Batavus Performance

Hi i was wondering if theres anything i can do to my HS50 to get more top speed. Modifying exhaust maybe, or maybe a new performance one. i dont wanna do anythnig that will compromise the reliability, so i really dont wanna tear up the top end since finding anything for this bike is impossible. Any help would be greatly appreciated thanks

Re: Batavus Performance

mill the head, by a 15mm intake from motion left mopeds, mount a 15mm dellorto on it, mount a biturbo on it (requires exhaust header cut-and-weld), put better reads on your reed block (get the reed paper from treats hq). that's all anyone's figured out . . . though there are mythical batavus-bottom-end-with-a-scooter-top-end-that-just-happened-to-have-the-exact-same-stroke-parameters peds out there, or at least so i'm told.

Re: Batavus Performance

and if you do all that you'll hit 40.

Re: Batavus Performance

talk to devin at motion left mopeds. 1977 sells an intake that they make for a dellorto 15:15 so you can ditch that stupid 8mm encarwi. thats a good place to start.

Re: Batavus Performance

I have done all the mods listed and ported the cylinder and I get like 35-40. You can derestrict the stock exhaust by just taking out the second baffle. Just unsrew the bolt in the end of the exhasut and pull off the cover. Then pull out the baffle and screw it back together. also upjet one or two sizes. This should make you go closer to 30mph.

Re: Batavus Performance


I just bought the dellorto 15.15 carb for my batavus, and the custom intake from motion left, but want a little more info on the porting/ milling. Did you have that work done, or did you do it yourself?



Re: Batavus Performance

batavus is tricky. i spent a good year working on this one. if you actually get your bike to go 40 (high 30's) your low end will be aweful, ESPECIALLY if you are running a biturbo. If you run a 2 piece biturbo, run the original header pipe on the biturbo and fine tune your header length- that is where the difference is once you have milled the head, ported the cylinder and upgraded your carb (devin is the guy to go to). If you shorten the header to the point where you can't pedal anymore that is when you can get in the high 30's. You will hate riding it though. You are better off starting off with a longer header pipe and tuning it (slowly cutting it down) to where you easily hit 33 top and learn to live with that. You will at least be able to accelerate somewhat decently and not get run over when the light turns green.

If you are starting fresh, and have any experience welding i would figure out how to put a puch engine on that frame. a lot of people are figuring out how to do that and it surprisingly is probably the cheapest way to get a batavus going faster (solid 40s). no joke.

Re: Batavus Performance

🇮🇹💦 Of the Loin /

you can get a 12.12 dellorto on there no mods required.

also theres the clutch mod you can do as well

Re: Batavus Performance

Ask that kid from Jersey. He has big plans in the works if someone would just get him measurements for reed cages.

Re: Batavus Performance

Was that sinsire? or sarcasm lol either way i dont care


get the 15mm intake and carb, bolt it up

milling the head can be done by your self at home carefully, you go to a store and get a fake piece of marble, then get some sand paper of grits you find appropriate to sand down a head, then tape down the sandpaper to the marble and rub the head in a figure 8 on the sandpaper, being careful not to tip it one way or another, this takes time but is worth it as you get a perfect seal as long as you do it to the cylinder as well then finish up with some more fine sandpaper mill it down as much as you see fit but if you go too far and the piston hits the spark plug, then just add a really thin gasket to make it not hit but make sure theres adequate room for expansion of the metals, if you mill it down this far i strongly recommend the super gas at the gas station if not racing gas because it is high compression

i have heard adding base gaskets will improve speed as it does give the engine a longer exhaust port duration that changes the power curve but i have not done it so yeah

the reed is modifiable, you grind out the studs holding the reeds on and then after they are removed, file the area down flat, then grind out the thing in the middle of the two air flow passages, and get some Boysen reeds or what ever reeds you chose and tap some new holes in the reed and then screw on your new reeds allowing at least!!!!!! 1mm overlap on every side where the reed contacts the cage

i would strongly advise against the Biturbo because the specs are way out of proportion to this bike, but if you want simplicity, then go this way otherwise get any other pipe from a Puch or Tomos and make it fit with a little cutting and welding

the exhaust port in the cylinder is very restrictive and i would get rid of the "steps" in the port

match the cylinder to the case

get new rings if you are getting a lot of blow by and the wrist pin as this is probably worn as well maybe even a new piston

if the piston at BDC does not uncover the exhaust port all the way grind out the piston on that side until it does

if you want to get advanced, then email me but it does require extensive modification


should i post this in the wiki?

Re: Batavus Performance

What's the clutch mod all about?

Re: Batavus Performance

clutch mod is when you take apart the clutch and theres a spring thats in the shape of a circle with lots of ball bearings in it, you unscrew the spring fro its self and then dump the balls out, then replace every other ball with something lighter than the metal one, some here use rubber tube cut up i myself have tried this but when i tried to take it apart, the spring got deformed and is now useless, but well worth it i hear if you can complete it, i am looking for another route to this now

also ive heard some puch rear sprockets fit and a guy one here will make you custom sprockets if you send him the old one for measurement

Re: Batavus Performance

jason when are we working on that batavus?

Re: Batavus Performance

Sometime when the weather isn't so friggin cold. Which hopefully will be sometime soon. I'll need your help.

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