Tomos A35 Performance! (by mattology)
Tomos A35 engines provide a robust two speed transmission underneath a 49cc air cooled, reed valve inducted cylinder. Stock they should provide between 30 and 35mph, but with a few modifications, they can go much faster. With cylinder big bore kits thrown into the mix, Tomos can be very quick mopeds.
A35s are great engines. They are restricted pretty heavily from the factory, but with a few updates and modifications to the stock, untouched engine, you should easily touch 40-45mph. The most common modifications in order to get the most out of an A35 with simple modifications involves putting on a performance exhaust and a nice air filter / intake. When the bike has these modifications performed, and is re-jetted accordingly, it should be able to touch 40mph with stock timing and gearing.
Gearing is everything on your Tomos. Look up the gearing spreadsheet and you will see what your gearing setup will do for you.
Things to note:
- 25, 26, 27, 28, and 31t sprockets available for front FLAT setup.
- 26 and 27t sprockets available for front DISHED setup.
- Some A35s and A55s have dished front sprockets, depending on what bike the engine is from.
- The 31 tooth requires either an internal rotor ignition or a late nineties/early 2000's 12v 80W Iskra CDI flywheel that comes with a 4-pole stator setup. You can't fit a points flywheel setup on with a 31tooth sprocket.
- For maximum blast, 31t front, 20t rear. 70+cc kit recommended. (Very similar to 18x36 gearing on an E50 Puch).
- For maximum fun around town, 27t front 22t rear. Pretty much the defacto gearing setup for most Tomos bikes. Still super easy to climb up hills, and headroom for about 53mph up top without breaking anything.
- 22t is the best rear sprocket and easiest to do. You can get a 20t, but be warned: you will have to take a dremel to your rear wheel and/or turn it down on a lathe or mill. it's time consuming, and only really gives you room for 4more mph or so at the same RPM.
Throwing a kit on that bitch
Tomos A35s are great engines, but they do even better with a 70cc kit. You can "throw a kit" in literally one hour. It's super easy. I'm not going into mad details on here but here are the majority of them.
First, you can use any Puch kit. That's right. go on the Puch cylinder kit summary page and look up any cylinder you want. It will fit right on. Bam. Real talk.
but FOR THE TOMOS A35 KITS......
1. Alukit = torque, awesome kit. great price. Available from treatland. Same as Kstar, sometimes you get a kstar box, sometimes you get an alukit box. Good kit, works best with Techno Circuit pipe. With a techno estoril it maxes out around 9500 RPM. With a Techno Circuit around 9700 RPM. Great kit for the money. Doesn't come with reeds. Put your old reeds on or get some Polini reeds. Sreet price $110.
2. Airsal A35 kit = very similar to the Alukit. Port map is slightly more aggressive with exhaust timing but has slightly less blowdown from the measurements I remember taking. If someone can take port measurements or a port map, that would help. This kit is slightly slower on the low end but did about 2mph more on the top end in my experiences. So around 9800 RPM or so. street price $130.
3. Parmakit = this kit is a bit of a difficult beast. Beautiful bridged transfers give you lots of opportunity to increase and maximize the port time area on this kit. However, the base spacing is off. The squish is set too close with this kit on a typical single base gasket, no head gasket setup that works so wonderfully with other Tomos kits listed above. This kit has potential to be fast, but I haven't realized it yet. You will have to make multiple base gaskets to set the squish properly, and spend some more time tuning this kit in order to get the best power out of it. If you just throw it on you will have detonation issues. Street price $170.
4. DMP = torque, good kit. almost identical to Kstar. Haven't touched one in person so I can't supply that much more information. Talked to a dude at Whiskey Business 3 that said it was great. Street price $90.
5. RAPTOR kit. No. no. no. no. Waste of money. Don't even consider buying this kit. Shoot someone that recommends it. It's just an Airsal kit paired with a Dellorto 16.16, paired with a Technigas exhaust. No. Fail. Run. Not worth the $800 or whatever they charge. Bad hipster.
Note: Puch kits also fit on Tomos A3/A35/A55 motors. A custom exhaust header will need to be fabbed up because of the different exhaust angle on the cylinder.
TUNING! so important. seriously. if you're not going to spend the time to tune your nice kit, it will soon be part of the wall / table / shelf of shame. so spend the time dialing in your setup if you want to get the most out of it.
The stock SHA 14.12 carburetor is not ideal for tuning or high performance of any sort. This is because there isn't a needle to aid in the proper metering of fuel, and only a single jet to fuel the entire throttle and rev range. For a stock bike it is alright, if it's in great condition. For performance, even 50cc performance, there are better options.
There are now two readily available intake systems for the a35 bikes. the first is a 21mm phbg spigot style intake from treatland. The second is a "weak-ends" produced part that is designed for the 20mm mikuni VM carburetor. both are great parts that will allow you to get more fuel into your cylinder. Either carburetor choice has multiple jets to dial in the entire powerband, as well as diferent needle settings and tapers that are available.
i got sleepy so ill finish later
Looking for more power
Putting a ZA50 CDI on in place of the stock CDI setup is one way to get additional RPM out of your Tomos kitted disaster. Look at the Install Treatland ZA50CDI onto Tomos article for more information.
not for rookies, mostly for gurus. If you are still curious, read Graham Bell and Gordon Blair.
No need to be afraid of a little port work. If you're going to buy a bigger cylinder you might as well play with your stock and see how fast you can go on 49cc.
Following pictures are a start. Credit to Cupertino Zack:
And raise and widen your exhaust a few mm.
I did this conservatively and gained an easy 8 mph and more with a bigger carb and some decent tuning.
Don't be afraid, dig in!
if you're really taken it to the next level on your tomos, (which you probably haven't, unless you're well into the mid 60s) then it might be time to look into an aftermarket clutch system. that will last a little bit longer than stock. this is also what you'll need to do if you decide to do an HPI ignition on the bike instead of the wonderfully better treatland za50cdi.
dennis kreeft makes a wonderful ktm clutch setup onto the tomos a35. it's not for everyone. it takes a ton of work to set up properly and get the performance that you need out of it. i don't recommend it unless you enjoy working on your moped more than riding it. it also has a tendency to blow out your 1 way bearing for you pedal-equipped mopeders (that's like everybody) so you will have to either get a new one or replace it with one out of another clutch drum.
there is no easy way to switch over to an A3 transmission. you need an A3 crankshaft also, because the crank spacing is actually different. however you can use A35 / A55 parts interchangeably. One thing you can do is use an A3 primary if you want, it gives you slightly shorter final gearing. usually that's the opposite of what tomos guys want to go for however.
atf type F or type A might be what tomos recommends when using stock bikes, but for performance i haven't found that stuff to work very well at all. A better setup is to use a mixture of 50% atf mercon dexron , and 50% 85w140 gear oil. shaken, not stirred, and mix 700mL of that into the clutch. 700mL !? you might be confused thinking, that's more than double what the original tomos calls for! And you're correct.
but trust me, it works. try it. it works.
don't listen to douchebags telling you to 'cut the springs'. it does nothing except wear out your clutches faster. the springs arent the issue. don't listen to people telling you to cut weight off the clutch shoes either. that's not very smart either. unless you like pedaling home with stuff broken, then maybe it's a good idea.
it's time to eat so ill finish later