Monster Moto 105cc Clutch/Incline Problems

[FitzMiniMoto]

Hello,

I purchased a Monster Moto 105cc Classic with suspension mini bike for my son. He is loves it and it goes 27mph on asphalt. When he rides on grass and especially on inclines he has a problem getting the bike up and uses his feet. He is 125lbs so he's not tiny but not huge. What could be the issue? Clutch, Motor Power, both?

Thanks

 

[Nathannewbie]

Hello,

I purchased a Monster Moto 105cc Classic with suspension mini bike for my son. He is loves it and it goes 27mph on asphalt. When he rides on grass and especially on inclines he has a problem getting the bike up and uses his feet. He is 125lbs so he's not tiny but not huge. What could be the issue? Clutch, Motor Power, both?

Thanks

Power.
I rode a 80cc and I weigh 100lbs it couldn't get me up anything.
A 105cc is not much better.

 

[mr.ez]

Hello,

I purchased a Monster Moto 105cc Classic with suspension mini bike for my son. He is loves it and it goes 27mph on asphalt. When he rides on grass and especially on inclines he has a problem getting the bike up and uses his feet. He is 125lbs so he's not tiny but not huge. What could be the issue? Clutch, Motor Power, both?

Thanks

I have 4 of the b80 bikes,i weigh 180,and mine do good once they broke in.they all were very weak until break in.i have read a lot of complaints but I,m very pleased.you might want to check the brake caliper.all mine needed adjustments to alighn them with the rotor and the brakes were too tight.just a little brake drag will kill these little bikes.hope this helps'

 

[I74]

Need to put a HRM jack shaft kit on it, or switch out for a Predator 212.
Stock gearing is 6.8 - 1, on the 80's & 105's.
With the HRM 18 & 13t jack shaft kit, & the stock 11 & 75t sprockets,, that would give you a gearing of 9.44 - 1
You would probably loose around 5 mph top end though, but gain a ''whole bunch'' on bottom end, & put ''a lot'' less strain on the engine.
HRM'S kits come complete with every part you need including hardware & instructions., & are specifically set up for the MM - 80'S & 105'S.

 

[Nathannewbie]

Need to put a HRM jack shaft kit on it, or switch out for a Predator 212.
Stock gearing is 6.8 - 1, on the 80's & 105's.
With the HRM 18 & 13t jack shaft kit, & the stock 11 & 75t sprockets,, that would give you a gearing of 9.44 - 1
You would probably loose around 5 mph top end though, but gain a ''whole bunch'' on bottom end, & put ''a lot'' less strain on the engine.
HRM'S kits come complete with every part you need including hardware & instructions., & are specifically set up for the MM - 80'S & 105'S.

Where can you get this kit? will you give me a link?
I was going to do the predator swap for my 80 that I was going to give to my bro but 25mph would be plenty for him it just needs more torque.
I found one for $120 but for that price I might as well do the predator swap. Is that actually around the price it would be?

 

[I74]

Where can you get this kit? will you give me a link?
I was going to do the predator swap for my 80 that I was going to give to my bro but 25mph would be plenty for him it just needs more torque.
I found one for $120 but for that price I might as well do the predator swap. Is that actually around the price it would be?

Yea Nathen,
The HRM - ''Hot rod mini bike'' kit for the MM- 80 &105's, is right at 120,, + around 13 bucks shipping.
It is ''way'' more easier to install & set up than the BMI one I modded & pieced together on mine.
If you swapped to a predator, it would be a lot more work than installing a HRM kit, plus you would have to ''at least'' buy a 3/4 shaft clutch, & longer chain ect..

Comes down really to what you want.

Some reasons why I stuck with the Lifan 80, is because it hardly uses any fuel compared to a 212, runs really well,, & the quality of the internal parts are pretty impressive.
Ian

 

[Charles S]

The HRM/PMR jackshaft kit is $120, some people have had the plate bend under load (power) although I doubt 2-3 hp would bend it. Yes, it provides options in gearing, trading top speed (23 mph stock per MM's specs, so I would expect maybe 15-20 mph with a noticably higher ratio) for increased torque at the wheel. The jackshaft adds complexity and increases parasitic loss. The BMI jackshaft plate with hub is $39 but doesn't include the shaft and sprockets. A 212 Predator is $100 (add $25-50 for a good clutch, a Max Torque SS 3/4" #35 12T is $27 from BMI, 13T is $36, 15T is $48) and makes double the power, or more, of the MM Lifan 80/105 and won't need the added complexity of the jackshaft. I once saw dyno charts for stock 212 Predators, 7 hp for the non-hemi, 8 hp for the hemi, both rated 6.5 hp. I've tried to find the article with the dynamometer results but don't remember where/how I found it, probably stumbled upon it. If you want to stay with a Lifan engine, you can get a Lifan 212 for $139 from HD, regularly $189. Lifan claims their engines are assembled using "automotive grade" parts (crank, rod, piston, rings), I don't know whether they are higher quality than Predators and/or other clones, or not. You can limit the throttle opening on the 212 for beginners/young riders and increase it as experience/skill/age increases. No doubt in my mind, I'd choose the 212 swap. You may or may not need a new chain depending on how the current engine is mounted (forward/rearward), the current position of the tensioner and the tooth count of the new clutch sprocket, the crank would probably be a little higher on the 212. I'm not recommending a torque converter instead of a clutch because the small frame MMs require frame modification to fit a TC, something not practical for everyone.

https://www.bmikarts.com/Max-Torque...-a-34-Bore-for-Go-Kart-or-Minibike_p_721.html

https://www.bmikarts.com/Max-Torque-SS-Clutch-34-Bore-35-Chain-13T-or-15T_p_4679.html

https://www.homedepot.com/p/LIFAN-7...t-Recoil-Start-Gas-Engine-LF170F-BQ/205819157

https://www.oldminibikes.com/forum/...ith-predator-212-and-torque-converter.103977/

https://www.oldminibikes.com/forum/index.php?search/104560/&q=monster+moto&c[title_only]=1&o=date

https://www.oldminibikes.com/forum/index.php?search/104599/&q=mega+moto&c[title_only]=1&o=date

 

[Charles S]

An additional mod I would want to do to a 212 swapped small frame MM is extend the wheelbase by around six inches by relocating the rear axle rearward to help keep the front wheel on the ground, something similar to the photo I'll post but not so drastic (it looks like an 8" - 10" stretch).

Random internet photo, not my bike.

 

[Nathannewbie]

The HRM/PMR jackshaft kit is $120, some people have had the plate bend under load (power) although I doubt 2-3 hp would bend it. Yes, it provides options in gearing, trading top speed (23 mph stock per MM's specs, so I would expect maybe 15-20 mph with a noticably higher ratio) for increased torque at the wheel. The jackshaft adds complexity and increases parasitic loss. The BMI jackshaft plate with hub is $39 but doesn't include the shaft and sprockets. A 212 Predator is $100 (add $25-50 for a good clutch, a Max Torque SS 3/4" #35 12T is $27 from BMI, 13T is $36, 15T is $48) and makes double the power, or more, of the MM Lifan 80/105 and won't need the added complexity of the jackshaft. I once saw dyno charts for stock 212 Predators, 7 hp for the non-hemi, 8 hp for the hemi, both rated 6.5 hp. I've tried to find the article with the dynamometer results but don't remember where/how I found it, probably stumbled upon it. If you want to stay with a Lifan engine, you can get a Lifan 212 for $139 from HD, regularly $189. Lifan claims their engines are assembled using "automotive grade" parts (crank, rod, piston, rings), I don't know whether they are higher quality than Predators and/or other clones, or not. You can limit the throttle opening on the 212 for beginners/young riders and increase it as experience/skill/age increases. No doubt in my mind, I'd choose the 212 swap. You may or may not need a new chain depending on how the current engine is mounted (forward/rearward), the current position of the tensioner and the tooth count of the new clutch sprocket, the crank would probably be a little higher on the 212. I'm not recommending a torque converter instead of a clutch because the small frame MMs require frame modification to fit a TC, something not practical for everyone.

https://www.bmikarts.com/Max-Torque...-a-34-Bore-for-Go-Kart-or-Minibike_p_721.html

https://www.bmikarts.com/Max-Torque-SS-Clutch-34-Bore-35-Chain-13T-or-15T_p_4679.html

https://www.homedepot.com/p/LIFAN-7...t-Recoil-Start-Gas-Engine-LF170F-BQ/205819157

https://www.oldminibikes.com/forum/...ith-predator-212-and-torque-converter.103977/

https://www.oldminibikes.com/forum/index.php?search/104560/&q=monster+moto&c[title_only]=1&o=date

https://www.oldminibikes.com/forum/index.php?search/104599/&q=mega+moto&c[title_only]=1&o=date

Ya I was thinking that predator might be better too because then if I want to ride it its great and still has plenty of power.
It will cost $100 for the predator and another $100 for this kit which includes everything I need: https://www.gopowersports.com/mini-bike-6-hole-420-sprocket-chain-clutch

 

[I74]

An additional mod I would want to do to a 212 swapped small frame MM is extend the wheelbase by around six inches by relocating the rear axle rearward to help keep the front wheel on the ground, something similar to the photo I'll post but not so drastic (it looks like an 8" - 10" stretch).

Random internet photo, not my bike.
View attachment 246405

That is a ''looong'' chain.
Like the rims on that !
Looks like it might be a pretty good drag bike, as long as you could keep the chain on it …..

 

[Charles S]

That is a ''looong'' chain.
Like the rims on that !
Looks like it might be a pretty good drag bike, as long as you could keep the chain on it …..

Yes, it definitely is a long chain, has a tensioner though. An option for keeping a chain on would be chain guides, make them from a block of nylon or teflon.

The wheels are X7 pocket bike wheels, 8", hard to find. I was fortunate to get a couple of them at good prices from scooterdomain.com a while back. There are 6-spoke and 8-spoke versions, I like the 6-spoke better than the 8. The ones I got are 6-spoke, black with machined rim and spoke edges. All I have been able to find recently is an 8-spoke wheel/tire set. It would take some work to use one on the rear of a minibike; I got them to use on the front combined with a widened stock 6" rear wheel and 13x6.50-6 Cat Eye pocket bike tire (very close to same OD), can't see much of a stock 6" rear wheel anyway with the sprocket on one side and brake rotor on the other, paint it black and it disappears.

http://www.pocketbikesunlimited.com/R6WHEELS.html

 

[osu1978]

I would spend a little more and do a predator swap however the HRM jackshafts are strong as hell and held up great with my modified engine. No idea how someone would manage to bend one unless they rode the entire bike off a cliff.

 

[Charles S]

I would spend a little more and do a predator swap however the HRM jackshafts are strong as hell and held up great with my modified engine. No idea how someone would manage to bend one unless they rode the entire bike off a cliff.

I misremembered. Your comment caused me do a little digging, the problem was clutch and chain problems attributed to the clutch hanging off the end of the crank. I interpret that to mean the clutch was being pulled out of alignment (cocked) under load. My bad.

 

[I74]

Yes, it definitely is a long chain, has a tensioner though. An option for keeping a chain on would be chain guides, make them from a block of nylon or teflon.

from I74,
I ran across a pic of a bike this morning that looked like it had a solid nylon tensioner guide that reminded me of a solid nylon primary chain tensioner - block/shoe, for the late model ''Big twin'' HD Shovelheads & early Evo's.
Those are really stout, & I upgraded to one on my 76 Shovel, years ago ...……
I think it would be real slick to take one or two of those, & notch a lengthwise grove in them, & use them for guides on extra long chains.

 

[Charles S]

Yeah, that's basically what I was referring to, a block of nylon or teflon with a groove cut in it (or assembled from pieces) that the chain would run in.

 

[FitzMiniMoto]

Thanks everyone for the input!
Status update: took the boys out on the trail for the first time! My Monster Moto 212, His 105cc & other sons Black Widow go kart with 212 just put in it. 105 cc too underpowered for the sand, dumped it once, stalled out many times, then wouldn’t start.

Go kart & my bike no problems. Both have 212’s, coincidence? I think not lol

Debating on quick & easy predator 212 with 3/4” #35 clutch, no modifications needed (other than chain) OR
predator 212 with torque converter & frame modifications OR predator 212 with HRM jack shaft.

 

[FitzMiniMoto]

An additional mod I would want to do to a 212 swapped small frame MM is extend the wheelbase by around six inches by relocating the rear axle rearward to help keep the front wheel on the ground, something similar to the photo I'll post but not so drastic (it looks like an 8" - 10" stretch).

Random internet photo, not my bike.
View attachment 246405

That looks sweet! Now I won’t feel so bad about cutting his bike for mods because I want to re sell it! I can keep it and do this! Thanks Charles!

 

[Charles S]

Thanks everyone for the input!
Status update: took the boys out on the trail for the first time! My Monster Moto 212, His 105cc & other sons Black Widow go kart with 212 just put in it. 105 cc too underpowered for the sand, dumped it once, stalled out many times, then wouldn’t start.

Go kart & my bike no problems. Both have 212’s, coincidence? I think not lol

Debating on quick & easy predator 212 with 3/4” #35 clutch, no modifications needed (other than chain) OR
predator 212 with torque converter & frame modifications OR predator 212 with HRM jack shaft.

I don't think there would be any need for a jackshaft with the 212. The variable ratio of a CVT/torque converter would be nice to have if you're comfortable with modding the frame, I recently saw them for $41 w/ free shipping on eBay so no more expensive than a good clutch. You can modify the TC plate by slotting the mounting holes (or drilling between existing holes) and grinding down one gusset on the backside, allowing you to raise the driven for a better (and better looking) fit. They're heavy, I was somewhat surprised by the weight when I first picked one up. Even if you just go with a quality clutch I would expect a huge improvement with a 212.

Here's another thread that shows the TC plate mod.
https://www.oldminibikes.com/forum/index.php?threads/want-to-put-a-tc-on-a-coleman-ct100.141989/

 

[chipper]

Buy a Predator and be done , the jackshaft kit is a bandaid not a cure

 

[Nathannewbie]

I have 4 of the b80 bikes,i weigh 180,and mine do good once they broke in.they all were very weak until break in.i have read a lot of complaints but I,m very pleased.you might want to check the brake caliper.all mine needed adjustments to alighn them with the rotor and the brakes were too tight.just a little brake drag will kill these little bikes.hope this helps'

How do you check this?
I have an mmb80 that the brake us messed up on.