YX with 30mm Molkt carb Tuning Question
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Corza, the problem with those butterfly-valve equipped chokes, is that vacuum is meant to OPEN the butterfly as the revs and throttle settings increase. the problems i have noted with them, particularly on smaller engines (such as your 140) is that once the valve clearances open or close up a bit, the blow back, which Cactus has mentioned, creates a small drop in vacuum, which appears to be enough to allow the butterfly to close again... basically it has the effect of closing the throttle when you are trying to hold it open...
a really quick check to see if it is working properly, is to remove the air filter, start the bike, and while watching the back of the carby, rev the engine and watch the effect on the butterfly, as the throttle opens and closes... then hold the throttle wide open... the butterfly should open, and remain that way... if it flutters, or closes back up, you have a problem... ie there is not enough suction/vacuum to hold it open... to test it further, physically hold the butterfly open with your finger, then rev the engine. if the engine revs a lot cleaner, particularly up top, then yes, you have a problem, and it's most likely valve clearance related...
oh, and even though yours, and your missuses bike may have done the same hours running, it doesnt mean the valves will wear and seat, at the same rate.. If you weigh a bit more than missus, then your's will probably seat quicker, as there is a higher load on the engine during the running in period...
in case we havent made our point yet, check your valve clearances, lol, then do the carby thing i have just suggested, then pull the carby off, put it in a bucket of petrol, take three steps back, throw match in bucket. Whooshka. best thing for those carbies.
Then go on ebay, and buy an OKO 26mm flatslide. DHZ has them with everything you need, and ken can supply the jets you'll need to at least get you IN THE BALLPARK.
good luck mate, keep us updated
a really quick check to see if it is working properly, is to remove the air filter, start the bike, and while watching the back of the carby, rev the engine and watch the effect on the butterfly, as the throttle opens and closes... then hold the throttle wide open... the butterfly should open, and remain that way... if it flutters, or closes back up, you have a problem... ie there is not enough suction/vacuum to hold it open... to test it further, physically hold the butterfly open with your finger, then rev the engine. if the engine revs a lot cleaner, particularly up top, then yes, you have a problem, and it's most likely valve clearance related...
oh, and even though yours, and your missuses bike may have done the same hours running, it doesnt mean the valves will wear and seat, at the same rate.. If you weigh a bit more than missus, then your's will probably seat quicker, as there is a higher load on the engine during the running in period...
in case we havent made our point yet, check your valve clearances, lol, then do the carby thing i have just suggested, then pull the carby off, put it in a bucket of petrol, take three steps back, throw match in bucket. Whooshka. best thing for those carbies.
Then go on ebay, and buy an OKO 26mm flatslide. DHZ has them with everything you need, and ken can supply the jets you'll need to at least get you IN THE BALLPARK.
good luck mate, keep us updated
©orza™
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Ok was going to do thing tits up, but will check the valves first then! If they need adjusting, will do that and then once thats done, ill see how she runs, if its still not right will pull the carb appart and clean ect.
Really just want to get it rideable for now, specialy for the weekend, so may look at a new carby down the track.
Ill be pissed if i keep screwing oil leads cos its running to hot lol.
Really just want to get it rideable for now, specialy for the weekend, so may look at a new carby down the track.
Ill be pissed if i keep screwing oil leads cos its running to hot lol.
sean01
Legend Spanner Spinner
no sure if its been said...possibly has...
but bad tappet clearance can make an engine run hot....
anyways see how you go and keep us posted with any progress or problems
but bad tappet clearance can make an engine run hot....
anyways see how you go and keep us posted with any progress or problems
©orza™
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Ok, so i checked everything!!!
Intake valve .004
Exhast Valve .006
Main jet is 102
Float it perfect
And carby doesnt have a butterfly valve.
Had to put the clip back in the middle, was too rich half throttle, Blowing excess smoke and maxing out.
two things i came across one was there was no little rubber seal in the carby side to the pipe bit and the gasket on the other side of the plastic bit had broken so removed the plastic and made a rubber seal the same shape and put on it. seals tight now!
The other thing is. I dont think there is supposed to be oil in the lid of the exhast vale no? Bout a teaspoon. ran it and fixed and checked everything, then pulled the exhast valve lid off again and there was again bout a teaspoon of oil in there? Where is it from, is it normal and how do i stop it if its not normal. Any ideas....
Oh and i forgot mention before, but i did over fill it with oil the first time i did an oil change cos they all say they take 1100mls but thats way to much i found out! the book says .6oz which is 660mls, could that have something to do with it? It has been running with the correct amount of oil for some time now though, soon as i knew i took the excess out.
Intake valve .004
Exhast Valve .006
Main jet is 102
Float it perfect
And carby doesnt have a butterfly valve.
Had to put the clip back in the middle, was too rich half throttle, Blowing excess smoke and maxing out.
two things i came across one was there was no little rubber seal in the carby side to the pipe bit and the gasket on the other side of the plastic bit had broken so removed the plastic and made a rubber seal the same shape and put on it. seals tight now!
The other thing is. I dont think there is supposed to be oil in the lid of the exhast vale no? Bout a teaspoon. ran it and fixed and checked everything, then pulled the exhast valve lid off again and there was again bout a teaspoon of oil in there? Where is it from, is it normal and how do i stop it if its not normal. Any ideas....
Oh and i forgot mention before, but i did over fill it with oil the first time i did an oil change cos they all say they take 1100mls but thats way to much i found out! the book says .6oz which is 660mls, could that have something to do with it? It has been running with the correct amount of oil for some time now though, soon as i knew i took the excess out.
©orza™
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Hmmm ok, Still just seems to have that pop or backfire sound, it is running slightly rich but i want it that way so i dont screw my oil leads agian, specialy cos atm i am using my old ones which i repaired with gasket silicon and gaffa tape lol. but its not overly rich! and still seems to get quite hot, havnt taken it for a ride yet so dont know if it still hiccups in first and second.
©orza™
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Ran the bike a few times ova the weekend, seems to be a lot better, think i will adjust the valves in a touch, but other than that, it was smooth and clean and my repair job to the oil leads held up lol.
The oil leads on them are just rubbish! my partners bike has now sprung a leak cos it was just touching the other oil leads screw, think i may have to just bit the bullet and pay a fortune for some good ones to be made up!
The oil leads on them are just rubbish! my partners bike has now sprung a leak cos it was just touching the other oil leads screw, think i may have to just bit the bullet and pay a fortune for some good ones to be made up!
