HF 79cc with EZM clutch centermount build - how to gear lower

Attached are some pics of my build, from the ground up (kit wise !) - had mtn bike frame sandblasted, I painted with laquer base (suggest enamel base to others), most everything else is new - front forks, thudbuster seat post, etc.

This thing flies, the clutch is great. We have a lot of hills, I have a 56 tooth sprocket on the wheel, and would like to gear lower. The max size sprocket I usually see is 60 tooth, that isn't going to be enough for NH.

Right now, I am 30 mph +, I have been happy for the last 5 years at 22 mph and climbing hills with my Super Titan + Grubee 4G. I would be happy at 25 mph max with this new build, and hill climbing ability. I bought the clutch from custommotorbikes (thanks Lynn - you are great !) and the adjustable drive pulley she sells for the HF motor. I have this pulley opened up as far as possible without the belt hitting the aluminum of the clutch mount (see pic) for the lowest gear ratio I can get. I am not going to get lower I think with this arrangement.

Thinking of emailing EZM directly, to get a recommendation of a fixed drive pulley, smaller diameter for lower gear ratio. Wondering if I might need to put a heavier tension spring on the clutch, to pull in the slack of the belt better, I don't think the stock one will do the job with a small diameter drive pulley, where they will be a lot of slack ?

Anyway the clutch is great, and will be an improvment once I get the gearing down. AND there is another mod, besides defeating the governor (increasing carb jet with custom air filter) that AGK suggests for more power. But I got to get the gearing down. These motors are so cheap ! Beats buying a Hua Sheng for 2x - 3x the price, depending on type / power...

Oh, also see attached pic on my clamp arrangement to secure the EZM clutch to the frame as required by EZM. Made it from hardware store stuff + rubber pads from a sink mat (!) cut up. Not pretty, but will do until I have time to fashion a permanent clamp.

Thinking Gunther pretty good about finding / reading this things.

Yipee !

Big Kid

Thanks Bill

Forgot to mention in my post that my rear wheel frame arrangement is such that any larger on the sprocket and the chain will be hitting the vertical frame member. It brushes it occasionally now. I could lose the outer sprocket mount rag pad, or replace with something thinner, but my motor is as far over to the right as I can go. I have the sprocket dishing in as is, the chain alignment is perfect right now.

Wish I could forsee these things earlier on. Any ideas how I might solve the rear sprocket issue (besides going to a new frame !). Otherwise I am thinking a drive pulley on the clutch as posted.

)))))))

cb

azbill said:

I think your best/easiest bet would be to go larger on the rear sprocket
I have a 99cc predator and EZM Q-Matic
I use a 72t and can cruise at 30 all day long (fastest I have had it was 35.6)while climbing steep hills
AGK has some big ones at a reasonable price that bolt to a disc mount
http://www.affordablegokarts.com/mm5/merchant.mvc?Screen=CTGY&Category_Code=MTRBK PARTS

Click to expand...

Hey Bill, thanks for the link. I just moved the motor mount up a bit, which spread out the mounting plate, allowing the engine bolts to clear and slide all the way over. So I will be going with a 70tooth I think - now if I can just find the "disc mount" you are talking about, do you mean manic mechanic mount ? I don't want to use the standard rag mounts obviously on a big disk like that. I have a freewheel hub on the bag, just a touch over 2" diameter.

So many sprocket hole patterns, mounts, and rear hubs. So little time... ;-) Just if you know, otherwise I will figure it out eventually.


Chris

Desert Rat said:

Nice bike! I'm mounting mine the same way.
as to the ezm that's the only flaw I've found in their engineering
the idler should be pulling up on the belt not down and this is something
I will have to find a way to redo before I get mine running
best of luck
Ron
Also did you remove the governor or not? and if you
did was it metal or plastic? I only ask because I've heard the new 79cc's have a metal one instead
of plastic which the old ones were made out of

Click to expand...

Nah, I just took off the governor plate + spring at the top, that stops the functioning of it anyway. You pretty much have to tear down the motor completely, AGK has the instructions. I can't see tearing the whole motor down to remove it, can't see how that would improve performance - it can't be putting that much drag on the system ?

That would be great

Today I talked with Quentin at EZM

I ordered an AX 25 belt, I have an AX 26 on mine. I suspect the AX 25 might be an 1" shorter ?

I also ordered a 2.5 fixed pulley (not sure why, but it was only 6 bucks) and a "new" outer clutch bell support bracket (the U shaped thing) that has a breakaway piece so you can take the bottom of the U out and more easily change the belt.

I measure that adjustable pulley to be about 3.5 " in diameter. My belt currently is riding with the flat printed face about 1/4" in from the outer edge of the pulley - that is as far as I can open it without the belt hitting against the aluminum of the EZM plate.

Putting it another way, the adjustable clutch is open to where I can just see one thread on the adjustable center piece. It looks like I can open it quite a bit more.

Thanks

Just an update, no pics yet

I got the AX 25 belt from EZM, along with the new pulley side 'break - away' bracket that allows you to remove the bottom of the U piece to more (a lot more) easily access the belt. Quentin says they went to this new arrangement on the new pacesetter clutch types.

It was a bit tight getting the old style U bracket off, the pulley + belt is in the way. After I got the screws loosened up all the way, they wouldn't come out as the pulley + belt was in the way. By sliding the belt of the pulley towards the bottom of the U in the bracket (towards the left side of the bike, after opening the adjustable drive pulley all the way) I was able to get the screws out, although I had to use a screwdriver to direct them away from the pulley, and sort of knock them out. Probably a better way to do it, I am sure.

Anyway, the new belt fits great, and I can open up the pulley I think as far as would be useful, without the belt hitting the side of the mount like it was. It looks like I would also be able to crank the pulley tighter (for more speed) close to max, but the belt could be too small for the max. I think it is big enough, but I have to test this.

SO, looking at the old style U bracket I it looked as tight going back on as it was coming off. As far as I can figure, you HAVE to put the pulley + clutch in place first before you reattach the U bracket, again causing a problem getting the bracket screws back in - the pulley being in the way. You can't but the screws back IN at a slant obviously, it would screw up the threads on the 2 threaded holes.

Since this looked problematic, I went ahead and installed the new style U bracket. So I can't provide any help on how you would get the old style one back together after changing out the belt. You might want to call EZM for a tip - I am probably missing something. The pulley will slide off the shaft, there is a set screw (allen) - but again you have to put it back on before you reinstall the old style U bracket so it doesn't gain you anything. I would suggest finding screws other than what EZM installed, something with a screw head with a smaller circumference so it will fit past the pulley. I use a lot of words, hope you get what I mean.

Putting the new style U bracket on was not perfect. The screws EZM provided me also did not clear the pulley. In this case, the 'feet' of the bracket, where the screws go, is thicker than the old style U bracket, so it puts the heads of the screws closer to the pulley. EZM provided me with 2 allens head, and two machine type screws (the ones with the rounded heads), the allens head screws rubbed right on top of the belt, so they weren't going to work. The round headed screws would have just cleared it, were it werent for the lock washers I was also provided, these made all 4 touch the pulley.

No biggie, as I had 4 machine bolts in my own stock with rounded heads. I didn't use lock washers, just a lot of my do it yourself thread locker (cheap fingernail polish, works great). Since two of the screws have lock nuts anyway (the 2 that don't thread into the mount, they just go thru a hole, you attach the locknut on the other side) I don't think they are necessary for these. The other two thread thru the mount, into threads in the rear bracked. I am hoping the thread locker will keep these tight. Not sure why EZM didn't but lock nuts on these too. The protruding ends are tight up agains the back bracket, but I think I could get lock nuts on before I put the clutch on the motor. Someday when I have it off I will do this. Additionally, for the time being I am going to put a dab of 50 year silcone on the ends of these bolts, I have found this to do wonders to prevent bolts from vibrating loose...

So I got the whole thing togther, now the flat side of the V belt is like 3/4 " below the edge of the adustable pulley, instead of 1/4 " - so I gotta have more power now. This is where I am going to try it first this weekend. And the belt comes no where close to the aluminum mount, so problem solv-ed I think. Looks like the AX-25 vbelt is a better alternative for the EZM clutch for the HF, I will post results, with pics of above coming up.

By the way, for anyone considering an HF - EZM build, you will probably need to put a 3/4" spacer plate between the engine and the mounting plate. If you do not, the angle of the clutch with respect to the motor is slightly downward so it misses the exhaust mount, causing the inside U bracket (the one supporting the clutch in this case) to hit the motor mount. I made a spacer out of 2 pieces of 3/8" aluminum I got from McMaster-Carr, just epoxied them togther and drilled the mounting hole pattern thru it. Instead of the M8 16mm bolts provided for mounting by HF, I got some M8 35 mm bolts + lock washers - these fit the new arrangment perfectly. Just a heads up.

Way enough for now, sorry about that. I am a fanatic

Sorry about all that, here is a brief final update:

1. The AX 25 is a better belt to use for the EZM clutch with the 3.5 " adjustable pulley. It lets you use more range of the pulley - all the way to mostly open (lowest geared). I have about 2X the power now.

2. The retrofitting of the break away pulley bracket into the older style EZM clutch (the one with the one piece pulley bracket) works, with a minor modification. You need to get round head machine screws for all 4 mounting holes, and longer ones than the ones EZM sends you. And forget about lock washers, use thread lock. Otherwise the heads of the bolts will hit the pulley and / or belt.

3. Not so sure I would want to play with different belt sizes with the old style EZM clutch (above) without retrofitting with the break away bracket. Not too bad getting the one piece pulley bracket off, but beyond my mechanical ability to get it back on I think. Maybe EZM should start a FAQ.

Besides that I could still use a little more power. I got 30+ mph now, could go to 25 max, as long as I can climb. I don't think the AX 25 belt would be short enough to use with the "2.5 fixed pulley for the HF EZM clutch", looking at it, it looks like it would gear even lower than the adjustable cranked all the way out. I am going to call EZM again about getting the next shorter belt - want to try it with the 2.5" fixed pulley.

Have a blast !

BigKid

Another update:

I got an AX24 vbelt, previously (above) I have used AX25 and AX26 (AX26 was what was provided to me in the "HF EZM clutch kit" from custommotorbikes.com).

Currently I still have the AX25 in with the adjustable pulley. Actually it gets me around pretty well, even with most of the hills I deal with. The problem is I don't like how it slips when you are starting out, or going up a steeper hill. Still slips when I pedal as my single speed gearing on the pedal side is too low I think. The belts have to wear out, and the question is how long ?

I have the AX25 about .4" in from the edge of the 3.5" adjustable pulley currently. According to EZM, that means I am running at 2.7" inch on that pulley. Also according to EZM you can run at a minimum of 2.1" on that pulley, so I could open it up still a turn or so.

Again, the AX25 won't allow me to open it up any more or I will hit the side of the mount with the belt. SO someday when I have nothing else to do I will put the AX24 in, and open it to the 2.1" max.

Kind of liking the speed the way it is, about 5mph faster than my grubee 4G with Super Titan (Hua Sheng with longer piston rod for more compression). The 4G is better on hills if starting at a slow speed at the bottom. If I get some running room before a hill with the HF + EZM, it is actually better on hills - the problem is e.g. when I make a turn and am going up hill after the turn, starting from a stop. Then I am thinking the belt is slipping.

I will post again someday when I use the AX24, just in case anyone was still following this.

No, I didn't know such stuff existed, haven't had much experience with belts

Thanks ! Looks like a good product might be Sprayon brand belt dressing. They claim 50% increase in gripping and that this will work in outdoor conditions, not cause picking in dirt, etc. Can get it at Airgas and Fastenal.

I will give it a try and post - thanks again

Thats a bummer, it is one difficult thing to dissassemble, harder to get back togethere - I am talking about the orginal one with the one piece bracket that supports the driven pulley.

Again, there is a 3 piece replacement for the one piece, EZM is calling it a "break away bracket" and that DOES retrofit the older style. But you may have to get your own bolts for the legs it, as the heads have to be pretty flat not to rub against the pulley and/or belts. The breakaway piece is attached with 3 tiny flat head phillips head screws on each end. I found them stock at Ace hardware, I just replace them everytime I go into it.

I am not an expert on this thing by any means but maybe your belt is slipping ? If so, is the idler tension arm free, does it tighten the belt ? It also might be that the drive pulley is slipping on the shaft, maybe your key is damaged ? I had that happen.

I feel your pain, I have built about 6 of these bikes, all different kinds - the HTs, a rear mount chain drive, a rear mount friction drive, and grubee 4g centermount with the Hua Sheng and the Super Titan (high compression Hua Sheng). Each one I went thru a time of launch, fix, launch again, etc. Right now I am happy with my clutch situation of the HF79, with the AX25 (24 is too small yes), at about 2.5" adjustment in the drive pulley.

But, I have trashed 2 wheels now. First one was a Wheelmaster 12 gauge spoke 26" wheel with modified rag mount (mount has centering pieces to keep it concentric with the hub). Warped the wheel pretty good, beyond spoke adjustment - I should have monitored it, I was having too much fun. But I have to say I have found, if you have to start adjusting spokes on a new wheel, often it just isn't going to hold up moving forward.

My second wheel was a Sta Tru with the Manic mount (both of these wheels have been freewheel hubs) again 12 gauge spokes. Got it from custom motor bikes. Good for about 200 miles then I broke a spoke. Getting it fixed, but again I don't think it can take it.

I am sure some old timers just read this and smile. Anyway, my final solution I think will be to get the Worksman rear wheel with 11 gauge spokes from Pirate Cycles, they sell it with a Manic mount (although I am a bit confused, it could be a knock off - hoping it will fit the sprocket I have that fits the Manic mount). This is not a freeweel hub, it is a single speed coaster brake hub. Worksman doesn't make a freewheel hub that I can find anyway. Hoping I don't have to jam around with this TOO much to get it to fit on my MTB frame.

Don't give up - its worth it in the end, that next part will do it... ;-)

cb