How to diagnose an engine that won't start! Fixing the wrecked Yamaha YZF R125

How to diagnose an engine that won't start! Fixing the wrecked Yamaha YZF R125 | Part 3

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Күн бұрын

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@thepennydreadful95 10 ай бұрын

The decompression mechanism you was talking about is automatic. Its on the cog of the top timing chain, its a metal slider that opens the exhaust valve a fraction to allow easier starting. The mechanism is working on this engine, i saw that when you was doing the timing chain.

@StokedBuilds 5 ай бұрын

Thanks for the explanation. Its an impressive little bit of engineering.

@neksekots Жыл бұрын

Brilliant…. Very professional 👍👍

@StokedBuilds Жыл бұрын

Thank you very much!

@kxzty.7186 Жыл бұрын

Hi I have been watching your videos to help me figure out why my own yzf isn’t starting I would greatly appreciate it if u could help

@StokedBuilds Жыл бұрын

Hi there, it's hard to remote diagnose. I suggest joining a YZF R125 group on Facebook (I am in a couple) and post a video of your issues there and I am sure I or someone else can help you. Just follow the steps... 1) Do you have a spark? 2) Do you have compression? 3) Are you getting fuel? 4) Is your battery fully charged and are you getting the right voltages from your Stator / Magneto? 5) Is your Starter Motor busted? Start with those and see how you get on.

@mansukka_ Жыл бұрын

Hi. i wil gona wait another part of viedo:) do you know when we can see it? i got same problem on my r125 and it came out of know where when i was driving. So i hope you can help me! (sorry for bad english)

@StokedBuilds Жыл бұрын

Hi. Thanks for the comment. I am trying to be more regular with my posts. Its a learning experience for me! My issue was that I had bent one of the intake valves because I got the timing wrong. If its cutting out whilst you are riding then there could be a few reasons why, such as: Fuel Pump Failure Contaminated gas The battery might have an issue so check that and maybe replace it The Stator / Magneto might have a problem where its not delivering enough power to the bike Your spark plug might need changing, check that is ok You might have a compression issue that is worse at a particular power band. Try a compression test and make sure your piston rings aren't leaking and that your valve clearances are within spec and the valve seats are clean. Without seeing the bike in question, these are just a few ideas. Let me know if this helps.

@Alan_Stewardson 2 ай бұрын

Does the throttle not have to be wide open when doing a compression test ? . I know it does on dirtbikes

@StokedBuilds Ай бұрын

Yes it does. You are absolutely right. Not something I was aware of at the time :)

@adamgillaspy1 9 ай бұрын

mine use to start first time on the button no problems then started needing throttle to start it, then wouldnt idle would drop randomly and cut out. Garage had it for 6 weeks and said it was a cracked ht lead wire and spring missing from plug, 1 week later does the same again, now i cant get it to start at all to get it to my local garage 6 miles away. It does back fire when trying to start sometimes not very often though. im gonna try a new coil pack soon, any ideas before i buy one? thanks in advance.

@StokedBuilds 7 ай бұрын

There are quite a few things that this could be, so you just have to work through each of them one by one until you find the fault. Start with spark. So, check you are getting a spark from the plug. Sounds like you've tried a new HT lead and plug, so can assume that's ok. You can check the resistance on the stator to make sure there aren't any faults there. But it sounds like you are getting spark because it does run a bit. Then check you are getting air. If you have a carburettor then give that a good clean out and check the petcock. Make sure you are getting the right gas to air mixture. If you are running too rich or to lean (too much or too little fuel) that could be your problem. Then you need to check compression. Make sure your valve clearances are right, Get a compression tester to see if you are getting the right compression. Check there are no scratches and scuffs to the piston cylinder and that the piston rings are good.

@DTMotorcyclesEssex 4 ай бұрын

Brilliant video mate

@StokedBuilds 2 ай бұрын

Thank you so much!!! I really need to get the project finished finally!

@thepennydreadful95 10 ай бұрын

How did you set the valves without first setting the timer chain? that means your valves will be out as you need TDC to set the clearances to begin with. Its pointless doing one without the other.

@StokedBuilds 9 ай бұрын

Well.... I ended up with a bent valve!!! So... Yeah.