Head scratcher
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Hello again, the last week my bikes been wrecking my head it's a 1998 TDR125 and it refuses to rev above 6500. I've changed my needle height to lean and to rich no change. Don't think it's powevalve related as you can see it open fully if you rev it up in neutral. I'm a bit at a loss I've double checked everything, had low compression so changed rings and the end gap was all perfect, new airfilter. Adjusted valve and needle height. Not sure what else to check.
It's also acts odd. if your in first and you rev it up to 7000 and then slip the clutch holding it at 7000 it goes off like a rocket. But the minute you change into second it dies out and won't go any higher than 7000!
Anyone get any ideas? It's as if my powerband has ran way
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Yes it's possible to get the powervalve cables the wrong way, pretty sure that was a restriction on some models.
What I would do, take the exhaust, turn the ignition on, turn it off when the valve is flush with the exhaust port then disconnect the powervalve cables.
Ride it like that, if it's running rapid now then you know it's the powervalve.
Other things can be things like exhaust can have a massive effect
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Yeah thats the next thing on my list to do. See I've done a few modifications, it's got a derestricted exhaust and a the 3MB head, but up until last week its been perfect with heaps of power with the desresrict wire grounded. It started gradually coughing for a few rides then all of a sudden I started it one morning and it wouldn't rev about 7000
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If there’s a break inside you won’t tell by reconnecting it. It’d be the same
What colour is the plug?
Is the spark good?If you can’t dial in on the problem you’ll have to do a top end check eventually. Head off or at least check out the piston and rings through the exhaust port…
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I've rebuilt the top end, checked the ring gap all perfect new gudgeon pin and bearing too, it's running a brand new genuine yamaha coil right now. Is their any way of checking for a break with multimeter all the wires. Spark is perfect, but plug always comes out a little oily and black
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Oily and black is rich mixture. Probably where you’ve played with the needle/carb settings…
You won’t see a break inside the insulation.
I don’t know much about your model but it sounds like it’s rev limiting itself. If the wire (green?) isn’t properly earthed, or connected to it’s proper place (CDI?) the CDI might be defaulting to a ‘safe’ mode. I’ve heard of similar problems with bikes with the rev limiter read bulb in the speedometer…It’s the only thing I can think of if everything else is in good order like you said. It started off intermittent then failed completely…
You can do continuity testing with a multimeter. You may have to pierce the wire with a pin to make a testing point…
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Hey! Try running it with the ‘deristrict’ wire not earthed. See if there’s any difference…
The reed/read bulb refers to a dtr (don’t know what year) rev limiter…
PS have you cleaned out the jets and emulsion tube when you had the carb apart?…
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I've cleaned all the jets, but was wondering the emulsion tube refers to the press put large jet, that the main jet screws into, does that have some small holes going up the sides, I've only ever sprayed it with compressed air I've never removed it perhaps they may be blocked if they are present. I reconnected the wire yesterday and it made zero difference, I'll have a look to see if I have that read bulb. Thanks again @SpookDog
