Deeteemx
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Posts posted by Deeteemx
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In my eyes it is easier and cheaper to check the issue is not caused by a bad coolant ratio or other possible cause, than to strip the head down every time it starts blowing coolant out of the expansion bottle overflow. £10 for coolant and 10 min changing it compared to £25 and a few hours changing the gasket and coolant is a no brainer imo.
This thread makes me wonder how many head gaskets have been changed along with the coolant and the problem "fixed" and the cause attributed to the gasket, without the coolant given a second thought.
A slightly different jet size won't cause overheating, but one that is way to small will cause a lean mixture and will cause overheating.
more fuel = cooler engine . more air = hotter engine.
If you do have a blown head gasket Andy, then if it were me I would look into what is causing it to blow, otherwise you may keep changing gaskets, instead of finding the cause.
Vez.
Obviously it is best to check that the problem lies with the head gasket before dismantling the engine. One of the best ways to do this has already been mentioned by James, ie remove the radiator cap after the engine has cooled down and see if there is a release of built up pressure.
The black carbon on the head gasket, head and barrel has clearly shown where the gasket's have been blowing on the 15 or so cases that I have witnessed.
And a jet size that "is way too small" (why would anyone fit one of these?!!) would probably melt the piston before the coolant had time to overheat!
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Tap water on its own will boil and expand at a lower temperature than it will when mixed with coolant (anti freeze as it is called on here). Water alone turns to steam and is expelled out of the expansion points and will boil dry if not changed or coolant added to a good ratio.
Coolant has a faster heat transfer rate than water alone and mixing the two will change this rate depending on the ratio of water to coolant. Not using coolant at all will effect the cooling efficiency of the engines cooling system and increase the potential risk of damage to the engine, like for example a blown gasket (gaskets will expand faster being thinner) or even a warped head (if left unchecked long enough) as the metals of the engine will expand more than they would under normal designed operating temperatures.
Also coolant should not cause corrosion as it is designed not to with the anti-corrosive additives it has, but mix tap water with it and it has the potential to do so, which is why it is advised to use de-ionized water to mix with coolant which has less potential of causing corrosion.
I have witnessed first hand the expansion cap be blown off a DTR when tap water alone was used instead of coolant, when there were no other problems with the bike before or after (once the water was changed for coolant). Just because I made a bad call with the OP, it doesn't mean I just pulled the tap water issue out of my ass.
Why not try it out if you doubt me and run your bike for a while with no coolant and just tap water, then maybe post back here and show the result
I'm well aware of the cooling and anti corrosive properties of coolant.
I'm also aware that if a bike has an underlying overheating problem, or is ranted hard offroad, the extra few degrees boiling point provided by coolant could be critical. However, DTR's have a large capacity cooling system and large radiator for a 125, and are very unlikely to overheat in normal road use (irrespective of whether coolant or tap water is used) unless there is an underlying problem.
And as for posting back after I've run my bike with tapwater - well brace yourself, or look away now!
In more than 30 years of riding on the road, and competing in trials, motocross and enduros, I've used neat tap water on numerous occasions, particularly in my old YZ250. Yes, it did boil up occasionally when the going got really tough - the Weston Beach Race for instance, but so did a lot of other bikes. The only long term damage caused was to the drain bolt which went rusty! I've also used tap water in lots of road going DTR's that I've rebuilt, with no problems.
Maybe I was lucky, and I'm not recommending that others follow my example, but tapwater has never caused me the kind of problems experienced by James and Andy.
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Replaced the coil and ht lead as well early on, so not that- but checked just incase i have been really unlucky.
I am now working my way through the wire harness (the wires are 21 years old, so are black inside and hard to solder!). It is the last thing it can be. I'm not sure what other options i have got other than replace a few wires, as I doubt i would get a replacement 1989 dt wire harness. I'm guessing that the newer versions will be different anyway. Does anybody know if a newer (say 2004 DT) wire harness can be used for an older bike? - I accept some connection cutting and lots of soldering! Or have things changed beyond all recognition?
I HATE electrics, would much prefer a mechanical problem......them I can solve!
It should be easy to find whether the problem is electrical - simply take out the spark plug when the engine has cut out and see if it has a spark.
As OG says, you can take readings for the 2 coils behind the flywheel (on the engine) with a multimeter and compare them with the resistances shown in the Haynes manual.
The wiring loom is unlikely to be the problem as the ignition system bypasses most of it. The wires from the stator plate connect almost directly to the CDI. A loom from a post 1998 DTR is completely different....and loose connections on your battery will not affect the running of the engine.
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I know its a mix one, but i think he must have used tap water with it as it expands and pushed the cap off the expansion bottle! Ill flush it and put some different stuff in! Very useful thread, yet again!
Oh dear, sounds like another blowing head gasket! Losing the top off the expansion bottle is one of the first signs, as pressure builds up in the radiator. Its also a sign that the vent from the expansion bottle (where it connects to the sub frame) is blocked. This is a common problem on pre 2004 models, as the inside of the subframe corodes where overflowing coolant runs down inside it.
Using tap water to mix with antifreeze will not cause this problem...and neither will a slightly incorrect sized main jet.
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Anyone got a silencer from this model they are looking to sell lol!?!?!?
Was thinking of getting a DEP but i like keeping my bikes looking as they did when they left the factory. Also i cant afford to get the full system and it's probably not worth getting just the silencer.
Annoying thing is, ive got 3 spare silencers. 2 from 2002 models and one from an 86. 2 deps and a standard!
I AM A MORON!
If your other options fall through, I have a standard DT125RE tailpipe available in vgc (but has been given a coat of what looks like black high temperature paint). Paint is flaking a bit and silencer has a few specks of surface rust breaking through, but is very solid. £25 including postage, or possibly swap for one of your 1988-2003 DEP tailpipes?
Jerry
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I think your head gasket has gone, have you torqued down the head nuts or re-checked them. If it is this youll be pissed off when you lose your new coolant.
I'm with OG here!
DTR's are very prone to blowing head gaskets, even new head gaskets!
It is very important to thoroughly clean the surfaces of the cylinder head and barrel before fitting the new gasket. I know some "amateur" mechanics who've taken up to 3 attempts to do the job properly!
Make sure there is no damage to the mating surfaces, and tighten the head nuts in a cris cross pattern so that you don't warp the head.
Sorry, but I reckon you've wasted your £12!
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This was discussed as a possibility to change the way my DT125RE opens the valve, with the servo operating the opposite way from the older DTR's, it may make a difference and improve the performance.
Worth a try i reckon
Must admit i have never seen the numbers on the servo before, but i can't say i have ever looked for them. Are they under the rubber cover?
Edit: just another thought, but the servo is a basic electrical motor, if the + and - power supply were reversed i wonder if this would make the servo work like a DTR one.
I've not examined the operation of the DT125RE servo in detail, so don't know if they all operate backwards. It's certainly strange, and the bike's I've come across all seem to perform too well (without crossed cables) to have powervalves operating this way.
Have you earthed the green/black wire yet? I'm sure this effects the powervalve operation in some way.
And yes, the numbers on the servo are under the rubber cover.
As for reversing the power supply to the servo......I've got no idea if this would work!
May be worth a try (if you've got a spare servo in case it goes bang!)
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I have heard more than one account of the cables being crossed and when they have been uncrossed the bike runs very poorly. To get confused and connect them crossed would be a very unnatural thing to do imo, with the easy natural thing to do being attaching them straight.
There are so many differences in DTR's from year to year and UK version to Import version etc. that I think its entirely possible for something like that to come from Yamaha. I get the feeling either someone at Yamaha likes to experiment or has a very strange sense of humor.
Vez.
A lot of confused owners have asked me how the cables should be fitted because there are numbers ("1" and "2") where the cables attach to the servo and the powervalve housing. People often think the cable that connects to the number "1" position on the servo must connect to "1" on the powervalve housing whereas they should connect "1" to "2" and "2" to "1".
If a powervalve is incorrectly set up (eg where the powervalve is rotated anticlockwise 45 degrees or more beyond the open position), crossing the cables over will improve performance as this will cause the powervalve to rotate clockwise as revs increase, back towards the fully open position.
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I also saw a faulty servo, it did the dance of the sugar plum fairies and was obviously broken.
Here it is
http://www.youtube.c...feature=related
Also i believe that some DTR servos operate in a different manner as they have the PV servo cables crossed over before joining the PV.
Vez
Yep, that servo is on drugs!
A lot of owners get confused about which way to connect the powervalve cables, and some connect them the wrong way round by mistake. I don't think Mr Yamaha crosses the cables over at his factory.
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Interesting, i don't suppose you have any pictures of this circuit board ?
The only significant change there would be the power jet, with it being a basic journal/passage within the carb body and not a replaceable brass part like the other jets. Do you know this to be 100% ?
I have read somewhere about changing carbs on later models and this could be why
Vez
Sorry Vez, I haven't got any photos of the pcb at the moment, and don't know how to attach them to the thread (as you've already noticed, I'm still learning how this forum works!)
I discovered the pcb in a speedo I have that broke apart in an accident. Its quite an elaborate affair with lots of micro electronic gubbins attached to it. It may just be there to operate the temp warning light....or it may be something more sinister?!!
The Haynes manual gives detailed specifications for the 1989-98 and 1999-2003 carburettors, and I don't doubt their accuracy (although I haven't checked them). The manual says the power jet increases from a '60' on the earlier carb to a '95' on the later one. I think this jet is probably in the float bowl, near the bottom of the vertical passage that runs down the side of the carb.
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I have looked at my carb, there are no markings on mine either only the name Mikuni.
My engine no starts with 4BL.........
My frame no starts with JYA4BL..........
On the left side of my piston barel there is 3MBOO stamped.
I talked to a mate of mine and he said that the standerd main jet changed from 210 to 240 from the year 1999 onwards.
So maby you are right Oldgit
When I had my carb off for cleaning ages ago I prob did look at main size but for the life of me I cant remember what the hell it was.
Some carbs do have the ID mark printed (in black) just above the tickover adjuster screw. Older carbs don't seem to have it (or maybe its just faded away with age) but many of the later carbs that I have seen do have it.
Carbs from 1999 to 2003 (3RME models) do indeed have a 240 main jet as standard, instead of the earlier models 210. According to the Haynes manual they also have a different pilot jet, power jet, starter jet and float height.
Many people upgrade to a 240 main jet (pre 1999 models) when they fit a full performance pipe, but most don't bother when they simply upgrade the tailpipe.
I think all 1999 - 2003 models have frame numbers starting JYA4BL... and engine numbers starting 4BL...irrespective of whether they are an import or a UK model.
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From what i have read about the reed switch, it "retards" the revs at around 7000rpm. I may be wrong but i believe taping it out of the way is only 1/2 doing the job as i think it needs to be earthed to the frame. I noticed a great difference after earthing mine, but then i never tried just taping it out of the way. might be worth an experiment.
Anyone take a look at my thread in general and have anything that would be of any use? Any emails/contact would be fantastic, even if it were stuff i already know, just to put in my workbook and show that ive contacted people.
*EDIT* Also thought id ad, i dont know what my revs are so i cant comment on that as there is no counter, just a speedo that lights up in blue in the dark. OOh la la ( just cos it looks nice IMHO, not cos its french, cos its not..... Its a dutch import!)
The DT125RE from 2004 wasn't fitted with a reed switch....although they do have a very strange printed circuit board contraption inside the speedo!
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Being doing some research on the CDi's, On your model OG the cdi is apparently restricted in one of two ways ( i don't expect you to want to do any of these its more an info post).
The wires running from the box in-front of the 2-stroke tank ( IF its not a CDI ) would have to be switched around.
There should be a red, yellow, blue, and green wires coming from it, and these are the wires that are switching the cdi.
The red goes to a brown at the regulator.
The yellow goes to a red/white on the pulse coil.
The green to red/white at the CDI
The blue into a plug where the yellow runs from.
To remove the restriction:
Disconnect the red and blue and isolate them.
Join the yellow and green wires together.
Then join the 2 red/white wires together.
This should completely remove the restrictions on the CDI.
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IF the box is a CDI then the only way to remove the restrictions is by fitting parts from a pre 97 model. (probably the case with yours OG)
These parts are:
Complete wiring loom
CDI Unit, to fit a 3 wire servo unit
stator plate
flywheel
and a 3 wire PV servo
ignition switch (probably work around this)
light switches (probably work around this)
(also mention of the carb, but i can't see why)
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Imo the second of these two is a little over the top for what difference it would give and i have only posted it in-case any one else comes across this post and has the parts to do it.
This is, I believe is also the reason you have the partially restricted exhaust 3MB
(also there is a cat in my exhaust thats a pain to remove but is possible, will get some pics up on a different thread when i do it)
Vez.
I've seen a similar article refering to this mysterious "silver/grey box with 4 wires" that is apparently fitted to some 1997-99 models....but I've never come across a bike that actually had one fitted (and I've worked on a LOT of DTR's!).
ALL UK DTR's were originally sold with restricted exhausts (to comply with the 12hp learner laws), the earlier models had the cone at the manifold, the later "3RM" models have a restrictor in the expansion chamber. Although the DT125RE has a cat, their exhaust seems to be generally less restricted as this model normally performs well with just the green/black wire being earthed.
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I don't think OG has one of these, but i do on my DT125RE and noticed a little difference when i blocked it up, although my bike wasn't fully de-restricted so i do tend to agree with you. But i believe it came in later than 98.
And
to the forum. Always good to have another DTR fan in here Vez.
The restictor bottle on the side of the carb to airbox hose started being fitted to some DT125R's from 1998/99 but I agree that not all DTR's had them for the first 2 or 3 years. I've seen some that just had the mounting lug (for the top of the bottle) welded to the frame but no actual restrictor bottle. Not sure if the bottle had been removed by previous owners and the intake hose replaced with an old type version, or if the bikes were supplied like that from new.
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Fit one from a late 80's DTR to a newer model and you may change your mind
.And
to the forum. Always good to have another DTR fan in here Vez.
I did swap CDI's once (between a 1989'ish model and a 1996'ish) & didn't notice any difference. Of course it's possible that one or both bikes did not have their original CDI's before I swapped them!
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Please see page 1 as it has been done. Around post #32
And
to the forum. Always good to have another DTR fan in here Vez.
Oops, still getting used to the forum and didn't notice the thread went on to a second page! Whatamistakatomaka!! I've edited out the "preaching to the converted" bit now.
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Edit: Also to throw more into the confusion, i have yet to earth the black green wire that may change things at the pv.
Earthing the green and black wire is the easiest and quickest way to derestrict the DT125RE, Vez. It has a big effect. I understand that the powervalve does close slightly at high revs on this model if the wire is not earthed, but I'm surprised it actually rotates the wrong way. I would earth the green & black wire and see what effect that has.
I did have an early (1992) DT125R which I fitted with a powervalve servo (3 wire type)and that operated backwards sometimes. In the end I diagnosed a faulty servo.
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I'm new to this site and just been catching up on some of the chat. I know its a bit late, but the following may be of some interest to OG and his slugish DT.
I've rebuilt/restored/repaired and derestricted loads of DT125R's over the past 6 years and I can't help noticing that there's seems to be a lot of guesswork on this thread!
Up to 1997 the exhausts were only restricted by the cone in the manifold area that OG removed months ago. These exhausts can be identified by having 3MB...stamped on the front part of the expansion chamber. After 1997 the cone was not fitted, but the exhausts have a big restictor welded into the main expansion chamber instead (near the 2nd bend where the exhaust bends upwards). These exhausts can be identified by the code 3RM...stamped on them.
There always seems to be lots of speculation on internet forums about older CDI's giving more performance, but in my experience they make little difference.
Also, the bottle fitted to the side of the carb intake hose is indeed a restrictor (only fitted to bikes from 1998). Blocking it off, or fitting an earlier airbox to carb hose does give a small improvement in performance.
to the forum. Always good to have another DTR fan in here 
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Overheating DT125R Help pls
in Dual Sport, Offroad Bikes
Posted
Definitely worth doing the "radiator cap" test that James has described before taking the head off, Andy.
A lot of head gasket leaks on DTR's are relatively small and may not require head skimming or even a new gasket. I have repaired 4 or 5 bikes just by refitting the old (genuine Yamaha) head gasket covered with a thin layer of jointing compound (such as blue hylomar) on the inner and outer circumference.
So far I've had a 100% sucess rate using this technique, although other people I know have had less luck. You won't find this repair recommended in any manual, but it may be worth considering.