2-stroke engine swap ?s

[Aerostudent]

I just got a wierd idea the other day, and I was wondering what kind of merit it could have. I was reading about dirt bikes and DB engines and came across talk about a 250cc 2-t, Yamaha YZ250something I think. I was wondering if the engine would fit in a large 150 scooter. I am thinking of making a swap ;D if it would work. Also, I was wondering what would be involved in puting a 2-t engine into a 4-t scooter. I'm not very familiar with 2 strokers, so what would I need to add/subtract (besides the engine itself).

Thanks for bearing with my totally noobish question, ;D
Aero

[voodoosix]

putting a dirtbike engine in a scoot would take some serious fabricating. ive been kicking around the idea of obtaining a higher displacement rotax or leader scoot engine to drop into a joker retro type scoot

[earlwb]

Motorcycle engines have a clutch and transmission. So you would have to fabricate and weld up motor mounts and a swing arm rig. Then you have to figure out how to get it to shift with some sort of a shift lever modification. Then the clutch poses a problem as your left brake lever is in the way, so you need to fabricate a foot lever for the brake as well.
Unfortunately the crankshaft is too short to adapt over to the CVT.
So to make it really work well, you would need to machine a new crankshaft and cast and machine a new crankcase to use the engine upper end parts on the scooter. Not exactly a easy thing to do.

[Aerostudent]

yeah, I thought it would probably be a lot of work, maybe sometime in the future whough. I was just toying with the idea anywho, and really don't have the money and time to do much more than drive to and from school right now. It would be pretty sweet to have a high(er) displacement scooter that is not a "touring" style. I have a racing style and wish it was faster, but I don't really think that a touring model is my style, I don't even really think of them as "scooters," maxi-scooter fits them pretty good though. But bikes have crotch-rockets, why can't we have scooter crotch-rockets ;D . Anyway, thank for hearing out my idea and replying.

Aero

[earlwb]

No problem, I am always coming up with wild thoughts too.
I was recently pondering about what it would take to make a four cylinder scooter engine using four 50cc four stroke engine parts. Air cooled or go for water cooling. do I go for separate cylinders and heads or make a unitized head and cyclinder arrangement. Do I go for water cooling or air cooling. etc.
of course a DOHC 4 valve 180cc scooter engine was on the mind too. I'd like a desmodromic head setup with that too. Water cooling would be even better.
many years ago, I had considered a 1200cc single cylinder 4c engine in a motorcycle. I like big singles actually.
then there was a Cushman scooter rolling chassis with a industrial diesel engine in it. That would be neat.
One of these days maybe.

[swampsniper]

earlwb said:

No problem, I am always coming up with wild thoughts too.
I was recently pondering about what it would take to make a four cylinder scooter engine using four 50cc four stroke engine parts. Air cooled or go for water cooling. do I go for separate cylinders and heads or make a unitized head and cyclinder arrangement. Do I go for water cooling or air cooling. etc.
of course a DOHC 4 valve 180cc scooter engine was on the mind too. I'd like a desmodromic head setup with that too. Water cooling would be even better.
many years ago, I had considered a 1200cc single cylinder 4c engine in a motorcycle. I like big singles actually.
then there was a Cushman scooter rolling chassis with a industrial diesel engine in it. That would be neat.
One of these days maybe.

A 1200CC thumper would boost you into orbit faster than NASA, LOL. Am I the only one old enough to remember manual spark advance?

[earlwb]

Think compression release and electric starter. yeah I remember manual spark advances too.
it was a cylinder, piston and head off of a radial aircraft engine of some sort many years ago.

[YellowScooter]

the last of the big-cc little scoots was the Dragster. I keep hearing talk of them making a comback to the US. "in 6 months" is what I keep hearing steady for the past 2 years now.
Just an overly publicised rumor I'm afraid.

[zeeks]

A guy can do anything with the right attitude, but hey WHEN you do, she'l fly, so hold on.

Good luck bro ;D

[earlwb]

here you go, how about a Vespa 750?
A four cylinder DOHC 750cc engine gives it a lot of pep too.
www.youtube.com/watch?v=f0bI241wPNY

[wireburn]

earlwb said:

No problem, I am always coming up with wild thoughts too.
I was recently pondering about what it would take to make a four cylinder scooter engine using four 50cc four stroke engine parts. Air cooled or go for water cooling. do I go for separate cylinders and heads or make a unitized head and cyclinder arrangement. Do I go for water cooling or air cooling. etc.
of course a DOHC 4 valve 180cc scooter engine was on the mind too. I'd like a desmodromic head setup with that too. Water cooling would be even better.
many years ago, I had considered a 1200cc single cylinder 4c engine in a motorcycle. I like big singles actually.
then there was a Cushman scooter rolling chassis with a industrial diesel engine in it. That would be neat.
One of these days maybe.

How about this one?




350cc, 4 cylinder, 2-stroke. Ya baby!

-Mike

[earlwb]

I love homemade engines. One of these days....

[Aerostudent]

Dude that's awesome! I even looks cool! And I know that it kinda has to be that way, but the exhaust pipes out of everywhere is a little wierd looking. As for more crazy ideas, I was thinking the other day of a "simple" 250 swap, or a 250 twin (ninja 250/something else). But this time I have a donor vehicle. I have one of those little gheto mini-bikes like they sell at pepboys (3.5hp B&S) that hasn't started in years, so I am going to eventually get a new engine for it, and since it has oodles of space, I though I might go a little bigger with it. I do want 4stroke though this time, as I don't want to mess with oil in the gas. This minibike swap thing seems a little more like it will happen sometime sooner than a 250 2t into my scooter ;D even my mom thinks it's a cool idea.

Aero

[ryan_ott]

Hey everyone I haven't been on here in awhile due to work and other projects. I have a good one for you. Here is a Tomos moped originally 49cc, I built new mounts to mount a Lifan 125cc 4 speed engine on. There were alot of things that had to be made to make this work but it was worth it. This is one fun toy.

[earlwb]

ryan_ott, that is pretty neat for sure.
I like it.

[ryan_ott]

Thanks Earl,
It was alot of fun to built. I pretty much had to redesign the frame to handle all the extra power. Alot of welding had to be done to made it strong. Its a blast to drive it only weighs 140 so it moves easily with 13hp and 4 gears. I've made plenty of creations like this one. This is one of my favorites.
Ryan

[90GTVert]

ryanott said:

Its a blast to drive it only weighs 140 so it moves easily with 13hp and 4 gears.

What mods are done to the engine? I ask because stock 125cc Lifan/Zongshen/etc... engines don't make 13HP... even the versions with big valve heads. My 114cc makes about 10HP, and thats with high compression big bore, race head, cam, intake, carb, etc... You probably have about 7HP if it's still stock or only has filter/exhaust. Check out some of the big bore kits for your engine. I've seen them make 20HP. I've seen a built, nitrous, 137cc engine go over 100mph and get there pretty fast too. Just something to think about, maybe you already knew it, maybe not.

A friend of mine just picked up a Tomos like that, we are considering putting my 114 in it. Seems like it would be fun around town.

[ryan_ott]

This is the big valve engine, piston swaped for Hi compression one. Lightened oil slinger and flywheel. Motor has been ported larger cam put in. I threw almost everything at it except for a crank. I'm estamating the HP I haven't taken it to a dyno. I strongly believe its really close to 13. Ok 12.5 rounds up to 13. ;D

[90GTVert]

ryanott said:

This is the big valve engine, piston swaped for Hi compression one. Lightened oil slinger and flywheel. Motor has been ported larger cam put in. I threw almost everything at it except for a crank. I'm estamating the HP I haven't taken it to a dyno. I strongly believe its really close to 13. Ok 12.5 rounds up to 13. ;D

Gotcha. I'm used to people believing the HP ratings from Chinese manufacturers.

[ryan_ott]

90GTVert-
Did you get the message I sent you?

[90GTVert]

Yeah, I just hadn't checked my inbox. I always for get without a popup. Replied now though, thanks.

[Aerostudent]

Hey Ryan, is that you selling the Dr. Pully Variator/sliders on ebay? If not,

90GTVert, I think it was you that referenced a homemade boost bottle on a mid-bike, how did you make it? I am still kinda throwing around the idea of something like that on my scooter and was hoping for some info. If you feel it shouldn't be discused here in the 2t section, you can post on my thread "Tuning Blog" in the 125+ sec, or PM me. Or if you want to totally ignore me that's ok too ;D

Aero

[ryan_ott]

Yes thats me selling the Dr. Pulley stuff on ebay. I'm just trying to feed my 2 stroke stroker project. ;D

[90GTVert]

aerostudent said:

90GTVert, I think it was you that referenced a homemade boost bottle on a mid-bike, how did you make it? I am still kinda throwing around the idea of something like that on my scooter and was hoping for some info. If you feel it shouldn't be discused here in the 2t section, you can post on my thread "Tuning Blog" in the 125+ sec, or PM me. Or if you want to totally ignore me that's ok too ;D

Boost bottles are for 2 strokes, not 4 strokes. Haven't seen them used on 2 stroke scooters really. I assume the reeds on scooters are more efficient and don't allow the boost bottle to work very well. I noticed less difference with a boost bottle after I put reeds on the midbike. If you still wanna know about boost bottles, I can point you in the right direction, but don't bother on a 4 stroke.

[earlwb]

Aww heck, and I thought you guys were talking about Nitrous.
Darn it.

[Aerostudent]

Yeah, that'd be great if you could point me in the direction. I was kind of curious what it does in theory and practically. I was thinking up (what I assumed a boost bottle would be) to be used for crisper throttle responce. I figured it would connect somewhere between either the filter/carb or the carb/engine and be like a pool of extra air and/or air/fuel that could be used imediately. I am probably wrong though, so please correct me (if needed).

Earlwb, I wish we could get someone to talk about NOS...Everytime the topic comes up, it seems to die after about 2 posts, or just before the person gives results. Like that shop bike someone posted recently. He was about to do NOS, the *POOF* no more posts for like 2 months. I would like NOS on my scooter, more for the fact that it would be RICE, Racing, and just plain cool!

Aero

[90GTVert]

This thread has all the info you should need. There is a link there that will explain the function of a boost bottle. Your idea of a boost bottle's function is right on though.

www.pocketbikeplanet.com/30-midbikes-superbikes/416-how-formula-making-your.html

I used the formula in that thread to make a couple for 2 stroke midbikes with good results. No dynos or any real hard evidence, but it passed the old seat of the pants testing. Also very cheap and easy, can't argue with that.

As for the nitrous, I've seen it in midbikes as well. The main problem with nitrous is the cost vs the result. It can work, but most aren't willing to do it when they think it over. Yes, you can gain horsepower and torque from a nitrous kit on a small displacement engine. Unless you have a kit lying around, it won't be cheap. Nitrous around here is $4.00 per pound. You shouldn't use it for much more than 10 seconds at a time. These small engines are air cooled, and nitrous causes a sudden burst of heat. You could put the same amount of money into engine modifications like heads, cam, carb, etc... and use your power all the time. If you have an already upgraded engine, some of these little suckers don't have the best head studs, block castings, etc... They have been known to bend head/cylinder studs, rip them right out of the block, and all sorts of fun stuff once they are making a little power. I'm not saying you shouldn't try it, just make sure it's what you want first. It should also be attempted by someone with general knowledge (aka if you cant keep your engine in proper tune now, don't add to your problems with a nitrous kit). This isn't just referring to you Aero, just some general knowledge for anyone reading.

[Aerostudent]

Thanks for the link and the advice. If I take the chance of ripping my engine through the seat, I might have to wait on the NOS untill I have some extra time and money (yeah, like that will ever happen ) and untill I know what I am doing a little better. I have seen small kits on ebay for a decent price (10lbs, 5 lbs, and 2lbs ), so that would be the way to go cost wise.
Do you think a boost bottle would have any effect on a 4stroker engine? It seems like it might, but nowhere near as much as on a 2-stroker. Again, just kicking around some ideas.

Going out to finish carb tuning on my GS-R...

Aero

[90GTVert]

aerostudent said:

I have seen small kits on ebay for a decent price (10lbs, 5 lbs, and 2lbs ), so that would be the way to go cost wise.

You may want to steer clear of a 10lb bottle on a scoot. If you wanna make it really obvious to everyone, a 10lb bottle would be a good choice. If you want any chance of hiding it a 2lb or 5lb bottle would do much better. Not sure how familiar you are with nitrous and bottle sizes, so just to be clear of how big 10lb bottles are here's a pic of 2 of them in a friend's car. Think about how big that would be on a scoot. A 10lb bottle also weighs about 24lbs when filled (unless you're gonna spring for carbon fiber).



If your confusion is because of capabilities of each bottle and not physical size... .8 pounds of nitrous is supposed to make 100HP for 10 seconds. That said, with a 100 shot people commonly get 6-8 passes with good bottle pressure with a 10lb bottle. That said, 10lbs is a lot of nitrous for a 1-5HP shot.

aerostudent said:

Do you think a boost bottle would have any effect on a 4stroker engine? It seems like it might, but nowhere near as much as on a 2-stroker. Again, just kicking around some ideas.

It may make some difference, but I wouldn't expect anything. Do it if you feel like experimenting, not because you really want power/response. I would think playing with the torque spring would be a better option (and proven) if you want it to feel more responsive.

[Aerostudent]

Hey, thanks! If I do put NOS on it, it will be a 2lb bottle. I didn't know exact sizes, but I did know that if cars run 10,15, and 20lb shots, I figured 1-2 would be about perfect for a scooter. Any advice on torque springs? I was thinking of either ordering a stiffer one, of putting a shim under my current one (simulated stiffer spring) which would give easier downshifting right? Thanks!

Aero