DT125R ARCHIVE

bkray · DTR Senior Member

Coolant issues.

the only way is YAMAHA DTR · Guru

is the radiator cap F@cked try fitting a new 1 ?

bkray · DTR Senior Member

would a dodgy rad cap cause it to be over pressurised?

Sgt-syphilis · Guru

what about water pump issues? or the hoses to and from rad/engine/resv are not working properly...?

the only way is YAMAHA DTR · Guru

no underpressurised would cause it to over heat, pressurised water has a higher boiling point, if the rad caps gone the the coolant will go up to the header tank

bkray · DTR Senior Member

ok, sorry im such an effort. but, my rad cap seems fine, its when i stop, it starts coming out my overflow tank, my bike doesnt overheat unless there isnt enough coolant in the rad, so the coolant s getting replaced by air at somepoint. i dont have a clue about the water pump but i believe the hoses are fine. :) cheers for all the help guys.

Wilksiee · DTR Respected Member

not sure if we're talking about the same thing, but i think i have exactly the same problem.

i top up my radiator and it stays level like normal whilst the bike is cold, but then as soon as i take it out after about 5 minutes, the water level in my radioator drops & goes into my coolant overflow thing at the back of the bike.

i'm not too fussed about it...ill just keep emptying and topping back up as it isn't casuing me problems, am going to try a new head gasket though. just wondering do our problems sound the same??

bkray · DTR Senior Member

yes, that is exactly the same as my problem... atleast i know its not just me... its the third time in a row its happened, was told its my head gasket everytime but i took it to the garage twice, and this time i even done it myself. and its still happening. so long as i top up the rad, it doesnt overheat. just concerned it might make matters worse.

the only way is YAMAHA DTR · Guru

a waterpump/ head/ cylinder gasket might be leaking into the engine, also ar you bleeding the system when you fill up?

bkray · DTR Senior Member

I do bleed the system correctly, im certain its not my cylinder head at all. :/ ive got no idea about a water pump though.

Wilksiee · DTR Respected Member

i just replaced my water pump gasket so i doubt it would be that. certainly is a weird problem, mines been doing it for about 3 weeks ish now and no problems have happened and never comes close to overheating.

mines an import, dunno if urs is aswell and wether this makes a difference

bkray · DTR Senior Member

no, mines not an import. :/ and well, im gonna end up replacing all the hoses... maybe even the rad itself cause ive got a spare one sitting in my room. i mean, the first two times, i took it to the garage, and they said they had sorted it, and replaced my head gasket both times... i thought they wouldve been able to sort it.

carl13671 · DTR Senior Member

Take the rad cap off while its running and look if the water bubbles in the rad or flows.

If it bubbles its got to be the head gasket.

tripr · Guru

+1 on that m8 check the rad for water/air movement ,, i bought coutless cheap gaskets an they all did this like yours even lost my collant bottle lid from it exploding .. get a proper gasket on it m8 sorted mine out there only 12 quid ,,, if all else fails buy another top end for it.

the only way is YAMAHA DTR · Guru

take the thermostat out and drop it in boiling water to see if it opens fully

bkray · DTR Senior Member

it bubbles. O.o ive already checked that... and the thermostat is ok. i guess im gonna need a whole new top end? its the third genuine gasket ive just put on, it started doing it straight after it warmed up the first time, the times before, it was just before i finished running it in.

This means im gonna need a whole new top end? because ive spent hundreds on trying to get it sorted. :/

the only way is YAMAHA DTR · Guru

are you blowing the head gasket, maybe the heads been overskimmed and to much compression,

tripr · Guru

yeah the bubbles tell you its shot again m8 if you have tried the proper gaskets, are you doing the bolts in the right order then retightening after some engine use.
strange question but are all the head studs in the cylinder ok. once one of mine threaded an wasnt doing the head up tight enough causing this , I pulled the cylinders stud staight through the top nut overtightening,,,, maybe worth a look,,,,,

ya cant get rid of that bike m8 its so nearly there ,, an its stunnin

ill keep my eye out m8 see top ends going quite cheap alot on ebay

http://www.ebay.co.uk/itm/YAMAHA-DT-125-RE-CYLINDER-HEAD-AND-BARAL-/220839652367?pt=UK_Motorcycle_Parts&hash=item336b11ac0f

-- Edited by tripr on Sunday 28th of August 2011 10:54:10 PM

the only way is YAMAHA DTR · Guru

dont see how changing the cylinder will help. unless theres a hairline crack in the bore or from the water galleries into the transferports,

dirtpoor · DTR Senior Member

i had same thing forgot to torqe up my cylinder and head when i rebuilt it all my water went black an white and a foamy rust was coming out the bottel didnt start doing doing it for a few weeks thou.

bkray · DTR Senior Member

Ok, heres something to ponder on. its had 4 skims that i know off, and probably quite a few more before that, and its looking pretty small whatever the middle bit is called. you reckon it is overskimmed? i got another cylinder head upstairs. its from an old dt. about 90? so different model because ive got a newer engine in? i can get some pictures, but could i just swap the head straight over? after a skim of course, its looking pretty neglected.

tripr · Guru

yeah try that m8 give it a clean an slap it on there 4 times skimmed will make a smaller compression area probably blowin the crap outta ya gaskets

satelliteone · DTR Senior Member

also check the barrel for flatness when ya got the head off, steel ruler across the top too. I have two barrels here that need skimming. and the heads. GenuineYam Gaskets.. stealers are 26 quid, for the 4FL gasket

I blame yam for the ****e idea, should of been O ringed.. like the Rotax engines.

then again, the only barrel and head that was O ringed the Tzr125rRR SP engine. Rocking horse pooo...

Torque even, and use genuine.. good luck chap.. i know ive been down the same road..

bkray · DTR Senior Member

well, Tripr, its been skimmed more than 4 times in its life, id say atleast 6 times? if not more.

And i had no idea that the barrel had to be skimmed too, i might get it apart again soon, and skim that myself.

Wilksiee · DTR Respected Member

instead of buying ****ty gaskets made by a company, try a genuine yamaha head gasket...ive been told this WILL fix the problem, im gunna buy a genuine yamaha head gasket probably next monday, so if u havn't fixed the problem by then...ill let you know how i get on

bkray · DTR Senior Member

well no, it wont fix the problem... This is my third genuine gasket in a row, bought from A.J.Sutton.

Wilksiee · DTR Respected Member

drain whole coolant system including the overflow bottle. then get the bike warm and add coolant then bleed the system & then top up again. try replacing your rad cap or borrowing someone elses just to try.

im going to try all theese things when i can (monday) will let u know if either of theese things work for me

zo0op · DTR Senior Member

I had the same problem with my old engine, take for a blast pull up put it on its stand and water would piss out of the expansion overflow, get another barrel an head of ebay and give that ago also check the water pump... Does the temp cage suddenley shoot up to the red? Duno if they have temp gauges on the newer dts?

zo0op · DTR Senior Member

My bad thought yours was the new shape because of the front light lol

Dingle001 · DTR Senior Member

In my humble opinion this sounds like a cracked/porous head or maybe a cracked barrel. The barrel is unlikely to be warped, but take the head off and run a steel rule over the mating surface of the barrel and see if you can get a fag paper under it - just in case. I definitely wouldnt continue with a head that has been skimmed so many times without checking the squish clearance (piston to head). If this is too small it can cause serious problems.