Hi there,
I recently rebuilt the top end on my dt125r 1990. New piston and rings, little end and rebore. The first 100 miles everything went smoothly. Since then it has started to get hot ( about 3quarters up the dial just under the red)
Loads of coolant is coming out of the overflow pipe of the expansion tank under seat! Anyone know what this could be, possible air lock? How do i bleed it properly?
Any help would be appreciated thanks :)
Well ive bled the system and still same problem! :(
I find when i stop it goes right up with in 2-3 seconds but as soon as i ride and rev the **** out of it it literally goes down within a second, almost looks as if its as quick as the rev guage... any ideas?
That looks to me like a blown head gasket. The system is getting pressurised and the rad cap is venting the excess pressure into the expansion tank. If you rebuilt the top end with a pattern gasket then rebuild it again with a genuine Yamaha gasket. Pattern head gaskets dont always work on DTs!! Also, check the head for flatness before you rebuild it. Must be within about a thou (0.001 in or 0.025mm). That's a fag paper under a steel rule. Hope this helps.
Upadate, after taking in the info i have gone and ordered a new genuime headgasket from padgetts motorcycles so shouldt be too long. Im then going to check head for flatness and then put it back together again! I will let you all know if this works and thanks again, people on this forum are very helpful!! :)
When I rebuild mine last month, I lapped the cylinder head and the cylinder before fitting everything back together, all that involves is getting some fine grit wet and dry, then some WD40, and then place the wet and dry on a flat surface and oil it, then move the cylinder/head in a figure of 8 motion until the surface is a uniform shiny silver, then you should be level and flat on both surfaces and it'll achieve a much better seal.
I've attached a before and after picture to show you what I mean :)
-- Edited by mammoth200 on Wednesday 20th of April 2011 10:13:36 AM
You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
Got my genuine one on order, cant wait!! So annoying not having it on road especially when its blazing hot and the fields are calling me to hoon round on lol!!!
Well as you guys said it was the headgasket!! :( it was a pattern one and it wasnt sealed properly by the front so it was blowing into the cooling system hence the pressure and leaking etc!! Im going to do as advised above and use wet and dry etc to sand it down slightly and fit my genuine gasket which i hope arrives tuesday! Checked the thermostat just incase and was working perfectly!!
Dont wanna sound like a geek but cheers for all your help people, being new to the 2stroke scene i didnt know alot and youve saved me alot of time and expense!
I will post up when its done to tell you the outcome and upload a few pics of the scorched gasket lol. Thanks again :) Lewis
Good lad, hope it all works out and your back hooning around again!
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You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
*myns doing this same problem, but ive had the head of alot, i had a genuine one didnt ride it but didnt seem like it did this, then i had one pattern one , and i started riding it up the road , to wear the engine in before it had m.o.t .ON PRIVATE ROAD .Then i had to get the head off, again , and used a pattern one , and as i went to the m.o.t tester i heard BANG and the back cap flew off .
AND now it just pushes water out the back, going to check for a air lock, ive tryed to look but how do you bleed the collant system properly. thanks alot
Myn was definantly the head gasket as it was scorched where it wasnt sealed properly. As for bleeding you have to unscrew the bolt on the side of the thermostat housing and let it run until no more air or bubbles are coming out. This is what i was told anyway. Have you checked to see if your head is warped?
Well , last night it was going mad, the bike would not rev over 7 k , and sounded dead .
Thought it was head gasket so i put a genuine one on , old one , well i say old i just took it off to replace the piston ring , never been riding before but im like that worired LOL .
Any way , going to test ride inabit , but the back is not pressureing and hissing and bubbling any more, plus why it wouldnt rev over 7k , is the main jet had fell out into the bottom of the carb LOL.
I see some of the lads in here have problems checking for warped heads, yes you can use straight edges but its alot of messing about, one tip I learned years ago to check a warped head, more with cars but works to with bikes, is to get a piece of glass, smear some "NEW"engine oil onto it, place the head onto the oil, then look underneath if it is o.k you'll see a continuous unbroken face,
No using your glass coffee tables either cos your mums/missus's will go mental, lol
Thinking about it, a tips section on the forum might come in handy, ey Seiki?
So i took Mammoth200's advise and sanded the head down, fitted my genuine headgasket and tightened to right tourqe and hey presto she is all fixed! Running perfectly with no overheating or loss of coolant through expansion tank. Trust me i put it through its paces to make sure! Thanks again guys
You are one person, out of 7 billion people. On one planet, out of 8 planets. In one starsystem, out of 100 billion star systems. In one galaxy out of 100 billion galaxies
a lil update mine has been leaking water non stop since i got it today i took my barrle and head off my exhaust is filled up with cosdic soda and i noticed water was leeking into my barrael but it still starts and runs fine just smokey not sure if its a real one or a patten one how much will a proppa one cost
