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stirlinggaz |
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stirlinggaz World Chat Champion
Joined: 22 Jul 2007 Karma :
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Posted: 15:57 - 06 Jul 2017 Post subject: 2T mixture. Too much oil? Help? |
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Hi,
Having a dumb day & have got a few basic things wrong already today.
Anyway, when running a 2 stroke engine & choke (cold start) is switched OFF (which it SHOULD be after starting) the engine is struggling, almost cutting out & definitely not revving as high as it should & will cut out completely if throttle is opened fully.
However, if I put the choke to ON, the engine is idling fine (maybe a little high) & it will rev to the max, right to Wide Open Throttle.
So, do I have my mixture totally screwed up & have TOO MUCH 2t oil in? (its pre mix)
That's what my heads telling me anyway
Am I right?
Or have I REALLY f*cked up & not put enough 2t oil in, & its running incredibly lean, risking seizure.
Help?
I'm watching the tennis till I'm 100% sure
cheers,
GAZ |
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Polarbear |
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Polarbear Super Spammer
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TbirdX |
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TbirdX Crazy Courier
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jaffa90 |
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jaffa90 World Chat Champion
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stevo as b4 |
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stevo as b4 World Chat Champion
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Teflon-Mike |
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Teflon-Mike tl;dr
Joined: 01 Jun 2010 Karma :
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Posted: 17:43 - 06 Jul 2017 Post subject: |
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Sounds like my strimmer...
1/ What bike or engine? & Is it designed or set-up to run on pre-mix?
If it's deigned to run on an auto-lube system, delivering 2T oil to the crank-case via a pump, then adding oil to the petrol, will make the carburation 'weak'; as you have a carb set up to mix aprox 5% fuel to air by volume; oil isn't fuel, so adding 2% or more il into the petrol, means that the carb will be trying to mix the same volume of pre-mix to the air going through it... but there isn't as much actual fuel in there as it's expecting.
2/ this may be a major over-complication.... like my strimmer, I can never remember which way the bludy choke is 'on'! Are you sure you are turning it on, not off?
3/ What does the plug look like?
Always the start point on any engine, and matter of course to clean and or replace on a 2T before trying to fault find!
4/ How did you mix the fuel & when?
Lawn mower does rather suffer from condensation in the fuel, each spring. The Cota, in years past from crap in the tank, inadvertently added from petrol from rusty gerry can, or funnel full if filth.. could be you have a clogged jet from contamnated fuel, if old or not so careful in the mixing.
IF your pre-mix was too thick; then I'd expect the motor, if it ran, to be very smokey, and not 'clear' when warm; probably be rather 'wooly' on throttle response, and possibly wisper or foul the plug and peter out and refuse to re-start, rather than beg choke.
So does suggest, choke lever dohw moment; crud in fuel, or not set up to run pre-mix at all. ____________________ 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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stirlinggaz |
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stirlinggaz World Chat Champion
Joined: 22 Jul 2007 Karma :
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Posted: 06:23 - 07 Jul 2017 Post subject: |
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Hi all,
& thanks for the replies
Firstly, my apologies, I should have put NBR in the subject/title cos it ain't a bike, its a "brush cutter" (big strimmer) of unknown origin & dubious build quality.
But being attached to a 50 odd cc 2 stroke engine, I thought there would be enough similarities between it & those older 2t bikes from the past, before auto-lube pumps & when the black art/science of pre-mixing was commonplace & understood.
It was more the theory I was interested in, as to why putting the choke to ON made it behave the way it did, by revving high & letting me open the throttle fully, but only when the choke was ON.
I know I have got my mixture wrong, as I was very careless about the way I approached it, whereas, previously I was really quite ocd about it all.
Anyway, i guess i should dump the remainder of whats left in the fuel tank & start again, going back to being quite exact, in how much oil I should add to the fuel as its obviously much more important than I previously thought.
The recommendations are anything between 25 to 1 & 60 to 1 (that seens to me to be quite a big variance) according to the instruction sheet, what's actually printed on the side of the engine & what's suggested on the interweb (I did search a bit before posting on here)
I guess the combination of a new NGK spark plug, fresh fuel, too much cheap mineral oil & a clueless operator has sent it haywire.
I'll mix up some,....say.....33 to 1, to start with...using 330ml of petrol & 10ml of oil in lots of 3, making a total of 990ml of fuel & 30ml of oil.
I have a mixing bottle, marked with various ratios but think I'll go back to my ocd way of using a 50ml syringe for the measuring out the oil & a litre bottle for the fuel.
Everything was OK, till I trusted the supplied mixing bottle.
I"d really like to understand why it behaved like that though & if it was dangerous to continue to use it at full throttle with the choke ON
I'm now glad all the 2 stroke bikes I have owned, all had oil pumps because my unblemished record of 0 (yes, zero) blown up bikes would have been shattered many times over.
cheers,
GAZ
ps : sorry for going all Teflonian |
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redeem ouzzer |
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redeem ouzzer World Chat Champion
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stevo as b4 |
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stevo as b4 World Chat Champion
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Kickstart |
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Kickstart The Oracle
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stevo as b4 World Chat Champion
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Kickstart The Oracle
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bypass2 |
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bypass2 Trackday Trickster
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lingeringstin... |
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lingeringstin... Trackday Trickster
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redeem ouzzer World Chat Champion
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Polarbear |
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Polarbear Super Spammer
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Posted: 16:15 - 10 Jul 2017 Post subject: |
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Phew, I really wish I had known that diesel could have been used instead of 2T oil years ago. To think Yamaha were so stupid to suggest you should put oil in their 2 strokes. It would have saved me a fortune.
They obviously knew fuck all about 2 strokes
I wonder if they had tried diesel in their GP bikes they would have gone faster
____________________ Triumph Trophy Launch Edition |
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stevo as b4 |
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stevo as b4 World Chat Champion
Joined: 17 Jul 2003 Karma :
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Posted: 18:54 - 10 Jul 2017 Post subject: |
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I suppose the best test for it would be to get say 3 identical motocross bikes, all with a new piston fitted. Then run them up on a dyno to get a baseline figure on a piston with say 1hour on it.
Bike 1, petrol and synthetic pre mix race competition oil.
Bike 2, petrol and 20% diesel.
Bike 3, petrol and caster oil.
Then ride them back to back on track, same riders. And then race them in a few MX events as well as practice play around riding, until they get close to the 15hr service life of the top end.
If any of them blow up or seize first they lose. Otherwise strip them all down at 15hrs and measure everything from piston wear, ring gaps, bore measurements etc, as well as looking at how coked up they are.
Im willing to bet that the complex synthetic esters show less wear than other types of oil, and also diesel. If any of the alternative lubrication bikes suffer seizures then youd have a good case for how synthetic oil is or isn't designed to reduce friction and have more seizure resistance? |
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Old Thread Alert!
The last post was made 6 years, 263 days ago. Instead of replying here, would creating a new thread be more useful? |
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