In frame Predator fricton drive build

[wayne z]

Here's what I came up with for exhaust system. Still need to work on clamps some, and paint it.

Has a nice mellow tone, much quiter than the stock muffler, Has a nice motorbike sound.

I tried it without the muffler and it was LOUD but beautiful. Runs WAY better too, I saw 40 MPH rather quickly. Wind it up good and let off and get that funky statacco sound.




Don't wanna bug the neighbors or cops, so I put the muffler back on.

 

[wayne z]

Better try a test hole with that hole saw. My experience sometimes they make the hole oversized. You can dress the OD of the teeth by lightly turning the bit against the side of bench grinder wheel and testing again.

If yer drilling aluminum, the bits gonna clog with aluminum, you have to stop frequently and knock the buildup off with a screwdriver.

The best thing i have found to prevent aluminum buildup and cool the bit is plain ole Windex, works incredibly well .

 

[wayne z]

OK, Now that the exhaust is behind me, I could hear the noisy rockers real good, so I decided to check them.

The exhaust rocker was way loose. There is a compresson release bump in this cam, just before TDC and that is where the valve clearance was set by some chinaman.

I wanted quiet so I set the valves to the very minimun noted in the engine manual.

It was then very hard to start. The compression bump was kicking in too much, ang there wan't quite enough compresson for easy reliable starts.

So I re-set them to the max recomended in the manual, and now it starts easily again.

I don't fell comfortable with cams with bumps near tdc on compresson stroke. I feel like it's gotta reduce performance some. If I ever have it out, Im gonna take it down some.

The valve adjustment hardware is very sturdy and well machined. Takes a 14mm and 10mm wrenches

 

[cannonball2]

Yeah, my 79cc HF had massive clearances, sounded like a thrashing machine!. I noticed the exhaust release also. When I opened it up I expected something like a Briggs or Honda valve train. Wow, that thing is massive and the valves are angled too. Pretty impressive!

 

[WayneC]

WayneZ,

Great build! Is there any chance of getting a pants leg caught in that belt/pulley setup? Any plans for a shroud or guard? Also, did you use anything to insulate the motor from the mount; or is it just steel on steel? I'm thinking of using some rubber washers between the bottom of my HF79 and the mount. Just wondering if it's even necessary.
Thanks
WC

 

[wayne z]

Yes, I plan on adding a guard and other refinements after I finish tweaking things. Haven't had any trouble with pantsleg, though it is hazardous without a guard.

My engine runs very smooth with very little vibration at any rpm. I wouldn't bother with rubber in the mount.

 

[WayneC]

Thanks for the info. Minor setback for me. I just tried firing up the HF79 and couldn't keep him going unless fully choked. Then when a little warm it wouldn't even stay running that way. It's been properly stored in my shed and I used fresh gas and oil to start it so I'm guessing the carb passages are crusted up with dried fuelahol. Will have to pull the carb and clean before I get started on my project.
But thanks again!
WC

 

[MaxPower]

Will have to pull the carb and clean before I get started on my project.

Affordable go karts has a high preform-ace carb if you don't want to go through the trouble of cleaning. affordablegokarts: 79cc Parts

 

[wayne z]

Ok, here's an update on the Predator in frame fricton drive. I have over 100 miles on the odometer now. No problems at all. no noticable tire wear. very smooth and quiet. Did I say Fast? Seen a scary 38 mph many times. NO MESSY, FUSSY CHAIN LOL, Luvs to cruise 30-35 mph

This concept works well , the large dia roller is way more efficent than the usual small dia ones. And these lil motors just look right with the cyl foreward.

I am going to change it some by adding my freshly made 3.5 " knurled roller and a Maxtorque clutch on the engine, instead of the 3" clutch/roller on the jackshaft now. Here's my new roller.

 

[cannonball2]

Really, really nice Wayne!

 

[WayneC]

Whoa! That's some roller.
Good to hear things are going well with the bike.
WC

 

[wayne z]

Hi all, I've done some more r&d with the In frame fricton drive.
I installed the 3.5" knurled roller and a 4" jackshaft pulley. The roller is depressed into the tire 3/16".
I decided to try a manual belt clutch with a cable operated idler before I forked out the bux for a Maxtorque bearing clutch. I would be more in touch with roller slippage this way too. There is WAY less pedaling drag with the belt clutch and large roller than with the bushing clutch that I removed.

When I got it running, it was raining, so I got to try out wet performance.
The roller hardly slipped at all at first. but after about 10 miles, and the fresh burrs of the knurls wore down, i could detect a little slippage when i hit wet spots while accellerating.

Had no trouble pulling the steepest hills wet, didn't have to be too carefull with the throttle, with the efficency of the large roller.

Was geared a little tall, it still wanted to do about 38, but had trouble taking off from a dead stop. Lotta belt squealing while slipping it for speed enough to completely engage it without getting jerky power pulses or killing the engine.

[/ATTACH]
Still need to tweak it some . A slightly wider belt, and maybe a 4.5" pulley to drop the revs some to cruise at 30mph.

This drive train is very quiet. Never realised how much noise a chain makes.

I think that the larger rollers is the secret to a good, efficent fricton drive that doesn"t slip much or wear the tires so fast.
I can't wait to try a grinding wheel. With the large OD that equals less slippage, it may not wear the tires too bad dry, and grab real good wet.
Tires are cheap and easy anyways.

Dry use should be awesome with the 3.5" steel knurled roller though.

Sorry about the random spacing of the pix, :~)

 

[wayne z]

I forgot to mention something that baffeled me a while.

All the threaded holes around the pto are 5/16" SAE fine thread. All else is metric. Took me several trips to hdw store to figure it out LOL. Go figure.

 

[rustycase]

Great work, Wayne!

Are you going to stack 3 or 4 mini grinder disks for the new drive wheel?
They got em for both steel and masonry, different diameters, too.
Haven't a clue what might be best for this application, wet or dry, but they are sure cheap enough at HF.
rc

 

[scotto-]

I believe he is going to use a bench grinder wheel, not angle grinder wheels.....lol. Bench grinder wheels are for grinding steel, not bricks or concrete.

Great work, Wayne!

Are you going to stack 3 or 4 mini grinder disks for the new drive wheel?
They got em for both steel and masonry, different diameters, too.
Haven't a clue what might be best for this application, wet or dry, but they are sure cheap enough at HF.
rc

 

[cannonball2]

I forgot to mention something that baffeled me a while.

All the threaded holes around the pto are 5/16" SAE fine thread. All else is metric. Took me several trips to hdw store to figure it out LOL. Go figure.

Yeah thats kinda strange, I just retapped all the holes that were metric to SAE, Mine used a metric crank bolt that I felt too small, went to 1/4". Regarding roller size, on my Lifan/Schwinn I started with a 2.4" roller, had a wonderful top end of 38mph. Put my Tiny Tach on the ungoverned Lifan and found it would turn 5400 when fully wound out. But the 2.4" roller is not ideal in the world of hills where I live, really looses it on bigger hills. Pull offs required a lot of clutch slipping and pedaling, especially starting on an incline. So I went to a 2.2 " and its much better, lowered the top speed to around 33, but takes off and climbs much better. My governed Lifan runs a 2" and a 1.875". I pull the trailer with the 1.875 and even with the trailer it climbs exceptionally well. So my conclusion that for direct drive with a lift clutch 2.2" is the most "comfortable" all around roller, you guys in the flats got it made!

 

[WayneC]

Great info guys.
WayneZ - What made you decide to go with the even larger roller and jackshaft pulley? Are you looking to get higher top end speed or just experimenting? That seems like a really tall ratio for that engine. Looks like a neat setup tho.

One thing I was leery of when shopping for pulleys is those cast ones you're using. There were warnings on the labels noting for elec. motors only; not for gas engines. So I got steel. I don't know if the engine spins fast enough to destroy a cast pulley but it may have enough torque and power to do so. Call me overly cautious I guess. Keep an eye out for stress cracks starting.

2 questions on your build if I may: 1 What air filter are you using on the 79? I have one just like yours but the adapter I have won't work on this carb. 2- what size tubing are you using for the exhaust?
WC

 

[wayne z]

I went with the large roller for performance and efficency, not for gearing.
I am using the cheap pullies for now . They don't explode, they crack at thr keyway sometimes from the engine pulses. I think EZM, Stanton and others have used them successfully.
I am now using a 5" pulley on the jackshaft. It tops out at about 32mph. With the 4" pulley and the 3.5 roller it topped out at 38 mph.
Think I will try a 4.5" pulley to get a comfortable cruise rpm at 30mph

.My engine is not the 79cc It's the 99cc version



I had to severly modify the air filter adaptor to make it work. I bored out the inside some on the lathe, and shaved off about 1/4" from the face, to make it thinner so the original carb studs would be long enough.

Then I sawed notches from the stud holes of the adaptor so it would straddle the studs.

I had to ust flangeless nuts to bolt it on instead of thr original flanged ones. The flange nuts interfere with the air filter's socket.

I had to notch the rubber stop flange inside the airfilter a little , filled the adaptor notches with RTV. After curing, I clamped the filter on.

The exhaust pipe is 3/4" conduit. I packed the original exhaust manifold with sand and angle iron scraps on each end and used a torch to heat and bend it about 10 more deg. Also took some 3/8 rod with rounded and bent ends, and heated the manifold and worked some of the flatness out of the manifold bend ,from the inside.

I then sawed off the flange, and used a bench grinder, dial calipers and file to round and dress the manifold to fit snugly inside the conduit.
A standard 1/2" hotdog muffler fits snugly in the pipe, held on with a crossdrilled hole and a wire pin.

I have been looking at grinding wheels listed on E-bay. Never knew that there was so many types and sizes.
I'm lookin for a 2" wide by 3.5 dia. might use something narrower and stack them.

 

[rustycase]

Wayne, you had mentioned the kool sound of your straight pipe, without the muffler, but decided to run it to avoid undue attention, then got a power loss, of course... I was thinkin... again...

Perhaps you could try going to a larger diameter pipe for the long, straight run.
... a size pipe that same muffler will fit INTO...
Slip the muffler into the exhaust pipe and clamp it over it.

Also, I noticed the type muffler you are using. It has a flange halfway down it's length??? stuff it in the exhaust pipe to that point???

THEN, you could drill some holes in the rear section that is sticking out beyond the pipe, and put a sleeve over the muffler which could be rotated to allow those holes to release gases and back pressure when you are in an area where a bit more noise might be tolerable.

I saw it on a YouTube video... 'Don Hall tests a 1915 Indian' I think???
He showed the 'Town & Country exhaust' which he said, "Goes from Braap, Braap, Braap to Chitter, Chitter, Chitter, with the flip of a lever."

You had also mentioned a need for a wider belt?
I'm trying to understand the various belt sizes, and what might be common and inexpensive, for this application.
Does anyone know an information source that would explain "All about drive belts" ???

...You had noted that 3/16" pressure, of deflection to the tire applied by the roller seemed to work well all around, then had only a little trouble when wet, or going up a hill. Would it be possible to include a very small degree of adjustment to the drive roller pressure against the tire which could be made while going down the road??? Near as I can tell, we're only talking about an 1/8" travel necessary to make a significant difference in the drive capability???

Thanks for the GREAT thread!
Best
rc

 

[wayne z]

Hey RC, Thanks for the reply and the muffler ideas.

There's not that much power loss with the muffler, got more power than needed anyway. But that strait pipe sure sounds good.

I have an Kubota belt on there now. it rides way down in the pullies. A Napa belt will ride at the top edge of the pullies. Prolly take more abuse than the narrower belt too.

An adjustable roller in in the works, with a jackscrew and knob for control. just gotta work out the details.