young grease monkey]

please use a different bike... you will be much happier down the road. get a cruiser with a coaster brake hub and 12ga spokes, shouldn't be hard to find on craigslist.

go to www.afforablegocarts.com, find the guide to modding the 99cc predator. it's all the same for the 79cc. remove the governor. you can buy their throttle linkage, or copy what i did:

http://s1244.photobucket.com/albums...tion=view&current=2012-08-19_21-21-21_228.jpg

i like my way. i twisted the throttle arm using pliers and a blow torch, then cut a slot in the end for the cable. of course, you will need springs. i also made a new link arm out of 3/32 music wire, you can use the stock one if you want. the length determines the progressive rate of the throttle.

 

[Nehmo]

please use a different bike... you will be much happier down the road. get a cruiser with a coaster brake hub and 12ga spokes, shouldn't be hard to find on craigslist.

I'm in Kansas City, and although viewed from the outside it looks like a comparatively large metro area, in terms of bike usage, it's a small town. On any street in Kansas City, Kansas, which is the part in which I live, you will see a thousand cars go by before you see one bike. In fact, on my own street, I've never seen a bike go by. What I'm saying is that the Craigslist bike pickings will be slim around here. I must rely on Walmart.
And even when I buy bikes from Walmart, I only buy the discounted ones (left out in the rain, etc.). I pretty much have to work with a limited number of options because I have a limited amount of $.

If the main issue is the spoke weakness, re-weaving a wheel with 12 gauge spokes is not beyond my abilities. But I'd have to order the spokes first, and I want to get this done soon.

go to www.afforablegocarts.com, find the guide to modding the 99cc predator. it's all the same for the 79cc. remove the governor.

By "modding" do you mean just removing the govenor? If you found it successful, then I'll probably do it, but for now I'll put off the tweaking until later. At this point, I'm going the direct route to getting something just going.

you can buy their throttle linkage, or copy what i did:

http://s1244.photobucket.com/albums...tion=view&current=2012-08-19_21-21-21_228.jpg
i like my way. i twisted the throttle arm using pliers and a blow torch, then cut a slot in the end for the cable. of course, you will need springs. i also made a new link arm out of 3/32 music wire, you can use the stock one if you want. the length determines the progressive rate of the throttle.

Where is your thread associated with that pic? And what hand control did you use?