Switchblade (pipe)Dream Build

PsychDoc said:

still seeking information- I bought a bike- seemed a fair deal - $175-
First hurdle- front brakes- any help is appreciated.

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Ok Doc, welcome to the forum. I think you got a deal on the Nirve, plenty of room for any of the motors mentioned & CVT with 4 cycle engine style options abundant for vertical, leaners to the rear, horizontal; take your pick. CVT is a good option, probably the "easiest" with sliding drive ratios and no hand clutch. In reality be prepared for more than a few problems along the way. I used to buy all the parts first and then then order what I really needed later and that's expensive and frustrating as well. Frame, engine and drive first, then some more. If your keeping the fork brakes and wheels are also a now item. Engine size 100cc to 212cc fine, laws are what they are & enforcement is quite subjective in application most places.

Front brake. Your fork looks to be made for a Sturmy Archer type brake. I prefer a caliper disk setup, either way you'll need a new front wheel/hub. The SA drum hub laced into the wheel or a disk rotor ready wheel/hub for mounting the rotor. I've bikes with both type brakes and the disc as I said is my preference. I use the mechanical caliper, but many prefer the hydraulic. Both stop you quickly. If your just doing the front for now and using a coaster rear brake I'd go 203mm front rotor. If you go with a drum brake get the largest you can afford & still fit. Don't buy wheels with spokes less than 12 gauge (10 is better) 36 spoke lacing. I don't see post mounts on the fork for mounting the disk rotor so a $10. axle adapter and the correct offset adapter for the rotor will be necessary as well. Brands: I prefer Avid calipers and rotors, but others are ok too. Sturmy for the drum hub. Wheels steel or aluminum, prefer steel, and stainless spokes.

I suggest showing photos of both sides of wheels, bike or motor etc. when asking for advice it really helps not to guess what you've got. Also when you get close to deciding on an engine take into consideration that the CVT is designed for specific engine output shaft size 3/4" is common and the drive line runs on the left side of the bike from the riders seated position & with the entire drive train rotating counterclockwise, from the riders perspective, on the left side.

It's a process Doc. Think first, study, ask questions, design,adapt and then purchase parts with which to build...then repeat in steps. Enjoy and have some fun with it!

Rick C.

I've used various Lifan motors over the years and found them to be well made for the price. Would I prefer Honda at twice the price? No way. Same price or close price? Certainly! I've had quality issues with the Chinese CDI used on some Honda clone Lifan's, but replacements are cheap in price to match the quality of the electronics. You will likely replace the carb on either the Honda or the clone with a Mikuni or Dellorto carb anyway, at some point,
so carb quality isn't a big deal either.

Four horsepower is plenty, but is it ever enough? Horsepower requires $$ spent upfront and along the way as well. Know what you need and ignore what you want, unless your prepared for the cost. Have $$, then build or buy what you want!

Rick C.

PsychDoc said:

Maybe should have started with this...
Goal(ish) cruise at 30mph, top out at maybe 40mph?
Another option- Lifan lf152f-3q it is alternately advertised as 79cc or 97cc the harbor freight site lists that as the ‘compare to’ the 79cc predator. However the lifan has a verticality oriented cylinder. It looks like the Honda gx100
View attachment 102569

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I have one of these Lifan's mounted with a Comet cvt, just sitting & waiting for a frame and me to build it. I ran it a few times and it starts easily enough, but that's about I know about them. The output shaft is 5/8" so required a bushing to fit the 3/4" Comet drive. 99cc? Rated at 2.5hp, about the same as a decent China Girl 2 stroke, so unless you're 275 lb. the cvt might cruise 25 to 30 mph with right rear cog.

Rick C.

That Lil lifan is a great motor ..I like it with a 3 speed.. it works well.Heres a pic of the lifan from a few years back

The 120 is good, best with a clutch. Not 100% sure about fit but the head bolt pattern is the same as all similar small blocks up to 212cc. So maybe the gx160 head is an upgrade with larger valves. I think with some minor work you can get a 120 up to 6hp or more.

The CVT is loud and clangy, and eats a huge amount of power. Also it sometimes breaks. Somebody I used to know had driven spring issues, I had driver springs blow up on my frequently. On a 3hp it eats maybe 1 or 1.5hp and just always seems to want to engine brake really hard soon as you come off the throttle. It is much better suited to a mild to wild 212 with power to spare. Single speed clutch geared for 40mph max gives a good 25-30mph cruise with OK acceleration.

With that frame I’d drop the motor as much in the frame as possible, run the cylinder vertical or even tilted forward slightly, and run the tension side of the pedal chain above the blower housing under the intake. Might still need to run a wider BB but just slightly. You can move the motor a little to the left and run your clutch on the jackshaft to save some width.

Tricky build to motorize for sure.

Tony's right motor needs to go low. Running a really small front pedal sprocket gains room forward & wide pedal levers might be required as well to clear motor cases. If the pedal chain won't clear the motor a set of idlers (cog &/or roller) below the engine and bottom bracket can route the chain under the engine case.

Rick C.

PsychDoc said:

And what about sprocket selection? Seems the tav2 has a 1:3 ratio- then a drive sprocket of 10 or 12 teeth- then straight back to the rear? Am I getting this right?

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Oh yeah, that’s the other thing. TLDR; get it running with a clutch first; do not design it for a cvt. You will not be able to gear it reasonably with a small engine without custom work and/or also an additional jackshaft. You might just barely be able to gear it reasonably with a 212.

CVT setup and tuning is a complicated process which involves multiple sliding scales of compromise.

Yeah I think I put way too much energy into this.. prefer to see a running bike two years from now than saying told you so... here’s my $50 vertical motor build... yes I was in the same shoes as you trying to save $80 going with a cheap motor that Looks Good... ended up blowing it up twice and rebuilding with a 212 that never blew up... those gc160s blow up and it doesn’t take much. Gl with your build

https://motorbicycling.com/threads/beginner01s-first-build.44801/