So Close!...
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@SpookDog Just been reading about your headgasket situation.
On another thread you commented that you've blocked off your carb warmer circuit using allen bolts and copper washers; potentially this means your cooling system is no longer self-bleeding when you refill the coolant (the stock thermostat has a small bleed hole but it's tiny, <1mm so there's no guarantee this isn't blocked).
If you have an air pocket right at the top of the head, the coolant may not be pressurising which will lower its boiling point and lead to overheating (and an air pocket will itself lead to a hot spot as there's less coolant there to carry away the excess heat). Possibly increasing the likelihood of your headgasket(s) to fail.
Try refitting the carb warmer circuit banjos so you can disconnect the hose at the thermostat housing until coolant free of air bubbles emerges when refilling the system (this is how Yamaha and Haynes recommend bleeding the cooling system). If you don't want the carb warmer circuit you can just run a hose straight from one banjo to the other so access to the carb isn't affected.
Considering how much trouble you've had with ebay gaskets etc., I'd also invest in a genuine Yamaha gasket and maybe a new thermostat (or at least remove yours and test it),
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2 weeks and still have a functioning head gasket and cooling system š Iām not counting my albatrossās yet but itās looking good...
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Cheers for the input. Iāve tried various new and older but tested thermostats. Iāve tried different head nuts & washers. Studs locktighted and not, finger tight and cinched up tight. Tried the head to frame mount tight and ānot tightā thinking there may be too much stress on the head through the mount. I think Iām on my fourth different head & barrel combo. Using pure water at the moment, also changed my 2stroke oil thinking that there may be some kind of reaction between it and the gasket covering...
Gasket has always leaks at a different point. Always between the gasket upper surface and the head apart from the one time last time when it leaked both sides of the gasket...
Any idea or input is appreciated greatly, but yes I always put the gasket UP the proper way š ...
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@SpookDog I am at a total loss as to why you're having so many problems.
Next thing we need to check is the compression. If you're running like million PSI compression then that would explain something.
I mean, these bikes were exported globally so you really shouldn't be having this much issue. They are also very basic and you really have to be doing something wrong to be having this much trouble.
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Iām hoping that itās good to go this time. Iāve ran 3bn and different 3mb& 3mb-p heads. Nothing radical š ...
The thing is I been doubting myself for a while but I really canāt see anything wrong with my method...
If it fails again Iām gonna do a pic by pic slideshow of my methodology to see if anyone can point out anything obvious Iām missing... -
My only real doubt is my lapping technique for clean old gasket crap off and prepping the barrel top and head mating surfaces. Iām gonna get a new peice of plate glass and new wet n dry for future endeavours...
I might just get them skimmed/finished by PJME as well. I have a barrel that needs a new rebore and they were the best finish Iāve ever seen on the bore...
Iāll get there sometime soon. The bike is running better than it ever has before since I got the carb jetted proper. I just need to fit my new 3.50 rear tire and lower the gearing so it gets into the power band in 5th & 6th easier...
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@SpookDog What I mean is, if you're running a super thin base gasket, lapped the head a million times + lord knows what someone else did in its life, it could be running super high compression. You've somehow magically managed not to blow the engine up through detonation, but instead are blowing the head gasket...I am really clutching at straws here though.
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I canāt say Iāve upset them per se, but they have been pissy at me for sure. I think that they get jealous of your life and then try and drag you down to their level of hell...
There are some messed up creatures out there!! ā ļø -
@SpookDog Crazy your gasket problems as done loads of engines and every head gasket from cheap white ones in those cheapo full gasket sets to athena gaskets and never had a problem. On barrels always use blowtorch on studs and 40 years working on 2 stroke engines and never snapped a stud yet. Remove studs then piece of glass with 240 wet & dry on barrel and head and 100% flat, I use my cooker hob as it glass really strong and it
doesn,t move about, just do mine when the wife is out.lol -
Thatās the stuff! Old mirrors can be good as well š
I always use heat for stud removal as well. The only time I didnāt I snapped a stud, it had only been in for 6 weeks and not even tight! In hindsight it was too new and shiny (came with a head and barrel I brought) and didnāt have the dimple on the top. Was a cheap fleabay copy I think...
Iāll have to try 240 drift. I canāt remember what I used before. A nice even Matt finish and a check with a steel rule is my usual MO. Head and barrel. The barrel base is more awkward but I use a square glass drinks coaster...
My latest iteration is still hold up. Itās been nearly a 1000 miles now š¤ ...
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I know, but I canāt figure it out! Not to blow my own trumpet, but I donāt think Iām doing anything wrong with my methodology or workmanship. Itās consistently lasting for weeks after fitting (about 1000 miles this time) If it was my idiosy it would fail straight away, not last 100ās of miles of normal use!
Iāve tried 3 or more different head & barrel variations. So itās not the barrel or head to blame!
Tried different makes of gasket.
Ditto base gaskets for the barrel.
Different coolant, pure water combinations. Different 2stroke oils, ect. Just in case one of them was reacting with the gasket coating!
Different carbs. Different jetting combinations!...The only thing that is constant is the exhaust. Iām thinking this because there is always a rattling~knocking noise when Iām idling along at very low (but not closed) throttle in any gear. I thought it was piston slap at one point in time, but itās done it with various barrel and pistons. It might be pre/miss~firing maybe? (I heard about a similar rough/flat spot that cleared up with an exhaust change) It kinda ties into a problem Iāve always had with a low rev stumble/flat-spot that happens when I crack the throttle slightly, that I always took to be a jetting issue that I could never resolve...
Iām really fuckin clutching at straws here, I know! I just canāt imagine what else could be causing this. Iām even thinking about building another bottom end š
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What is your squish gap?
Is it easy to fit the cylinder head engine to frame mount bolts, or are they under some strain?
Are you using some form of stock jetting?
What are your exact symptoms of head gasket failing? Pushing water out the expansion bottle? Temps raising into red?
Condition of radiator/cap? -
@SpookDog have you checked the radiator pressure cap? Is it faulty or is it the correct one? They have different pressure settings and they are vital to keeping the correct temperature. My dad once spent over Ā£500 on parts he didn't need for his over heating car then found out it was a failed pressure cap causing it.
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@Calum it sure does get overlooked. I think most people fail to realise the importance of this part and the problems it can cause. Obviously the correct term is pressure cap, as it regulates the coolant pressure which in turn regulates the coolant temperature.