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GeorgeeHoward

Yamaha DT125R

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Sorry for posting this in three different places, just wasn't sure what to do.

Just got my Yamaha DT125 R 1999.

I have a little problem with it, it runs fine at low revs but as soon as it gets to around 6000 revs it bogs out, also as soon as the throttle is opened fully it does exactly the same. It's not a restriction as the amount of revs it bogs at changes every time. Thought it was a dirty carb but its not that as had it all cleaned up and didn't stop the bogginess. Been told it could be my coil so I've brought a new coil.

Any other ideas on what it could be?

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Who cleaned the carb and how was it done?

Was the float height and jets checked for issues and sizes?

Is the air filter correct?

Has it fresh fuel in it?

Is the fuel tank clean inside?

Is the petcock clean?

Does it have a clean inline filter?

When was it last running fine?

That should do for a start.

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The carb was all cleaned out by a trained mechanic, not a dodgey job or anything. Air filter has just been fittes. When I first brought the bike it was bogging out just the same and the power valve was disconnected and my mechanic thought it was that, that was bogging it but it wasn't. After I had the carb cleaned out it did run better, bogging out at around 9000 revs but I had my tank sprayed. The sprayer had a falling out with me and sprayed inside it so at the moment I have little flicks of paint inside the tank which is probably bogging it out more now as its back to the 5000 revs.

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Paint flecks *inside* the tank??!!

I think I have an idea why you're having problems...

I don't know your exact bike, but 9000 seems a little high on the ol' revs there... Mine actually redlines at that point!

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2 strokes are pretty agricultural but there are somethings they do not like.

Spraying the inside of the tank is not good. The tank needs to be really clean inside. I would take the tank off and the petcovk (fuel tap) and see what kind of condition they are in. Small bits of grime will block things really quickly. These WILL find there way into the carb. I would still take the carb off and check it for cleanliness, the float height and jets (size and how clean). Have a look at the fuel cap. Is the vent working properly?

How does it idle?

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It was bogging out beffore with the old tank though, so that's not the complete problem. A new tank has been ordered. I'm riding a Yamaha DT125R, it was sitting absolutely fine at 3 quarter turn on the throttle but as soon as you open it up fully on the throttle it bogs out completely in any gear.

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If it was one problem I would say it is the carb main jet then.

Edit - I removed the same post in the workshop.

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Okay thank you. I have ordered a new main jet and needle for my carb, and like I say the coil as I've been told it could be that breaking down

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Na coils won't go that way they work up untill a certian thresh hold then break down take Dirtydt's advice.Clean the tank and filter the tank fuel line.

But the jet my be different in size than the 1 you ordered why not just clean out the old one? Chances are you will find that paint in the carb when you open it up and thats all your problems.PS don't forget to clean the pilot jet and the emulsion tube (The part that the main jet fits into) as well when your in there.

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We can only offer advice, It is up to you if you want to take it or not. There are a lot of 2 stroke lovers on the forum - that includes me and I have 3 at the moment - Down to you now.

Diagnosing a fault over the internet is not the easiest of tasks, but stick with the plan and you will get there the cheapest way possible. You may even learn something on the way. You seem to have a coil fixation. They do break but, given the description you have told us, I would repeat the same advice.

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The plan is to get the bike running well.

Start doing the checks suggested and then come back and let us know what you did and what difference - if any - it made. Do the cheapest and easiest things first and we can go from there.

Even if something you check doesn't make any difference to the running, it does eliminate this as an issue.

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Okay I will do. Yesterday when I was out, this may sound very stupid, but i only just realised that the bike only bogs after a certain point on the throttle. It's not to do with the revs as I can get it to 10k easy in every gear as long as I hold the throttle at a certain point and don't turn it any more. It doesn't quite hit its top speed but it gets up there slowly

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If thats true about holding the throttle at 1 piont then the bike is rich,most likely but could be extreamly lean,what colour is the plug?

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Could also be a blocked up exhaust system

have you the right settings on the carb for the year of bike,,,,air screw turnouts,,,,,,idle speed.

like the rest were saying,,,,,start doing the checks to eliminate causes

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Hi just an update on my bike. Done all the checks I was told to, had carb cleaned out thoroughly and got new jet and pin in there and still done the same thing. Moved the pin down 2 notches so its on its leanest setting and that's how it's running its best. It's pulling loads with amazing acceleration but when you get up to around 75mph in 5th gear and click it into 6th it sometimes just dies down to 70mph and other times it will go to 80 and carry on accelerating but will nog if throttle is opened completely. Last night when riding home it started to bog a lot more again for no apparent reason. It's nothing to do with paint this time as I have a new tank now on the bike and I cleaned all the petrol filters, any idea?

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Had the same problem on my 150cc carb when I was working on it. Checked all components including carb as I suspected fuel delivery was to blame or an offset fuel/air mixture screw but turned out being electrical. I woul clean carbs, check plugs and filter for proper working capability then make sure your carb screws are set correctly as in the fuel/air mixture. If this doesn't work check all vacuum lines for cracks or loose connections as this flaw.can wreck havoc on an engine. Lastly if the problem comes down to it check your stator for proper functioning as this was my problem spot when encountered, good luck.

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My dt was always like this, you had to catch the revs just right otherwise youd lose 6th gear amd have to knock it back down to 5th. I think its because the dt has pretty high gearing, once 6th catches the bike would fly!

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