Overheating DT125R Help pls

[Vez]

Good to hear you have sorted it.

The carb is heated and with no thermostat this will take longer to happen, may explain the flat spot. 

Vez.

[AndyDtr08]

Good to hear you have sorted it.

The carb is heated and with no thermostat this will take longer to happen, may explain the flat spot. 

Vez.

Just had a read through. Must have missed this thread before! Glad theres a happy ending to the story. Also very useful to me. My 2002 DT i rebuilt with a friend who then ducked out due to financial issues! I recall him sorting the coolant out. 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!

[Deeteemx]

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.

[Airhead]

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.

+1 with all of that, another head gasket blowing and tap water will not cause any problem at all, the only downside to tap water is

1, it will freeze in winter and wreck your radiator

2, it does not contain corrosion inhibitors

Thats all

as a short term measure it would be fine...in summer

And when I say short term I do not mean all summer long, just until the shops open.

[Vez]

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

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.

[AndyDtr08]

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

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.

Hmmmmm. Now im even more confused, haha! Well, i remember when i rebuilt the engine i had fears of a warped head so i, as OP did, got a plate of glass with wet and dry paper and it looked like the problem there had been sorted. The other thing that makes me think it's not the head is the fact that there is no compression loss. It pops like a real beaut so i'd be suprised if it were. When i have the time, i'll flush the coolant and replace with a mix that i know is right. As you say vez, it's gotta be worth £10 quid rather than having the head off and ruining, what could be, a perfectly good gasket. It wont be for a few weeks though i expect as i've gotta get all the preparations for the documentary in place but i'll be sure to report back my findings!

*EDIT* Not sure if i mentioned before, but the bike has only done about 10 miles round the drive and up and down the pavement outside my house since i rebuilt it. If that has any bearing on anything let me knwo

[Airhead]

*EDIT* Not sure if i mentioned before, but the bike has only done about 10 miles round the drive and up and down the pavement outside my house since i rebuilt it. If that has any bearing on anything let me knwo

10 miles since a re-build eh, couold it be airlocked, iI dont know if this can happen but if so will render the cooling useless and have the net result you say. Vez i'm not doubting what you say about the elevated boiling point, with a 50/50 water antifreeze mix the BP would be something like 135C, this will be further increased when you take into account pressurisation. In hindsight it may have been unwise to say what I did, since this was not a 'can i use it in emergency ?' case.

BUT, knowing how COOL my bike runs .........

[Vez]

 Andy, Have you re-torqued the head nuts since fitting the gasket and running the bike a while?

With the bike only having done low miles since the gasket was fitted i wouldn't think it was the coolant unless it is 100% tap water and is being revved high and ridden hard/abused as it was in the case i witnessed. With the coolant i use there should be at least a 50% coolant 50% de-ionized water mix. There are warnings on the bottle about lower ratios causing engine damage over time.

I can't see a compression tester showing up a small head gasket leak, as i would expect a leak to open up as the bike gets hotter and parts expand, but i may be wrong.

Personally i don't trust the piece of glass and sandpaper method to fix a warped head. It has to be plate glass and not rolled glass (it has ripples from the rolling process) and also at least 1/4" thick to stop it flexing under pressure. Even then i wouldn't be too confident it would sort a warped head out. An engineer skimming it is the only certain method imo. 

If you have the head skimmed (which you probably should) you may as well take the barrel along and have that done to get a good mating surface and up the compression slightly too, imo that is.

Vez.

[Vez]

10 miles since a re-build eh, couold it be airlocked, iI dont know if this can happen but if so will render the cooling useless and have the net result you say. Vez i'm not doubting what you say about the elevated boiling point, with a 50/50 water antifreeze mix the BP would be something like 135C, this will be further increased when you take into account pressurisation. In hindsight it may have been unwise to say what I did, since this was not a 'can i use it in emergency ?' case.

BUT, knowing how COOL my bike runs .........

Just a little annoyed at the moment and it doesn't take alot to set me off on a rant at the best of times.

I'm not willing to continue a discussion about the pressure aspect of water and coolant in a bike, its just too much like being at college and its still the holidays yet!   

In an emergency i would pee in my system to get me home    (used canal water to get 5-6 miles home once)

I've heard of the airlock bit causing issues, but never knowingly experienced it myself. Only way to check would be to measure the amount of coolant that the bike takes from empty at a guess. Also i believe some bike garages have a machine to remove the air from a cooling system (a bit like a brake bleeder) but can't say i have ever seen one.

I swear you have pedals on your DTR with the temps it runs OG! The 250 main jet maybe the reason. I'm willing to bet that my hot RE runs a 210 main jet and with the cat stopping proper flow of hot exhaust gases it may explain a little.

Vez.

[AndyDtr08]

Hmm. yeah well its definately not 100% tap water as its pink! The other part of the "partnership" works in halfords and always thinks he knows best so i trusted his judgement, but since seeing him work on his 2 DT's (before they were both stolen recently) i have reason to believe otherwise!

I have a number of friends who are engineers so i'll ask one of them to skim the head and barrel when i have to chance to do some work on it. The bike is stored outside at the moment (covered and secure) but is there any risk in not getting this done soonish, presumably even if there is a leak the coolant will only be passed the leak when the engine is running, and at this time the compression would stop coolant from getting into the bore. I run the bike regularly.

when i ran it today i did notice that the smoke was quite rich. I didnt have time to run it for any length of time and dont want to rev it highly, or have any place to give it a good blat to clear the pipe so it may just be that. I did think it looked fairly white though so this with the coolant pressure leads me to thinking it probably is a gasket problem. Is this logical?

Might make the time next weekend to get it apart. Only problem is ive got the 86 in the garage + my DTRE+my dads kettle+ my brothers SR125, and the parents always want to get one car in there too! (its a double, were not a family of clowns ) so it might not be til ive completed the 86!

[UltimateJames]

Just to let you know my expansion cap blew off a couple of times ! god knows how i didn`t loose it lol, also when the bike has been run and cooled down try taking the rad cap off and if it blows pressure out its not good and looks like the gasket i reckon also smell the water does it smell of petrol ? . Also my bike was running fine with no loss of power at all.

to remove air locks loosen the carb heater pipe on the thermostat side of head until the coolant runs thru without air,

I tryed the glass with wet n dry but it didnt work for me and for £25 to have it skimmed you might as well get it done as it saves buying another new gasket if it dont work for you (wish i had skimmed it to start with cos it cost me 2 gaskets and 2 litres of coolant). iv done quite a few miles now since and everything is perfect now just need to put the thermostat back in as its taking ages to get it up to temp, cant win lol.

One other thing i wont be using cheap gaskets again either, use gen yamaha ones was only £9 + vat.

[Airhead]

One other thing i wont be using cheap gaskets again either, use gen yamaha ones was only £9 + vat.

From where?

[AndyDtr08]

Just to let you know my expansion cap blew off a couple of times ! god knows how i didn`t loose it lol, also when the bike has been run and cooled down try taking the rad cap off and if it blows pressure out its not good and looks like the gasket i reckon also smell the water does it smell of petrol ? . Also my bike was running fine with no loss of power at all.

to remove air locks loosen the carb heater pipe on the thermostat side of head until the coolant runs thru without air,

I tryed the glass with wet n dry but it didnt work for me and for £25 to have it skimmed you might as well get it done as it saves buying another new gasket if it dont work for you (wish i had skimmed it to start with cos it cost me 2 gaskets and 2 litres of coolant). iv done quite a few miles now since and everything is perfect now just need to put the thermostat back in as its taking ages to get it up to temp, cant win lol.

One other thing i wont be using cheap gaskets again either, use gen yamaha ones was only £9 + vat.

Ok, thanks. I'll do the same. I expecte i can get a friend to skim it for free so it's definately worth doing. Tempted to get him to do the other one whilst he's at it, just to be safe.

[Deeteemx]

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.

[Deeteemx]

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!

[Deeteemx]

Ok, thanks. I'll do the same. I expecte i can get a friend to skim it for free so it's definately worth doing. Tempted to get him to do the other one whilst he's at it, just to be safe.

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.

[UltimateJames]

From where?

Padgetts Ltd

- www.padgetts-motorcycles.co.uk

234 Bradford Road, Batley - 01924 478 491

[AndyDtr08]

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.

Thanks, i keep coming back to the thread and everytime it makes me want to go out and start fiddling but i really should concentrate on the uni work!

[satelliteone]

yup normal water is fine, u would need an antifreeze in the winter.Never heard such horrlicks! with adding stuff to water for this or that or other. come on use your sense. not only that, u instantly told me earlier that i was wrong about an exhaust!.. common chap.. pls make 100% certain ur right before flaming. make u look like a right pratt.

DTr are terrible for holding head gaskets. Useless design IMO. the gen yam gaskets seem to work better, but why ohh why did`nt yam use O ring technology.. or better gasket design..the head is so small no wonder its warps.

and gettin a torque wrench on the head!.. whilst in the frame.. im thinking of changing the design my self. plain copper gaskets. laser cut!