27 tooth sprockets/Bi - Turbo

Hi guys,

I've been checking this group for awhile and I keep reading about 27 tooth sprockets and Bi Turbo mufflers for Tomos mopeds. Currently I ride a stock 1999 Tomos and I have some questions.

What size of sprocket is in a Tomos Targa? How much more mph will a 27 tooth sprocket give me? Is this type of modification difficult? Can I damage my bike by using a bigger sprocket? I also read that this modification will reduce acceleration but give me higher top speed. How much acceleration is lost?

What about Bi Turbo mufflers? Will this and a 27 tooth sprocket give me more speed? If so, then how much more? From what I understand installing a Bi Turbo requires some welding. Is this true? I would like to do these modifications myself so as to keep the cost down.

I do a little highway driving (about 3 miles) every day. Will these modifications allow me to go at least 50mph?

I am seriously thinking of doing some or all of these modifications and I would like some feedback from you more experienced moped riders out there.

All help is greatly appreciated.



Hi, I've got a 2000 Tomos Sprint, and have just finished going through an upgrade.

I went with the speed kit and all, but before changing everything I tried out just the

new sprocket and the BiTurbo. The BiTurbo gave me about 5-7 more mph, and the

new sprocket gave me about another 5 mph. In total the combo will give you another 10 mph (your mileage may vary). That was in a sprint, I would think it might be a little more effective in a Targa. My top speed was 30 (33 with tailwind)

and after just the sprocket & BiTurbo, my needle sat right on the 40.

The sprocket will require a slight modification to the case. There is a reinforcing rib on the case in about the 9:00 position that needs to be ground down slightly to make room for the slightly larger diameter. If you''ve got a dremel too, it's a snap.

First you take off the case, and then, flaten down the one edge of a washer beneath the nut that is bent up to prevent the nut from moving. Removing the nut

is "lots" of fun. I had to go out and buy a bigger adjustable wrench, and then whack at it with a hammer to loosen the nut. My bike only had 100 miles on it so

you may not have such a hard time.

If you are not changing the cylinder, you can go with the 1 piece muffler, and it should just be a bolt up change. My kit came with a two piece. The clamp that is supposed to hold it together was a piece of cr@p, and it did not line up with the mount on the swing arm (too low). Luckily I have a friend at the local muffler shop who welded the pieces into one for me this weekend. It still sits about an inch below the hanging bracket in the back, but I just got a piece of steel to fit, drilled

two holes, and mounted it all together. My friend was afraid the welding needed to heat and bend the pipe would discolor and possibly peel the chrome. He loves the chrome/gold muffler on a moped :-)

With the BiTurbo in, you will want to change to a side kickstand. The old one will drag going around corners, cause the new muffler gets in the way of the kickstand coming all the way up.

I tried the sprocket before the BiTurbo, and I lost a little acceleration, enough to notice, but not enough to care. Once I had the muffler on though, my acceleration was much better than it was before changing the sprocket. If you do them both, you will be much better off, but I don't know about 50 mph

Re: DejaVu

Thanks for the info Ray. Right now I am getting 35mph on a flat road and a boost of 10mph would probably do me just fine. I live in Canada (250 miles north east of Toronto) and will wait for warmer weather before I begin any modifications. I am glad to hear that your modifications are working out. I don't think I'll go to a 70cc speed kit. From what I hear, they are very hard on the bike and have a tendency to cause break downs.

Thanx again!

T. Clark

Re: DejaVu

hey ray. how is your speed kit? how fast is it? i am considering getting one and wanted to know what it is like. how long are you in 1st gear for? well thanks bye

Re: DejaVu

The speed kit is great so far. Cruises comfortably at 40, I can get it to 50 or a

little over, but the engine screams at that speed, and I just don't like it to

sound like that. Lot's of people have said to stay away from the 70cc kits.

I haven't had any problems yet, but I was also starting with a fresh ped, and

very carefull about everything I did. This isn't to say that they were wrong, I

may just not be having the problems "yet". It will cost you more to do the

muffler/sprocket/carb/70cc all as separate items, but I would say to try everything

but the 70cc first and see how that treats you.

It shifts out of first between 13-17 mph

My goal now is to either make a 30 tooth sprocket, or a bigger back wheel, or

some way to get a smaller sprocket on the back. I seriously want to see the

speedo wrap all the way around

Re: DejaVu

when i had the kit, i was able to get the needle to come back all the way around. all u need is the 27 tooth sprket, and be sure ur not going uphill (flat ground) and duck down as low as u can. Getting under the wind REALLY makes a big difference at high speeds

Re: DejaVu

gimmiejimmie /

keeerist Ray,

50+ on a ped, what's next,Dover Downs or flat tracking at Harrington?

it's possible to push these bikes to those extremes and I bet you will,

but a panic stop in traffic at that speed is toilet paper worthy,

consider beefing up braking, when I'm going 35 on mine, I don't think about those skinny ass little tires and the 1 inch wide brake shoes when granny pulls out in her buick.

more speed&power ...bigger brakes

but it sure is fun passing all the cagers stuck in traffic and you are making progress with a smile. hell,you wanna go faster, search earlier posts about nitrous oxide and helmet mounted rocket boosters. Ides of March...Junkyard Wars....and gimmejimmie.

Re: DejaVu

I wanted to get the ped to beef up for shock factor when riding in traffic. So far

it has been just what I wanted. Got to pass 3 guys in a clunker escort the other

day. The two passengers were laughing so hard they were in tears. The driver

is going to hear about it for a long time.

I've only had to make one sudden stop in traffic so far, your assesment of the

situation was correct. A definate adrenaline rush to say the least. Frequent

brake replacement will be necessary. Where can I get the bigger brakes you


Did you mention Dover Downs because you knew I was from dover, or was that

just a bizarre coincidence ? A neighbor of mine could get me in and on the

track, but you've got to be going about 80 to hold on to that banking, hmmmmm

It's funny when I get behind a car and you see them looking in the rear view. The

light turns green, and they spend more time looking back at you then ahead of

them. They gradually start going a little faster, and look puzzled when you are

not falling away in the mirror. If the lane is clear, it's fun to pull up along side

when they look back out their windshield.

Re: DejaVu

Was that wrap around on a Sprint or Targa ? Mines a Sprint

I'm on flat ground, got the 27 tooth, got the speed kit, got the BiTurbo, I weight

about 210. I'm running 4oz to a Gallon while the engine is new, and I'm still

not sure the carb is jetted/adjusted correctly. The extra oil would be my first

guess, but I don't know how much the oil takes combustion down.

Re: 27 tooth sprockets/Bi - Turbo

were can i find people who still ride honda spree get advise ect.?

Re: DejaVu

gimmejimmie /

I knew you were from Dover, I asked earlier about DE because of relatives of mine live near Bethany Beach. As far as bigger brakes, I guess you would have to go to a disc set up on the front since that's where most of the braking is needed. That would involve changing the forks or lower legs.

Theres a funny joke somewhere in these postings about a moped passing a muscle car or sports car. If I find it, I'll pass it on to you, it's a hoot!!

Re: Braking.

Reeperette /

I had some enhanced brake pads for the Tomos Golden Bullet, but I can't recall where I got them, I think they might have been offa Casal to begin with.....but tires also affect stopping distance, as does getting better cabling and levers, you can find slightly heavier brake cables or adapt from motorcycle cabling, and the larger levers (the one's that come on the Golden Bullet/Targa are pretty good) give you more pull on the cables.

As for tires, those Cheng Shins are really helpful in that respect.

Just try not to fly over the handlebars once you upgrade, eh ?

"Eat tha street, real men eat CONCRETE !"


Re: Braking.

I can imagine the looks on the faces in traffic while doing an endo.

Re: Braking.

Reeperette /

Endo ? not familiar with the term, but over the bars now....heh.

Reason I hate enclosed chain drive is cause if the master link breaks, the whole chain wraps around the rear sprocket and jams, instead of flyin off.

Imagine tying a rope to a fencepost, and the back of yer 'ped...then takin off and gettin a nice head of steam up....then runnin outta rope - it's kinda like that.

I had that HAPPEN, but luckily it was as I was pullin an illegal U-turn through a grass median strip, and I was wearin a helmet at the time, so no chance of being run over by traffic....however I did come down headfirst into a rock, left a nasty chip in the helmet, and when I took it off and looked I was like - dayummn, that coulda been my skull, ick.

Needless to say, I wear a helmet, but an openface 3/4, cause anythin more is like stuffin yer head in a trashcan and hittin it with a mallet.


Re: Braking.

You sure do write some funny stuff.

Endo(ver): that cool, braking front wheelie move like in mission impossible

Re: Braking.

Ron Brown /

That would be a "stoppie"

Re: Braking.

more knowen as a brakie!!!


"Endo" comes from the dirtbike world where you might get out of control and go "end over end" (usually at fairly high speed... not good).... endo.

The street squids have mistakenly (IMO) borrowed the term to their world where you can lift the rear wheel 30 inches off the ground with the powerful front brakes on modern sportbikes.

Thats a brakie or stoppie to me.

Re: Brakie

SteelToad / Ray /

I think if I tried it, you could call it a "Pavement Inspection"

Re: 27 tooth sprockets/Bi - Turbo

i have the new 2001 tomos targa and i would like to know where to get a cheap biturbo muffler

Re: 27 tooth sprockets/Bi - Turbo

Chris MWH /

We have the biturbo for $80.00

Chris MWH

Re: 27 tooth sprockets/Bi - Turbo

i'll buy a bi turbo from you. Are you a moped parts tore?

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account