wild foamy Posted November 20, 2008 Share Posted November 20, 2008 hi everyone. am looking to upgrade the carb on my DT50MX, i think the original is 14/16mm or something like that but most 50cc performance carbs are 21mm. so i got looking on ebay and came across this: http://cgi.ebay.co.uk/OKO-21mm-RACING-CARB...%3A1|240%3A1318 would this work with my DT50MX? regards Steve P.S. i am already running a bigone expansion pipe and exhaust and plan to add a Polini 65cc kit, i understand re-jetting will be required and i am happy to do that Link to comment Share on other sites More sharing options...
JimR Posted November 20, 2008 Share Posted November 20, 2008 hi everyone. am looking to upgrade the carb on my DT50MX, i think the original is 14/16mm or something like that but most 50cc performance carbs are 21mm. so i got looking on ebay and came across this: http://cgi.ebay.co.uk/OKO-21mm-RACING-CARB...%3A1|240%3A1318 would this work with my DT50MX? regards Steve P.S. i am already running a bigone expansion pipe and exhaust and plan to add a Polini 65cc kit, i understand re-jetting will be required and i am happy to do that Hi Steve If your ok with the protracted work to make it run right ..... there are clues in the ebay description, such as we do jets (sold sepperate etc). It would be good to know what the carb has as stock (jet wise) and as your original manifold is an internal type and the illustration shows an external one it would be good to know if a reed block/manifold is avalible for the DT, then you may have to junk the oil pump, as I guess you know that the engine is fed oil by the 2 bits you need to replace, unless the carb or manifold have provision for the autolube to work you will have to go to mixing fuel, not to bad but a pain having to carry oil (just incase the garage hasn't got any) to mix at fuel stops. In my day most garages had 2 stroke dispensers but today I guess they would look at you 'gone out' but I must add I have been caught out by a garage or 2 that forgot to refil them ... 2 rebuilt engines on my Yam L1 to prove it ... I diagress !!! So to recap you need to check out with the ebay seller exactly what spec the carb and manifolds are so you can make a plan in order to fit it .. Regards Jim Link to comment Share on other sites More sharing options...
wild foamy Posted November 20, 2008 Author Share Posted November 20, 2008 is that not a reed block on the underside of the carb?, i've been and had a look at my DT carb and it does look very similar... in regards to removing the autolube then if that is the case i will find a different carb which does not require the autolube to be removed, purely because i am lazy and like the conveniance of not needing to ready-mix the oil have emailed the seller and am awaiting a response EDIT: my jets are around 80-90 sized as i am running a bigone exhaust and K&N style air filter and the mixture is now just about right (not exactly sure on size though) Link to comment Share on other sites More sharing options...
JimR Posted November 20, 2008 Share Posted November 20, 2008 is that not a reed block on the underside of the carb?, i've been and had a look at my DT carb and it does look very similar... in regards to removing the autolube then if that is the case i will find a different carb which does not require the autolube to be removed, purely because i am lazy and like the conveniance of not needing to ready-mix the oil have emailed the seller and am awaiting a response nope the reed block is the bit screwed to the cylinder (via 4 pan head screws) that the original carb pushes onto which makes your carb external, hence the screw (with a 10mm nut built in) the picture shows a carb that fits to an internal rubber type manifold carb this could fit but there will be some work to produce the reed block internal rather than external .. from memory the RD/DT80 was configured this way but as those bikes 'self destructed' from new you may have a problem finding a manifold to suit. I dont blame you wanting to use the oil pump my 65mph FS1 still uses the pump works sound but the 70mph plus people seem to think its bad ...oil mix 32:1 , 52:1 etc Yam produced a pump that altered that ratio across throttle opening why bother changing it .... but with no oil tank what a good place to store the sarnies ! Regards Jim Link to comment Share on other sites More sharing options...
wild foamy Posted November 20, 2008 Author Share Posted November 20, 2008 Ah i understand now thing is i am trying to get my DT50 to hit atleast 50mph but still have enough power left to get up hills and tthe like whilst laden with a bit if luggage (prepping for my ireland tour, lol) i can go for a 13t sprocket on the front (currently running 12t) and a 44t on the back (currently a 45t) and will be adding a Polini 65cc kit to help it pull to top gear, with the stock 50cc barrell it will pull to about 40mph, but if i put a big bore kit on i want to add a bigger carb to let it breathe better and get best results from it. is there a place i can get a carb that will fit but not at a rediculous price? EDIT: found the same item being sold by a differente seller, this features a rubber boot/adaptor thingy to go on the carbs' internal manifold and connect it to the reed blocks' internal... erm... manifold? O.o http://cgi.ebay.co.uk/SCOOTERS-RACING-CARB...%3A1|240%3A1318 as you can see im new to all this engine and carb lark... all a learning curve though Link to comment Share on other sites More sharing options...
wild foamy Posted November 20, 2008 Author Share Posted November 20, 2008 Just had a look in the garage and have seen that the original carb goes over the manifold on the reed block and is held in place by a jubilee clip. so would the second item (with the rubber boot) work? Link to comment Share on other sites More sharing options...
JimR Posted November 20, 2008 Share Posted November 20, 2008 thing is i am trying to get my DT50 to hit atleast 50mph, i can go for a 13t sprocket on the front (currently running 12t) and a 44t on the back (currently a 45t) and will be adding a Polini 65cc kit to help it pull to top gear, with the stock 50cc barrell it will pull to about 45mph, but if i put a big bore kit on i want to add a bigger carb to let it breathe better and get best results from it. is there a place i can get a carb that will fit but not at a rediculous price? Hi there is no need to change it ..... the big bore will allow the bike to rev (as long as the base gasket is ok and you dont have that silly one ring piston, why not use the original carb (why do you need a 21mm carb, that may not work at all well and the original may be better) your time may be better spent looking at the reed block, opening the reeds, but not to far as they may snap. Adding a big carb then leaves you open to 1) jettting at the high end 2) progression and low range add the big carb if you want but I guess you will waste money Regards Jim Link to comment Share on other sites More sharing options...
wild foamy Posted November 20, 2008 Author Share Posted November 20, 2008 well you have more experiance with bikes so i ill follow your advicen leave it for now. once i get paid the bike is having a complete overhaul over Xmas, new tyres, brake shoes, clutch, big bore and a few other bits and pieces to tart it up a bit. the original reeds will be replaced with fibre reeds so i wouldnt think snapping them would be such a problem Link to comment Share on other sites More sharing options...
JimR Posted November 20, 2008 Share Posted November 20, 2008 well you have more experiance with bikes so i ill follow your advicen leave it for now. once i get paid the bike is having a complete overhaul over Xmas, new tyres, brake shoes, clutch, big bore and a few other bits and pieces to tart it up a bit. the original reeds will be replaced with fibre reeds so i wouldnt think snapping them would be such a problem Ok you could let me do that but I guess you are to far away from me .. if the stops are opened to far the reads will break if they are steel or fibre I guess you do know what you are doing but if I'm doing an Irish trip I would perfer a bike that does the job and not fail at Fishguard !!! Link to comment Share on other sites More sharing options...
wild foamy Posted November 20, 2008 Author Share Posted November 20, 2008 i can do most things (change brakes, tyres, e.t.c) so am confident with that sort of thing, but my knowledge fo carbs and fuel systems doesnt really go beyond air intake and jet sizes. i dont want the bike to be completely cannibalised so that it goes like sh*t off a stick but ceases up after 2'000 miles, i just want it to go a bit quicker and have enough power to get me around ireland without dropping to 30mph at every incline. hence why i am giving it an overhaul at Xmas to get everything checked out to make 100% sure it is in good shape for when the time comes to go touring. the brakes and tyres don't need to be changed yet, but i will change them anyway as they were on it when i bought it and i've no idea how long they have been on there. the devil you know is the best devil Link to comment Share on other sites More sharing options...
Moderator Cynic Posted November 20, 2008 Moderator Share Posted November 20, 2008 Hi mate from personal experience with a DT that was clocked by the feds at 64mph, back when they had discretion, and had out run a RXS100 in the process. You are looking at the wrong things. Yes your carb has a 14mm venturi, other than that it is the same as the model preceeding yours which was 16mm and designed from the outset for a ful, power 60cc engine. The carb size wont make all that much difference at this stage, it may even be better to stay at 14mm as that will generate more torque (thinking of ireland here). The big bore you are talking about, when i was messing with 50's there were big bores and BIG bores. Some of them were worse than a std engine. I spent about 20quid more (worth about 15 pints at the time) on a Autesa (bad spelling) big bore, this came with a lighter gudgeon pin, chrome rings one being high compression and the piston had considerably bigger ports with an extra small one just under the rings. Does this sound familiar jim?? That ran rings round the cheaper stuff, didn't self destruct either apart from reg needing little ends and head gaskets. That ran with bigger main jet and a higher needle position, the exhaust was a fresco cut open and had the insides cleaned up modified for higher RPM. I had to have a little bit of metal taken out the exhaust port on the barrel to let it rev higher. I even had the reed block machined so i could run one rd350 (non ypvs) reed. The ig was pretty much as was except for a dt100 coil and running more advance than std and kept in perfect nick, and changing the higher temp plug regular. As far as gearing goes, 12-36 and 15-45 are exactly the same ratio but they will make your bike run very differently due to the implied ratio between the rear sprocket and the wheel its self, the smaller numbers being better. Don't forget a closer more tarmac pattern on your tyres intead of full on blocks can give you 3-4 mph. That little lot with a couple of drops of five star could get me to over 70mph in, i have to admit perfect conditions and i must point out it was a complete ba5tard in traffic or town stop start stuff. And i wont mention stopping ahem. I know i will never know but i hope the co#k that nicked it got his cumuppence VERY painfully. Link to comment Share on other sites More sharing options...
wild foamy Posted November 20, 2008 Author Share Posted November 20, 2008 sorry to hear it was nicked, there are some real assholes out there... smallest back sprocket available through my yamaha dealer is 44t, so i am having to go higher on the front sprocket to gear it up even more. any particular reason you went for a DT100 coil? will also change the seals, gearbox oil, spark plugs and bearings whilst im at it, just so i know it is in A1 condition (i am a bit obsessive, yes) Link to comment Share on other sites More sharing options...
Moderator Cynic Posted November 20, 2008 Moderator Share Posted November 20, 2008 sorry to hear it was nicked, there are some real assholes out there... smallest back sprocket available through my yamaha dealer is 44t, so i am having to go higher on the front sprocket to gear it up even more.That is because you are only looking at DT parts, i think mine came from an RS100 any particular reason you went for a DT100 coil? Higher output, the winding resistances gave bigger output voltages to keep the plug clear at the comp ratio's i was running. That was done on the advice of a tuner i knew at the time i cant quote real numbers, didn't do much for points life tho. will also change the seals, gearbox oil, spark plugs and bearings whilst im at it, just so i know it is in A1 condition (i am a bit obsessive, yes) I am going to repeat my DT was a complete bit#h in anything other than ideal conditions. It used excessive fuel was overly loud and needed constant maintanance like new points,head gaskets, plugs. You will have to decide when you will stop as soon you will be trading convenience with performance. Oh and i made sure it looked as standard as possible. I was doing the Q thing long ago. Link to comment Share on other sites More sharing options...
JimR Posted November 20, 2008 Share Posted November 20, 2008 sorry to hear it was nicked, there are some real assholes out there... smallest back sprocket available through my yamaha dealer is 44t, so i am having to go higher on the front sprocket to gear it up even more. any particular reason you went for a DT100 coil? will also change the seals, gearbox oil, spark plugs and bearings whilst im at it, just so i know it is in A1 condition (i am a bit obsessive, yes) there is no reson to fit a dt100 coil bar expense the dam thing had the same resistance via primary & secondary windings as the DT50. Big bores as long as you dont ring the nuts out of them every time they run fine as long as they do the polish period (run in). but I must admit some factories produced better kit than others .... to date I got a 45mm bore for my FS1 it was poo, but the ebay 43mm bore is well better and appears to produce the same power with out the piston slap of the 45mm bore Regards Jim Link to comment Share on other sites More sharing options...
Moderator Cynic Posted November 20, 2008 Moderator Share Posted November 20, 2008 there is no reson to fit a dt100 coil bar expense the dam thing had the same resistance via primary & secondary windings as the DT50. Big bores as long as you dont ring the nuts out of them every time they run fine as long as they do the polish period (run in). but I must admit some factories produced better kit than others .... to date I got a 45mm bore for my FS1 it was poo, but the ebay 43mm bore is well better and appears to produce the same power with out the piston slap of the 45mm bore Regards Jim 20years to find the only advice i actually took from an 'expert' was coblers. I must of had a duff coil cos it did improve things. Link to comment Share on other sites More sharing options...
wild foamy Posted November 20, 2008 Author Share Posted November 20, 2008 considering the ebay kit is about £20 cheaper form yambits i may go with that, but i would rather have more displacement (in the polini kit) however if it is the kit which you had (which was poo) then i will stick to the 43mm ebay kit im familiar with running-in engines as i have various model cars and planes which use I.C engines, although they only take about an hour or two to run-in Link to comment Share on other sites More sharing options...
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