CRF150R horizontal motor

I saw this the other day and instantly wondered how bad my CT70 frame/chassis would twist with something like this bolted up.

The thought was silly enough to put a grin on my face so I figured I'd post it.

Hopefully this is in the correct section.



I'm actually not sure if it's a 150 or 250? Could be a 450 for all I know. Maybe someone here might know?

There's a couple guys building some pretty crazy motors in the Philippines(I think). They either add a cylinder or mix and match Top and Bottom ends from different years, different models or even completely different manufactures.

They re-engineer the hell out of thier motors using SUPER basic equipment. I've seen a few videos of running motors and they actually sounded pretty good. I have a hard time imagining any of them running for very long and wouldn't doubt it if they blew up immediately after the videos were taken!lol

Maybe they'll run forever.

I've seen guys in Australia reconfigure the bajeezus out of a few different motors and thiers are reliable. They do use more modern/hi-tech tools to build their motors though.

Google Allen Millyard. I particularity like his Kawasaki V8

IDK, there are certain mods that I find very unsettling, for anything but a limited-use application. Welded-up crankshafts, offset crankpins, aftermarket race heads with roller rockers, thick plates machined to graft-on huge overbores and ultra-long crankshafts top that list. That's a friggen ton of welding done to the cases. Assuming it's been done perfectly, by a consummate professional welder with years of experience, then properly machined, it's still "pave & shave". Those case castings were never intended to hold this kind of force. Adding indeterminate effects of massive welding to the equation doesn't improve the odds for longterm success and that's not just my opinion. I am NOT saying that this cannot work; it's certainly possible. What I am saying is to consider the engine & tranny as a complete, balanced, system. Increasing displacement & compression is the (comparatively) easy part. Once you've got the top end making those huge "bangs", the rest of the motor & trans has to be able to withstand the increased loads.

Now consider the percentages. This began as a 49cc motor. Honda took it out to 72cc, then 89cc and stopped there. We've seen tunes as big as 124cc...~250% original displacement. 250cc represents a five-fold increase. How's that likely to work, without major upgrades to the lower end? It's the equivalent of taking a 5 liter (~300ci) V8 out to 25 liters (1500ci). Yes, I know that there are other differences here but, it does illustrate the point.

IMHO, the hot ticket would be Z50-compatible (motor mounts) billet cases that fit the CRF150/230/250 top end and internals. That way you'd get big power, OEM durability and "plug & play" installation...of the engine itself. There'd still be the matters of wiring, fueling and a radiator, if running a water-cooled top end.

As for what the frame will hold, it's going to depend on torque and mileage. Somewhere around 30-35hp, the torque limit of the stock frame will be exceeded and the frame will fold like a deck chair. It's been done. Best, educated, guess is that the practical limit of displacement is ~250cc...with a conservative tune.

IMHO, 25hp is closing in on the ragged edge of sanity. That's enough to clip the 90mph mark, risky on a closed course. On the road, it'd be suicidal-stupid. I could see running this level of power, with rider restraint keeping speeds within reason and enjoying the effortless ease of maintaining freeway speeds. That's something I leave to younger riders who are still invincible. On a bike this small, anything much beyond mid-60s is best for the occasional short blast...and then only on a properly setup bike with world-class suspension, braking & chassis mods, all of which add-up to a four-figure parts total.

I'm already seeing builds that are wildly overbalanced...lots of power and little-to-no chassis/suspension/braking mods. The biggest Chinese motors available, at present, should make more than enough power to easily eclipse 80mph, with plenty of torque. There will be failures, only a matter of when. Expect to see stress cracked frames, swingarm issues, damaged shock mounts, hub failures and, likely, brake failures too. When I see 70mph+ power combined with a braking system, front end, shocks & swingarm that, combined, cost less than the exhaust & wheels, I cringe. Even more disturbing is seeing knobby tires on such builds. There's not a knobby out there with more than a "J" speed rating and knobbies aren't exactly the hot ticket for corner-carving. This isn't me being doom & gloom. The laws of physics have no mercy, let alone a sense of humor.

The potential to build some scary-fast (for their size) little bikes is closer at-hand than ever. There is, however, a LOT more to realizing a safe (by motorcyle standards) machine with a good balance of rolling chassis mods to contain that power, for road riding.

I feel that I've taken some of these engines out beyond where they should be taken...every result was the same....they grenaded after use...some more than others. I've taken a set of z50 cases out to a 143cc with a 56 crank and 57 top end...i could have taken it out to 59mm on the top end. It ate head gaskets and cracked the cases. I put new cases on and it did the same. On a set of chinese midblock cases, I put a 67.8mm crank and 60mm bore...that blew apart after about 10 hours.

I think bob has a good idea here...if you can machine something from scratch that aligns with the stock engine cases we'd be golden. Honestly, if I were looking to do this, i'd machine a set of cases that matched our bolt pattern and accepted 100% of parts from a grom.

racerx said:

I'm already seeing builds that are wildly overbalanced...lots of power and little-to-no chassis/suspension/braking mods.

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I ran across this video and your words instantly came to mind.lol

I do know that the Pihrana 150cc e-start is no longer available. I tried three different vendors, no sale. They all told me that the new e-start 190cc was a more popular option now.

I say no way! Too heavy & powerful for the ct70 frame. With all the things needed to accommodate it like Suspension, brakes & tires, that would start to eat up some Buck$! More than $1.5K in my estimate, that's almost half a Monkey!

Ive been trying to read the tea leaves as of late..
The 2020 honda Monkey is gonna be offered in blue this time; its a 125cc EFI. No wrenching and no DMV title bull shit! Hell I might just take a test drive,!

Any combo, setup, or bike for that matter, will have its compromise(s). If there's one machine that will do everything well...I've never so much as heard rumors about it. You pays your your money and takes your pick; then you live with it, so do your homework.

For a bike that's actually ridden, i.e. will see more than short-duration, highly-specialized (like racing) use, suffice it to say that speeds above 60mph are going to comprise a very small percentage of the total operating hours. It's more a question of how you want those miles to be vs. what the available budget will support. There's a lo-o-o-o-o-o-o-ong, subjective, discussion in this.

From what I've read, the Daytona Anima 190 sounds like a good motor as long as you don't beat on it. The Piranha 190...I'm not sure. I think that's a relatively new engine.

I've heard that the 190 is comparable to a Honda based 125 built with good quality (tb) parts.

The new Monkey 125cc would be easy...write a check, go for a ride. I think 60mph is gonna be top speed with that bike tho. I think it's a mild tune right from Honda. If you're satisfied with the power and speed, and you don't start tweaking stuff, it'll probably run forever, trouble free.

Yep, write a check and Go to Jail! My account says that will not be happening.

I hear that Monkey 125 is a very nimble bike with a good seat and a 4 speed manual clutch for cruising.
The Grom is sporty, but seems for a younger Gen. I think the Monkey would do good on these country/rural roads, it could even handle short freeway bursts if need be but ive found plenty of back roads that go right into town.

Maybe at end of year when the new models come out, they might want to make a sweet deal...
For now it's the Trail-70!

That’s a big ol check though!

I saw this 3 week old Monkey for sale on Craigslist’s today.



I had NO idea they were going for that much!!

I also didn’t know they were gonna be Fuel Injected or have ABS either. I guess that stuff ain’t cheap.

Great topic and comments.

Quick math would suggest this is how the new Honda Monkey 125 sale will occur.

Your monthly payments
loan amount $6,000
Interest rate 5%
Number of years 5yrs
Monthly payment $113

tcislander said:

Great topic and comments.

Quick math would suggest this is how the new Honda Monkey 125 sale will occur.

Your monthly payments
loan amount $6,000
Interest rate 5%
Number of years 5yrs
Monthly payment $113

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Or ....
Sale price. $3995
TTT. $200

Out of pocket $4195. Pay cash. It doesn’t take too long to save that if you try. Probably in time to get an end of model year deal in Blue

Or, wait a couple of years when there are lots of them on the used vehicle market. It's the early-adopters who usually pay huge premiums.

They’re for sure cool.

I just couldn’t do it. I’ve paid crazy money for tiny bikes before but they’re rare enough to somewhat hold their value. Some have increased in value.

Like racerx said, I’ll wait. I’m a pretty patient guy, maybe by 2030!lol

EFI would definitely be bitchin. I just want the motor(and everything needed to make it run) and the front end.

I guess the wheels and brakes too.

I wanna strip it like a high plains buffalo!haha

Gene2313 said:

EFI would definitely be bitchin. I just want the motor(and everything needed to make it run) and the front end.

I guess the wheels and brakes too.

I wanna strip it like a high plains buffalo!haha

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If I get one, I'm handing $3k in cash and use my own finance for the rest.

Anyway, right now you can get a smoking deal on a used Honda Grom esp the early ones. I think the New Monkeys may have something to do with it, Could be they're trading em' in for the Monkey. They have the same engine and front end as the Monkey.

The new Monkey is a catchy bike and at first didn't think that much of it, until I did some research. I like what i see/hear but will need a test drive first.

That guy is smoking some good stuff if he thinks he is getting $5500. There is one with only 32 miles for 3700 or best offer on Ebay in Louisiana.

There are also; I've found ~new-- really low mile late 2000 model, Honda Rebel 250's that dealers still have, some as new old stock! Finding a clean low mile Rebel would peak my interest.

OLD CT said:

That guy is smoking some good stuff if he thinks he is getting $5500. There is one with only 32 miles for 3700 or best offer on Ebay in Louisiana.

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Haha I agree. The dudes crazy to think that taking $200 off the price is gonna cut it for 3 weeks and 112 miles. Never mind it being the FIRST 3 weeks and the FIRST 112 miles!lol

I was in diapers when I first heard “you loose $1000 just driving it off the lot”lol

Adam-NLV said:

There are also; I've found ~new-- really low mile late 2000 model, Honda Rebel 250's that dealers still have, some as new old stock! Finding a clean low mile Rebel would peak my interest.

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That’s interesting. I have a couple of n.o.s. minibikes.

Those Monkeys are pretty heavy, something like 230lbs. If I remember right, a CT70 is around 140ish? Nearly 100 lbs if that’s right. Not that a little weight, in the right place, is bad. I was just a little shocked.

Gene2313 said:

That’s interesting. I have a couple of n.o.s. minibikes.

Those Monkeys are pretty heavy, something like 230lbs. If I remember right, a CT70 is around 140ish? Nearly 100 lbs if that’s right. Not that a little weight, in the right place, is bad. I was just a little shocked.

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If memory serves, nominal weight of a CT70 K0 model was 156lbs. They gained weight, at least up the 1978 model...simple math, they hung more equipment on the bikes.

230lbs, for a bike this size, is downright porkly...imho.