As the acknowledged expert on extracting the most power from the smallest 2 stroke can I please ask: Theoretically, if one was going to "modify" the exhaust port on a 2 stroke moped (for instance a TS50) where would one file, and more importantly, where wouldn't one file. TIA -- Dan L (Oldbloke) My Bike 2000 Honda CB500 M'boy's Bike 1990 Suzuki TS50X (Heavily fortified) BOTAFOT #140, DIAABTCOD #26
Next..... -- Dan L (Oldbloke) My Bike 2000 Honda CB500 M'boy's Bike 1990 Suzuki TS50X (Heavily fortified) BOTAFOT #140, DIAABTCOD #26
The whole lot of ports need moving up. You need to make a spacer shaped like a base gasket from aluminium and sandwich it between two base gaskets, then skim the top of the barrel to restore the compression ratio. You will need to make a proper expansion chamber. You will need to put stronger springs in the centrifugal clutch so you can reach the power band while starting off. Get a book such as Bell's Performance Tuning - 2 Strokes to see where the ports should be. The last moped I looked into had an exhaust port that was oval instead of round, but it was obvious where it needed grinding. A bigger carb would help.
Suzuki TS50? 1977--? TS50 has no centrifugal clutch..It`s multi-plate same as any geared bike. Couldn`t hurt. Not really, the idea is to make the best of what`s provided.In this instance and without details a mild tune would involve... [1] Reed valve induction...replacing the std metal reed petals with 0.3mm carbon fibre reeds (£9ish) this allows them to open sooner and close quicker allowing more induction a less blow back through the reed valves. [2] Rotary valve induction....carefully taking out 0.5mm of the leading edge of the circular valve to allow earlier and more induction without compromising the transfer. [3] Correct jetting...believe it or not any carb will run a bike [9]without a throttle slide or needle.. as long as the pilot system is set-up right and the cap is blanked the bike will run. Concentrate on the mid/full range which is controled by the needle position ( move the lil `E` clip UP the needle to weeken and DOWN the needle to richen, most have 5 slots) Don`t mess with a Dremmel and grind stone on the barrel ports, they make no real difference to performance until you start swapping exhausts, going into resonance and back pressure, etc. You can increase flow by flowing the exhaust port without touching the specs as it enters the barrel just by smoothing the ridges and polishing..however carbon build-up normally ruins all the hard work in the first 100 miles or so:-( Mail me for any probs you have as I can return diagrams etc better than posting it. Save UKRM loads of unneccessary 50cc shite as we know everyone on here is a wheelie hero/RTB/track God/and excellent mechanic and have no need of service mechanics/torque wrenches or advice ;-) -- Petel . 02 M2 Buell. C90-ZZR. [9] It does run but don`t touch the throttle, it`ll bog out. http://homepage.ntlworld.com/peteh1/website/index.html
AMMENDMENT: 1990? Just read your sig! Twist`n`go or geared stroker? There is a huge difference between the two. I can help on both but need details on make /model and configeration...I.E geared/reed/rotary valve/carb make and size plus any more info inc. pre-mix or auto-lube oil/plug sizes and rating...easy just post a URL link to your son`s bike, a brochure scan or photo will be good enough and I`ll source the make and model.
Okay, details as follows: 1990 Suzuki TS50 http://www.motobykz.co.uk/Suzuki/Suzuki.htm 2 Stroke with Autolube, 49cc Bore: 41mm, Stroke: 37.8mm, compression ratio: 7.1:1 Reed Valves, 5 manual gears Trail type bike Mikuni VM15SH Carb, 67.5main jet replaced with a larger one (not too sure, but it's about a 97 I think). Plug: NGK BP6ES Bike currently maxes out at just below 40mph, ideally we would like to get nearer to 50mph. I have inspected the piston /barrel, and they seem fine (no scoring), also, I decoked the head and exhaust port last week, and the reeds appear okay to me. This weekend we plan to replace all the gaskets, as the barrel to crankcase one is a homemade cardboard one, and there is evidence of loss of compression around the head gasket. The exhaust bolts are fucked, so I plan to replace these with studs to get a good gas tight seal. Also, the inlet side of the barrel seems to have been filed out to a circular profile, whereas as standard it is oval. I decoked the exhaust a few months ago, but that is another story altogether which resulted in an eye / caustic soda interface. I may fire up the barbie and cook the fucker tomorrow to loosen any stubborn crap. Any advice you can give would be much appreciated. Regards -- Dan L (Oldbloke) My Bike 2000 Honda CB500 M'boy's Bike 1990 Suzuki TS50X (Heavily fortified) BOTAFOT #140, DIAABTCOD #26
<snipped> Morning ;-) There are several ways to go...Big-bore..Tuning the std bike... etc but it all involves money and luck! The first thing I`d do is take out the reed block and check if the petals are plastic (normally a white/biege colour) or metal (use a magnet) then replace them with carbon fibre items. An old part # but it might help is BY8610 for Boyer carbon petals for the TS50X. Big Bore is £75ish. That takes you up to 69cc and into the Gray Zone as far as law and 16 year olds is concerned. Part# is IM8BBTSX. My apoligies to the guy that suggested a bigger carb last night ( and I dissmissed the idea) because it might help with both the above. Get yourself to a breakers and grab a Mikuni VM20ss off an old Yam DT 100.You might have to cut away part of the rubber boot from the VM15 to make it fit or get the original rubber inlet manifold with the deal. Should`nt cost more than £20ish depending on the breaker. ID# on the carb is 3A360 and they run a #130 main as std. Suggest going down to a #100 and try from there. Air screw out 1.5 turns. Air filter....Your call....Junk the airbox and run a K+N onto the original rubber boot that went to the airbox, not direct onto the carb mouth as resonance with too short an inlet tract can ****-up the jetting and you need a sort of plenum chamber to get the carb to work properly over a wide rev range. Use the original airbox but make sure all the airways and inlets are at least the same surface area as a 20mm carb. Surface area of a circle is Pi x R squared (I think) ;-) Might mean drilling some holes in the box in the quest for speed but remember most of these airbox designs are not for maximising power but for minimising noise and emmissions. Exhaust...Your call...Junk it and find and expansion chamber from an old RD or simply lessen the baffleing by drilling more holes. All this will create more noise and might weaken the auto-lube mixture to the point of seizure! I`d reccommend setting the oil pump to normal spec (where the marks align) then going 2-3mm over the line so the pump is running richer, use a good synthetic oil and check it`s not Pre-mix only! (I`ve done that and pre-mix dos`nt work well in an auto-lube system). Finally go colder on the plug. Try a BP7ES or if you can get one a fine wire race plug # BP7EG. HTH and g`luck. -- Petel . 02 M2 Buell. C90-ZZR. http://homepage.ntlworld.com/peteh1/website/index.html
The reeds are (I think) Boyesen Racing Reeds (according to the sticker on the side panel), but they look more like plastic to me. Don't really want to flaunt the law to that extent We are currently scannin ebay for a VM 20 Carb Tried changing the filter for a small jobbie my lad bought from the local car shop, but the inlet was just too small. We have resorted to the the old airbox, which has been drilled, and we have halved the thickness of the filter media. We will look for a K and N cone type with a similar diameter to the carb inlet. There is no baffling in the exhaust, and the end can is a Dep tuned jobbie. I barbecued the exhaust today for about 2 hours, and managed to loosen quite a lot of crap. I haven't investigated the pump yet. We are currently currently running a BP6 so a plug change is next on my list. Many thanks. Today I removed the head and Solvol'd the combustion chamber to a mirror finish with a Dremel clone. I also Dremelled the exhaust port to a smooth profile (it was very rough) and polished, as recommended. The bike still maxes out at 40, but doesn't feel so stressed. Also, at 40 it is only at 8000 RPM, so I reckon changing the front sprocket to a smaller one may release a few more revs. I will keep you posted. -- Dan L (Oldbloke) My Bike 2000 Honda CB500 M'boy's Bike 1990 Suzuki TS50X (Heavily fortified) BOTAFOT #140, DIAABTCOD #26
They did two types under the `Racing Reed` name. You really need to go carbon fibre, it`s a lot more flexible but with the right amount of stiffness to stop blow back and loss of crank compression. We swopped plastic for carbon on a new Suzuki Katana twist`n`go and the differrence in throttle responce was instant. Don`t limit yourself... A VM 22 will fit as will a Dell Orto 21mm. It`s all in the jetting. You can custom build the airbox by buying Mallossi Red Filter foam. It`s always better to run with an airbox of sorts (no matter how many holes in it ;-) Do a Google for .....Taffspeed...PMtuning...Chiselspeed..and Beadspeed. Any of them stock this filter foam and it`s very free-breathing. Cost...about a fiver for a sheet. Er... do it! What`s the red-line? 8 grand seems about right to me. Most 50cc strokers make max power at 8-9k and gain nothing over this benchmark. Remember we are talking a single cylinder here...not a Kwack triple or Aprillia RS250. Leave the front sprocket (14/15tooth?) go down on the rear. From EG. 40-38 or 36-34. This will give you more top-end but decrease accelleration slightly. Also it means you won`t need a longer chain, just nick out a link if the chain is too slack, Let me know how you get on. -- Petel . 02 M2 Buell. C90-ZZR. http://homepage.ntlworld.com/peteh1/website/index.html
M and P seem to do CF reeds for the TS, this could be the next mod, although whoever replaced the last set severely overtightened the retaining screws and fucked up the heads, which will mean a major struggle to get them out, and replacement of the screws (could I replace them with conventional hex head bolts, or is there some technical reason for them being cross head type machine screws?) Will the carb to head casting be the same size on the bigger carbs, or will I need to have an adaptor plate made up? This very much seems to be the case, with no airbox it runs crap, and with just a gauze over the end of the airbox connecting rubber it runs crap. As the "media" is actually the packing foam from a set of crystal glasses, replacement with pukka stuff (or a K & N type thing is in order. Also, for some reason the standard airbox connecting rubber is too short, and has a habit of parting company from the carb. Will do. Indeed, the bloke we bought the bike from gave us the Dep pipe, as he had to remove it due to complaints from the neighbours. We did a long run yesterday (see separate BOTAFOT thread) and lubrication does not seem to be a problem ATM. Also, when on the move it produced very little smoke (this is a good thing, yes?) Around 11,000 It'll rev over this through the lower gears, which is why I suspect the sprocket sizes (I could be wrong though). Watch this space Why not the front sprocket ? Will do, cheers for your guidance, it's much appreciated. Having test run the bike by screaming around the local lanes, I can confirm that small strokers rock mightily. Now I definitely know I should have had one as a teenager. -- Dan L (Oldbloke) My Bike 2000 Honda CB500 M'boy's Bike 1990 Suzuki TS50X (Heavily fortified) BOTAFOT #140, DIAABTCOD #26