Hoping someone can help, Son has a DTX125 which is running "sluggish", i.e. lack of power when trying to accelerate. Neither the lad, (or myself), are anything close to mechanic level when it comes to sorting issues. One garage tried to claim the enigine needed a re build at around £1,200. We have changed the spark plug, ht lead, air filter etc. Bike was fitted with a DEP exhaust around a year ago. Son has tried adjusting tick over on the carb, which did help a bit, but issues continue. Someone advised the engine may need decarbonizing, but again, not sure how to do this. Can anyone help please, based in Dunstable, and hoping there is someone near by who might be able to come to our rescue!!!
What sort of mileage has the bike got. These engines are really restricted.
Sounds like someone has messed with bike. Changing the idle won't do much but change the tick over. You want to increase the jets in the carburetta. If they've put an aftermarket pipe thn it'll need up jetting.
Try taking the seat off and removing the snorkel out of the airbox. Does it run better or worse.
Check the powervalve.
When you turn the ignition on does the powervalve do the cleaning cycle? ( should be able to gear it whirl)
take the cap of the powervalve. Is it setup correctly. The prongs on the valve should be directly inline with the hole in the cylinder.
If you're unsure use the search function on this forum and search YPVS.
They are many factors as to why the bike is running poor. These are just a few.
I'm just bored so answering questions doesn't bother me.
What bothers me is that the answer is in the mass archive of a forum. You see these problems crop up a lot on this forum. A simple search and you'd find a million and one solutions.
If the engines less that 20k miles and has had all required maintenance then it's got nothing to do with the engine lol. It may not have been setup correctly. It would be really obvious if the engines nakered. Would sound like a bag of nails.
Apologies if I have offended anyone by not filling out all the bits and bobs when registering. In honesty I wan't sure if I would get a response. Thankyou for the advice callum. Bike has done around 15k (grey import, odometer is in km, roughly around 19k). The powervalve was replaced by a garage a month ago. Not sure of the service history, engine seems to sound ok when the lad rides it........
The ypvs was replaced? Odd. It's not what you'd call a serviceable part
I'd say that's where you start looking. Use the search function to find out how check to see if the YPVS is set up correctly. If it's setup incorrectly you'll ruin the performance. Is the YEIS there?
At around 15km you really ought to have had the piston replaced. The cylinder reviews and the correct over sized piston installed. Not a £1200 job. If you do it yourself it's a £150 job max. That's if you send your barrel off to be rebored. If you take it to a garage it should be more than £300 to have all that work done.
Changing the pistons on two strokes is just maintenance.
Right. I don't quite understand why you would change the valve. I'm not familiar with any faults. But if it's been changed by a non yamaha specialist then my best guess is that is hasn't been setup correctly. You'll need to have a look. That's where i'd start. If it revs fine in neutral then that's good.
Can you hear a rattle when you rev. It's hard to explain. But after that sort of mileage you might start to notice a little rattle coming from te top end. This is known as piston slap.
If it's not the pv then it could be the poor air to fuel mixture after putting on the AM exhaust
piston slap is usually heard on idle (got it on both my bikes :( ), try pinning the powervalve open and see how it runs, makes my dtre into a whole different bike, revs 2k higher and gears are longer
only reason to take power valve out is to clean or shave a bit off if over sized dont understand why it would need replacing. unless they did the orings on it and wanted to charge u a lot for it, sounds like ur local garage like ripping u coz engine rebuild should be around £300 for u 2 do it and thats with top stuff or £500 for a garge
