Runs with choke
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@OllieDTR I've always set the float heights on all my TM28SS carbs to 16mm and never had an issue ('93 3NC, '98 3MB and my '98 3NC on which the carb had been so butchered with silicone sealant down the vent holes etc. I ended up just replacing it with one good carb made of two spares). I read in the TZR125R Yamaha service manual that it's 15.5-16.5mm for that bike where the TM28SS is fitted (UK, France etc.) and I didn't have any other Yamaha service info at the time and so just went with it. The moulding line around the plastic parts of the floats is about parallel with the float bowl gasket face at 16mm and that is usually a good indicator that the float height is about right on most Japanese bike carbs.
I'm afraid Haynes never quite got their head around the fact the '88 DTR has a VM26SS carb (same as the original TZR125) and then changed over to the TM28SS flat slide in '89 after one year of production. So various editions of the Haynes manual for the DTR have some pretty big mistakes in the carb section; I think where they specify 20-21mm float height for the TM28SS they got mixed up with the VM26SS, and they list VM26 jet sizes for the TM28 in some parts of the manual, and in others they just say all DTRs have a VM26!
It sounds to me like the previous owner has cut a big hole in the top of the airbox "because YZ125" and this is probably what is causing the lean running condition as you say. It's certainly not helping so fixing this and refitting the snorkel before trying anything else is the right approach IMO
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I can always change float height back to 16mm not an issue, I’ve got the snorkel hopefully coming tomorrow so I can patch the airbox up and have the correct amount of air coming in as it should be so can work from there as it’s all guess work without
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Off the top of my head it does say 21mm in the Haynes manual, but like @HOTSHOT-III says, they make fux ups all over the place with carbs and wiring diagrams just being ones I’ve had ‘problems’ with
…21 sounds like such a big leap for a carb with the same bowl as the other iterations. But, like you said, you can always change it back. I’d try anything if I was in your shoes bud…
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Have you checked the gasket on the carbs slide body? Or the slide top? Anywhere that unmetered air can be getting in? Cracks in the rubber mount even? I personally can’t see the air box being the problem, but it’s a good idea to put every variable back to standard…
If it helps I’d be up to lending you my spare carb to see if swapping it out makes any difference. The jets I have for it are richer, I accidentally opened up the .25 pilot and I only have an aftermarket 250 main for it, but it works…
It’s in Poole…PS have you got the little tube connecting the power jet from the throttle body to the bowl? If that wasn’t connected it could suck air in there…
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The airbox on the DTR is pretty restrictive to be fair. Was a common modification by a lot of people tuning their DTRs to cut the entire top section of the airbox off, when these bikes were a dime a dozen.
I purely ran a pod filter on my DTR and am very happy with how it performs. Cutting the box these days seems sacralige but that's just how it was back then.
Either way, when you're diagnosing faults it's always good to go to known working.
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The only thing that the pod filter would affect would be the power jet…
Ram Air used to make a kit for the Z1000’s (back at the end of the last century!) they used to supply a drill tap and ‘recalibrated’ screw-in brass jet because it looses some of the ‘suction’ caused by the standard long air intake. Interesting stuff!…
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A different carb sounds like my next step mate after the snorkel as I can’t think where it could be coming in now, everything is sealed with new gaskets so if it’s not the snorkel it’s the carb,
I’m in Weymouth Dorset so only down the road, I might have to take you up on the offer of borrowing it mate to see what it idles like if that’s the case I’ll be purchasing one soon as I know
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The only other thing I can think of air getting in is…
So the reed rubber bit where it goes onto the reed valve that has its own gasket doesn’t it the rubber bit, I’ve put a gasket onto that as it’s got a reed spaced air wouldn’t get in there would it? Or would it be best to take that gasket out and just put it without as it is from factory?
Thanks
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There’s a gasket below the metal reed valve. None above (and between) the reed valve and rubber intake (it has its own seal). If you’ve fitted one strip it down and try again. The inlet is the most likely cause for your symptoms…
Do you have much hands on experience with engines, or is this a first bike?
One of my first experiences with the dtr was an almost Invisible split in the rubber mount… -
I’ll take the gasket off today mate, I’ve had a couple dts and mx bike I’ve always done rebuilds on but this one seems to be testing me…
I’m currently running 240 main
25 pilotWent for a ride on choke then turn choke off when moving goes for Abit then bogs when let off and try to use throttle again just bogs but flick the choke back up and runs again
Am I thinking it’s lean?
I’m off to get some brake cleaner in a minute and going to test for leaks again
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I had to ask, I honestly don’t think that you’re as big an idiot as me
I just don’t understand where an air leak big enough that changing the jetting as you have, has made no difference, can be…Again, sorry, I have to ask! You are spraying and checking while the choke is off? When I sprayed even a tiny bit near where the leak was my engine stopped ‘hunting’ and settled down.
Yours will tick over without choke yes? But be all ‘fast & twangy’?There are only so many places air can enter unmetered
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Fixed it!!!
So airscrew didn’t have a o ring so put one in.
Also when I was checking air leaks nothing, so I thought I’d take carb out and check all rubbers, where the jubliee clip tightens up onto the carb on inlet there was a hairline crack under the clip which I only saw when I flexed it about. so put the carb back on and sprayed like 2mm away from the place I saw the crack and sure thing revved up. So that’s why I didn’t rev before when I sprayed because I had to be really really close to it!After all that
I’m glad though crazy how a tiny tiny little crack can do that but where it was hidden under the clip it didn’t pick up the brake cleaner until really close.Thank you everyone been a couple of stressful days but that’s a win and learn something on the way
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@OllieDTR Cool you've fixed it
Here you go bud, DTRe 1D01-1D03 (2004-onwards) wiring diagram as discussed:
I'd still try those washers above and below the carb needle E-clip, stopping that moving up and down too much will be no bad thing. And here's a pic of my airbox when I sealed it up, this is why I like to take them out to do this so the part you've glued can sit on the bench horizontally while the glue goes off. While you've got the Seal-All out you can also replace the foam on the back of the filter element holder where it slides into the airbox as this is another thing "previous owners" miss, it rots out providing another route for dirt to get in. 5mm air filter foam is pretty cheap on eBay etc.
https://www.repairingproducts.co.uk/product/seal-all-gas-oil-resistant-adhesive/
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Fuxin sweet! All you have to do now is make sure you got the right jetting for the carb!
Have you got another rubber inlet? I can probably flog you one if needed. I went through a spell of snapping them up after I had my ‘cracking up problems’…
I did ‘inject’ silicone sealant into the split and around it for a temp fix. Nothing beats a good seal though…
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Result ay mate! Was on the phone with @HOTSHOT-III and we was running through some stuff and made me think to double check and check again everything.
I’ve just picked my spare one up from my mums so will be putting that one on tomorrow.
As regards of jetting I’ve got
4th clip on needle
240 main
.25 pilotI’m sure that’s correct for my year as it’s an DTRE engine.
I just wasn’t sure if I needed to upjet at all as I’ve got dep, Boyseen dual stage reeds and 1mm oversize re bore?I will do a plug chop when it’s all running properly and go from there
