Et4 125 4t bad low speed and pull off .
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Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Tue Nov 03, 2020 10:47 am quote
Leader engine walbro carb.
Cleaned carb, new diaphragm, new intake manifold.
Carb seams to work on bench, blow in slot on intake slide goes up and down.
Acelarator pump shootin fuel and springing back ok.
Does not pull off well from lights and really struggles two up, plenty of power when gets goin, bit jerky at Minimum throttle so was thinking lack of fuel but mix screw not making any difference, worse I'd say when wound out, about on one turn at moment., Float seams to be working when bench tested.
Any ideas, should I just buy new kelvin carb for 130 ouch.
Could it be a vaculm leak or incorrect valve adjustment
What's proper number of turns on mix screw
Please help as really winding me up now.
Member
Lx 50 2t
Joined: 06 Sep 2020
Posts: 41
Location: Bath
Tue Nov 03, 2020 11:34 am quote
Hello!
Have you checked the air filter and fuel lines?
Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Tue Nov 03, 2020 11:58 am quote
new air filter sprayed with filter oil
replaced vacuum fuel tap last year with transparent hose too, so definitely see fuel to carb.
gonna try float height, maybe too low, causing hesitation low speed poor performance
clean idle circuit and secondary jet
retest auto choke, dont think preheater does anything but prevent carb icing, as if ever a prob in uk
starts ok, idles fast, then idle slows as autochoke closes i presume
Member
Lx 50 2t
Joined: 06 Sep 2020
Posts: 41
Location: Bath
Tue Nov 03, 2020 3:03 pm quote
It seems just a mixture problem. There is not an ideal position for the screw, just try until you find a good balance. Start with a rich position (if it is mixture screw, you have to unscrew for more rich; the other way round for air screw) and see if it changes. You also need to play a bit with the idle screw.
Also, when you check the float turn the carb upside down and the line on the float should be parallel to the side of the carb.
Addicted
GTS 250ie Super, Italjet Velocifero, Scarabeo 150, S50,ET4
Joined: 22 Nov 2016
Posts: 553
Location: Winston-Salem, NC
Tue Nov 03, 2020 3:37 pm quote
Are you sure it's the engine and not the CVT? The A/F screw should give you a nice steady idle and when you blip the throttle it should rev up nicely with no stumbles.
Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Tue Nov 03, 2020 4:49 pm quote
Going down the carburettor rabbit hole at present, will admit the transmission may be the issue but still need to work through to understanding carburettor fully before ruling it out and looking at CVT.
Addicted
2010 S50 Modified "Punkin"; 2003 ET4 Malossi 187 "ISO"
Joined: 18 Feb 2017
Posts: 574
Location: Deepinnaharta, Texas
Tue Nov 03, 2020 6:45 pm quote
Air Leak
Greetings:

There is no possible adjustment of the air screw that will work across the rev and throttle range if you have an air leak. On my ET4, there was a hose associated with the US evaporative recapture canister that was clearly pulling air and caused me to buy the more modern Keihin carb. It didn't work much better until I deleted the system with its leaking hose. Search for my thread for details. There was nothing wrong with the Walbro carb after all, but the Keihin has easier-to-find jets and components, so no regrets.

Use brake cleaner, carb cleaner, or an UN-lit propane torch to search for the source of your leak. I am confident you will find one.
Enthusiast
Derbi Boulevard 125 4t
Joined: 05 Feb 2020
Posts: 73
Location: Lithuania
Tue Nov 03, 2020 11:00 pm quote
If no air leaks, i would check CVT. I was having bad takeoff too, checked valves, timing, air leaks, air filter, new carb, but eventually it was bad CVT adjustment. Biggest surprise was torque spring, as it looked like stock, but for some reason i needed much heavier (+1.4gr from stock) rollers for CVT to work. I bought Pollini blue spring, which should be slightly stiffer compared to stock, but it was much lighter compared to my "stock". With Pollini blue torque spring i got CVT to work with stock - 0.3gr rollers. Added 0.5mm fuzzy washer and i have very good takeoff, good uphill speed.
I tried Dr. Pulley sliders, they gave even better takeoff, better RPM curve and slightly higher top speed, BUT they flip over in less than 100km and i need to disassemble CVT...
Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Sun Nov 08, 2020 10:50 am quote
Had the carburettor off twice and shot carb cleaner through all the passages, all are open and seam good, jets passages seam open and ok. cant think what else i can do but replace carb. still slow to pull off.
thinking of getting replacement polini variator and clutch spring.....perhaps used good tested carb.
no evap systems in uk
Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Mon Nov 09, 2020 8:14 am quote
If I change weights from 10g to 9 5 it will increase low end torc acceleration,
I can also change clutch spring, for polinni +20 spring, but what roller weight would I need then.
Or can buy a variator kit with clutch spring from 60 or over 100 ish for polinni or Malossi,
My variator does clatter alot while driving, even though I installed new 10g weights, and oem Belt, maybe a sign of wear.
I hear the clutch springs are tough to fit.
Addicted
GTS 250ie Super, Italjet Velocifero, Scarabeo 150, S50,ET4
Joined: 22 Nov 2016
Posts: 553
Location: Winston-Salem, NC
Mon Nov 09, 2020 8:45 am quote
What size weights are you using? The ET4 stock variations take 19X17 weights. Too smallll and the will clatter. Be sure when you tighten the variator nut that the belt is loos and well out of the way or you won't get the nut truly tight and always use a torque wrench and tighten the nut to the correct torque.
Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Mon Nov 09, 2020 8:54 am quote
Hey, standard 10gram weights, think I assembled correctly, put belt on washer, as said in manual,then torqued up with torque wrench. Not come loose, changed weights and slides and oem parts. Should be correct parts. Was clattering before I changed rollers, ones I removed looked ok, weighed up at 10g. Still clatters
Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Tue Nov 17, 2020 9:05 am quote
Have bought another carb, used walbro, taken off a running scooter as thought had carb fault, but turned out it was fuel tap, so claims it good and been tested, was only cheap on eBay 24 quid, so can't hurt having spare.
I have been studying cvt issues,
Could be belt pinch, have installed new belt but it seamed to work fine when revved engine, so thinking clutch issue is likely, bearing in mind though the engine had only done 6000 miles it did sit unused in garage for 15years.the clattering is probably clutch pads hitting clutch bell, I did clean clutch with parts cleaner as was not reversing, was very dirty, inside bell, so could be sticky pivots or weak springs so I can buy new complete clutch assembly 90 quid, or attempt clutch overhaul, but what tools will I need and what parts.
Member
et4
Joined: 12 Oct 2018
Posts: 32
Location: devizes
Thu Nov 19, 2020 9:35 am quote
Ordered second hand clutch and torque converter pulleys, complete unit but no clutch bell
also ordered shims set for variator, it does feel a bit like it's trying to start in second gear, so maybe a spacer or two will help. Think correct parts fitted , just clutch too old and pivots sticky, twenty years no maintance and off road for 15+. Will update when I have parts to try tuning transmission. May look order 9.5 gramm weights to try.
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