batavus tune-up

motormike /

I have a 1977 Batavus HS-50, its a 20 mph version. And this is what ive done so far

first I got a bigger 35 mph carb off of a mobat I completely cleaned it out absolutely every peice spotless, then i pressed the restrictor bushing out

of the intake pipe and bored it out about 2mm larger mostly to remove the ream at the bottom, then i got new points and a new condensor set those to specs. and finally I removed the rear baffle in the muffler. So after doing all this its top speed is 15mph. It takes off great and quite quick but when I get the rpms higher it boggs down and topps off at 15. So then I took the air filter and air filter box off and the power boosted about 5mph reaching 20. This time it didnt bogg out as bad but it seems like it has more of a power potential. So whats my problem, is the dwell of the magneto off and not firing on time, is it chocking on too much fuel, is there not enough fuel. I read freds guide and he mentioned that if i run it without a filter that the motor will starve for oil/fuel mix and lock up so if its my air intake thats the problem what kind of filter could i put on there.

by the way Im hoping to reach a top speed of about 30

and the engine has about 90 psi compression is that low for a moped? im mostly used to working on autos and 90 seems kind of low on the scale.

thanks for your time

never swarming but always destroying


Re: batavus tune-up

Ron Brown /


I have a 1978 Batavus Starflight. The label says it is a 25 mph version. So far, I have bored out the carburetor between the slide and the manifold, to the same size as the rest of the intake and cleaned/adjusted everything. Without the air cleaner I get about 25 although I can't swear to the speedo accuracy. It has improved a lot since I started and I am now playing with the jetting.

Brian, who posts fromm time to time, is working on a tuned exhaust for the Batavus. Look for his posts.

You do not say whether you de-carbonized the motor and exhaust port. If not, you should do this and check the timing.

Do a plug chop at max speed and see if you are too rich or lean. This makes a huge difference.

Keep us posted.


Re: batavus tune-up


I recently fitted a Tomos Bi-Turbo exhaust to my 25mph Starflite. I now get a good 33mph out of it, and the performace is better overall. Steve

Re: batavus tune-up

i was wondering if it sputters alot? when i took the baffle out of my '76 batavus bingo after awhile it started and wouldn't stop sputtering until i put the baffle back on, it's supposed to be the 30mph version but it takes some time to hit 30, really really slow acceleration, so im still working on modifiing it a bit

Re: batavus tune-up

hi, i have a kawasaki ar50. i had the same problem as you, it feels like the choke is on all the time right? if so the problem is with the carb. the main jet in your carb is too big so too much fuel is going into the engine and just clogging it up. a little word of advice, don't put a too small jet in your carb or your engine could seize...

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