1979 ATC 70 engine swap - Piranha 125cc or 140cc

[Tas Wheeler]

Hi there all,

Recently saved this poor little fellow from his not so loving previous owners and plan on giving him a new lease on life.

I was initially set on using the Piranha 125cc manual clutch with modded to pull start, but after reading through the threads on here and other sites I'm beginning to consider going to the bigger 140cc.

The 125 seems to fit in nicely and easily to the standard frame, does the 140 fit the same or require changes to the frame? Are there any advantages/disadvantages to either that would make my decision easier?

Cheers Matt.

[Tri-Z 250]

Hi there all,

Recently saved this poor little fellow

The 125 seems to fit in nicely and easily to the standard frame, does the 140 fit the same or require changes to the frame? Are there any advantages/disadvantages to either that would make my decision easier?

Cheers Matt.

The 125 is power enough to be dangerous and hurt you quick. At some point the frame could use a streach and 140cc might be it. Riding a 125 before manual clutch it was pleanty of fun. 3 gear uphill wheelies just gassing it. It was an impressive combo and rideable but you get the feeling things happen quick on small frame big motor combo.

[Tas Wheeler]

The 125 is power enough to be dangerous and hurt you quick. At some point the frame could use a streach and 140cc might be it. Riding a 125 before manual clutch it was pleanty of fun. 3 gear uphill wheelies just gassing it. It was an impressive combo and rideable but you get the feeling things happen quick on small frame big motor combo.

Thank you for the reply,

So in your opinion I would need to "streatch" the frame to fit in the 140?

I guess I really just need confirmation of weather the 140 will bolt right in with out making major changes to the frame. I have read conflicting threads on here and else where that it will fit in a standard frame and that it won't.

I know about the other issues with the intake manifold and exhaust and that wont be an issue for me to overcome, just would prefer to keep the trike looking as stock size as possible.

Thanks again.

[Mosh]

The 140 pretty much has the same general fit as the 125. You just need to notch the frame at the rear motor mount to clear the case.

The 140 technically is supposed to run an oil cooler that will present its own mounting challenges.
I have built 2-125 piranha 70s and ridden the 140. Imho the 125 is more than a handful and the 140 wears you out hanging on to it. You can ride the 125 better. I weigh 206lbs and it hauls me up anything with power to spare. I suffered my of my worst atv injuries on the 125 when it crawled up my leg and threw me all over the place and broke my hand. It got away from me that fast. The 125 is a little more reliable than the 140 as well. Mine is going on 4 years old with no problems. From a guy that has ridden both, the 125 is the better of the two.

[Tas Wheeler]

The 140 pretty much has the same general fit as the 125. You just need to notch the frame at the rear motor mount to clear the case.

The 140 technically is supposed to run an oil cooler that will present its own mounting challenges.
I have built 2-125 piranha 70s and ridden the 140. Imho the 125 is more than a handful and the 140 wears you out hanging on to it. You can ride the 125 better. I weigh 206lbs and it hauls me up anything with power to spare. I suffered my of my worst atv injuries on the 125 when it crawled up my leg and threw me all over the place and broke my hand. It got away from me that fast. The 125 is a little more reliable than the 140 as well. Mine is going on 4 years old with no problems. From a guy that has ridden both, the 125 is the better of the two.

Thank for the reply Mosh I was hoping that you may chime in, to be honest the video in your post of one of your 125 piranha 70's is what initially had me sold on the 125, before I started thinking about the 140.

Well that's two reply's with pretty much the same conclusion, so the choice seems to be made.

Let the build begin!!!

I may be in touch in the near future in regards to a new 70 seat.

Thanks again

Cheers

[CRAZY70MAN]

Thank you for the reply,

So in your opinion I would need to "streatch" the frame to fit in the 140?

I guess I really just need confirmation of weather the 140 will bolt right in with out making major changes to the frame. I have read conflicting threads on here and else where that it will fit in a standard frame and that it won't.

I know about the other issues with the intake manifold and exhaust and that wont be an issue for me to overcome, just would prefer to keep the trike looking as stock size as possible.

Thanks again.

You do not have to stretch the frame to bolt in a Piranha140. I have built several and they fit with minimal grinding of a few of the frame areas. I have ran oil coolers on my 140's and 150 but have ran them the last 4 years with no external coolers and they cool just fine. Mine do get abused on my flat track lap after lap on hot summer days regularly. Either motors are good, I have used and rode both. I personally stick with the piranha 140 because of it's availability of a local dealer in my area and its use in a dozen other bikes I race with. Throw a 26mm carb and the right pipe on it and it really comes to life! Either route you go I am sure you will enjoy. Just thought I would give ya my feedback. Enjoy and hang on my friend

[fastatc70]

I have built a couple of atc70s. From 184c to a restored Xmas special. I prefer the 125 for trails. Very well behaved motor. The backyard races I will run the 140cc. And usually only take out the 184cc for car shows or in the sand pits.

Stick to the honda style heads. The 26mm carb is great especially the 606 model. I haven't run an oil cooler in any of the builds even the 184cc motor. I don't race but they are riden hard.

The motors have the same bolt pattern as the stock motor but the frame that runs between the motor mounts will need to be ground to match the contour of the new motor. The exhaust should be replaced because of the added HP and I think the 140 may be a little longer in length. I know the 155cc and larger motors are longer.

Starting the motor is a little tricky, I like the pull start and prefer it over anything else. The ignition on the Chinese motors have been unreliable and I recommend replacing it with Honda xr or CRF stator plates, flywheel, and CDI boxes. I have pics on where you need to modify the pull starter and how to attach the grabber cage to the factory honda flywheel without spacers.

[big specht]

I want to know what those rear fenders are off of?? As for the motor you could put a 146 kit on it. As for the oil cooler I would run one you would be amazed at how hot the oil gets , we have maxed out a 220 degree gauge.

[Tas Wheeler]

Either route you go I am sure you will enjoy. Enjoy and hang on my friend

Yeah still tossing up between the two. I'll be sure to take your advice there.

Cheers

[Tas Wheeler]

The ignition on the Chinese motors have been unreliable and I recommend replacing it with Honda xr or CRF stator plates, flywheel, and CDI boxes. I have pics on where you need to modify the pull starter and how to attach the grabber cage to the factory honda flywheel without spacers.

Thanks for the info, will be in touch soon to discuss more.

Cheers

[Tas Wheeler]

I want to know what those rear fenders are off of?? As for the motor you could put a 146 kit on it.

PO put those fenders on. They are off one of the little china quads, a 50cc Kazuma Meerkat, I'm pretty sure. The don't really fit all that well without a bit of mods to the seat and fender brackets.

As for the 146 kit, that was one of my thoughts, I think I might start with the 125 and then if its not enough then I'll have that option.

Cheers

[59GMC]

i just brought my 82 110 into school for a top end freshen up. My teacher said he has a 140 that i am welcome to the top end. Is it possible to just swap the 140 cylinder, head and carb onto the factory honda 110 motor? or a 125 top end for that matter?

[Blown 331]

i just brought my 82 110 into school for a top end freshen up. My teacher said he has a 140 that i am welcome to the top end. Is it possible to just swap the 140 cylinder, head and carb onto the factory honda 110 motor? or a 125 top end for that matter?

I doubt it. Most of the 140/150 etc motors are based on an ATC70 engine which it totally different than the 110. Unless your teachers 140 is an ATC110 engine with some type of 140cc big bore but I highly doubt it. But if you have an ATC125 top end that should work on the ATC110. But if its a China 125 based on the Honda 70, then that will not work.

[59GMC]

ok thanks for the info

[fastatc70]

i just brought my 82 110 into school for a top end freshen up. My teacher said he has a 140 that i am welcome to the top end. Is it possible to just swap the 140 cylinder, head and carb onto the factory honda 110 motor? or a 125 top end for that matter?

Depending on who made the 110, the bolt pattern should be the same as a factory honda motor. The 125 and the 140 motors have a bigger space between the cylinder studs. The top end more than likely will not fit. Sorry.
Again depending on the motor but the 125 and the 140 motors are the same except for the crank. Longer crank on the 140 motor.