keep blowing front cylinder o-ring

[D-Roc]

since the beginning of this season i have blown three o-rings on the front cylinder. the first time i thought it was just old, the second time my buddy suggested i remove the spring/fall cooling restrictor. this was good until tonight, it blew again for the third time. i am still running single cooling and am not 100% sure dual cooling would make my motor run any cooler as i am currently feeding my pipe from my head. if i ran dual cooling i would feed one line to the motor and the other to the pipe. I guess it could have a less restricted flow with dual cooling and allow it to run cooler but right now the water temps are still cool. i am dropping the cylinder off to deck the top to ensure it is true and to tighten up my squish. i ran this motor all last year without any problems and the only thing i changed is the new msd total loss. Anyone think of anything else of why a o-ring keeps blowing? Think I should run dual cooling? :dunno:

 

[Matt_E]

I had that problem last year with my Frankenstein 760 and a Riva head.
I finally sold the Riva head and went to a stocker with headgasket.
Haven't had a problem since.
I don't know if the cylinder or head was to blame.
If it was the cylinder, the headgasket probably makes up for it.

 

[#ZERO]

What cylinder head are you using and what's the bore size.

 

[D-Roc]

ada 35cc domes on my 82mm 61x

 

[#ZERO]

You must have an uneven sealing surface.

I'd check the surface of the cylinder and head with a straight edge; also look at the edge of domes for imperfections.

You can sand out most problems using a piece of wet/dry 150 to 320 grit sandpaper with some WD-40 on a smooth piece of glass or lapping plate.

 

[D-Roc]

okay thanks, i am decking the cylinders and i will check the head/domes. should i keep the domes in the head and sand it on the glass or remove the domes and do them individually?

 

[#ZERO]

It's most likely the cylinder surface but if you find a problem with head I'd leave the domes in place while lapping the surface.

 

[brentR]

im running dual cooling on mine and its actually too cold pipe side

 

[orangefinger]

Did you swap domes front to back ? ...

I have had a dome this year where the groove of the O-ring was too big, some machining error and the O-ring when squished basically just escaped in the extra space of the groove and did not seal the cylinder....

 

[SUPERTUNE]

STOP!!!!
DON"T lap the head with the domes installed!!!!!!!!
Lap the head WITHOUT the domes!!!
'O'....bad advice! sorry
ADA head shells are machined to a depth of .499, domes are machined @ .502
This gives you the .003 thousandths interference fit you HAVE to have for an ADA head to work on a freestanding sleeve that Yamaha cylinders have.

 

[D-Roc]

okay so far no harm done, i only got as far as cleaning the head/domes. i dropped off the jug at my machinist today as well. i have a current squish of 0.052 and told him to deck the top of my jug 0.007-0.012 to get my squish around the 0.040 - 0.045. Was this a good thing or bad? basically i just want my cylinder true so the ada will seat proper. should i go ahead and lap my ada shell? if so then do i lap my domes after too? my one dome that is giving me problems had a little ding in it but i could not feel any high spots. i think i can throw in a new extra one if that is the right thing to do. Thanks for the input fellas. i hope i can get it fixed, i am down to my last o-ring. lol.

 

[SUPERTUNE]

ADA heads and domes do go bad, mostly caused by detonation over time that causes the domes to wiggle little by little over time and wear down the seats in the head and some on the dome face where the o-rings are mostly, but I have seen wear on the top of domes too. Measure both domes for thickness and compare the two against each other to see if maybe you have one bad dome.

 

[waxhead]

STOP!!!!
DON"T lap the head with the domes installed!!!!!!!!
Lap the head WITHOUT the domes!!!
'O'....bad advice! sorry
ADA head shells are machined to a depth of .499, domes are machined @ .502
This gives you the .003 thousandths interference fit you HAVE to have for an ADA head to work on a freestanding sleeve that Yamaha cylinders have.

Good advice you have to have that intefernce to stop it blowing o-rings
Have you checked the sleeves havent dropped this is very common on 61x cylinder
you will need to remove cylinder and machine it if this is the case

 

[D-Roc]

i measured the problem dome and on the spot where it seats against the actual shell i was getting about .501-.502 so i am going to swap in a new dome to make sure. thanks guys i will let you know if keeps me out on the water.:friday:

 

[D-Roc]

my machinist decked 0.006 off the top and he said the front cylinder was low compared the the outer part of the cylinder. i ended up putting in a new dome up front just in case the old one was rattling around a bit over the past few blow outs. It ran really good today and gave me no problems. I did notice that when i was running out of fuel i got some more power so i am now going to lean the carbs a bit to clean up the revs. thanks for the help fellas.

 

[waterfreak]

ADA heads and domes do go bad, mostly caused by detonation over time that causes the domes to wiggle little by little over time and wear down the seats in the head and some on the dome face where the o-rings are mostly, but I have seen wear on the top of domes too. Measure both domes for thickness and compare the two against each other to see if maybe you have one bad dome.

bingo, I had the same problem with my ADA head a couple years back. Like chucky said, it was the top of the dome that started to spin a bit causing the surface to wear and create enough clearance to eventually blow o-rings. I actually had to replace the head shell too.

 

[D-Roc]

that makes sence, i am concerned about that still, it usually takes about 3-4 rides till i blow the o-ring so i am still not 100% sure if i got it fixed. I am hoping i don't gotta replace the shell. we'll see.

 

[waxhead]

So the sleeves had dropped
Thats real common with these engines

 

[Speedfreak]

Excuse my ignorance but I have never experienced a blown o ring... What are the signs? Is it when the pisser sputters exhaust? What about water in the cylinder is that a problem?

 

[D-Roc]

i can actually hear it when it goes. and yes the pisser sputters water instead of a constant flow. usually by the time i make it to the dock the water is turning to steam and smoke. and there is a slight loss in power. the water in the cylinder has made some vertical markings, i just gave my cylinder a light hone and put it back together cause i am attempting to make it the season before i bore up to 83mm. probably not the best advise but that is what i did.