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| Will94312 |
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Will94312
L Plate Warrior
Joined: 09 Jan 2012
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 Posted: 15:47 - 09 Jan 2012  Post subject: Yamaha DT50 1994 |
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Hi there all, im fairly new to this biking stuff but i have encountered a problem with my bike.
I came on a road where i was doing 40 when my bike was then losing speed 40 down to 30.
i then came to my turning put it in neutral waiting to turn into the road. put it in gear and then it stalls. I pull it over to the side of the road, change back into neutral and then kickstart it again, its fine in neutral and then i change back into first where it then stalls.
I am new to this so if anyone can help me that would be brilliant  |
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| Teflon-Mike |
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Teflon-Mike
tl;dr
Joined: 01 Jun 2010
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Posted: 16:27 - 09 Jan 2012  Post subject: Re: Yamaha DT50 1994 |
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| Will94312 wrote: | Hi there all, im fairly new to this biking stuff but i have encountered a problem with my bike. |
OK; so I'll start with asking stuff so obviouse it may seem dum.
| Will94312 wrote: | I came on a road where i was doing 40 when my bike was then losing speed 40 down to 30. |
It's a moped; its designed to make 3.5bhp and do 35mph (true speed) flat out. With that little power; (Fit lad on an excersize bike, when I was at school managed to record just over 9bhp on the Dynometer Physics teacher had rigged up to it, to give you an idea of how 'little' that amount of power is; 9bhp ought to be enough to do 60mph, but I douvt many are fit enough to sustain it very long!)
It doesn't take much of a slope, let alone a steep hill for it to start bleeding speed. So was the road flat? This could be quite normal.
| Will94312 wrote: | i then came to my turning put it in neutral waiting to turn into the road. put it in gear and then it stalls. |
This sounds quite normal too... learners stalling at junctions. Whats your clutch control like?
Though, could be a dragging clutch. This wouldn't help. And could be 'fine' when the engine is cold, but start dragging as it gets hot.
But could be a host of other problems.
| Will94312 wrote: | I pull it over to the side of the road, change back into neutral and then kickstart it again, its fine in neutral and then i change back into first where it then stalls. |
So bike starts and runs when not in gear... OK, could still be clutch drag, or may be that the engine wont take 'load' which could be a bunch of other issues.
| Will94312 wrote: |
I am new to this so if anyone can help me that would be brilliant |
Lets start with the simple and obviouse; HILL. if so thats where your speed went. If not, or its not that steep; then you are down on power.
Petrol?
Do you have some? Running flat out, engines use more petrol than when they are just ticking over. If you are low on fuel, you can get fuel starvation, and that will often feel like running out of petrol with sort of stuttering or misfiring engine. did it feel at all like that? If so, then you may have run out of petrol, or been on the point of switching to reserve, OR just got down to a point in the tank where some 'sludge' in the fuel pick-up screen is choking fuel flow. Sludge or gunk in the fuel tap; or the sediment bowl of teh fuel tap, van have same effect, then the fuel line and float bowl for the carb.
OIL?
Your bike is a two-stroke. It doesn't have an oil-sump like a four-stroke. There are 4 'phases' of a 'power cycle'; Induction, Compression; Power & Exhaust; on a four stroke engine, each 'phase' is done above the piston on a seperate 'stroke'. In a Two stroke engine, the induction & some of teh compression is done UNDER the piston in teh crank case. Hence you cant have oil sloching around in there; so oil is squirted at the bearings with a pump, in tiny quantities, and is washed away and burned by the fuel and air passing through the crank-case; so it is called 'total-loss' lubrication, and you have to keep the oil reservoir topped up with light 'Two-Stroke' oil, or the engine can sieze.
The Gearbox, is in a seperate chamber and has its own oil, contained in that chamber, the cogs splashing around in it. As its not worked as hard as in a four stroke engine circulated round the hotter bits; on a two-stroke gearbox oil is often neglected. This MAY be the cause of your clutch problem; but worth changing the gear-oil as course anyway.
Back to the two stroke oil; if the reservoir is low or empty; its possible that running 'hard' under max load, (doing indicated 40mph) that the engine has got hot, and run lean on oil and 'nipped up' or shown early signs of nipping up.
Check the two stroke oil; check the two stroke oil lines and the pump. There is a pipe coming from the cover on the side of the engine going to the carburettor; with a little oil 'pre-mixed' in teh petrol for safeties sake; you can pull that line off with the engine running, and holding your finger over the hole you pull it from to plug the leak, look for oil coming out when you rev the engine.
THIS is where having the Haynes manual can be helpful. If you dont have one; get one.
The auto-lube pump is driven by the engine, but there is a cable off the throttle that adjusts the feed rate depending on engine load, and it can take a bit of fiddling to get it adjusted correctly. Details of how are in the book.
Spark-Plug
Spark-Plugs are a good indication of what engines are doing; if you take them out you can compare the 'colour' to photo's in the manual and it tells you allsorts of useful stuff, like whether the engine is running rith or lean or hot or burning too much oil.
Two-Strokes also are 'plug sensitive' and like nice clean, preferably new spark plugs quite often. A new one would probably be a worthy investment.
Clutch
I cant remember how many gears my DT had, I think it was six, but cant be sure. ANYWAY, six gears on a bike that only does 35mph. It takes quite a bit of sturring and hence clutch work, and these things do wear out eventually from a lot of clutch dump wheelie attempts, and max rev clitch slipping 'Drag-Starts'... They also tend NOT to get adjusted very well by teenagers more used to BMX's and adjusting the brakes with the cable 'play' adjustor on the handle-bar lever, rather than adjusting the cable properly at the brake caliper end.
It has been err....quarter of a century! since I built my DT50... but I recall clearly that the clutch is on the primary drive side; right hand end of the engine behind the primary drive cover, and there is a rod passing through the very middle of the main-shaft that pushes on a ball-bearing, that pushes on the clutch inner basket to open up the plates, to dissengage drive.
Over the other end of the mainshaft, on the left hand side of the engine is a cam, that pushes the rod down the middle, which is on a shaft, and that has a lever on the end the cable tugs.
BUT there is a screw and lock-nut adjuster, I THINK behind an inspection cover on the end of the mainshaft, and to 'properly' adjust the clutch and compensate for wear in the actual clutch plates you have to set that screw and lock-nut.
Just adjusting the cable ONLY compensates for stretch in the wire.
As said, twenty five year old memory; you need to check the book to see actual procedure. Its not tricky; just follow the instructions; and ought not take too long, or many tools.
BUT, that is my 'best guess'... its the clutch adjustment.
Get the book; check the petrol & oil levels; do a bit of basic servicing. Ought to sort you out pretty well, unless there is something pretty 'horrible' happened.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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| dangerousdave |
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dangerousdave
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| Posted: 20:35 - 09 Jan 2012 Post subject: |
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I used to have a DT50, was a great bike !
My DT50 couldn't hold speeds of above 40mph consistently unless it was held wide open. Any change in road surface could scrub off mph, on hills easily losing 10mph.
Mine had the usual 65cc big bore kit, fresco exhaust, racing reeds etc, combined with cheap oil and heavy throttle hand meant the engine would seize up from time to time. Usually when flat out, it would either loose power completely and roll to a stop, or lose power momentarily then appear to run ok. When it cut out completely it would usually start again, but be pretty temperamental, simular to what you are describing.
Its a little tough to work out what is going on with your bike. Is it making rattling noises which it wasn't before ? Does it still respond well when you turn the throttle, or is it a bit flat?
Stalling when changing from neutral to first, with the clutch held in, is usually just the clutch needing adjustment. Thats easily sorted.
And like Mike said above, a new spark plug every now and then solves a lot of grumpy behaviour from these motors 
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1988 Kawasaki KMX 200
Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50 |
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| Teflon-Mike |
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Teflon-Mike
tl;dr
Joined: 01 Jun 2010
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| Posted: 21:17 - 09 Jan 2012 Post subject: |
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| dangerousdave wrote: | My DT50 couldn't hold speeds of above 40mph consistently unless it was held wide open. Any change in road surface could scrub off mph, on hills easily losing 10mph.
Mine had the usual 65cc big bore kit, fresco exhaust, racing reeds etc, combined with cheap oil and heavy throttle hand meant the engine would seize up from time to time. |
Mine had a Gianelli, and made it out to 70cc eventually, with all the rebores it had from siezing up on me! My Grandfather actually got interested in this project; and it was actually HIM that got carried away tuning the ruddy thing! Pulled a book out of the attic from his days working on Areal race bikes in the 50's. Stuff he did is now common two-stroke practice, but a dark art back then; the crank-cases, con-rod and crank were all 'filled' to reduce crank-case 'free' volume, with a mixture of epoxy resin and aluminium filings; they use PTFE these days! Damn thing was rather rapid for a 50.. we managed to get it to a nadgers over 70mph over measured half mile.... only trouble was we couldn't get two way average, little bugger would usually blow its crank-seals!
Got VERY good at swapping crank seals on that engine, until 'Pops' crafted a retaining plate to go over each one, screwed over the seal to the cases... that 'solved' and prospect of it holding together for more than five minutes... started nipping up, until we got the oil feed spot on... and JUST as it was starting to get reliable to get to and from college on; some twit in a Triumph Spitfire SMIDSY'd me and wrote the thing off!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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| dangerousdave |
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dangerousdave
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| Will94312 |
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Will94312
L Plate Warrior
Joined: 09 Jan 2012
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| Posted: 22:58 - 09 Jan 2012 Post subject: |
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well basically after this happened at the junction and now it wont start at all i just start it on neutral and then change into first and now it just stalls..... My dad and brother either think its the spark plug, gearbox oil or the clutch has gone??? and dangerous dave my bro has the KMX 200 |
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| dangerousdave |
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dangerousdave
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| Posted: 23:54 - 09 Jan 2012 Post subject: |
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I'd say:
1. Check the clutch adjustment.
Does the bike pull forward a little before it stalls ? Does it make a loud clunk when goes into 1st?
If YES to any of these questions then the clutch needs adjusting. This is done by the barrel adjuster on the end of the lever.
2. Is the bike fitted with a sidestand switch ?
This stops the engine when the bike goes into 1st gear to prevent driving off the stand down. They can stick, and stop the engine when a gear is selected.
I think it's likely to be one of these things.
It makes good sense to check the usual things while you're at it: check/replace the spark plug, clean/re-oil the air filter (unless it's holed or hardened then replace, check battery has good charge).
One other thing I had with my DT was water getting into the spark plug cap/cable fairly regularly. It needed spraying with wd4O regularly. However, with this problem it wouldn't start at all.
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1988 Kawasaki KMX 200
Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50 |
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| Teflon-Mike |
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Teflon-Mike
tl;dr
Joined: 01 Jun 2010
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| Posted: 10:35 - 10 Jan 2012 Post subject: |
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| dangerousdave wrote: | I'd say:
1. Check the clutch adjustment.
Does the bike pull forward a little before it stalls ? Does it make a loud clunk when goes into 1st?
If YES to any of these questions then the clutch needs adjusting. This is done by the barrel adjuster on the end of the lever. |
NOoooooooooooooooooooooooo!
See my comments earlier. The barel adjustor on the levers is NOT for adjusting clutch (Or brake if cable brakes) travel!
The barel adjustor ought to be adjusted in to about two turns from fully out, and the clutch (or Brake) CABLE adjusted at the actuation end.
If there isn't a screw adjustor for the cable on the engine, before the cable pulls the release lever, there will be a mid-cable sleeve adjustor, and THIS only adjusts the 'slack' in the cable to compensate for stretch in the inner cable.
The actual CLUTCH is adjusted on a screw & lock-nut mechanism on the actuation rod INSIDE THE ENGINE
https://images.cmsnl.com/img/partslists/clutch-ty80a-19741975_bigyau0887a-9_f111.gif
See parts 18 & 19.
As the clutch wears the plates get thinner, so the springs push them closer together when the clutch is 'engaged'.
With a brand new clutch, you probably have 60Degrees of cam travel to push the plates apart.
IF you only adjust the cable, you pull the clutch cam round, to take up clerance on the actuation rod in the engine.
It 'works' so long as you have plenty of travel on the actuation cam, but at some point, you will, winding up the cable adjustors pull the cam round almost to it's 'peak' where you only have maybe 10Deg of cam travel and not enough 'ramp' to actually dissengage the ruddy plates.
THIS is probably why the bike has a dragging clutch! NO-ONE has ever adjusted the clutch 'Properly'... they have done what they did on a push bike and merely tensioned the cable on the 'slack adjustor' on the handle-bar'!
THAT like I said, you leave about two turns from fully 'in' until whatever it's tugging on is properly adjusted at the other end; be it a push bike brake, a motorbike drum brake, a motorbike clutch or whatever else.
And you ONLY use it to adjust the 'free-play' or 'slack' in the cable to make sure that the cable isn't held in tension when the lever is released.
More of that screw wound out to put tension on the cable, the less threads are in the lever bracket'; when you pull the clutch or brake the more that 'load' is put on less and less metal, and the greater the chance that the adjuster will bend or break; NOT good if its working a brake!
Get the Manual; check the Routine Maintenence Section, see 'Clutch Adjustment'; it WILL explain the exact procedure for taking up the clerance on the clutch rod and plates to bring that cam back round to where it ought to be via the screw and lock-nut; THEN explain you adjust the cable after.
You'll probably find you suddenly have an AWFUL lot more clutch travel, and your dragging problems will go away, and it feels like a different bike to ride!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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Old Thread Alert!
The last post was made 14 years, 97 days ago. Instead of replying here, would creating a new thread be more useful? |
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