1989 DT 50 MX Running problems and parts help please...

[sword70]

I have 2 DT 50 MX's ones a 1989 other a 1991 model and both are cdi with 65cc kits on and non stock reeds, stock exhausts.

After tearing one to bits and cleaning up all electical connections, replacing coil, spark plug, strip and clean carb etc i finally got one up and running but it struggles to tick over for more than a few seconds, rev's a bit spluttery then gives up and stops and then takes several kicks to get going again.

I have double checked the carb is clean and been blown out with compressed air, set the left screw 1 1/2 turns out as per haynes manual but can find no info on setting the throttle stop screw at all.

I have done a compression test and that is perfect, nice spark from the new plug and coil so thinking i have carb or fuel issues and trying to set it up as close to stock as i can to get it running and warmed up before tweaking, i tried adjusting throttle stop screw in or out about 1/4 turn at a time several times to see if that helped and still no reliable starting and running.

Carb's i have are both Teikei 14mm ones with 40 pilot jets, both needle jets have 80 stamped on them and one main jet has 100 on it , other i couldnt read so according to haynes manual my pilot jet is correct but main and needle are not stock??

Been trying to find carb repair kits for these and drawn a blank, ideally would like new gasket, float valve, jets etc and kinda start again with a clean slate before tweaking but no joy so far.

As this bike will be for my son to travel to and from work over the next few months i want it to be as reliable as possible so am calling out for any help or info above and beyond what haynes tells me please.

I am not against fitting an aftermarket carburettor onto this or sending the 2 i have away to be sorted if it all gets beyond me so any advice to get this one running sweet would be much appreciated.

[Airhead]

i'm unfamiliar with the teikei carb but...always try a couple of brand new plugs before you do anything else

[sword70]

Have 2 new plugs and think the old 2 kicking around so might try again tomorrow.

Pulled my back out 5 days ago so this endless kicking the bike over is taking its toll, will get my son to pull his finger out and get kicking the bike over for me while i mess with the carb adjustment and try swapping the plug over to see what difference it makes.

[wild foamy]

from what i remember, my DT50 had a stock main jet of 98, with the big bore kit on and a bigone exhaust and expansion pipe i jetted it to about 110 and moved the needle up one position.

check the colour of your spark plugs, this should be a rough indication of mixture, struggling to start could be an indication of lean running

[sword70]

Think i might have sussed it a little, bike keeps flooding very quickly.

I have 2 carbs both different jets in etc but otherwise identical, removed plug, cleaned it and sprayed easy start on and blew with airline to help remove previous fuel then refitted.

Bike seems to start relatively easier and rev's although a bit spluttery then dies, pull plug out and its wet.

At the momment it only runs for 15-30 seconds before dying and not starting again until plug cleaned and refitted.

Struggling to find off the shelf carb repair kit or jets without measuring threads and dimensions so going to hunt a bit more, been told possibility of new carbs still available from Yamaha at about £130 but local yamaha dealer couldnt get me off the phone quick enough and not very helpfull.

Other alternative is fitting a new dellorto 17.5mm carb so that might be my next step, just trying to get info on these carbs not having a choke fitted and how to rig one up before buying

Thanks for all your help so far, i think i have been working on too many vehicles the last couple of weeks and getting a bit blind to the obvious, pulled back aint helping either :-)

[Airhead]

your crankcase may be flooded, remove the sparkplug, leave the ignition and fuel tap switched off and then shove it around the street in 3rd gear (with help)...this will expell any excess fuel in the case....Then try again

[sword70]

Ah, good move, would have overlooked that and killed the motor :-)

[Grouch]

your crankcase may be flooded, remove the sparkplug, leave the ignition and fuel tap switched off and then shove it around the street in 3rd gear (with help)...this will expell any excess fuel in the case....Then try again

Sorry if this is a stupid question but do you mean push it around in gear or with the clutch in? Wouldn't it be virtually impossible to push in gear?

[Wrenchface]

No clutch, in third gear with plug removed it should be easy to push around...

[sword70]

Well back still messed up so spent a couple of days trecking through the internet trying to find repair kits and got nowhere.

Settled for ordering a Dellorto 17.5 mm carb new, should be here tomorrow so will get playing once back is better.

Will probably just drain engine oil and replace, mates got a waste oil burner so always happy to take old stuff away no matter what extras it has in it :-)

I am a bit stubborn so will be stripping both teikei carbs down and measuring jets etc and searching some more for jets and needle to get them both back working properly.

[dzish]

Instead of kicking, remove the left cover case, and find the ignition magnet. It is fixed to the crankshaft with nut. So basicly if you can find tool wich fit to the nut, you can rotate the crankshaft with that nut. All you need to do is to rotate engine in correct way, and find a way to connect tool with hand driller.

So you have much faster rotation and bigger chances to start engine, or find some hill and push the motorcycle down... it should start.

Also it worth to be mentioned... Kick start shaft are not made someone to jump 10 hours per day. They crack very easy.

[blackhat250]

Has anybody looked at choke plunger,, is it seating,,,[ closed]

[dt502001]

Has anybody looked at choke plunger,, is it seating,,,[ closed]

as well as the choke... is the float height set to low might wan't to raize it a bit ,did you check the floats to make sure they float?

If the plug keeps getting wet it has to be getting to much fuel drying with a torch works much better.

The oil is only for the gear box so shouldn't be affecting anything to do with starting/running .

[sword70]

Finally my back is all good now so had chance to play a bit more on the old DT.

After stripping both carbs down and re-checking everything i spotted a slight groove in the float needle and as i cant find a replacement at the momment i used fine wet and dry and carefully removed the groove, double checked choke was ok and blew all passageways out and rebuilt.

Managed to get bike going again and rode it around a bit, seems a little flat on power so been tweaking the carb and still not happy as mixture screw has very minimal affect but getting closer now as spark plug is alot less sooty borderline clean just not that nice brown tinge to it just yet.

Bike still has a habit of flooding now and then if you failt to start it after a couple of kicks or if left to idle for too long and you stall it but as a rule it will start first kick most of the time.

Tried a mock up of the Dellorto phva 17.5mm carb i purchased and although at a push it will fit i need to do a few mods inlet side and get a longer throttle cable so taking my time on that.

Just out of interest i called a local yamaha dealer and they are on the case to track down any NOS spares kicking around mainly carb repair kits or complete new carbs and also looking at what if any other carbs may have been fitted to the DT or equivalent bikes as ideally i want this bike to be 100% reliable and would be nice to stock up on spares or swap the teikei carb for a mikuni or similar that is easier to get spares for.

If all else fails i am on the look out for an independant bike repair shop in the Swindon / Oxford area and will let someone who does this all day take a look before i throw all my toys out the pram lol :-)