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| Arnas |
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Arnas
L Plate Warrior
Joined: 03 Jul 2014
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 Posted: 00:35 - 03 Jul 2014  Post subject: Derbi Senda DRD PRO 50CC (Hard to start) |
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I had recently bought my first bike 50cc Derbi Senda DRD pro 2008 and recently it became really hard to start it, every time I want to start it I have to give it full throttle while pressing the starter for about 30 seconds (With breaks) and play around with it and after you can hear it grabbing and nearly starting and then after about 50 seconds it starts with the engine flooded, then takes few seconds to burn all the fuel inside. Or what I usually do is flood the engine as always and then bump it.
I had replaced the spark plug it gives of orange spark, there is no problem while riding the bike it rides normal. Before this problem only occurred on cold engine but now stopping for fuel has become a challenge since the engine doesn't want to start again.
I have no idea what the problem could be, I can't afford to take it to the mechanic as I don't have the money to pay £45ph,
If anyone has any idea what this could be I would be grateful.
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| Arnas |
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Arnas
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| P. |
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P.
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| MattWadz |
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MattWadz
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| Boxing |
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Boxing
World Chat Champion
Joined: 13 Mar 2012
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| Posted: 13:41 - 03 Jul 2014 Post subject: |
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When checking the spark, don't touch the frame then try and start it, just put it on the cylinder head. I learnt the hard way.  Didn't think the bike even had a spark, how wrong I was.
Can take the exhaust off and look up the exhaust port to see what the condition of the piston is like.  |
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Arnas
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| Teflon-Mike |
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Teflon-Mike
tl;dr
Joined: 01 Jun 2010
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| Posted: 22:47 - 03 Jul 2014 Post subject: |
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Err, hate to be obtuse ...No really, I do... OK, no I don't, fuck it!...
But lets start at the beginning here; You say you are flooding the engine, then bump starting it.
Are you using the choke, by any chance?
Its summer. You probably dont need it, or very much of it, for very long.
And if it doesn't catch after the first kick or prod or so 'on' choke, knock it off, open the throttle 1/4 turn, probably would.
Before running off looking for mechanical maledies... see if there is a 'knack' to starting the thing.
And do it with a brand new plug. Get a pack of four. Two-Strokes like them often... and they DONT like to be soaked in petroil too often, being 'flooded'.
Charge battery, and or get a new one; fit new plug, try alternative starting process, avoiding 'flooding' the engine, either no choke or half choke, or choke for a prod, then open throttle.
Report back. May not be anything wrong with the bike.
____________________
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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| Arnas |
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Arnas
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| Posted: 23:40 - 03 Jul 2014 Post subject: |
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| Teflon-Mike wrote: | Err, hate to be obtuse ...No really, I do... OK, no I don't, fuck it!...
But lets start at the beginning here; You say you are flooding the engine, then bump starting it.
Are you using the choke, by any chance?
Its summer. You probably dont need it, or very much of it, for very long.
And if it doesn't catch after the first kick or prod or so 'on' choke, knock it off, open the throttle 1/4 turn, probably would.
Before running off looking for mechanical maledies... see if there is a 'knack' to starting the thing.
And do it with a brand new plug. Get a pack of four. Two-Strokes like them often... and they DONT like to be soaked in petroil too often, being 'flooded'.
Charge battery, and or get a new one; fit new plug, try alternative starting process, avoiding 'flooding' the engine, either no choke or half choke, or choke for a prod, then open throttle.
Report back. May not be anything wrong with the bike. |
Using the choke doesn't seem to have much effect, only when the engine is flooded just before starting the choke helps a little to start it, I have already changed the spark plug and when I touch it to the frame and try to start I get an orange looking spark. Also as I said some times even if turn the bike off for few seconds getting back to start takes ages, right now the only way I start it is pushing it up a hill and then riding down it and kicking into gear and even this process takes around 2-4 tries. I am also using racing 2 stroke oil does that actually have any effect? |
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| Teflon-Mike |
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Teflon-Mike
tl;dr
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| Posted: 03:18 - 04 Jul 2014 Post subject: |
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| Arnas wrote: | Using the choke doesn't seem to have much effect, only when the engine is flooded just before starting the choke helps a little to start it, |
This sounds perverse; 'flooding' is excess fuel in the engine, Ie the mixture is so rich, it 'dews' out of the air, turning back into a liquid.
The choke, is an 'enrichment device'; adds extra fuel to the air....
So if the engine was flooded, and wouldn't start... turning the choke 'on' ought to make matters worse, not better.
Is it a cable choke or a lever? Are you working it 'backwards' turning it 'off' when you think you are turning it on?
| Arnas wrote: | I have already changed the spark plug and when I touch it to the frame and try to start I get an orange looking spark., |
Yes, and that one could be buggered like the one it replaced. Two-strokes are very sensitive to spark-plugs, if the engine gets flooded, too often, then it can knacker the plug.
The petrol & oil mix that is being sucked in 'dews' on plug, and it can short out the spark, giving the electric a lower resistance path back to earth than jumping to the electrode.
But if it doesn't, the 'damp' on the white insulation of the plug 'nose', when you do get the engine started 'burns off', and can leave a sooty 'carbon' deposit which can get the spark' tracking down the carbon rather than jumping the gap.
It can also 'insulate' the nose from heat, making the plug run hotter, and propagating 'detonation' before the spark.
If you have running problems on a two-stroke, change the plug, even if the one you have is not that old, so often the problem WILL just go away.
And, first rule of diagnostics;
#1. PRESUMPTION IS THE MOTHER OF ALL FUCK-UPS.
When you are trying to find the cause of a fault, NEVER guess, and NEVER presume...
Just because you have a spark, in free air out of the engine, doesn't mean you have one inside the engine, or that its happening at the right time.
Free air is 15psi or 1 bar. When you put plug in the engine, you compress the 'charge' of air and fuel to around 10Bar or 150psi, so there's 10'x the 'matter' in the spark-plug gap, might hapily jump 0.5mm in free air, but under pressure is like asking it to jump the equivilent of 50mm of 'free-air'.
So if the plugs damp or sooted and the electric can find an easier path, it will... even though it didn't when it was out the engine.
| Arnas wrote: | right now the only way I start it is pushing it up a hill and then riding down it and kicking into gear and even this process takes around 2-4 tries. |
This isn't really helping the diagnostics, very much; its the only way YOU have found to start the bike; and we still haven't bottomed the flooding/choke issue.
What this starting method is suggesting is that getting the motor to turn faster and longer than it can be spun with the starter motor, can let it 'catch'.
This could be because the engine IS flooded, and making it pump a bit hard, blows the excess damp out the crank cases.
This could be because the ignition is 'weak' and fired off the magneto, motor has to be spun faster than the starter is turning it to make enough electric to get a decent spark.
It could also be that the idle jet in the carb is blocked, and the engine's getting no fuel through it, until the cranks spinning enough rpm's to suck enough air through the carb, it's got the suck to drag it up the main jet.
Could mean many other things; bore fucked, rings fucked, piston crown fucked, crank-case seals on the way out, reeds buggered; exhaust holed.... LOTS of stuff... all similarly not working when the motor is spun over on the starter, but that do work, if spun harder and faster 'bumped' down the hill.
Starter motor not turning engine over fast enough is 'common' variable; hence suggesting checking the starter motor, and battery are 'good' and spinning motor over as fast as they should, ought be pretty high up the list of things to check, though.
| Arnas wrote: | Also as I said some times even if turn the bike off for few seconds getting back to start takes ages, |
Again, not really helping us diagnose the fault... you have a cold starting problem... AND you have a hot start problem... so... you have a starting problem. Doesn't really eliminate any variables.
| Arnas wrote: | I am also using racing 2 stroke oil does that actually have any effect? |
To this starting problem? Shouldn't make much odds, to that, as long as it's being metered correctly. Do you put it into an oil tank, or do you 'pre-mix' it in with the petrol? An over metering oil pump wouldn't help starting; nor would an over rich pre-mix; but 'brand' shouldn't make much if any odds.
Now, you need three things for 'life'' You need pressure in the pot, a spark in the pot and juice in the pot.
All we know right here right now is you have a spark OUT of the pot... and you THINK you are 'flooding' it... which begs following MattWadz's and Paddy's advice of putting a compression tester on it; but sticking your thumb over the spark plug hole and turning the motor over without the plug out can give you an idea of whether its making 'some' compression.
And that if you do a long bump, it can start, where it wont on the starter.
Second Rule of Diagnostics
#2 - Follow the Logic - Don't do 'Random'
Third Rule of Diagnostics
#3 - Eliminate the Variables, remembering Rule #2
4th Rule of Diagnostics
#4 - Check the obvious & Simple first
So, back to top; check your starting procedure; double check choke is 'on' when you think, and 'off' when you think.
Check the starter system; long-bump makes it start, so is it simply that the starter motor is slow? Does the starter motor labour like the battery is flat, or scream hapily wirring the engine over at a fair lick? Is battery knackered? Is starter knackered?
Then, thumb over spark-plug hole. Can you actually hold it there whilst you spin the engine over?
Now, with fresh new plug... good starter spin, and positively sure of the choke... what does it do, when you try starting...
No choke, no throttle... spin and if it don't catch... check plug. Is it 'wet'? Is it very wet?
Clean it; try again, half choke... spin and does it catch... check plug.
Clean and try again, full choke... spin and does it catch.
Back off, no choke, 1/3 throttle... spin and does it catch?
No choke half throttle, spin and does it catch?
No choke FULL throttle, spin and does it catch?
If still nothing... time to dig deeper...
But, give the exhaust a good look over. Look for any rust-patches that could contain pin holes; look for poor joints; and if you get the thing to catch, look for leaks when the throttle 'blipped', particularly at the exhaust flange, and the early part of the pipe after the cylinder.
Then, look at the carb; remove, strip, and clean... and repeat 'start tests'... on a clan, preferably another new plug.
If still no joy? Well, getting a better compression test reading than the thumb over plug hole, may be needed, but even then, needs to be done properly, especially on such a little engine... and may be time to bit the bullet and give it to paid mechanic.
Or getting serious and digging deeper into the guts of the motor, and pulling the reed-block off, the cylinder head and barrel, and inspecting piston and rings and bore and stuff.
BUT, you are going to have to spend some money, and at the very least get a work-shop manual for the thing, to tell you what compression readings you should get, what reed clearances should measure up at, what torque wrench settings to use for cylinder head studs, and that soft of thing, as well as the step-by step instructions to pull stuff apart.
Old joke for you; three engineers in a car, an electrical engineer, a software engineer and a mechanical engineer. Coming down a hill, the brakes fail, and they crash into a bank at the bottom...
Electrical engineer, is convinced its a problem with the Anti-Lock Braking System, pulls a multi-meter out of his pocket and starts testing connections on the brake pad wear indicators.
Mechanical engineer is convinced its a problem with the brake caliper, grabs a spanner and starts undiong the hoses.
Software engineer, says "Fucked if I know what is wrong with it, but I think we should push it back up the top of the hill, and see if it does it again"
How many times you pushed this thing up the hill? And its STILL doing the same thing... and the problem is still there....
Stop pushing it up the top of the hill, and crack out the Haynes manual, and spanners and start trying to fix it!
You are unlikely to make it worse, than 'it don't work', so effort spend following the logic, and doing the practical things that can be done, is going to be much better spent, than pushing it back up the hill, again, isn't it?
Its a logical system, so follow the logic. DONT presume, CHECK. and start with the simple and easy first, eliminating variables.
IS the problem SIMPLY you aren't doing it 'right' when you try starting it. Not being patronising, not suggesting you are think, BUT, check and double check, and eliminate the variable. You say its a new bike to you, it may just be you don't have the 'knack' or you have guessed the choke lever positions wrong.
Onto the starter system, make sure it IS turning engine over fast enough
Onto spark plug; sensitive part of the equation, eliminate THAT one, with a new one, and a couple of spares in case something else is fucking them up soon as you put'em in.
Check the compression with 'rule of thumb' at the very least while you have the plug out..
Then move on, and if you still cant find the 'knack' to get it started, DOUBLE check everything again, before moving onto carb....
____________________
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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Arnas
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