1992 DT125R, a bit slow to warm up, did I cause any problems on my ride?...
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Sounds like the thermostat has been removed. My bike usually just overheats...don't know why but DTs just seem to run ridiculously hot. So I've removed my thermostat now! Great, sits at 60 degrees all day long which is where I want it to be. But as a consequence it'll take a good while to warm up.
What you're describing though...now. It should be absolutely rapid from cold, the risk here is that under load you'll cause a heat seizure and destroy the cylinder...
Sounds like there could be a few issues that you need to work through. First identify whether or not the thermostat has been removed or has gone bad, I.E. always open.
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I've no experience of any other of these bikes, but compared to other bikes I've ridden in the past, she seems really slow to warm so she's happy off the choke.
Anyway I'd set off the other day and ridden about 4 or 5 miles after warming her up, then stayed chatting with my buddy for about 20 minutes, and then left.
It wasn't a cold day but she needed the choke on to fire up and run, left it like that a couple of minutes, turned the choke off and set along the way.
All was fine until I pulled onto the main road and accelerated up the hill behind the line of traffic, when the bike suddenly faded just below 8k/did want to rev-through, so I upped a gear and it pulled along again nicely until it hit about 8k rpm again, then back to fading, repeat for the next gear change. The fading felt like when the fuel is running out, like a weak mixture fade, and the effect kept up for most of the way back home, then cleared going up the hill on my last straight home and flew fine.
Did I just get too impatient, and the effects were just too weak a mixture for the temps of the engine, or is there a chance the engine was just too tight still and I could have rubbed the rings/piston/bore a little?
Also, are these bikes usually so fast to cool and so slow to warm up, or have I got an oddity/issue?..
Cheers me dears!
Shaun/FloWolF
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DTRs always needed choke to start in my experience, even on the hottest day in the summer. When I swapped to a VHSB that problem went away. But whenever I use the bike these days it needs choke.
my Yamaha 
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Thanks for the replies guys, I'm sure it's fine, hasn't given me any trouble since, but the dial does take a fair bit to start creeping up at all, so maybe it has had a 'thermostat delete' done. I'll find out eventually!
You have a temp gauge? Mine never goes up more than 5mm above the green/cold line in normal running. If it’s the middle of summer it might go to about 1/3. Anything above that is a ‘code brown’ for me
…I’ve asked around if that’s the normal place but didn’t get any real feedback. One day I plan on correcting it so that normal is dead centre with a resistor…
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Well it gave me hell with this today, cut out twice and refused to restart until 5 or 10 minutes had elapsed, then ran a mixture of perfectly/somewhat held back.
It looks like crud in the carb doesn't it, and from what I can see and have read the carbs on these are a PITA to get off and on again, especially with the carb-warmer plumbing and the fact I'd have to do all this kerb-side in front of the house, and I'm more battered than I generally look, so this may have to go to the guys at the bike garage when I get a few dollars spare again, d'oh!
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Well it gave me hell with this today, cut out twice and refused to restart until 5 or 10 minutes had elapsed, then ran a mixture of perfectly/somewhat held back.
It looks like crud in the carb doesn't it, and from what I can see and have read the carbs on these are a PITA to get off and on again, especially with the carb-warmer plumbing and the fact I'd have to do all this kerb-side in front of the house, and I'm more battered than I generally look, so this may have to go to the guys at the bike garage when I get a few dollars spare again, d'oh!
@FloWolF The carb isn't that difficult to get off the DTR and you'll make a much better job of cleaning and setting it up than some bike shops. Make sure you tap out the emulsion tube (the brass tube the main jet screws into) and thoroughly clean it and the carb body around it as a lot of people miss this, the holes in the tube get blocked over time and eventually it just starts four-stroking at medium engine speed one day.
The air bleed for this is just in front of the carb-to-airbox rubber on the right, it's a tiny hole so make sure this is clear as well and replace the hose with Yambits pink drain hose. This needs to finish between the rear shock and crankcases as supplied by Yamaha. A few years ago during a restoration I had the bright idea of making this tube longer and routing it through the loop behind the brake pedal with all the other tubes for neatness. The bike ran awful and it took a lot of analysis before a light bulb eventually went on above my head; if the end of this tube is hanging in the breeze 3" below the engine, the air metering is affected by road speed, wind direction and all manner of things! Snipped it off at the roadside to the same length as original and it cured the problem instantly.
Invest in a MX bike stand (the type where you roll the bike over it then press a pedal to raise it) and then the bike will be vertical as it's very off-putting having the side you need to get to leaning towards you when on the sidestand. It's useful for a lot of other stuff as well like cleaning, chain lubing/adjustment, oil level checks etc.
Getting the seat/plastics/tank off makes it a lot simpler to undo the carb top screws, get the carb-to-airbox clamp completely off and this allows you to just push the rubber out of the way towards the rear shock and pull out the carb.
You can also make life easier by bypassing the carb warmer circuit by just running a single hose straight from one banjo to the other, one of the CW hoses currently on the bike will probably be about the right length for this. Don't do away with it altogether as it makes the cooling system self-bleeding and prevents air bubbles getting trapped in the cylinder head, but carb icing isn't really an issue in the mild UK climate.
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@FloWolF The carb isn't that difficult to get off the DTR and you'll make a much better job of cleaning and setting it up than some bike shops. Make sure you tap out the emulsion tube (the brass tube the main jet screws into) and thoroughly clean it and the carb body around it as a lot of people miss this, the holes in the tube get blocked over time and eventually it just starts four-stroking at medium engine speed one day.
The air bleed for this is just in front of the carb-to-airbox rubber on the right, it's a tiny hole so make sure this is clear as well and replace the hose with Yambits pink drain hose. This needs to finish between the rear shock and crankcases as supplied by Yamaha. A few years ago during a restoration I had the bright idea of making this tube longer and routing it through the loop behind the brake pedal with all the other tubes for neatness. The bike ran awful and it took a lot of analysis before a light bulb eventually went on above my head; if the end of this tube is hanging in the breeze 3" below the engine, the air metering is affected by road speed, wind direction and all manner of things! Snipped it off at the roadside to the same length as original and it cured the problem instantly.Invest in a MX bike stand (the type where you roll the bike over it then press a pedal to raise it) and then the bike will be vertical as it's very off-putting having the side you need to get to leaning towards you when on the sidestand. It's useful for a lot of other stuff as well like cleaning, chain lubing/adjustment, oil level checks etc.
Getting the seat/plastics/tank off makes it a lot simpler to undo the carb top screws, get the carb-to-airbox clamp completely off and this allows you to just push the rubber out of the way towards the rear shock and pull out the carb.
You can also make life easier by bypassing the carb warmer circuit by just running a single hose straight from one banjo to the other, one of the CW hoses currently on the bike will probably be about the right length for this. Don't do away with it altogether as it makes the cooling system self-bleeding and prevents air bubbles getting trapped in the cylinder head, but carb icing isn't really an issue in the mild UK climate.
You mean like these?:
https://www.24mx.co.uk/product/proworks-heavy-duty-mechanic-stand_pid-PM-0097143
Thanks.
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You mean like these?:
https://www.24mx.co.uk/product/proworks-heavy-duty-mechanic-stand_pid-PM-0097143
Thanks.
@FloWolF No worries, yes the 24MX one looks good
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@FloWolF No worries, yes the 24MX one looks good
Thanks.
Well that's not on the cards at the moment, I spent all my funds buying the bike and getting it on the road heheheh.
I'll likely see if I can borrow my buddy's garage, prop it up in there and do the full tank and plastic off job to get it off then I can clean it and refit more at my leisure. Will also give me chance to drain the tank and check the tap filter, but to be honest 32 years old or not, this hasn't been used much and appears well looked after so that's probably all quite clean.
I used to love doing shit like this, I'd dive right into an engine blind/no books or internet and tear it down and rebuild with basic tools, but I'm fooked now, body rather beat and enthusiasm almost dead and buried, heheh.
Cheers again!
