Runs with choke
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Whereabouts? I’ve got a slightly enlarged.25 & a 250 main you could try. If you do have the later carb the .25 airscrew is supposed to be 1 & 1/4 turns out. I’d try your setup at 1/2 to 3/4 turns…
I bounce between blandford and Poole…
PS I got a good copy jet at sportax racing. Couldn’t find a genuine in the UK
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Update:
Took the carb apart again, checked float height 16mm
Everything is perfect emulsion tube is missing an o ring, all the kits I see don’t come with one, but on my other dtr carb it has one. Where is best to get a rebuild kit that actually is decent rather than the Chinese cheap stuff? My needle is also bent, what needle code has everyone got?
Thank you,After that if nothing has changed then the left hand side seal has gone already I’m taking it even only being just fitted maybe the cheaper seals don’t last at all
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Little update: changed pilot jet from 22.5 all the way to 27.5 and no difference in running without choke, air screw not doing anything, put the needle to the richest possible still nothing, so it’s got to be an air leak only place now is the left hand side crank seal, I’ve replaced them all but they was only eBay ones so could be that, so gone with viton high quality one now.
What is the float height guys for the TM28ss? It’s at 16mm at the moment
Thank you -
If it’s your first time fitting them you may of fuxed up the inner spring or not seated them level. I’ve done it myself, more than once. You don’t have to split the cases to replace them…
I need to reread your thread to see what carb you have fitted. My memory is not wot it used to be
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2004 onwards:
1DO I.D. mark
210 main
17.5 pilot
5J40 needle 2nd clip from Top
Q2M (938) emulsion tube
2.8 throttle slide cutaway
15.5 ~ 16.5 float heightYou may have an earlier carb though. Check the marks your needle & tube have on them…
The earlier one is:
I.D. 3MB00210 main
22.5 pilot
5J25 needle 4th groove from Top
Q-2 tube
2.5 throttle slide cutawayTry and suss out what carb you have by the slide cutaway. It’s stamped on it somewhere…
I may have a needle you can borrow to try swapping out. Let me know the markings on yours & slide…
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Thanks @SpookDog
My needle is NJ25
I’ve copied all them settings for my carb and still the same runs good with choke but soon as you turn it off it revs high then dies so definitely a lean state.I’ve ordered a viton crank seal now as I bet it’s that. Being cheap quality this one must of some how broke in the process of install.
As the air screw doesn’t change anything so got to be an airleak there as no where else it could be, as all the other gaskets, are
OEM from fowlers headgasket
And the rest of the gaskets are Vertex so decent
I just ordered a seal kit from eBay for £20 for the lot so that probably explains why the crank seal has gone already lol. These nitrile ones are not strong and no good with fuel I’ve heard.Other seal is arriving Tuesday/ Wednesday so I’ll update you then.
All the best everyone and thank you
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I inadvertently dimpled the side of my seal when I fitted it. I used a flathead screwdriver and was careful, but the contact area you want to hit is only about 1mm of the outermost edge. I only ever use an old seal as a buffer now and use a tube
Good luck… -
Got the flywheel off this evening and just as we suspected, crank seal failed, lesson learnt! Got new one coming tomorrow
Someone’s had a little go before and marked the outside of casing, I drill a little hole, screw a screw in and pull the old seal out. Lucky inside is fine
EDIT: when putting new one in i’m going to do what you said @SpookDog use this old one as a “buffer” would you say to put a little oil on the inner so it doesn’t ruin the lip?
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Red rubber grease is the best I recon…
Yep, make sure the casing is clean ally, no white oxidation or crud. Then anything that helps it slip in easily. Then push it in with your thumbs. Then gentle, even tapping. It’s so easy to distort the seals ‘face’ and sealing lips
Good luck bud! You’ll get there…Just re-looked at the pic. That’s pretty much what happened to me. Hell of a learning curve. I did it to fork seals as well! 🥴 What did you use, a socket, or extension bar?…
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Seals arrived today! Didn’t get time to put it in as finished work late and wanted a fresh head on it.
Yes I’m going to do both sides, I’ve removed both seals the other day by drilling a small hole in them and then use a screw couple turns and then pull it out.
I’ve got with high quality viton seals this time as fuel and high heat resistant
Finally can put the bike back together tomorrow! Being the electric start engine that’s 2004+? Correct?
So carburettor settings is and correct me if I’m wrong
240 main
25 pilot
4th clipOh I’ve also ordered a snorkel for the airbox as previous owner decided to remove it but I’ve always found they run better with them in.
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Update:
Changed crank seals, no change, so I thought I’d check everything again, cleaned all jets, checked float height and it was 16mm, so I did some research and the float heigh is 20 - 21mm it says in the Haynes anybody got there’s at that?
Alittle better but not full fixed, so I thought fresh fuel Abit better again can get it to bog on rev now but will rev past,Thing I’ve ruled it down to now is air…
Previous owner cut the airbox, so I’ve ordered a snorkel and what I’m going to do is stick a plastic cover back onto the top of the air box and then cut out a slot with a dremel so the snorkel fits so it’s back to oem, as when you rev it you can hear the mass amount of air being rushed in.I still don’t know why people remove the snorkel and cut the airbox.. Yamaha has probably done so much testing and that is what is best for the flow and feed of air. So I’m 100% certain it’s that as makes sense now runs on choke so that means it’s getting more fuel and when you’ve got more air you’ll need more fuel so choke is the answer.
If someone can please let me know on the float height if I’m wrong above thank you !
Hopefully it’s here before weekend and then I’ll be back to update you all
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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…
