Climbing hills, real ones.

Lotus

New Member
Aug 13, 2020
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Howdy,

1st post and happy to finally join!

Wasn't sure where to post this, as I'm new, but here we go.

I've been interested in making a fresh hill climber for hiking/mountain bike/dirt bike trails.

I am chill as a cucumber if I can't go faster than 25mph max speed, as I know with these engines there are limitations and I'm after torque for climbing vs speed.

Base:

*26 inch Steel frame mountain bike with suspension on front fork (I can't machine a rear mount setup to use a Next bike suspension, etc. ATM)
*66 / 80 cc 2 stroke or 49-100cc 4 stroke kit (help me find an affordable kit, please)
*56-60 sprocket rear
*26 inch wheel/tires
*spring chain tensioner mounted to clutch side
*dual break lever
*possible head replacement if any oriented towards torque / climbing power > speed
*ngl bpr7hix spark plug

Help!
*Where to find affordable:
+4 stroke kit or 2 stroke?
+56-60 sprocket and adapter ($30 or less)
+Head built for low end torque and cooling for possible constant hills [unless sprocket takes care of that anyway] ($30 or less)
+What exhaust ($30 or less)

Contemplation station:

*PORTING FOR TORQUE LOW END TORQUE:
+Keep it simple with cleanup or try and round the exhaust and intake or widen exhaust? I'm afraid to raise or lower either.
+Aftermarket carb or just buy jets for the stock carb? (I'll cut extra junk out of/off the nt with a hot knife if the nt is recommended)
*lap the head only a tiny bit? (Sand paper/glass/600 grit)

I'm just looking to make a safe, comfortable, reliable (lol) toy. I will break it in with 44t sprocket not the 60t, by the way, then 60t or 56t is for after break in period when I use it for its purpose.

Thank all of you for your wisdom and call-outs. Feel free to call me an idiot and fix my bad ideas as needed, lol.
 
Last edited:

Tom from Rubicon

Well-Known Member
Apr 4, 2016
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Lotus,
Welcome to the forum, contribute what comes of this thread.
Lynne, at https://mbrebel.com/ will set you up including 56T final drive. Being a old customer I have a direct line. My machine shop also did were work for her bartering service for goods. Totally honest and many years of 2stroke experience.
I need new wheels for a Huffy rebuild. Guess who gets my business?
Tom
 

LR Jerry

Well-Known Member
Dec 19, 2011
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Rockwood, TN
Since you want to off road you'll get lots of help with the engine setup. As for the bike itself there's several threads on how to do full suspension builds. If you don't want to go that route I recommend at least getting a suspension seat post. I also suggest double walled rims and a rear cassette hub instead of a freewheel. The freewheel axles are prone to bending. I'd also suggest getting a 2x9 drive system which gets shifted like this lowest to highest 1(1-6), 2(4-9) for 12 non redundant ratios. If a gear is too easy or too hard to comfortably maintain a cadence of 70-90 it means you're in the wrong gear. You can get bicycle computers with a cadence meter on it fairly cheap off eBay.

Because you'll have engine assist I recommend a 9 speed 34-14 cassette and 28, 38 chainrings. Be in 1(1) before stopping on stops going up hill; all other stops use 1(4). Mountain bikes can take real beatings unless you plan to weld in reinforcements on the bike get a bicycle shop mountain bicycle. This label is put on department store mountain bikes
schwinnwarn1.jpg
 

Lotus

New Member
Aug 13, 2020
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Lotus,
Welcome to the forum, contribute what comes of this thread.
Lynne, at https://mbrebel.com/ will set you up including 56T final drive. Being a old customer I have a direct line. My machine shop also did were work for her bartering service for goods. Totally honest and many years of 2stroke experience.
I need new wheels for a Huffy rebuild. Guess who gets my business?
Tom
Thank you for this! I appreciate the welcome, connection, and information. I bookmarked the page; I really like that they are easy to contact in the event I have a custom order hehehe. Hoping to score a sprocket set/adapter combo and a few other odds and ends ;)

I hope the rebuild goes smooth for you! This seems to be quite the fun hobby.

Since you want to off road you'll get lots of help with the engine setup. As for the bike itself there's several threads on how to do full suspension builds. If you don't want to go that route I recommend at least getting a suspension seat post. I also suggest double walled rims and a rear cassette hub instead of a freewheel. The freewheel axles are prone to bending. I'd also suggest getting a 2x9 drive system which gets shifted like this lowest to highest 1(1-6), 2(4-9) for 12 non redundant ratios. If a gear is too easy or too hard to comfortably maintain a cadence of 70-90 it means you're in the wrong gear. You can get bicycle computers with a cadence meter on it fairly cheap off eBay.

Because you'll have engine assist I recommend a 9 speed 34-14 cassette and 28, 38 chainrings. Be in 1(1) before stopping on stops going up hill; all other stops use 1(4). Mountain bikes can take real beatings unless you plan to weld in reinforcements on the bike get a bicycle shop mountain bicycle. This label is put on department store mountain bikes View attachment 105509
I am incredibly grateful for advise on safety and durability. My wife and I want them to be built for safety and reliability, not speed, so this is right up my alley. I was hoping to find a way to add rear suspension but am very 'green' in that regard so I have a lot of thread lurking still + lucky find in my area for a frame/bike. I definitely will have to upgrade tires! The bumps with the torque will be deadly to standard wheels I bet, lol. Any affordable examples of wheels that are reliable and functional? I'm very new to the merchants for this hobby...

Thank you both!


Having a hard time picking an engine kit ATM, so its a good thing I have other planning to do lol.

 

LR Jerry

Well-Known Member
Dec 19, 2011
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Rockwood, TN
any cons to the shift kit other than upfront cost?
I am starting to think its best to spend 130 on one vs all the other $ upgrades.
Getting a cheap one can be expensive in the long run when you have to upgrade parts because parts failed in the cheap one.
You also want a very good bicycle chain. I like the SRAM 870 or the KMC 899X. You should also carry with you a quality chain breaker tool and Quik Links. Don't get one of those pieces of junk breakers from Wal-Mart. I got a motorcycle grade chain breaker off eBay for $10. You'll have to file down the push pin so it'll fit through a bicycle chain plates and roller.
20200815_211638.jpg
 
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5-7HEAVEN

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Aug 2, 2008
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any cons to the shift kit other than upfront cost?
I am starting to think its best to spend 130 on one vs all the other $ upgrades.
Not so much cons, but words to the wise:

Always keep a spare chain on the bike,, cut to length.

Be sure your bottom bracket (BB)has lots of space on the inside. If not, when your chain jumps, it doesn't snag on anything and snap.

Before replacing the original BB, measure distance between seat tube and original chainring. When you set up your shift kit, set your drive train the same amount.

Use 2 chain guards on the drive chainring sprocket AND a chainguard between the derailleur's First gear and the spokes.

Always keep your derailleur properly adjusted.

As you might imagine, the biggest con is broken chains.
 
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Lotus

New Member
Aug 13, 2020
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Getting a cheap one can be expensive in the long run when you have to upgrade parts because parts failed in the cheap one.
You also want a very good bicycle chain. I like the SRAM 870 or the KMC 899X. You should also carry with you a quality chain breaker tool and Quik Links. Don't get one of those pieces of junk breakers from Wal-Mart. I got a motorcycle grade chain breaker off eBay for $10. You'll have to file down the push pin so it'll fit through a bicycle chain plates and roller. View attachment 105516
you read my mind!!!! I was taking a peak at these to throw in my bag that i'll take with me anytime I ride. I appreciate the heads up on just getting a heavy duty one for motorcycles and modifying it slightly.

thank you also for this recommendation: SRAM 870 or the KMC 899X - I will absolutely be investing in 2x heavy duty chains (1x to toss in my bag)!


This is what I would do If I was you..............
and............

Yes, It is expensive, but in the long run, your ahead of the game. You might beable to pick that Honda GXH50 up for cheap because they now have the new GX50's out.
Thank you for the recommendation my friend :). I was considering 4 stroke if I wanted to "go all out" and burn some holes in the pocket, lol. Ultimately I would love to have 4 stroke with the shift kit, but I think I honestly will end up doing that later down the road. I think due to simplicity sake and due to what i'm familiar with/comfortable with + affordable if i toast it- i'll probably stick with an affordable 80cc 2 stroke. Trust me, I want to rock the 4 stroke for many reasons, but overall I can build the 2x really cute setups for my wife and i for the price of 1 fully setup 4 stroke (almost). We are both light/small riders, so it should work!

Not so much cons, but words to the wise:

Always keep a spare chain on the bike,, cut to length.

Be sure your bottom bracket (BB)has lots of space on the inside. If not, when your chain jumps, it doesn't snag on anything and snap.

Before replacing the original BB, measure distance between seat tube and original chainring. When you set up your shift kit, set your drive train the same amount.

Use 2 chain guards on the drive chainring sprocket AND a chainguard between the derailleur's First gear and the spokes.

Always keep your derailleur properly adjusted.

As you might imagine, the biggest con is broken chains.
Yeah, my friend I've been making a mental list of stuff to keep in a "bike bag".

Cut-to-length chain and spare tube + will definitely be in there lol.

Thank you for the advise on the bottom bracket. thats actually a really good idea to make sure that if the chain pops, it wont snag/lock up and mutilate so many things in the process. I'll have to think about how to approach that when i'm able to locate a solid bike to start with for the foundation .rd.

I'm all about safety, so i agree and think its a great idea to attach chainguards. I'll have to ask you more about that spacing you are mentioning in ref to shift kit when i get down to the gnitty gritty of that part, as i'm banana braining right now and not following, lol
 

5-7HEAVEN

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Aug 2, 2008
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When you do get your bike, take a measurement from the innermost chainring to the seat tube.

When you set up your drive sprocket on the bottom bracket(BB), that's the LEAST distance you want from the sprocket to the seat tube.

I believe mine was 30mm distance.

Be sure your BB is wide enough to accommodate.

Mine was too narrow.
I broke many many chains, because there wasn't enough room down there, and the chain would snap on the (too long)M5 studs I was using to conjoin the chainring sprockets.
 
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Lotus

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Aug 13, 2020
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When you do get your bike, take a measurement from the innermost chainring to the seat tube.

When you set up your drive sprocket on the bottom bracket(BB), that's the LEAST distance you want from the sprocket to the seat tube.

I believe mine was 30mm distance.

Be sure your BB is wide enough to accommodate.

Mine was too narrow.
I broke many many chains, because there wasn't enough room down there, and the chain would snap on the (too long)M5 studs I was using to conjoin the chainring sprockets.
Dang! I'm sorry to hear you toasted so many chains! I genuinely appreciate the headache and $ reducing pro tip. I'll take as many 'anti' chain 'pain' tips as I can get since I may do shift kit hahaha.
 
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Lotus

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Aug 13, 2020
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Anyone have porting advice/where to focus-trim for low end torque/climbing power vs top end high speed? I dont need to go fast, just gotta have some guts to climb on the low end.

Thank you guys!
 

Lotus

New Member
Aug 13, 2020
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I have scrapped the idea of a shift kit for now and am also contemplating 4 stroke vs 2 stroke for this situation.

I'm going for simplicity and ease of use, as my wife (with little bike experience) will have one as well. I think centrifugal clutch may help for simpler braking/accelerating when maneuvering in the woods for beginners.

Hardest part is keeping cost down, otherwise I may consider a Mini bike and just throw a larger sprocket on it. (I wanna make a bike/kit though, let's be honest; it's a lot of fun.)

I appreciate all of you; thank you!
 
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Citi-sporter

Active Member
Jun 16, 2014
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North Bend, Or,
These engine as set up have pretty broad power RPM range I've heard that the long, bent intakes meant to clear seat tubes improve low end power. In other words they make the engine pull from a few hundred less RPM. I find that the stock CG engines are pretty fussy about carbs and intakes. My 48cc doesn't really make enough power until it's turning about 3~3.5K RPM, with stock gearing that's about 8 to 11 mph.