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Twpsin |
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Twpsin L Plate Warrior
Joined: 19 Oct 2021 Karma :
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Posted: 21:40 - 19 Oct 2021 Post subject: Lexmoto Michigan EFI 125CC Has A Problem |
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Hi there!
So, I’ve been having some issues with my bike (Lexmoto Michigan EFI 125cc) for some time now, and I need some advice from people who have more experience than I do!
It’s having some engine trouble which is causing it to no longer idle, and when you touch the throttle it completely dies; before you say it is the Carb, it is an electric fuel injection, and I shall explain the tribulations I have gone through with that aspect of the bike below. This has been something I have been working on for a few weeks now and I am completely stuck.
So, backstory!
I’ve had this bike for just over a year and it’s been great, however for parts of this year it has been sat in the garage whilst I was finishing off University. Since coming back home, I have been attempting to get her started again, with minor victories and setbacks.
The electric fuel pump was faulty and did not fire, so it has since been replaced and works great, and it has had a new fuel injector. This improved things massively as it started well, but new problems have presented themselves in the bike struggling to idle for longer than 10 seconds; it starts well, but then dies off, and if you touch the throttle, it kills the bike off, unless you rapidly twist from max rpm to
minimum, which seems to force some air into her.
Firstly I thought this was an air intake issue, and so disassembled the throttle body to check it over and give a small clean, so all is good. Next I thought it could be a fuel issue, however have double checked all of this and it is working well, and the spark plug has also been checked and is working well.
So, I am very stuck. It seems to be an air related issue, however I have no idea where to move on from here: I cannot tel if it is getting too much or too little air, and I have tried running the bike with the air filter in and out of the air box with no detectable difference occurring. I have even bought a new battery to see if it was an issue with power, but this has changed nothing. Now it has begun to lead me to whether compression is an issue, however this bike can be made to run if you rev hard and let it go, and occasionally gets into a rhythm and idles very well.
I am really stuck and have no clue which way to proceed, so some guidance around what to check would be a lifesaver, as I really want to get back on the road!
If you require anymore information please do not hesitate to ask, and thank you for reading through this fairly long, very erratic post. |
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WD Forte |
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WD Forte World Chat Champion
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Twpsin |
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Twpsin L Plate Warrior
Joined: 19 Oct 2021 Karma :
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WD Forte |
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WD Forte World Chat Champion
Joined: 17 Jun 2010 Karma :
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WD Forte |
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WD Forte World Chat Champion
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Twpsin |
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Twpsin L Plate Warrior
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Mysteriass |
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Mysteriass Nova Slayer
Joined: 06 Apr 2015 Karma :
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Posted: 09:45 - 22 Oct 2021 Post subject: |
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Could be a bust sensor, probably one of the engine temperature sensors.
When a sensor busts, it can send crazy bullshit back to the ECU. The ECU assumes the crazy bullshit is real and takes its vaccine...I mean it responds to the crazy bullshit by altering the fuel flow. It's like the ECU doesn't watch Alex Jones or David Icke - it just believes what it's told by minions of the fat controller.
So let's say, for example, that the engine temperature sensor is bost. The sensor reports to the ECU that the engine is 100c and the ECU craps itself and tries to provide an appropriate fuel delivery for a 100c engine right off the bat. Obviously a cold engine won't find much joy in trying to run on that.
I'd find out what engine your chinese version is based on. Then get the haynes manual for it. That'll give you the sensor test ranges and how to do them. Hopefully your chinese copy will be near as dammit enough to work.
The other thing you might be able to do is get a wireless bluetooth ECU test kit and mobile app. Then you can see if a sensor is giving a mal-reading and either manually adjust it on the fly or reset it.
Take a look : https://youtube.com/watch?v=VZJF09Z7MMo
I haven't got much love for EFI but if you can get over being pissed off about it, do a bit of reading and watch some videos about it, then things start to make sense and you'll be able to diagnose EFI problems yourself. |
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steve the grease |
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steve the grease Crazy Courier
Joined: 26 Jan 2018 Karma :
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
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Easy-X |
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Easy-X Super Spammer
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Twpsin |
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Twpsin L Plate Warrior
Joined: 19 Oct 2021 Karma :
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Posted: 22:26 - 25 Oct 2021 Post subject: |
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So, an update on the trials and tribulations of the last few days.
I bought a Bluetooth OBDII reader, which has been really useful, as it has allowed me to look more into the ECU. I have drained out the old fuel, clean out the lines, and inspected the inside of the fuel tank properly, as well as bought new fuel and ran it through a little to see if it has made a change. It did not, but it’s good to do.
I bought some new engine oil and spark plug, and did an oil change, which has improved the running of the bike a little, and did also need to be done, so a nice bit of maintenance which I can tick off.
Whilst perusing the sensors tab of the app my OBDII unit uses, I saw the intake manifold absolute pressure was very strange. It’s base reading was 12.75 psi, and when the bike turned over and hit around 6 psi it fired, but I could not get it to stay at this level for long because of the idling issues.
This has now lead me to whether compression could be a bigger issue than I first realised, and could mean the MAP sensor could need replacing, or whether the compression of the bike isn’t up to scratch.
The lambda sensor could be a culprit, so I shall look into that as well.
Any thoughts of where I could go from here? I went to a bike shop today and had a chat with the receptionist, whom mentioned valve clearings could be a possible culprit, but since the bike does turn over and I can get it to run, that would make that void, right?
My knowledge on how pistons and compressions works with engines is a bit of a gray area, so some enlightenment and education would be greatly appreciated! |
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Easy-X |
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Easy-X Super Spammer
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Mysteriass |
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Mysteriass Nova Slayer
Joined: 06 Apr 2015 Karma :
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Posted: 23:40 - 25 Oct 2021 Post subject: |
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Bit of a cop out, but you could replace the entire throttle body (EFI's equivalent of a carb). Sensor and all.
Something like:
https://www.ebay.co.uk/itm/363590511720
Great thing about many 125's is that you can buy a bulk of bike bits off ebay for the cost of one consultation with a mechanic. Even if you don't know what the problem is just keep replacing parts until it works. It'll still end up being cheaper than taking it to a garage and you get a pile of spare parts to hoard, click your claws over and barter in the coming Mad Max world.
Those Chinese 125's ... all the rage in the wastelands.
Even while I'm fiddling with something trying to fix it ...always nice to know there's some fresh bits on their way for when I inevitably break the very thing I'm trying to fix. Only to find that there's something else entirelly wrong with the "working" part I ordered therefore needing more bodges and yet more parts and even more harsh language. |
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WD Forte |
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WD Forte World Chat Champion
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Twpsin |
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Twpsin L Plate Warrior
Joined: 19 Oct 2021 Karma :
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Posted: 18:43 - 01 Nov 2021 Post subject: |
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[quote="WD Forte"]So its compression now is it?
Probly needs new piston rings then
Is the chain slack too?[/quote]
So, another update for you all!
I bought a compression tester, and after this test my compression came up as 80 psi, which of course is not good. So, I have taken the cylinder apart, changed the piston rings and replaced the base and head gasket.
In putting the cylinder back together, I now have no compression: 0 PSI. Today I double checked and adjusted the engine timing (and am pretty sure I have it correct after watching some YouTube videos on a 4 stroke engine, if anyone has anymore information on this it would be great!)
Tomorrow I shall be checking the valve clearances after ordering a feeler gauge, so hopefully that should make some change, however if nothing comes of this, I am very worried that I have fucked up the compression more so than I already was, after taking a lot of time to put the cylinder head back together just as I had found it.
If the valve clearances does not sort the lack of compression, I feel I will have to send it off to a mechanic, which I really don’t wish to do.
Help! |
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
Joined: 16 Aug 2013 Karma :
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Twpsin |
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Twpsin L Plate Warrior
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
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slowasyoulike |
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slowasyoulike Scooby Slapper
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A100man |
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A100man World Chat Champion
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Easy-X |
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Easy-X Super Spammer
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Posted: 20:58 - 01 Nov 2021 Post subject: |
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Zero compression?! Step 1 would be just stick your thumb over the spark plug hole and see if you feel any push back just the verify the gauge hasn't spontaneously busted. Even with a valve stuck open a little bit you should feel something.
Once you've figured that out (I'm sure it'll be something simple) you have to be careful when refitting the timing chain on any 4-stroke. Depending on the specific engine there'll be a system of timing marks that need to line up.
For an example scroll half way down the page where I did a barrel change on an old 50cc scooter:
https://www.bikechatforums.com/viewtopic.php?t=327425&postdays=0&postorder=asc&start=25 ____________________ Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter |
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slowasyoulike |
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slowasyoulike Scooby Slapper
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
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Robby |
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Robby Dirty Old Man
Joined: 16 May 2002 Karma :
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Posted: 10:28 - 02 Nov 2021 Post subject: |
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Just to be clear, you rebuilt the top end when the problem is likely to be a failed or dirty sensor.
On the initial compression test, was the throttle open or closed? Compression tests must be done with a wide open throttle. 80psi would be about right for a closed throttle.
Anyway, right now it's timed wrong, or you fitted a new piston without any piston rings. Either way, it all needs to come apart again and the job done right. Haynes do a manual for Chinese 125s, which will show you how to do it. Make sure all the gasket surfaces are totally clean (new gaskets required again), and you should also remove the valves to see if you bent them by getting the timing wrong.
Remember, timing can be out by 180 degrees and still look OK. Or it could be out by 90 degrees and smash all the valves.
You've turned a small problem into a big problem. Everything needs to come apart, be cleaned, checked and reassembled properly. Worth replacing all the sensors while you're at it, the time for a cheap fix is a long way behind you. |
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stevo123 |
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stevo123 Nitrous Nuisance
Joined: 10 Aug 2004 Karma :
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Old Thread Alert!
The last post was made 2 years, 137 days ago. Instead of replying here, would creating a new thread be more useful? |
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