DT125R FORUM

@spookdog

Ah yes that’s the one !

I thought I should update this as I did fix the problem and never stated what fixed it on here. After all the messing around all it turned out to be was a split vacuum hose on the carb which I didn’t notice when I cleaned the carb originally. I had the hose off originally to check it wasn’t blocked but didn’t notice the small split in it. Thanks for all the suggestions though

@spookdog thanks for your responses. I’m going to put everything back standard and double check the carb is spotless I’ve decided before I loose my Head with it all. It won’t go past 6k in any throttle position. I feel like it’s electronic so just want to rule everything else out first

@spookdog im going to put it back to standard and see how it runs and work backwards I think. Do you know if there a decent guide to doing to power valve with pictures or even a video? I just want to make sure it’s definitely right, I’m no mechanic but I like to do it myself so I can learn how it works in case of future problems

@calum it ran really well after I moved the Reed switch and done the power valve. Had all the power I want up to 11k rpm. Just seems to have got worse over time, just won’t rev past 6k rpm. I pinned the power open as I saw in one of your other posts but it still did the same. I’ll check the Reed is far away enough from the speedo tonight as it feels like a restriction. Other than this the bike runs perfectly.

@spookdog I cleaned the carb out and couldn’t see any blocked jets but I didn’t take the needle jet out. Might try this just Incase

@spookdog It’s progressively got worse I think. All I have done is moved the read switch, put a full dep on and turned the power valve so it works. It used to do it after 40mins of riding but not it seem to do it constantly. Won’t got about 6-7krpm it just cuts back. I might try what you done with the oil pump just to rule another thing out. It’s massive annoying specially as I don’t a 100 mile long distance trial today and had to put up with that all day.

Is there an easy way to temporarily disable the oil pump? I just want to check if it’s not packing up? It all looks correct but my plug is still oily and the bikes still cutting back at around 6-7krpm. I’ve checked the power valve isn’t the problem by pinning it open, took it for a ride and was still having the same issue. I was thinking of trying to pre mix the fuel and disable to oil pump to work out of its this causing the problem.

I’m running out of ideas with it. Failing this I guess it’s the ignition breaking down.

( I have cleaned out the carb, fuel line and the tank also and now put back on the original exhaust )

Any ideas I’d be grateful

@calum cheers I’ll check that just Incase it’s some thing stupid. I’m doing a 100 mile long distance trial in a couple or weeks so want it running right if I can get it to

@declan just another though, I should probably checked that everything is earthed properly and that’s it’s not just something stupid like that? Do you know where the earthing point are on the bike. I had a quick look but couldn’t see anything obvious?

@declan I was thinking about jetting too but don’t want to mess with it too much as It used to ride fine before so I don’t think it will help me out

@calum I’m hoping this does the trick for me too where did you buy yours from?

@declan ah cool I’ll give that a go. So you’ve never managed to fix your problem of cutting back. It’s driving me mad I need to try and work it out

Is there a way to check if the ignition is breaking down? I’ve checked everything mentioned above and cleaned the carb out etc. But still the book it’s cutting back intermittently at about 8000rpm. Before I split the casing and check seals I want to make sure I’ve checked everything else.

It seems to run perfect for about 20mins riding the then seems to start and progressively gets worse. Could this be as it warms up the ignition is failing

TIA

@markus-w good shout, i use it every couple of months so ill give that a try as well.

Thanks for the reply’s, I’ll pin open the powervalve and check that and while I’m there I’ll take the carb out and give it a clean as it’s not been taken off in the two years I’ve had it, the bike doesn’t get a great deal of use. It has a new air filter in it so that should eliminate that being a problem.

@calum what is the easiest way to temporarily pin the powervalve open to test this ?

@calum cheers ill give that a try first, see if i can rule one thing out at a time. i want to mess with as little as possible as my mechanical knowledge is near nothing, although i di like to try and understand how it all works and learn for future.

i turned the powervalve quite a long time ago so it was flush with the port and it ran fine with plenty of power for 5 or 6 long rides after that so I'm guessing that's set fine? it just recently its starting cutting back around 6000rpm and really spluttering. i haven't messed with any jetting on it thats all complete standard still. i did notice the spark plug was slightly black with a bit of wet oil but that's about it. is it worth just putting a spark plug on that burns hotter? current one is a BR9ES

i got the bike completely standard as a french import with 8000k on the clock. i put a full depp system on it, have turned the powervalve so its flush and moved the reed switch nothing else has been touched.

After fitting a full depp system and turning the power valve so it’s working as it should, should I be re-jetting the carb if so what did you find works best? Currently it cuts back at top end after 6000rpm. I’m just wondering if this has something to do with it??