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Graham2

Help needed please. Carb set up. 125pro

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Hi,

I need some advice please.

My bike is running extremely rich.  

It is an immaculate, extremely low hours, 2013 125cc TXT Pro.  It is still on its first tyres and chain!  The bike was / is immaculate and when I first bought it three months ago several experienced club members tried it and assured me it was a very good one, one expert tried some serious climbs on it! You could easily believe it is three months old.  I have been riding it regularly for about three months and it became difficult to start, first I assumed I was struggling with technique and this forum helped with that.  I clean and oil the air filter every trial. 

I have changed the gearbox oil twice, last time three weeks ago.  Putoline 75W  Light Gear oil.  Six long rides rides since.

The starting became a real issue, I stripped and cleaned the carb (no obvious issues) and changed the plug two trials ago and the bike was running reasonably.    But, the plug was very black when I changed it and the bike was reluctant to rev beyond half revs on a climb, although it would clear if free revved with no load. 

I started this weekend trial and the bike did not run very well, I tried turning in the mixture screw, although it made little difference it seemed a bit happier 1.5 turns out.  I am concerned because the basic setting is approx three+ turns out.  After about an hour the bike cut out and refused to restart, the plug is extremely black again, beyond sooty it was like a baked on black layer ( new plug that trail).

 

What I have done today.  Stripped the carb completely and blown out all the holes with an air line, again no obvious issues.  The carb is a standard carb with PHBL26 on the side.  New plug fitted.  Removed and cleaned air filter and the whole airbox, all looks good, no obstructions.  Every thing looks in really excellent condition.

The carb has a number 40 slide and a number 36 needle.  The circlip on the needle was on the second from the bottom groove, I have moved it to the third one up to drop the needle, I am expecting this will weaken it?

I restarted the bike with some difficulty and warmed it up.  I tried to adjust the mixture/air? screw and it does not seem to make a lot of difference... but is maybe happier at one and half turns out, still along way from the 3+ suggested on the forum.  I believe screwing it in makes it leaner?

Everything else seems in excellent order.  I have not done anything to the exaust, surely this cannot be clogged with so few hours?

I used up the remainder of the litre of oil the seller gave me and I am now using Ipone R2000RS fully synthetic.  I use 65ml for 5litres. The bike has always been a tiny bit smokey but only slightly.

Plug is BPR5ES as sold me by Gordon Farley in Guildford

Ideas please.

Are the slide and needle numbers standard?  Where should the circlip be on the needle?  How far in can I screw the air screw if the bike runs well?

can the exaust be clogged and causing this?  

Is the oil OK?  I have use about a litre since a bought the bike, so about 15 gallons.  The bike was so immaculate, I doubt it had more than a couple of tanks run through it.  The problems may have started since I changed to Ipone 2T oil?

 

many thanks, sorry about the length of the text..

Graham  riding with Berkhamstead and Hook Woods clubs

 

 

 

 

 

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Maybe a bit of a long shot, I rememeber a few people having trouble with the choke sticking on the dellorto carbs. Maybe worth checking the plunger is operating correctly and the seals in there are good.

 

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hi, thanks, a good thought.

I completely stripped everything down including the choke, so I have covered that option.

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I’m far from an expert but if everything fueling wise is good and as it was when running right then you could be looking in the wrong place.

Maybe crank seal is leaking and it’s burning gearbox oil, hence the rich looking plug.

As above worth checking spark is good and cover the basics before digging too deep

Edited by dan929

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I doubt the 2t oil is an issue. Have you checked your getting a good spark, ignition problems should not be ruled out. 

Edited by b40rt
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thanks for the ideas,

I had discounted crank seals as the gearbox level has not gone down but I will watch it.

Ignition?  I am pretty sure the spark is good, it is the seriously black plug that worries me

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As b40 says, sounds ignition, woodruff key damaged, broken? Try swapping cdi from another bike. 

If you check woodruff key have a look at wiring on stator. 

Could be crank seal, if standing a long while not used, that’s the worse thing, main bearing sat unoiled, condensation from cold then warm etc, causes corrosion on bearing? 

any white smoke from exhaust? Head o ring leak?

just a few ideas?

good luck!

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Oh dear........

you have me worried.

it smokes a tiny amount, by which I mean more than I expect for the hours but probably about right for a five year old bike..

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It's a 2 stroke, they smoke. Burning gear oil smells quite differently to 2t oil. 

Crank seal on dry side would normally make it run lean, i.e. not a black plug. 

Woodruff key tends to be instant, not gradually getting worse, and the result of a stuck open throttle "incident"

If it was running well before, the jetting etc should be right. 

Edited by b40rt
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Hi B40,

thanks for working through it for me.  I am not sure what to do next.  I will try and ride at Great Brickhill at the weekend.

I will buy a flywheel puller and pull the flywheel and check around ...nothing to lose by having a look.

I will pull the exhaust apart and check for carbon

like you say jetting should not have changed if it right before, however, I have lowered the needle vale one notch to try and lean it down.  I am not discounting the fact the last owner may have fiddled with it.  So far no one has been able to confirm if the number 36 needle and 2nd up circlip position is standard.

 

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You never mentioned what size jets you have and that you checked the circuits. The choke has a jet too and that oring on the jet needs to be good.

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If it ran fine with the current needle, jets etc you can discount those as being the issue, float condition/ height all ok? my money is on a weak spark type issue.

 

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Hi everyone, thanks for all the advice. It is probably time to close this thread.

quick update as part of the thank you.

The total carb clean, a new plug and dropping the needle one notch has improved things to a point where I am not so concerned.

It still runs a bit rich and the air screw needs winding in more than the standard setting (i.e. one turn out and is usually three or so) 

When it is running, it runs well and performs very well but it does smoke more than we think normal, i.e. the club experts view when I rode yesterday.  I had to change the plug half way through my ride yesterday as it was getting sooty ( it became difficult to start).  Yes I ride quite gently but I do rev it occasionally fairly hard.

I hear the view that my timing/and or spark may be out but I am told it is running too well for that.  Not discounted but parked for the moment.

I checked the exhaust by pulling out the rear packing.  Dirtyish but still some large areas of white/clean packing

Several of you kindly suggested, from my text that if it was a sudden change it could not be carb setting.  In fact I do not think it was was quite so quick I think it was creeping up on me/and may have been an issue since I bought it ( fairly new to me/three months)

I am going to go back to Putoline oil, I was using Putoline and moved to Ipone ( like you I suspect this has nothing to do with it but it is the only thing I changed around the time I recognised the problem.. 

I have been given the standard carb/jet/slide sizes by Trials UK. I will check these when I next strip down.

Trials UK state for 2013 125 TXT Pro.  36 needle/40 slide/36 pilot/105 main jet from factory but GasGas uk fit 115 main jet.

 

Happy new year folks

Graham

 

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8 hours ago, Graham2 said:

 

It still runs a bit rich and the air screw needs winding in more than the standard setting (i.e. one turn out and is usually three or so) 

 

 

In is rich !

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Hi, you have me worried.   Are you sure?  Jim Snell of you tube fame insists that out is rich , in is lean.

I have just spent an hour trying to find the post on this site that I originally trusted, but i 

cannot find it

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