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Post by 1260dave on Nov 27, 2011 21:25:41 GMT 1
i have a problem on my 4lo its losing power and missing once it gets hot, I've had the problem since I've owned the bike, blasting it round the neighborhood in short bursts is fine but get in on a duel carriageway at 70mph for more than a mile once its hot the problem starts, if i back off the throttle and reduce the speed its OK
Ive got 31k carbs on it and k+ns 290 mains
i had pwk 28's on it as well, with the same problem
Ive also changed all of the electrical components, no change, its doubtful if they were faulty they would have had the same fault but who knows
its got me stumped so if anyone has any ideas
cheers Dave
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Post by arrow on Nov 27, 2011 21:32:56 GMT 1
Is it on autolube or premix ?
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Post by oldelsieboy on Nov 27, 2011 21:38:24 GMT 1
i have a problem on my 4lo its losing power and missing once it gets hot, I've had the problem since I've owned the bike, blasting it round the neighborhood in short bursts is fine but get in on a duel carriageway at 70mph for more than a mile once its hot the problem starts, if i back off the throttle and reduce the speed its OK Ive got 31k carbs on it and k+ns 290 mains i had pwk 28's on it as well, with the same problem Ive also changed all of the electrical components, no change, its doubtful if they were faulty they would have had the same fault but who knows its got me stumped so if anyone has any ideas cheers Dave Get rid of the K&N's & fit a standard airbox  OEB |
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Post by 1260dave on Nov 27, 2011 22:09:26 GMT 1
i will give the airbox a go
i'm running it on premix at 175ml in five ltrs, tried it at 125ml like most of the mx boys pistons were picking up, its been rebored since then, norbo runs his race bike at 200ml, so i thought i would try 175ml still the same
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Post by arrow on Nov 27, 2011 22:14:34 GMT 1
Just under 29:1 you are running should be ok. Deffo a jetting problem then, as above try the standard airbox.
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Post by billy on Nov 28, 2011 0:45:44 GMT 1
It's probably running rich on full throttle. I had the same problem when I had 280 mains in mine and premix. Now I have 260 mains and it's much better on WOT, although it's still on the rich side. I have the original airbox on though with no filter or snorkel.
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Post by oldelsieboy on Nov 28, 2011 20:10:13 GMT 1
If the problem occurs with 31K carbs & pwk's surely it cant be jet or needle related  Would be a massive coincidence if it was  OEB |
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Post by 1260dave on Nov 29, 2011 16:27:38 GMT 1
i've dropped the needle to the middle notch, it was on the bottom grove, so as soon as it stops raining i'll see if its better or worse, i'll try 280 mains as well,
i can
t plug chop it till ive run it in i've only done 300 on it since the rebore
cheers for your thoughts up to now
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Post by 1260dave on Dec 2, 2011 23:46:14 GMT 1
took the bike out tuesday after droping the needle, it will hold 70mph all day long now but it cuts out when you try to rev it up when on tick over, got some 270+280 mains to try tommorow
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paulo
Thrash Merchant
Posts: 406
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Post by paulo on Dec 3, 2011 21:57:38 GMT 1
What pilots are you using ?. Got 31K carbs also, but with YPVS motor, auto lube, some porting & microns fitted - had to up to 25's with 260 mains, needle currently set at third notch from the top. Running not too bad, very useable - slight flat spot, but my needles aren't prefect, some slight marking evident.
When i lifted the needle one notch for some reason it messed the take off from stand still up, so had to up to 25's - pilots 1/14 turns and pulls lovely now, also in 6th pulls nicely up to the ton. Only slight problem is something when you down a gear or too, the bike holds back slightly then takes off like a bat out of hell. Thinking about new needles now, but happy with the overall ride of the bike now - sick of messing about - just want to ride the thing now !
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